HN Gopher Feed (2017-10-12) - page 1 of 10 ___________________________________________________________________
Hyperloop One Becomes 'Virgin Hyperloop One'
275 points by mpweiher
https://techcrunch.com/2017/10/12/hyperloop-one-becomes-virgin-h...-virgin-hyperloop-one-with-virgin-group-investment/___________________________________________________________________
dmix - 8 hours ago
Despite the fact there are more billionaires than ever, it's funny
how small the group of bold innovators are. It always seems to be
the same few people.
dx034 - 6 hours ago
I'd argue that Bill Gate's work has a better return of investment
for society.
larkeith - 4 hours ago
IMO, we need both types - Gates' work improves society in our
current world, while Musk and Branson's investment kickstart
the scientific and technological advances needed to further our
civilization.
ballooney - 7 hours ago
No, it?s different people doing it, but the same few people
funding it. Like VC.
kumarski - 8 hours ago
Something I wrote a while ago.... w/ back of the napkin
calculations.......Why I wouldn?t invest a money into Hyperloop-
Stabilizing a single fault line risk pylon is more than $250K.- How
many million are needed for vacuum pumps to evacuate 100+ million
cubic feet of of pipe to 100 Pa?- Hot air discharge needs to go
somewhere. For every 1 bar pressure, you need ~200 to ~400 cubic
meters of volume which is larger- This seems very much like one of
those Andy Grove Fallacies.- The hyperloop is a mega engineering
project on the ground. Nobody on their team is a civil engineer.
Looking at their team objectively, there seems to be a mismatch of
competency.- At its core, the science i good, the cost-economics do
not work. Das ist nicht gute.
Analemma_ - 8 hours ago
When Musk first said that an LA<->SF Hyperloop could be built for
1/8th the cost of the equivalent HSR, I chuckled and then waited
for the punchline, which still hasn?t arrived.It?s a cool idea
and I do want to see more prototypes and feasibility studies, but
people need to get off the hype train (no pun intended) and be
realistic about the cost.
hbosch - 7 hours ago
Okay, we'll bookmark this for the future. Amtrak estimated a
HSR/"bullet train" from D.C. to Boston would cost ~$151
billion. Since LA to SF will only be two stops, and we can
assume Amtrak estimated at least 4 (Philly and NYC) let's bring
the number down closer to $100 billion to make it even.Do we
think the Hyperloop costs are more or less than that? 1/8 of a
theoretical $100b is $12.5b -- is $12.5billion for Hyperloop
unreasonable? I have no opinion on cost personally, and I don't
know economics, but this $151 billion from D.C. to Boston was
floated by the established US player in rail infrastructure.
Anything less than that number is fantastic, right?
dx034 - 7 hours ago
You cannot compare D.C to Boston with SF to LAX. The east
coast has much denser population so that you need more
tunnels. LAX to SF HSR would not cost $151bn. Start and end
are expensive but the part in the middle is "relatively"
cheap.
hbosch - 5 hours ago
Right, for comparison's sake I chopped off $51 billion
bucks from the Northeast Corridor projection in the
interest of balancing out the two.Just because I felt like
doing some more Google-fu, I found an article in the LA
Times[0] that says a California HSR/bullet-train project is
going to overshoot it's original budget (and deadline) of
$68 billion. There's a lot of info out there about this
project, and it's potential overruns, but let's forget all
that and just stick to the original planned cost: $68
billion, so, about half of the cost of Amtrak's
northeastern bullet. Let's use that number for our
comparison.If we are going to hold Elon to his "we can do
it for 1/8th the cost" blurb, then we are giving him like
$8.5 billion to use for his SF/LA Hyperloop. Still, that
doesn't sound unreasonable, right? He'll get a good deal on
tunnel boring with his other company, and fuselage
manufacturing can be handled by SpaceX. When it comes to
financing, I don't think it's a major issue compared to
other infrastructure works out there.Like I said, though,
I'm just going off the top of my head. I don't know finance
or economics or vacuums or magnets.There's a new LIRR train
being dug in NYC called East Side Access. This is a
commuter rail line, and is going to cost ~$10 billion or
so[1]. Logistically these aren't the same, obviously, but
if adding to the LIRR is worth ~$10b then surely the
Hyperloop experiment is as well, right?EDIT: Also, just for
disclosure, I don't live in California and I'd probably
never end up using the Hyperloop myself so I'm neither for
nor against it versus any HSR. I just want to entertain the
idea that cost shouldn't be the main focus of discussion
IMO.___0. http://www.latimes.com/local/california/la-me-
bullet-train-c... 1.
http://web.mta.info/capital/esa_alt.html
pavs - 6 hours ago
I don't think Musk want hyperloop to be built above the ground.
This is just my own personal opinion, not sure if that's how
it's going to work, but in one of his interview (TED? I think),
he mentioned one of the reasons for his Boring company, was it
would be relatively cheaper to build hyperloop - because the
atmospheric pressure will be lower underground - and since you
don't have to worry about building large infrastructure for
only one purpose (hyperloop) - the cost will be much much
cheaper. Because under ground tunnels can be build for both
hyperloop and roads for cars and it scale better than above
ground.I don't think above ground is economically and
technically feasible, there are just too many unanswered issue
that almost no one has answer to. Not to mention it will be
very very expensive and time consuming.
opencl - 4 hours ago
Tunnel boring is orders of magnitude more expensive than
railway construction, at typically ~a few hundred million
dollars per mile vs ~a few million dollars per mile. I know
Musk has plans to magically make tunnel boring significantly
cheaper but you need two orders of magnitude cost reduction
to make the tunnel digging not cost more than an entire above
ground railway.Cost references: https://tunneltalk.com
/TunnelTECH-Apr2015-Arup-large-
diamete...https://www.compassinternational.net/railroad-
engineering-co...
grw_ - 5 hours ago
Why would atmospheric pressure be lower underground?
Chathamization - 8 hours ago
> When Musk first said that an LA<->SF Hyperloop could be built
for 1/8th the cost of the equivalent HSR, I chuckled and then
waited for the punchline, which still hasn?t arrived.Yeah, and
that proposal was for something with much lower throughput,
that didn't have stops along the way, and didn't even reach the
same areas (they saved money by stopping outside both cities,
which the rail line wouldn't do). It also assumed that the
tubes could just be placed along the highway meridians (a lot
of the money it was supposed to save was from this).
Pxtl - 6 hours ago
I'm not saying the hyperloop is a good or bad idea, but any
suggestion that it would be cheaper than the equivalent HSR
seems utterly insane. How could it possibly be cheaper? You
have the same ROW requirements, exponentially more expensive
track, and the overhead of the fact that it's brand new
technology. The fact that the vehicle itself might be cheaper
than an HSR train after the tech scales up is almost an
afterthought next to those costs.
reacweb - 6 hours ago
The track should be cheaper because hyperloop has (almost) no
impact on existing infrastructures. Expropriation costs for
train are huge.
Pxtl - 6 hours ago
How could the Hyperloop not require the same
expropriations? A giant tube isn't any smaller than a
train track. Is it the fact that it's elevated? Rail can
be elevated. Yes, rail is heavy, but so are giant
evacuated steel tubes.
pstuart - 1 hours ago
I think he's planning on making lots of
tunnels.https://www.wired.com/story/elon-musk-test-
tunnel/
zip1234 - 5 hours ago
Run it down the center of the freeway? Having stations
for trains in the middle of freeways isn't great for
pedestrians, but might be fine for long distance
transport such as hyperloop.
Pxtl - 2 hours ago
HSR is supposed to be log distance transport. It's I
meant to solve the exact same problems as Hyperloop, but
by powerful engines and streamlined railcars instead of
evacuated tubes.Again, why not put HSR tracks in the same
place you'd put a Hyperloop track? Put the station in
the same place. The tubes aren't smaller or lighter.
warent - 7 hours ago
To be fair, if Elon worked in the project for 40 - 80 hours a
week, he probably could get a team to accomplish it at 1/8th
the cost or lower.Consider he did this with rockets, getting
them to under 1/10th the cost
jandrese - 7 hours ago
With rockets he was competing with fat and lazy government
contractors for the most part. The hyperloop will be
competing with already cutthroat airlines, the goddamn
personal automobile, and, ...well, a fat and lazy passenger
train company.IMHO he'll be well over 1/10 the cost before he
finishes the thousands of land deals he would need for this,
even if he somehow got permission to build it over the
highway.
imron - 6 hours ago
> even if he somehow got permission to build it over the
highway.Hence the boring company.
ballooney - 7 hours ago
He hasn?t done that with rockets. He wants to eventually, but
he hasn?t yet. Let?s not let hype cloud facts.
nkoren - 7 hours ago
He's getting very close, if one is considering domestic
rockets. The standard-bearers were the Delta IV and Atlas
V, which price out at around $17,000/kg - $20,000/kg to
LEO, respectively. The Falcon 9 comes in at about $2,800/kg
to LEO.Comparisons with non-domestic rockets are
complicated by state subsidies and differentials in labor
costs. But the Falcon 9 is approaching the 10X mark even
before reusability has been priced in. Both the Falcon
Heavy (in a few months) and the (eventual) reusable pricing
should overshoot the 10X mark substantially.
Rebelgecko - 4 hours ago
Where are you pulling those numbers from? On ULA's
website [1] they say you can launch an Atlas V for less
than half the $/kg you listed[1] I went to
rocketbuilder.com and both LEO configurations I tried
were around $8,000/kg (and I didn't count the 20%
deduction for "ULA added value" since the numbers there
are debatable)
nkoren - 32 minutes ago
ULA has abruptly gotten way more competitive in their
pricing. A few years ago they were not. Their "Best deal"
for the Atlas V was a 36-rocket "bulk buy" priced the
lowest-tier Atlas V 401 at $164M/launch[1]. That does
9,797kg to LEO[2], or $16,740/kg.The GAO cites
$164M/launch as the price for the cheapest Delta V[3] (is
there some kind of threshold at $165M?), which when the
Falcon 9 was introduced could put 8,500kg to LEO[4], or
$19,294/kg. (It has since been uprated and gotten
slightly cheaper).Must've screwed up my calculations
earlier, because those aren't tallying. Anyhow, as you
can see, SpaceX is already around 7x cheaper compared to
where ULA was, and should cross the 10x threshold
shortly. Nice to see ULA responding to competitive
pressure, however!1: https://web.archive.org/web/20160324
172526/http://www.ulalau...2:
https://en.wikipedia.org/wiki/Atlas_V3:
http://www.gao.gov/products/GAO-17-6094:
https://en.wikipedia.org/wiki/Delta_IV#Delta_IV_Small
kbenson - 4 hours ago
Maybe you're looking in the wrong place for the punchline.
Perhaps it will be delivered in the final bill for the HSR...
martinald - 7 hours ago
Is this not an attempt to just derail CAHSR, or HSR in general?
Nearly every anti-HSR comment is now 'we should build hyperloop
instead!'.
Pxtl - 6 hours ago
That's impressively cynical, but Musk obviously stands to
gain a lot if people keep California using roads. California
wants to go green and he sells the best technology for green
road-based transportation.
kbenson - 4 hours ago
I'm not sure it really affects his electronic car business
one way or the other. Firstly, he isn't necessarily
selling Tesla's to people for commuting between SF and LA,
that's well outside his range, and as fast as the
supercharging is, it loses out to regular gasoline
refilling. Secondly, I'm not sure the amount of people
potentially served by the hyperloop is more than a blip in
the sales charts for even a regular car company (as
deciding factors for car purchasing decisions, it seems
relatively low to me).
yahna - 4 hours ago
heh.Reminds me of when an actual AI expert pointed out that
by making dire predictions about smart AI, that we are
nowhere near having, keeps eyes off the autopilot system
and the issues with that.
imron - 6 hours ago
To be fair, he also stands a lot to gain if Hyperloop
becomes a reality.
zardo - 5 hours ago
How does that work? He had an idea and promoted it. No
one's going to be paying him royalties for it.
imron - 4 hours ago
He's also building one, so he has a vested interest in
the technology being successful:
https://techcrunch.com/2017/08/04/elon-musk-reportedly-
plann...
loceng - 6 hours ago
People often, rightfully so, confuse the misappropriated name of
Hyperloop One with Elon's Hyperloop idea, his of which I believe
does have sound economics and certainly its pro list outweighs
Hyperloop One's technology.
andruby - 6 hours ago
Could you point out the differences in both technological and
economical approaches?
corpMaverick - 7 hours ago
Assuming your are correct and Branson knows it because he hired
good engineering advisers. Why would Branson get involved ?- It
is a cool project he wants to be part of and he is willing to pay
to see. (I would probably do that)- The benefit is not to reach
the goal but all the technology that will be invented trying to
reach the goal.
buckminster - 6 hours ago
Branson's business model is selling the right to use the Virgin
brand to other companies. The article doesn't say he made an
investment. It is rather more likely that they paid him.
puranjay - 4 hours ago
So basically Trump with more class?
neuronexmachina - 4 hours ago
...and fewer bankruptcies.
JumpCrisscross - 6 hours ago
> Why would Branson get involved ?Branson is notorious for
burning other peoples? money. Look at Virgin Galactic: it?s New
Mexicans? [1] and Floridians? [2] tax money plus some duped
Emiratis [3]. (They also pre-sold tickets [4].)[1]
https://www.theguardian.com/us-news/2015/oct/04/space-
travel...[2] http://www.airnewstimes.co.uk/space-florida-
promises-virgin-...[3] https://dealbook.nytimes.com/2009/07/28
/uaes-aabar-takes-sta...[4] https://www.smithsonianmag.com
/smart-news/
spacecity1971 - 8 hours ago
I wonder if the tube could be continuously woven from carbon fiber
and given an aerogel insulating wrap, then the interior coated with
ceramic? This would perhaps mitigate heat expansion issues.
yahna - 4 hours ago
I wonder where this company would be if the original paper was
written by pretty much anyone other than Musk.
lisper - 8 hours ago
All of the Hyperloop development efforts are ignoring the elephant
in the room: thermal expansion. If you do the math, the ends of a
viable hyperloop track will have to move hundreds of meters [1].
No one has yet advanced even a viable idea for how to deal with
that, let alone an actual design. Until that happens, the
Hyperloop is vaporware.[1] It's a trivial calculation. The thermal
expansion coefficient of steel is about 10^-5. A typical run of,
say, SF->LA is 600 km. Temperatures in the central valley range
over about 100 degrees. Multiply everything together and the
result is 600 meters.
iamgopal - 8 hours ago
Expansion joints are available since decades.
lisper - 8 hours ago
Not ones that will hold a vacuum.
madamelic - 8 hours ago
I am not an engineer. Is it impossible to create one? If a
tube is a vacuum, then the tube moves, I don't think that
negates the vacuum or does expansion and contraction make a
vacuum impossible? I wouldn't believe so.
dx034 - 7 hours ago
Impossible not. But expensive. And hyperloop is supposed to
be cheaper than HSR.
LeoPanthera - 8 hours ago
Not with that attitude.
dclowd9901 - 2 hours ago
Your comment may seem flippant, but honestly it seems like
people are more eager to be right than aspirational these
days.
Robotbeat - 8 hours ago
Did you try googling? Here's a whole bunch:
http://www.metraflex.com/metal-expansion-joints/
lisper - 8 hours ago
Let me be more precise: not ones that 1) will hold a vacuum
and 2) are available in the 3+ meter diameter that the
hyperloop requires and 3) provides the smooth inside
surface that the hyperloop requires and 4) are economically
viable.
nkoren - 7 hours ago
This kind of Hyperloop criticism is commonplace, but
strikes me as intellectually lazy. Did you read
Robotbeat's link? Particularly with respect to to the
MNLC Bellows Expansion Joint.> 1) will hold a vacuumPlain
wrong.> 2) are available in the 3+ meter diameter that
the hyperloop requiresThis is a simple manufacturing
problem, although calling a "problem" seems like an
overstatement. Obviously not everything to build a
Hyperloop is wholly off the shelf. If there is some
reason why this can't be built in larger diameters, then
that's certainly not obvious.> 3) provides the smooth
inside surface that the hyperloop requiresThe Hyperloop
runs on an air cushion. It's a hovercraft. Millimeter-
scale bellows ought not to be a problem.> 4) are
economically viableAnd here, you could be entirely
correct, and is why I'm not yet a Hyperloop true
believer. I'm not wholly convinced that this kind of
machinery can be economical over its whole life-cycle in
its intended service environment. But proving that this
is the case requires more than glib, hand-wavy
assumptions. You need to run the numbers. I have yet to
see any Hyperloop critic do that in a remotely convincing
fashion, whereas there are many Hyperloop engineers who
most assuredly are running numbers. Maybe those
calculations are wrong, but the only way to refute them
is with better calculations. Anything else is just dogma.
mrguyorama - 6 hours ago
HyperLoop does NOT run on an air cushion (remember, the
entire tube is supposed to be nearly evacuated!), but
instead floats on a maglev track.He's also missing
another requirement: 5) The entire track, including any
possible expansion components, valves, inspection
hatches, etc etc etc have to be at least mildly tolerant
to intentional or accidental damage. Running into a
sudden wall of air at 700mph is a good way to destroy any
passenger craft in the system.
jccooper - 6 hours ago
That depends on the design. In Elon's original paper
hyperloop the vehicles have an air bearing.
dmoy - 8 hours ago
I am curious, does an expansion joint not help here? Is it
impossible to make an expansion joint that deals with the kinds
of pressure involved?
olegkikin - 6 hours ago
Expansion joint is likely the way to do it, but I'm not aware
of vacuum expansion joints of that size. Even if it's possible,
it sounds very expensive to make and to maintain. Just like
everything in this project.That's the thing about Hyperloop.
It's not technologically impossible. It's just not economically
viable.
frahs - 8 hours ago
This is only if the tube sections all move together. This could
be handled at the joint between each tube section, and then the
joints would only have to move a fraction of that distance.
ErikVandeWater - 8 hours ago
Just to clarify - is the thermal expansion issue both in terms of
the length of the hyperloop and the inside diameter of the tube,
or just the length?Relevant discussion of thermal expansion with
high speed tracks:
http://boards.straightdope.com/sdmb/showthread.php?t=471152
lisper - 8 hours ago
It's a combination of things: the length, the fact that it has
to hold a vacuum, and the fact that it can't make tight curves.
If any one of these things weren't true the problem would be
easy. But they are all true, and that makes it really, really
hard. (Oh, and it has to have a smooth inside surface, and it
has to be manufacturable at a reasonable cost.)
pasta - 8 hours ago
Yeah, Elon Musk never thought about that because he was busy
landing rockets.Come on.. why do you think he did not think about
that?By the way, curves in the track can eliminate this when they
can slide a little. And I can imagine there are more and better
solutions.
lisper - 8 hours ago
> why do you think he did not think about that?Because this
issue has been brought up many, many times since the Hyperloop
paper was first published and no one has yet proposed a viable
solution.> curves in the track can eliminate this when they can
slide a littleBut you can't curve the track. The track has to
be very nearly straight or the G forces become intolerable.This
is the thing: lots of people glibly propose what they think is
a solution, but none of them actually work.
pasta - 8 hours ago
Elon has proposed a solution as others also already
comented.And why would large diameters not work?
lisper - 6 hours ago
> Elon has proposed a solutionReally? What is it?
cma - 7 hours ago
Elon can get things wrong. He already said after he had
announced and hyped hyperloop he had to delay the white paper
because it turned out his initial idea just didn't work and he
had to come up with a new one.In 2016 he said we would have
full level 5 autonomy in self driving cars within two years.
That means in all driving conditions a human could handle.That
seems exceedingly unlikely.https://electrek.co/2017/04/29/elon-
musk-tesla-plan-level-5-...
oconnor663 - 8 hours ago
Relevant: http://www.commitstrip.com/en/2016/06/02/thank-god-
for-comme...
drzaiusapelord - 8 hours ago
Musk has addressed this:Similarly, the proposal briefly discusses
thermal expansion: as the steel of the tubes heats in the hot
California sun, the metal expands. That expansion needs somewhere
to go. In high-speed railways, rails are allowed to overlap at
the ends, but that?s not possible in the Hyperloop, and so Musk
has a different solution:?Specially designed slip joints at
stations will be able to take any tube length variance due to
thermal expansion,? he explained. ?This is an ideal location for
the thermal expansion joints as the speed is much lower nearby
the stations. It thus allows the tube to be smooth and welded
along the high speed gliding middle section.?https://www.theguard
ian.com/technology/2016/may/12/hyperloop...I think the hand-
wringing over expansion is a bit over the top right now. Seems
like its a relatively solved problem and one the Hyperloop team
is taking seriously. I imagine the cost of engineering and
building giant slip joints is just part of the overall cost
package and probably a non-trivial part. I find it hard to
believe someone as relatively trustworthy and technical as Musk
is selling this concept knowing full well its impossible.Most
likely, this is a solvable problem the same way many difficult
problems were solved for cars, planes, and rails during their
inception. I read an analysis somewhere that the Wright brothers
solved 4 or 5 'hard' problems with their first plane. Their
competitors at the time weren't able to solve even one. I'm not
saying Hyperloop is guaranteed to work, but declaring it 100%
impossible seems overly pessimistic.My worry is a bit more
prosaic, if we gain progressive leadership in congress, we may be
looking at Euro-style high speed rail in many US regions, which
would invalidate the hyperloop concept. This seems less likely,
imo, but by far the saner move.
mrguyorama - 6 hours ago
Does he not realize that you can't just take up all the slack
at the ends? That would mean the pylons nearest the station
would be pushed over around 300 feet. How would the hyperloop
stay elevated without pylons?
cjsuk - 8 hours ago
Is there any material available with a negative expansion
coefficient that can be used to offset this?I ask because that?s
how you tend to work around thermal effects in electronics.
lisper - 8 hours ago
An electronic device contains many orders of magnitude less
material than a hyperloop track. There are all kinds of
materials that are economically viable when measured in
micrograms. Hyperloop track material has to be bought by the
kiloton.
clavalle - 8 hours ago
Compressable joints between each section?
indescions_2017 - 8 hours ago
We could replace steel with a low coefficient metal matrix
composite without sacrificing stiffness or long range strength.
It would blow out the cost structure however ;)Have also heard
anecdotally that condensation in the tube could be a real
problem. Even at near vacuum, the rapid pressure differentials
can cause buildups in front of and behind the speeding vessel.
lisper - 8 hours ago
> It would blow out the cost structure howeverSure, all of
these problems are solvable if you are willing to expend
arbitrary resources. But the whole point of this exercise is
to provide an economically viable mode of transportation.
(Isn't it?)
goodcanadian - 1 hours ago
Many replies mention expansion joints. There are also other
techniques that can be used: for example pre-stressing as is done
with continuous weld
rails:https://en.wikipedia.org/wiki/Rail_stressingOverall, it is
not a particularly difficult engineering problem.
DiThi - 8 hours ago
This point is clearly addressed in the paper: The ends of the
tube can slide 300 meters next to the station, and the tube is
not firmly attached to the pylons but can move to accommodate the
expansion.
lisper - 8 hours ago
No. The paper gets this badly wrong. It looks only at the
incremental thermal expansion between pylons, and neglects the
fact that in a sealed tube the thermal expansion will be
cumulative."These would absorb the small length changes between
pylons due to thermal changes, as well as long form subtle
height changes." [emphasis added]The cumulative expansion is
dealt with in a single sentence:"A telescoping tube, similar to
the boxy ones used to access airplanes at airports would be
needed at the end stations to address the cumulative length
change of the tube."But that's not enough. The entire track
near the ends is moving by this amount. That means that the
ends of the track are advancing and retreating over multiple
pylons (unless you can figure out a way to cantilever the track
over 300 meters). This is a completely unsolved problem.
losteric - 7 hours ago
I'm not this kind of engineer, but couldn't the pylon problem
be addressed by a sliding rail mechanism between the pylon
and the sealed tube? Or replicating the station mechanism at
each pylon? Maybe I just don't see the problem you're
pointing out.edit: in retrospect, I can clearly see the
problem with expanding shaped tracks.What happens to a long
S-shaped track? Think about expanding each segment of the top
curve... the turn radius increases and as does the length of
the turn. How do you support a tube that can get longer, move
outwards along the curve, and change angles at various
points? S is just an example, it seems to be a problem with
any number of turns (including 1)...I suppose one option is
to simply put it underground to stabilize ambient heat input,
and use heat extractors to manage heat generated by the
train. If the system shuts down, there might be some thermal
contraction but that's easier to manage (it's OK for track
segments to separate when trains aren't running - just warm
them up before operation)
inetknght - 7 hours ago
sealed telescoping tube between pylons then?
KekDemaga - 7 hours ago
That sounds really expensive.
hwillis - 3 hours ago
At this pressure you can use regular o-rings, which
already come in standard sizes up to a dozen meters
across. They're very affordable. I still doubt they'll
be necessary.
DiThi - 7 hours ago
How about you also copy the sentence that lies just between
those two?"As land slowly settles to a new position over
time, the damper neutral position can be adjusted
accordingly."And if that doesn't work, the tube can have some
kind of rails or just to roll over wheels on top of the
pylons. (my own thoughts as non expert)Rocket engineers with
advanced simulation tools[0] have been working on this for 5
months before releasing the paper. Do you really think they
somehow missed this obvious issue?[0]
https://www.youtube.com/watch?v=vYA0f6R5KAIEdit: Further in
the paper it says: "The tube will be supported by pillars
which constrain the tube in the vertical direction but allow
longitudinal slip for thermal expansion as well as dampened
lateral slip to reduce the risk posed by earthquakes."So
pretty much what I've said. The other quoted sentence refers
to placement of pylons themselves.
Gustomaximus - 8 hours ago
I dont know if this an elephant in the room. I'm guessing
engineers have thought about this and just not discussed it
publicly. They have some pretty smart guys.Also to nitpick, from
"the ends of a viable hyperloop track will have to move hundreds
of meters" - this doesn't have to be true. There can be
absorption points along the track. Overlaps. Or maybe they tunnel
the entire way where its cooler. Or wrap the tunnel in something
cooling and reflective. We dont have train tracks moving hundreds
of meters do we? I dont profess to know the solution, but do know
there are solutions somewhere.
lisper - 8 hours ago
> There can be absorption points along the trackSure, but these
have to hold a vacuum. No one has figured out a way to do
that.
supermatt - 7 hours ago
Isn't this what a syringe does?
alexanderstears - 7 hours ago
Except for the people who invented the accordion and bellows.
nkoren - 8 hours ago
I am assured by those in a position to know that thermal
expansion joints which hold a near-vacuum are an entirely
solved and essentially trivial problem.I do have some
concerns about whether they're a trivial problem within this
context. An engineering solution which works in small numbers
for PhDs in a lab isn't necessarily scalable to mass low-cost
manufacturing, deployed in the field and irregularly serviced
by workers of uncertain provenance. But evidently there is a
way to do this, at least.
dx034 - 7 hours ago
And, more importantly, can be certified for real world use.
Considering the speeds used, scrutiny will be extremely
high. Even if you use it for freight at first, the track
will be close to settlements and any accident could end up
in a disaster. The behaviour of trains on tracks is very
well understood (learning from accidents), the behaviour of
a vacuum train tube is not.
nkoren - 49 minutes ago
This is a very fair point. There might be components that
are routinely used in non-life-safety-critical
applications, but this is no guarantee that they will
pass certification scrutiny when they are in the critical
path for thousands of lives every day.I worked on an
autonomous vehicle project here in the UK about 10 years
ago (the Heathrow Pod). The certification process was
absolutely intense. And this was for a system that was
capped at 25mph; had we gone any faster than the
regulatory burden would have become very significantly
more onerous (below 25mph it wasn't necessary to test
vehicles and infrastructure to destruction; above 25mph,
it is).In this domain, there's a huge difference between
a cool engineering testbed, a private pilot project, and
running actual service for the public. If Hyperloop is
going to be doomed by anything, failure to appreciate
this fact is probably at the top of the list.
cjbillington - 7 hours ago
I work in a lab with vacuum systems that get heated and
cooled and we just have segments of flexible bellows like
this:http://www.pchemlabs.com/subcatagoryb.asp?pid=flexible-
bello...Not sure if the same thing will work at larger
scales, but I'm not sure its a fundamental problem.
ep103 - 5 hours ago
Not exactly like that, but yeah, the same sort of idea I'm
sure would work.
slobotron - 6 hours ago
Wowza, 5" bellow is $450, how cheap could they make 6' one,
even in bulk?
nbanks - 7 hours ago
Gas pipelines hold hundreds of bar of pressure; I don't see
how one atmosphere is a problem.
dx034 - 7 hours ago
Gas has no problem flowing around corners. Gas pipelines
are usually not straight lines. Hyperloop will have to be a
straight line, unless you want to kill passengers.
mrguyorama - 6 hours ago
Gas pipelines use Expansion Loops [1] to pick up expansion
slack. The problem is that, in order to push people through
the tube at 700mph at acceptable G's, you can't put bends
like that in the HyperLoop. If you try to send people down
a pipeline at 700mph, you would end up with paste at the
other side. Gas pipelines are surprisingly un-straight,
bendy, and bumpy[1] https://static.interestingengineering.c
om/images/import/2017...
jandrese - 7 hours ago
Wouldn't they just put accordion joints on the junction at
every pylon? It's not like the tube is going to be built as
one gigantic piece. It has to be assembled from parts.
dx034 - 7 hours ago
The vacuum is the problem. With HSR you also have small gaps
in the system to allow for expansion but nothing there
requires a perfect surface.
GuB-42 - 5 hours ago
AFAIK, high speed rails do not have gaps. Expansion is
controlled by brute force : lots of clamping and massive
supports.
SubiculumCode - 5 hours ago
I know there are feasibility questions, but have you thought about
how such travel could affect the course of U.S. politics?One could
feasibly live in Utah where land is cheaper, but still commute to
California for work. This would both lead to a purpling of many red
states, as well a providing a path for interior state natives to
find good jobs in coastal city centers.Knowing the status of
American politics where highly populated coastal states are
overpowered in the Senate by the seats of the near empty states in
the interior, one can see that if the potential for hyperloops is
realized, there will could very well be a massive shift of power
back to the populace with more equally distributed representation.
batrat - 8 hours ago
I see so many negative comments about this, but in my opinion
everything has to start somewhere. It doesn't matter how crazy and
impossible it looks, it will be done eventually (and we have plenty
of examples).Maybe we will not teleport in 2 seconds across the
globe or this project will die, who knows if we don't try.A little
bit of optimism doesn't hurt. Just saying.And for Virgin, it's not
my money, if they want to invest in a black hole sure they can.
simias - 7 hours ago
Your types of comment annoy me more than harsh criticism frankly,
at least criticism can be constructive, your comment is just
fluff.I mean, let's apply your logic to its logical conclusion:
we should never criticize anything, ever, on the off chance it
could end up working and then people would look back on our
comments and call us silly. On that note I'm just starting a
gofundme to create my own interplanetary travel agency, don't
forget to donate.Yeah, HN was wrong about dropbox (although some
of the criticism was a lot more specific and arguably accurate
than some make it up to be). Now let's fetch the comment threads
about color.com, about google plus, about the ubuntu phone, about
whatever other failed product we've already long forgotten
about.If HN is wrong about hyperloop, so what? You'll be able to
gloat about it in a few decades from your supersonic train seat.
In the meantime there are real, practical questions that need
answering and that's a much more interesting discussion than "wow
this is so coool" or "I wonder what Elon Musk's armpits taste
like".Do you think that the Hyperloop One folks are going to read
this thread and give up on the project? "Well, looks like we were
wrong, shut down everything folks". I can get this argument for a
small startup of one or two young entrepreneurs but for some
reason I don't expect Virgin Group to be that insecure.
QAPereo - 7 hours ago
I only wish that HN was similarly skeptical about near-term
Mars colonization. For a group of largely smart, educated
people, too many are willing to suspend disbelief for a
sufficiently charismatic person, or out of desperation.
christophilus - 8 hours ago
It's been said before elsewhere, but HN is the place to go to
find out why your project will never succeed. I've seen many
successful projects crapped all over here when they were in their
infancy / pre-success days. "Stripe?! 3% fees! So dumb. We
already have lots of payment gateways. It's not hard. You just
have to {list of many tedious manual steps}..."
jgalt212 - 7 hours ago
Stripe is an amazing enterprise, but we've yet to see whether
or not it will delivery steady profits, and profits anywhere
close to the 20 PE that stocks trade at.
ferdbold - 8 hours ago
My favorite is Dropbox. "Store all my personal and/or corporate
files on some third-party server?! DOA."
aswanson - 7 hours ago
I remember that thread. Hilarious.
KGIII - 6 hours ago
One of my favorites is on Slashdot. If you go there and
search for 'VMware' then you can find it.When VMware was
first announced and demoed, the commenters at Slashdot
declared things like it was fake, it was stupid, it was a
waste, it would never work, or that dual booting was a
better solution. They largely concluded that virtual
machines weren't a thing and happily congratulated
themselves for their brilliant insights.I'm on a tablet or
I'd dig the link out for you. It's one of my favorite
discussion threads on the Internet.
aswanson - 3 hours ago
Thanks, I really need to check that one out.
KGIII - 3 hours ago
I never tell people that they 'need' to do something, so
I'll say I highly suggest you do.So, to make it easier
for you - I've grabbed a laptop and dug out the
link:https://tech.slashdot.org/story/99/02/11/0939233
/multiple-os...I absolutely encourage anyone/everyone to
read the linked comments. It's one of my favorite
examples when a number of discussions come up.My
preferred time to reference it is when people say things
like, "Slashdot used to be so much better!" Or when they
say things like, "We had much better commentary back in
the day!"No, no they did not. In fact, it was never as
good as people recall it being. That is kind of what
makes it so wonderful and why I love discussion sites.I
am, by no means, innocent or superior. ;-)
aswanson - 3 hours ago
Reminds me, Im just as guilty. Check out my insights on
Amazon introducing the Kindle:
https://news.ycombinator.com/item?id=81804
KGIII - 3 hours ago
Yeah, we've all got comments from our past that we wish
we'd not made. Our seemingly brilliant insights aren't so
brilliant after all.Today's thread about Musk's
"Hyperloop" is good fodder to bookmark and look back at
in a decade. I have to wonder how many of the posters
will admit they were wrong, should this reach fruition?I
dug the link out for another person who replied. You may
want to take a
look?https://tech.slashdot.org/story/99/02/11/0939233
/multiple-os...There was a database glitch that messed up
usernames (I think that was after they'd added accounts,
my memory isn't that good so I'm not certain) but it's
still an amusing read. It really is a good example for a
variety of discussions. It's my favorite example,
actually.
aswanson - 1 hours ago
Thanks for that, belly laughing. One common thread of
these "brilliant" dismissals, mine included, is that they
undervalue how much people don't like going through
technical hurdles with products and how much they will
pay to avoid them and get on with what they want to do.
Also, for ambitious goals like hyperloop, many assume
technical challenges are insurmountable.
always_good - 7 hours ago
More like "uh, how is this different from rsync?"
rakoo - 7 hours ago
"Pfff I could just set up my own FTP server and mount it
with curlftpfs on my machine. I don't see what's new"
whipoodle - 7 hours ago
No, now it?s ?why do they need 1500 employees for file
syncing?!?
austenallred - 7 hours ago
https://news.ycombinator.com/item?id=8863> For a Linux user,
you can already build such a system yourself quite trivially
by getting an FTP account, mounting it locally with
curlftpfs, and then using SVN or CVS on the mounted
filesystem. From Windows or Mac, this FTP account could be
accessed through built-in software.This sounds like such an
insane proposition relative to the Dropbox we know today.The
top comment is being pedantic that it doesn?t technically
replace a USB drive because you have to install software and
have access to the Internet. Hilarious in retrospect.If the
biggest complaint someone can have is ?you have to have
Internet? you?re doing OK.
lmm - 7 hours ago
> This sounds like such an insane proposition relative to
the Dropbox we know today.Does it? If you used WebDAV then
you can mount a share in Windows or Linux even over the
Internet, and windows at least is good at caching it while
you're offline for short periods. For someone who has their
own always-on Apache it seems like this would replicate
most of the use cases for Dropbox. I think the point that's
being missed is simply that most people would rather see a
few ads or pay a small fee than administer their own
Apache, not that what Dropbox offers is technically so far
ahead.
austenallred - 7 hours ago
> For someone who has their own always-on ApacheI?m just
guessing on numbers, but that probably describes <1% of
the population. Most people think Apache is a word used
only to describe helicopters.
lmm - 7 hours ago
Absolutely, and that's why Dropbox is successful. But I
don't think the part you quoted is wrong as such; the
typical HN user really could put together a few
components and get something that does most of what
Dropbox does.
KGIII - 6 hours ago
A small point really, but I'm not sure most people would
only think it describes helicopters. I am guessing most
people would think it is a tribe of Native Americans.I
admit that it's just a guess, but it does seem
likely.Again, not a major point.
[deleted]
rtpg - 7 hours ago
There's also been plenty of valid criticism here as
well..."Hacker News hated Dropbox so..." Is a fun trope, but
Dropbox still isn't profitable ;)In seriousness I bet a lot of
us go though the thought process that we want to give
constructive criticism, since positive feedback isn't super
actionable.Feeling smarter than the rich people is always a
good feeling too (and cheap, since we aren't even betting our
own money )
ravenstine - 7 hours ago
My instinct tells me negative comments aren't actually coming
from the direction of "stupid idea! can't be done!". This isn't
to say there aren't significant engineering roadblocks to the
Hyperloop, but I don't think that's the root of the
negativity.People are pointing out the glaring flaws in the
Hyperloop idea, not because they can't or won't believe that
crazy ideas are possible, but in reaction to the media's reaction
to Elon Musk's PR. Surely I'm not the only one who wants to
upchuck every time that Musk makes a claim and the media drools
all over whatever he says. It even goes beyond the media itself
but how the public reacts to how the media reports Musk.
Otherwise smart people I've met have likened Musk to a modern day
Edison, or even Tesla. Musk's companies have achieved great
things, but he has more in common with Barnum than famous
inventors.Testing impossible ideas is wonderful. Musk's PR being
inflated by the media, creating an audience of believer
sycophants, is a different story and I really don't mind people
blowing holes in the Hyperloop theory if the newsprint-spewing
public isn't going to get that from technology reporters. I'd
bet Hyperloop critics actually like the idea at one level or
another, and hate to see such ideas looked at with pollyanna
eyes.
ghostly_s - 7 hours ago
He operates the first-ever successful private spaceflight
company. (You can quibble with this but it's something close to
the truth). Likening him to Barnum is a little insulting.
ravenstine - 7 hours ago
That's not something I would contest, and I don't think I
implied such a position. I(and presumably others) actually
like impossible ideas but dislike the rampant lack of
skepticism in the direction of Musk, therefore criticism of
his company's proposals is justified and not necessarily
coming from the direction of "it can never work".Likening him
to Barnum would perhaps paint him as a little more nefarious
than Musk actually is, but I wouldn't consider that
insulting. The man was a master promoter. But perhaps he's
not a good analogue because their "products" are very
different. People liken Musk to Edison, and they did both
own technology companies that produced innovations, but
that's where the similarity ends.
always_good - 4 hours ago
Let's be honest. People criticize because it's easy, makes them
feel good, and because they have no skin in the game.You might
like the idea that it's some sort of reasoned rejection of Elon
PR, but it's not. Just make a Show HN sometime.
rco8786 - 8 hours ago
Right. Could you imagine what people thought/said around the
advent of commercial airliners or heck, even automobiles?
wallace_f - 7 hours ago
My favorite historical example of this is that of the nautical
screw.Orwell mentions it in one of his lesser-known essays when
discussing the problems with arguing about economics(1).>"When
the nautical screw was first invented, there was a controversy
that lasted for years as to whether screw-steamers or paddle-
steamers were better. The paddle-steamers, like all obsolete
things, had their champions. Finally, however, a distinguished
admiral tied a screw-steamer and a paddle-steamer of equal
horsepower stern to stern and set their engines running. That
settled the question once and for all. And it was something
similar that happened on the fields of Norway and of Flanders
[referencing economic questions]."1 -
www.orwell.ru/library/essays/lion/english/e_saw
TremendousJudge - 8 hours ago
Or turbojet trains[1][1]
https://en.wikipedia.org/wiki/Turbojet_train
pavel_lishin - 8 hours ago
Or Ekranoplans[2][2] https://en.wikipedia.org/wiki/Ekranoplan
mrguyorama - 6 hours ago
or flying cars, or jetpacks, or a million other ideas that
just had "engineering problems" that were supposed to
revolutionize transportation.
kaolti - 8 hours ago
Totally with you.
sschueller - 8 hours ago
I'm not saying it can't work and we shouldn't try our
best.However from what I have seen so far I am quite disappointed
as even known issues aren't addressed at all. As if the people
involved are blindly going at it instead of working with people
who know something about pressure vessels etc.Sure sometimes you
need an outside perspective but not like this.
felipelemos - 8 hours ago
Care to elaborate?
LaikaF - 8 hours ago
Thunderf00t has a good video on the problems with
it.https://www.youtube.com/watch?v=RNFesa01llkHe has some
other good videos (solar roadways) but tends to spend to much
time bashing creationists.
johnking - 7 hours ago
Thanks for the video reccomendation, super interesting.
lmm - 7 hours ago
> It doesn't matter how crazy and impossible it looks, it will be
done eventually (and we have plenty of examples).Or it won't.
Most companies fail, I expect most ideas do too.> A little bit of
optimism doesn't hurt. Just saying.Yes and no. Optimism is
worthwhile but realism is important too. It's cool that private
companies are pursuing these ideas and I wish them all the best,
but when I see people claiming that e.g. California's high speed
rail is overpriced/pointless because of hyperloop then I want to
scream. We shouldn't let our enthusiasm over these hyped ideas
detract from implementing the more pedestrian approaches that are
proven to work and address our very immediate needs.
Gustomaximus - 8 hours ago
So much this. Especially when people chime in with some minor
detail means it will fail because clearly 'must not have thought
of it' if they didnt mention in some 400 word press release.Its
like Elon going into trucking and people saying the range isn't
sufficient. The guy is pretty darn smart. I'm confident he
understands trucking range and has some solutions, and simply
isn't discussing it for secrecy and/or succinctness.
cowsandmilk - 7 hours ago
> if they didnt mention in some 400 word press release.There's
a lot of in depth criticism of hyperloop based on Elon's 57
page paper. It is hardly a case of gut reactions to 400 word
press releases.
Avshalom - 8 hours ago
Yeah but in this case every solution appears to be turning it
into a normal train so we aren't even getting anything novel
out of it anymore.
ada1981 - 5 hours ago
Didn't expect to see Dick putting his name on this one...
uptownfunk - 8 hours ago
Lots of comments about how this is not feasible, but wasn't
spaceX's vision of a reusable rockets similarly not feasible at the
outset and they've since been making some quite considerable
progress towards this.
lmm - 7 hours ago
A reusable rocket was not just feasible, it had already been done
with the Space Shuttle. "We'll do what the Space Shuttle did but
50x cheaper" is ambitious to be sure, but it's not at the same
level as "we'll do this completely new thing that has never been
done before".
platz - 8 hours ago
HN certainly did _not_ take a "not feasable" stance on spaceX's
vision of a reusable rockets.
Animats - 3 hours ago
Maglev in a tube is a proven technology at full train scale. Here's
the Chuo Maglev from the inside.[1] 500KPH in tunnels. They're not
pumping down the tunnels, just plowing through on sheer power and
money.The Chuo Maglev makes the Hyperloop One look like a toy
project. Watch the video. They have a production-quality train,
with tourists and whiny kids riding it, going 500km/h. They've hit
603km/h in tests, but don't run it that hard normally. This is the
first section of track between Tokyo and Osaka via Nagoya. Planned
opening to Nagoya is 2027. Japan's Alps are in the way. They're
tunneling straight through. Longest tunnel segment is 25km and it's
being drilled now. 90% of the Tokyo-Nagoya segment will be in
tunnel. Stations in Tokyo and Nagoya are under construction. The
line will probably run 3-4 trains an hour each way, like the
existing Shinkansen.Hyperloop potentially has a higher speed to
900-1200km/h, but that may not be achieved in practice. The Chuo
Shinkansen has a turn radius of 8km, and passengers don't have to
be strapped in. Hyperloop would need 4x the radius to go twice as
fast with the same ride quality. Laying out a route with a 24km
turn radius severely limits where track can go.Strapping everybody
in and pulling 0.5G sustained is not going to go over with
customers. Commercial aircraft usually stay within +-0.25G. Maybe
0.5G in mild turbulence, and customers don't like it.[1]
https://www.youtube.com/watch?v=HZ6dYhHIol8
nihonde - 2 hours ago
Amen. If you want a fast train in 2017, hire the people who have
been winning in that department since 1964.
Robotbeat - 3 hours ago
The biggest problem people have with Hyperloop is because it
certainly seems like Elon Musk just waltzed into the high speed
rail debate and Dunning-Krugered some crazy scheme that doesn't
look anything at all like conventional approaches to the problem
and thus doesn't jive with any common sense we might have built up
around different transport methods.But that's kind of what Elon
Musk does: he Dunning-Krugers himself into a new industry every
couple of years, using a simplified, undergraduate physics level of
analysis to find something that (to an optimistic non-field-expert)
looks like a better solution to the problem.And the most annoying
thing of all is that he usually succeeds. Often in spite of his
original idea being technically wrong. For instance, Falcon 9 was
supposed to be recovered with parachutes... that didn't work, and
people who were working on vertical landing rockets told them that,
but at the time Elon just rolled his eyes and said "just use
parachutes." But SpaceX/Elon found out the idea didn't work and
switched to the "correct" solution and got it to work operationally
(and with paying customers) much faster than people who had been
working on the problem for years before.The moral of the story is
that it's often better to be able to execute fast even if you start
out wrong than to take your time with the right answer.
evanlivingston - 3 hours ago
The moral might be that hubris along with billions in cash can
accomplish the things the person with hubris set out to do.
Robotbeat - 3 hours ago
Elon Musk didn't start out with billions of dollars, and he has
almost no liquid assets (he borrows against his stock when he
needs cash).But this is a good point. Lots of talented people
have good ideas that end up going nowhere because of lack of
capital for implementation.
JumpCrisscross - 3 hours ago
> Elon Musk just waltzed into the high speed rail debate and
Dunning-Krugered some crazy schemeI think it's incredibly
important to segregate Musk's work, i.e. SpaceX and Tesla, from
his proposals, e.g. the Hyperloop, modular infrastructure and
other things.
Robotbeat - 3 hours ago
Nah, the Dunning-Kruger thing applies equally well to Tesla and
SpaceX. He had no experience in either field before starting
those companies. It's just that he has, in spite of all
probability, succeeded and so you see them in a different
light.
c22 - 1 hours ago
Maybe his experience is in building successful companies.
[deleted]
biznickman - 7 hours ago
The viability of Hyperloop One should not be the focus in the
context of this article. That's not what this is about at all.It's
that Hyperloop One needed Richard Branson on board because Elon
Musk is creating his own competitor now. This is an incredibly
smart move to ensure the survivability of the business from a
publicity perspective.Branson has a history of doing things that
people thought impossible or just a bad decision (like creating an
airline company). Public perception is the name of the game at this
stage, not just feasibility. From that perspective, Hyperloop One
has effectively done one of the only strategic moves remaining at
this point that ensures it has any chance of persuading a
government to select them as a preferred vendor (or continue doing
so).
detritus - 7 hours ago
Branson's missing a d from his almost nominatively-determining
name ? the guy's got a talent for self publicity over challenging
the incumbency, which for the most part he hasn't since launching
Virgin Airlines and Megastores, which were both back in the 80s.
detritus - 7 hours ago
Downvotes? Presumably not from Britons or anyone who knows
anything about the guys history?So what HAS he done then, other
than brand anything he can then offload to third and fourth
parties to run the businesses for him?And don't say Virgin
Galactic - that's just some clever peripheral branding to
encourage the likes of the downvoters here that he is in any
way novel or dynamic.He's marketing clever, not strategically
or developmentally-so.
waegawegawe - 6 hours ago
Well, you're criticizing him for only acquiring things and
slapping his brand on them. But the criticism is leveled in
the context of him investing in an unproven technology. It
seems like your comment would be more apt if he were taking
an action that follows the pattern you are criticizing. For
example, if he were acquiring a computer company and calling
it Virgin Computing or something.
detritus - 6 hours ago
That's fair enough, I suppose. I guess I simply distrust
his motivations beyond self-aggrandizement and inflating
the idea that he's somehow an ideas man, when I can't for
the life of me think of anything novel he's done for
literally decades.I'm coming across like a 'crab in a
bucket' here - I've nothing against the guy or his success,
but I'm not for one second convinced he's 'challenging the
impossible'.
adventured - 6 hours ago
He's worth $5 billion. He's a high-school drop-out dyslexic
that started from nothing. He built a successful airline and
record label, along with countless successful branded
companies whose success partially rides on the vast effort he
has put into building his own well-known brand - a
substantial feat unto itself.Yes, golly gee, what HAS he
done.
detritus - 6 hours ago
I trust my respone to 'waegawegawe' pads out where I'm
coming from.He has a certain reputation here in Britain,
however we here in Britain also have a certain reputation
of shitting on people's success - I sincerely hope that's
not how I'm coming across here.Anyway, this is tangential
nonsense, I'm sorry for diluting discourse!
kbenson - 4 hours ago
> however we here in Britain also have a certain
reputation of shitting on people's successThat's okay, I
appreciate you loaning us John Oliver. ;)
detritus - 2 hours ago
In a sense, I think you gave him to us. You often do :)
dom96 - 6 hours ago
While what he has done should be commended, I don't think
it's fair to say that he "started from nothing". His own
mother was an entrepreneur, obviously not as successful as
him but come on, he went to a "prep school" for goodness
sake[1].1 -
https://en.wikipedia.org/wiki/Richard_Branson#Early_life
adventured - 6 hours ago
The point is that he built his businesses from scratch,
and did so with a significant learning disability that
meant he struggled to understand even basic P&L
statements and balance sheets. His mother didn't build
his record store or record label. His mother didn't build
his airline. His mother didn't build his brand.His early
business successes were built from nothing. They weren't
seeded with millions of dollars. They weren't inherited.
He rolled one success into another.This obnoxious notion,
so common on HN, that someone has to crawl out of a ditch
with not a penny to their name, or they're not self-made
or deserving of any credit for their own success, needs
to stop. It eliminates nearly every possible success
story that could exist (which is of course the whole
point). It's nothing more than a base envious desire to
drag someone down because they've been successful.
gaius - 3 hours ago
he hasn't since launching Virgin Airlines and Megastores, which
were both back in the 80s.There's a jar of Branson Pickle in
every home in England!But his moves into healthcare are looking
extremely dodgy and of course he lives offshore in a tax haven.
DanBC - 3 hours ago
> There's a jar of Branson Pickle in every home in England!Is
this humour? The pickle, and beans, are
Branston.https://en.wikipedia.org/wiki/Branston_(brand)> But
his moves into healthcare are looking extremely dodgyHis
healthcare stuff is really dodgy. There are already serious
concerns about care and treatment at his places.
dom96 - 6 hours ago
I don't know much about that, but ever since the 'Traingate'[1]
spectacle I've lost all respect for Branson.1 -
https://www.youtube.com/watch?v=47fqjA8CwGE
detritus - 6 hours ago
For me the sheen came off his lustre a bit back when I was
trading at festivals, and at his 'V' festival the only cola
drink that was allowed to be sold on-site was the God-awful
'Virgin Cola'.Minded me of the sort of criticisms he'd level
at the likes of BA back in days of yore...
nsxwolf - 7 hours ago
"Branson's missing a d from his almost nominatively-determining
name"Wat?Edit: This has been a fun puzzle. I read the Wikipedia
article for "Nominative determinism" and I've been swapping the
letter "d" into various positions of his first and last name
trying to figure it out. No luck yet!
eradicatethots - 7 hours ago
I also was confused, but they probably mean ?Brandson?
detritus - 7 hours ago
Yes, there we go. I'm genuinely surprised it was anything
other than fairly obvious. Perhaps his reputation's
different away from the UK?
[deleted]
[deleted]
detritus - 2 hours ago
I'm massively wary about posting chat here (with fairly
good reason) but thanks.There should be an allowance for
balance and humanity in HN comments. Not everything need
be ultra-violet literal on the spectrum!x
JohnDotAwesome - 7 hours ago
I was thinking "Richard" - "d" = "Richar" or "richer"
excalibur - 8 hours ago
....Are they going to rename it in the future based on the number
of pods that have gone through its tubes?
leke - 8 hours ago
I see they are using the term "extremely low pressure tubes"
instead of vacuum tubes.
a-b - 5 hours ago
I?ve been curious for a while if hyperloop and boring company are
complimenting each other.
arketyp - 8 hours ago
I feel that name has got to be a double entendre.
sova - 7 hours ago
Seeing as it'll be the first hyperloop? Or are you talking about
the maiden voyage?
alexozer - 8 hours ago
Keeping a plain miles-long tube at at least 90% vacuum seems pretty
hard to me, especially when needing to deal with evacuations and
possible breakages. Why not divide the tubes into discrete sections
gated by movable airtight caps that side away while passing
through? If one section repressurizes due to evacuation or some
other fault, so be it.
maxerickson - 7 hours ago
If you have a breakage or stopped capsule you anyway have to shut
the whole thing down.
[deleted]
Animats - 5 hours ago
When does Hyperloop One get a go on the Dubai - Abu Dhabi line?[1]
That's quite feasible. Straight route across flat, open
desert.Hyperloop One is a maglev vactrain. It doesn't "fly"
aerodynamically, like Musk's original plan. This means a more
expensive track in the tube, but higher riding height. Musk's
original plan required a ride height of 0.3mm to 1.3mm, which means
a really smooth tube. Maglev clearances are typically 1-2 cm, which
is much easier to maintain over many kilometers of tube. Also, only
the track has to be flat; the tube can have seams and expansion
joints, so it can be fabricated by standard piping techniques.
Vehicles can draw power from the track; Musk's original design was
battery powered. Maglev track is expensive, though. That's why
maglevs are rare.If somebody in Dubai has the money, there's no
reason it shouldn't work. Japan already has 42km of maglev running,
part of the Tokyo-Osaka maglev route under construction, with full-
sized trains. That's mostly in tubular tunnels. Hyperloop One is
easier than that.Hyperloop One's test track uses a 3.4 meter tube,
instead of Musk's original 2.4m tube. Maybe larger in the
production version. Musk's very optimistic cost proposals are
based on his undersized tube. Hyperloop One will work, but it may
not be all that cheap.[1] https://www.youtube.com/watch?v=3fu-
6IDp3Fo
manigandham - 8 hours ago
The engineering has never been a problem, vacuum-tube trains are an
idea that's been around for centuries. [1] Removing friction and
air resistance is a simple physics problem, and there are already
operational maglev [2] trains so putting them in a low-pressure
tunnel is not a major revolution.The real issue is the viability of
such a transport because of the cost, complexity, and construction
effort involved. We (in the USA) can barely build a high-speed rail
line effectively so a Hyperloop competing with existing
transportation options doesn't make economic sense currently. Take
a look at what happened to the Concorde program for a similar
example of great technology that just couldn't survive as a
commercial service.1. https://en.wikipedia.org/wiki/Vactrain2.
https://en.wikipedia.org/wiki/MaglevEDIT: Yes, the engineering
effort is not easy, but the science is pretty straightforward.
We're not discovering new physics here...
reacweb - 6 hours ago
Boeing has failed to build an hypersonic aircraft and as a result
has done a lot of legislative lobbying to ban Concorde. Despite
the petrol crisis and these annoyances, Concorde was still
slightly profitable until the end of its life:
https://www.quora.com/Why-was-the-Concorde-retired-in-2003-d...
noonespecial - 6 hours ago
>We (in the USA) can barely build a high-speed rail line
effectivelyWe went to the moon. We send car sized rovers to Mars.
We certainly can (in the technical sense) build a friggin' train.
Its a political problem that keeps us from doing it. So its more
like "we won't build high speed rail", and there are plenty of
interesting reasons why this is so.The point is that the mystical
sounding Hyperloop might be just what the doctor ordered to shake
up the political landscape and get something to budge because
ooohh... futuristic! It might just be a brilliant end-run around
the current political stalemate. At the most local level it has
the potential to turn "nah, I don't want a train running through
my back yard" to "oh wow, my community is part of the enlightened
future of humanity!"
manigandham - 6 hours ago
Sure, it's a combination of political/social/economic factors
but "futuristic" doesn't seem to have much impact right now (if
it ever really did). NASA's trip to the moon was funded by war
motives and we've since had the decline of both the space
station and the shuttle programs. It's great to see SpaceX
doing new things but there's definitely profits in reducing
launch costs (again driven by war and business motives).What
exactly is the Hyperloop going for? Short trips are already
served by buses, subways and light-rail. World-wide trips won't
be feasible against air travel anytime soon, and will probably
require the same security procedures as flying because of the
speeds and risks involved, especially if crossing national
borders.So connecting major metros is the potential scenario
but airlines have already proven that the vast majority want
wifi and food so we can be productive and entertained in
transit rather than paying a big premium to save a few hours.
noonespecial - 5 hours ago
Yes airlines are the first thing that spring to mind when I
think of wifi, food, and convenience during travel.Call me an
optimist but it's high time for something new to shake things
up. I don't care if it's a magic tube train or just some
really nice selfdriving busses.
manigandham - 4 hours ago
You're obviously talking about transit for the mainstream
in which case it's not perfect but airlines provide the
best combination of speed, comfort, and service today.
Let's not forget that you're actually flying in the air in
an incredible machine.We already have plenty of cheap bus
drivers though so I don't see what self-driving buses will
do...
jahnu - 7 hours ago
"The engineering has never been a problem, vacuum-tube trains are
an idea that's been around for centuries. [1] Removing friction
and air resistance is a simple physics problem""simple"Getting to
Mars is a simple delta-v engineering problem. Nuclear fusion is a
simple magnetic field engineering problem. Self driving cars are
a simple programming problem.Don't ever change, Hacker News.
throwaway231231 - 6 hours ago
Thank you. It's always easy till you start doing it.
manigandham - 7 hours ago
Ok, we did get rovers to Mars decades ago so I'm sure you know
what I mean here, but you seem to be making my point that it's
not worth it.Simple isn't the same as easy, but an evacuated
train tunnel with air or magnetic tracks does not require new
science. The physics are well understood and simple. The hard
part is evolving the tech to be reliable and cheap so that
people will use it and pay for it - but that doesn't seem to be
within economic reach, and that's before factoring in
construction and upkeep.
rz2k - 6 hours ago
I had the same reaction to the comment though I don't think I
disagree with you. I think it was referring to engineering as
simple rather than just calling the science and even a proof
of concept as being relatively simple.Reducing the amount of
steel used in a bridge or a building is part of engineering.
The Concorde wasn?t just a failure to understand what level
of demand the world economy could support, it was that they
didn?t solve the problems necessary to make it viable at
scale. In that way it was not a complete product, it was a
proof of concept.Or, another example, it is not market
dynamics alone that have changed the economics of what?s
feasible with transistors. It is engineering that has made
them viable at a massive scale.
manigandham - 6 hours ago
In the end it's all the same. New science, tech, or
strategies, it all takes investment which requires a return
of some sort so it's hard to imagine any business take this
on considering the alternatives that already exist (and are
continuing to get better). Maybe governments can invest in
this for public good but that seems unlikely
politically.For example, nuclear is a great power source
and we can definitely invest much more but suddenly solar
and wind have beaten the economic curve through constant
evolution and are better candidates to explore today.
sigmar - 6 hours ago
>so putting them in a low-pressure tunnel is not a major
revolution.>evacuated train tunnel with air or magnetic
tracks does not require new science. The hard part is
evolving the tech to be reliable and cheap so that people
will use it and pay for it - but that doesn't seem to be
within economic reach, and that's before factoring in
construction and upkeep.You seem to be suggesting that a) we
could have done this before because the tech has always been
there. b) we can't do this now because the tech is not
reliable or cheap.I'm not sure how you can rectify these two
arguments since this tech is more reliable and cheaper now
than it ever has been.
manigandham - 6 hours ago
Yes it's possible to build, but no it's not cheap enough to
make money on = not worth building.We can build lots of
fantastic things today but they would cost trillions so
clearly are not a good idea. You also missed the ending
about construction + maintenance, those will be the real
costs and aren't likely to become radically cheaper.
sigmar - 4 hours ago
To the generations that traveled the world on boats,
constructing flying machines that move faster (and
required more tech/maintenance) also probably seemed like
an unknown of whether it would be prohibitively expensive
or not. I'm grateful that they didn't wait long to
explore the possibility, which is what Virgin is doing
here.
manigandham - 4 hours ago
Maybe I'm communicating poorly here but the tech is not
the problem. We don't need to invent anything new, we
know how to do it. It does need to get cheaper but the
construction and maintenance costs are gigantic and that
hasn't changed for any big project over the last
century.Jetliners are complex machines but it's the
entire infrastructure of airports and traffic control
that actually make it possible, which is only viable
because people choose to pay for it. Massive
infrastructure does not build or take care of itself, and
if it did, that would be a far bigger revolution than
just building a train.
idlewords - 7 hours ago
"We can barely build a high-speed rail line effectively...'There
is no high-speed rail line in the United States. The nearest
thing to high-speed rail is the Acela Express, which hits 240kph
on 40km of track. But this is weaksauce by modern standards.
Pxtl - 7 hours ago
And honestly, if you want to solve the USA's environmental
problems, 200kph commuter rail would probably be a better
investment than HSR or Hyperloops.
ant6n - 6 hours ago
Definitely agree that more, better transit would have a much
bigger impact.But I'd say the problem of commuter rail is
frequency, coverage station locations, acceleration, level
boarding, dwell times etc etc. Given that line speed is
dictated by acceleration and dwell times, top speed is really
far down the list of priorities.Also, top speed of commuter
rail is already up to 200km/h (e.g.
https://en.wikipedia.org/wiki/ALP-45DP).
Pxtl - 6 hours ago
I guess it's just my own experience in Ontario - the GO
transit trains look like they travel at about 110kph or so,
and once you figure in their slow acceleration and frequent
stops that means they're quite slow. Outside of the worst
part of Toronto rush hour (which is notoriously bad)
they're actually slower than the comparable coach bus from
my area (Hamilton).The overall average speed is a paltry
50kph.When the train is slower than the coach bus, why even
have a train?
ant6n - 5 hours ago
The average speed is governed by acceleration and dwell
time - the issue for GO is lack of electrification (which
increases acceleration), and lack of level boarding
(which decreases dwell time).50km/h average is actually
quite fast. I mean, a radius 50km from downtown is a huge
area already. We have to densify inside that radius, not
sprawl people further out because the trains are so fast.
This means for example we need more stations, so that
more developable land is within walking distance of
service.
Pxtl - 2 hours ago
> This means for example we need more stations, so that
more developable land is within walking distance of
serviceThat's what lrt and subways are for, not the big
commuter GO trains.
ant6n - 1 hours ago
That's the crux of what's wrong with commuter rail
thinking in North America: "Serving the city is what the
subway is for". Your original post, asking for 200km/h
commuter rail, is a sign of it.There's a meaningless
separation of modes based on technology, and ascribing
attributes to them. In Japan or Europe, the technologies
are converging and so are the modes. Any infrastructure
will have it's utilization maximized, and may function as
what North Americans understand as 'commuter rail',
subway' or 'light rail' all at the same time.The result:
more coverage, more service, better integration of
services, more overall effectiveness, more ridership,
less reliance on driving.
ant6n - 6 hours ago
200kmh/h is the generally accepted threshold for high speed
rail.EDIT: from the UIC website:"In any case, high speed is a
combination of a lot of elements which constitute a whole
"system": infrastructure (new lines designed for speeds above
250 km/h and in some cases, upgraded existing lines for speeds
up to 200 or even 220 km/h),..."http://uic.org/highspeed#What-
is-High-Speed-Rail
[deleted]
saosebastiao - 7 hours ago
Everybody talks about the engineering challenges, which have been
beaten to death. Elon Musk has a pretty respectable track record of
making things that seem technologically infeasible and making them
happen. He's not in charge anymore, but I trust that he wouldn't
put his name on something that's not possible. Even if it wasn't
possible, I'm not the person to make that critique.The bigger
challenge, IMO, is economic. High speed trains make a lot of money,
but their revenue has little to do with competing with airlines
over significant distances between large cities, which is what the
Hyperloop is attempting to supersede. The financial success of high
speed trains has much more to do with their ability to rapidly
start and stop in lots of intermediate urban areas within a
corridor. I know this goes against the popular narrative about why
high speed trains are popular (OMG they can compete with air
travel!!!), but the narrative is wrong.The revenue of HSR has a lot
more to do with the number of cities that it services than the end
to end speed. If you look at ticket revenues on successful HSR
lines, terminus to terminus tickets typically make up <15% of total
revenues. The rest is made up by the remaining cartesian set of
city pairs. Even if you could add up all possible market share
(trains, planes, cars) between terminus cities, it would still be
less than the total revenue for that line, due to the additional
cities it serves. Even with the gradual growth in power levels for
high speed trains, with some now capable of 360kph, end to end
speeds have basically gone unchanged. What has changed with more
powerful trains? The lines have more stops now...they serve more
cities, with the higher power levels used for faster acceleration
and deceleration. More cities means more revenue, whereas higher
speeds have already hit strongly diminished returns.Maybe with
Hyperloop being really fast could grow the market and monopolize
market share between Alpha cities, but that would still be a
stretch if the goal is economic viability. People see hyperloop,
they crave its speed, but the costs are too high and revenues are
too low to just serve the endpoints. But if you decide to serve
intermediate cities, you slow it down, and it no longer becomes the
object of technological lust, and nobody will want anything to do
with it.Among economic historians and really nerdy train
enthusiasts like me, this isn't a contentious point. The same
economic delusions were a primary causative factor in the
overhyping of railways during railway mania, best exemplified in
chapters 16-20 of Collective Hallucinations and Inefficient
Markets: The British Railway Mania of the 1840s [0], which is a
masterpiece of economic history IMO. Anybody in charge of building
out some version of hyperloop should do themselves a favor and read
it, and then work on not repeating history.[0]
http://www.dtc.umn.edu/~odlyzko/doc/hallucinations.pdf
_zachs - 7 hours ago
Imagine if half of these commenters were around when the Wright
brothers were pioneering aviation?
delecti - 6 hours ago
I have no doubt that there was just as skepticism about the
invention of aviation.
mrguyorama - 6 hours ago
This kind of skepticism would have been perfectly acceptable had
the Wright Brothers wrote three pages of guesswork and napkin
math instead of actually building a plane.
kowdermeister - 6 hours ago
> instead of actually building a
planehttps://www.youtube.com/watch?v=jjv7bB9hy0k
platz - 8 hours ago
I could see investors wanting to fund this simply for the PR
benefits; whether or not such a system is actually viable.Or,
perhaps they'll spin a few technologies out of it.Or, perhaps they
want to grow a network of related companies+technologies that they
can re-purpose to another venture in the future.
sschueller - 8 hours ago
When are we going to address the elephants in the room?Just the
tube alone: - largest pressure vessel in the world. How do you
keep it at near vacuum? - Thermal expansion over such a large
distance, especially if the top of the tube is warmer than the
bottom. - Safety, how does an evacuation look like if the tubes
are sealed?. There are many more. Some how I feel like this is a
"pipe" dream. Lots of marketing, very little engineering.
The_Double - 8 hours ago
I haven't done any work on hyperloops. But expansion seems to be
a problem already solved by industry a long time ago:
https://en.wikipedia.org/wiki/Metal_expansion_joint
bjl - 8 hours ago
Metal expansion joints can't hold a vacuum.
MrBuddyCasino - 8 hours ago
Quick googling says otherwise: http://www.spiroflex.hr
/expansion-joints-vacuum-technology
MrBuddyCasino - 8 hours ago
Sounds promising:- Resistance to high and very high pressures-
Large movement absorption- Early leak indication (in case of
damage) via standard check hole- Complete burst resistance-
Possibility of permanent leak monitoring in critical media
dmix - 8 hours ago
> Lots of marketing, very little engineering.It started as a
technical whitepaper, not a marketing campaign, and multiple
companies are building experimental models. I don't think this
critique is accurate or fair. There have been far worse
vapourware and hype-only concepts that haven't gotten close to
hyperloop's tangible progress.No tech can be perfected from the
planning stage either, it takes talent, money, and time - and you
can't get those things without a bit of hype, the key is keeping
it balanced.Regardless the concept seemed feasible enough to some
very smart people and people with money to spend, where they see
it's worth the R&D.I don't really see what the big risk or
downside here of exploring this? Considering the rewards could be
very high if it does work and otherwise there has been little
innovation in transportation in 50yrs, it's not like there are
some obvious alternatives are being neglected.
scott_karana - 3 hours ago
No, the whitepaper came after the start, which was Musk
publicly bragged about how he and his engineers could do the
rail project better."More marketing than engineering" seems
accurate to me.
TremendousJudge - 8 hours ago
>it's not like there are some obvious alternatives are being
neglectedA high speed train like the ones they've had in Europe
for a long time? You know, the ones that regularly reach 300
km/h? If that's not fast or flashy enough for you, what about
Maglev? It actually exists, and the tracks are extremely
expensive even though they don't even have to maintain low air
pressure
Robotbeat - 5 hours ago
We have natural gas pipelines that have to maintain a far
higher pressure difference, and they are in the same order of
magnitude in diameter. They're not expensive. Way less than
high speed rail lines per mile.
dmix - 4 hours ago
> A high speed train like the ones they've had in Europe for
a long time?I don't see what the US political inability to
build infrastructure has to do with my comment. Plenty of
countries are still building highspeed trains and iterating
on that model... and plenty of non-US countries are looking
into hyperloop, the first ones to adopt it will likely be
outside of the US, as that's where most innovation is these
days. And regardless there's always plenty of room for new
ideas.Unless you think these billionaires should be backing
American transportation mega-projects instead? There's plenty
of roadblocks there outside of access to capital, where a
highspeed train will likely cost 2-3x the initial
projections, even if a private company does it. Not to
mention the US is a car-heavy market. It seems like a risky
project for any non-government entity to take on as it will
be packed full of political risk and direct involvement
either way...The US rarely builds major projects anymore
except in the defense industry. And almost every major
defense project of comparable size ends up being billions
over budget or cancelled.
logicallee - 8 hours ago
Out of curiosity, have you ever built anything big? I say this
because the tone of your comment is dismissive, however it seems
quite low-effort. I can translate your criticisms into
criticisms of building subways in 1863: - if you build a subway
it will be the biggest underground railway ever built. - Rocks.
They could fall in front of a subway car and cause a huge
accident. - safety. what if all the lights and power go out?
Also how would anyone breathe down there. And my criticisms seem
stronger, not weaker, than yours. Today all cities with robust
subway systems benefit hugely from them and all of these issues
have been resolved.The criticism you've offered seems equally
low-effort, so this is why I'm curious if you've ever helped
design and build any large-scale project.I don't like gratuitous
negativity on HN and it's against the rules here.
M4v3R - 7 hours ago
Also, planes are a terrible idea. I mean how do you evacuate
people from them if something goes wrong? I think this whole
airplane thing is just vaporware.
KekDemaga - 6 hours ago
The question isn't "will this ever work?", the question is
(while keeping with your airplane analogy) is Elon Musk's
design closer to the Wright brothers airplane or Da Vinci's
ornithopter. I'd guess the latter personally.
logicallee - 5 hours ago
The Wright brothers had a bicycle shop, whereas Da Vinci
was more of a painter.The main thing Musk has in common
with the Wrights is running an electric car transportation
company and sending private rockets into space via SpaceX.I
think you should revisit whether that makes it more Wright
brothers or Da Vinci.
dx034 - 7 hours ago
The question is if we want to accept the risks. In the early
days of subways, trains, planes and cars, accidents were
frequent and many people died until we figured out the safety
aspect. Today's society is much more risk averse. I don't think
the general public would accept several fatal crashes before
the system is safe.
jfindley - 6 hours ago
It's easy to come up with reasons why something won't work.But,
usually, it's more productive to start with the understanding
that other people are smart too, and that they may have thought
of these problems. In this particular case, I believe that the
original white paper addresses these points. I'm not a
structural engineer, so I've no idea if their solutions are valid
and I'm not saying that it's never okay to criticize, but this
reads to me as if you may have fallen into the trap of forgetting
that the people who designed this are very smart people, and thus
likely thought of the obvious problems.
Filligree - 8 hours ago
The pressure tube doesn't need to be at near-vacuum. By the drag
equation, air resistance is proportional to pressure; merely
cutting pressure by 90% would reduce air resistance by the same
amount, and that's trivial with perfectly ordinary pumps.Serious
vacuum pumps are not required. This is not to say that keeping it
airtight won't still be a major engineering problem, it just
isn't as near-impossible as near-vacuum would be.To cope with
expansion, you'd need to use sliding plates--which, yes, will
make it harder to keep the air out. That's going to be an
interesting challenge.
wlesieutre - 8 hours ago
Doesn't the Hyperloop concept rely on not having a perfect
vacuum? It's supposed to suck in air on the front and blow it
out the bottom as an air cushion. Without the air cushion you
just have "maglev in a vacuum" instead.I'm sure that's also a
fast mode of travel, but like you said, the vacuum part of it
takes a lot of money.
Robotbeat - 5 hours ago
Does the vacuum part take a lot of money? I would think that
if anyone knows, it'd be someone like Elon Musk who has built
a spacecraft company from the ground up.For many of Elon
Musk's projects, I get the idea that Elon is mostly just
bringing broad, multi-domain knowledge to bear on industries
that have been siloed for a very long time. So everyone
scoffs at a long vacuum tube and using turbomachinery, etc,
but for someone with a physics background with extensive
knowledge of the spacecraft environment, turbopump rocket
engines, and all the subsystems and ground testing systems
that enable all this, it really isn't far-fetched at all.
Most physicists (of the experimental kind, i.e. those who
have to have hands-on knowledge fabricating things in
addition to theoretical background) that I've talked to
understand his ideas and think they're fairly
reasonable.People seem to base most of their criticisms on
the fact that it's different than what we already do without
a fundamental, first-principles understanding of the system.
wlesieutre - 2 hours ago
A real vacuum (or very close to it) would be expensive,
yes. That's what Musk designed the hyperloop to avoid; it
works with a "low pressure" tube instead. His original
hyperloop proposal paper outlines this in the intro:http://
www.spacex.com/sites/spacex/files/hyperloop_alpha.pdfAnothe
r extreme is the approach, advocated by Rand and ET3, of
drawing a hard or near hard vacuum in the tube and then
using an electromagnetic suspension. The problem with this
approach is that it is incredibly hard to maintain a near
vacuum in a room, let alone 700 miles (round trip) of large
tube with dozens of station gateways and thousands of pods
entering and exiting every day. All it takes is one leaky
seal or a small crack somewhere in the hundreds of miles of
tube and the whole system stops working.However, a low
pressure (vs. almost no pressure) system set to a level
where standard commercial pumps could easily overcome an
air leak and the transport pods could handle variable air
density would be inherently robust. Unfortunately, this
means that there is a non-trivial amount of air in the tube
and leads us straight into another problem.The "another
problem" being that if you just do low pressure, it means
your pod has air in front if it and has to pushing that air
around (or if that air has nowhere else to go in the
forward tubing, trying to compress it, because not enough
of the air can squeeze around the pods at the edge of the
tube). That's what the hyperloop is getting around by
sucking air in the front and blowing it out the bottom.
Working as an air cushion is something of a bonus, and if
everything works out right it also lets you avoid the
expense of maglev.
[deleted]
Faaak - 8 hours ago
The CERN LHC tube is a 27km circle of vacuum and near-zero
temperature, and they don't seem to have a problem with that
(granted, they had some but it's solved now).Frankly, yes, there
may be issues, but I'm confident that the Human race will be able
to overcome those.
ginko - 8 hours ago
The LHC's vacuum pipes are 6.3 cm in diameter..
iamgopal - 8 hours ago
What, really? What's with all those mega photos we see
everywhere ?
Analemma_ - 8 hours ago
Most of that is the magnets around the beam tube, with the
associated power and refrigeration equipment. The beam tube
itself is quite small.
konschubert - 8 hours ago
Those are the detectors. And the magnets around the tubes.
delecti - 6 hours ago
This picture shows a cross section of part of the LHC.
Those two yellow lines sticking out are the actual tubes.
Everything else is equipment to manage the particles
(detectors, containment, magnetic propulsion).And for a
sense of scale, a human can comfortably stand in that
tunnel next to it.Image: http://www.tut.fi/cs/groups/public
_news/@l102/@news/@p/docum... From here:
http://www.tut.fi/en/about-tut/news-and-events/tut-and-
cern-...
eutropia - 8 hours ago
Yeah, LHC's is the largest in the world at just 15,000 cubic
metres -- equivalent to about 1 km of hyperloop tunnel
(assuming 14ft diameter mentioned in the Boring Company's
FAQ)
bmh_ca - 8 hours ago
I love how you've capitalized "Human", as if to say there were
some other race competing to complete the Hyperloop. :)
TremendousJudge - 8 hours ago
What about building a high speed train? Proven technology,
works in a lot of countries. LA to SF in 2 hours. Is it really
that bad?
drzaiusapelord - 7 hours ago
Someone made the argument that in the US our rails were built
by men half killing themselves for low wages and with very
few safety standards. That means a modern buildout is much
more expensive than it was historically and the political
will to build that budget is difficult or
impossible.Hyperloop is a run around that problem. Largely
autonomous/low staffed boring that's non-union labor, non-
public sector can make a lot of progress quickly. There's no
public sector union demanding x amount of jobs, x amount of
pensions, and other expensive regulations or union
concessions. Musk's Boring Company thinks it can build
tunnels for a fraction of the cost privately without much
public sector regulatory weight and they might be right.HSR
is the saner idea, but without Congress funding it, its just
not going to happen. Obama made a big push for it during the
stimulus but more conservative states decided against
accepting the money for both ideological and financial
reasons. Once enough states say no, then the rail can't go
very far, and the project eventually died:First, Tea Party
conservatives in Florida and wealthy liberal suburbanites in
the Bay Area began questioning their states? plans. Then,
just as Joe Biden was calling for $53 billion in high-speed-
rail spending over the next six years, a crop of freshly
elected Republican governors turned down billions in federal
money for lines in Wisconsin, Ohio, and Florida. Finally,
Republicans in Congress zeroed out the federal high-speed
rail budget last month.http://www.slate.com/articles/technolo
gy/technocracy/2011/12...
dschep - 6 hours ago
Re: unions, there are sandhogs unions, wouldn't they be
relevant? Ex: http://www.sandhogs147.org/
gok - 7 hours ago
It'll be more like 3 hours, and it will end up costing around
$100 billion. It would be dramatically cheaper and faster to
subsidize free plane tickets between LA and SF for the next
50 years.HSR works well in places with high density and
competent infrastructure construction strategies. California
has neither.
dx034 - 7 hours ago
Trains have a much higher capacity. Most people currently
drive the distance which leads to more accidents and a lot
of lost time.$100bn is too expensive to make sense but I
don't understand why it should cost that much. There are
not that many tunnels needed, esp. if you start/end north
of LA and south of SF. European rail projects are also
expensive but still a fraction of the cost.
jandrese - 7 hours ago
Thermal expansion is at least easy to manage if your system is
kept near 0K in operation. It's only an issue when the system
is turned off.
mtgx - 6 hours ago
How safe would the hyperloop be from tube
implosion?https://www.youtube.com/watch?v=T9bpUfWy8WgI guess it
would depend on how well they engineer the whole system, but who's
going to watch over the hyperloop building companies to do that
right?
peter303 - 8 hours ago
Hope it fares better than Virgin Galactic which is at least eight
years behind schedule (first commercial flights proposed for 2010).
jandrese - 7 hours ago
Didn't Virgin Galactic go on hiatus after the test pilot died?
glbrew - 5 hours ago
Great youtube video that presents huge barriers to the
hyperloop:https://www.youtube.com/watch?v=RNFesa01llk
[deleted]
daemin - 6 hours ago
Just as a thought experiment, could the promotion of these
"hyperloop" projects be a clever political ploy to misdirect/divert
attention and prevent a viable high speed rail network from being
built?Elon's main business is electric cars and (one of) Branson's
is airlines. So a reasonable competitor to both is fast and
cheap(er) public transport along a major travel corridor in the
USA.This means that by promoting this alternative to high speed
rail as faster, cheaper, better, they are undermining public
support for a real project, which could mean its end.
0898 - 6 hours ago
Branson's also in railways ? Virgin Trains.
daemin - 6 hours ago
I think Branson gets into almost everything, like a bigger form
of an Angel investor. In that regard it makes sense to use the
brand and money to make many small seed stage investments.
Twirrim - 4 hours ago
All Branson has left is a partial holding of Virgin Atlantic on
the flying business side of things. Virgin is in the train
business, and has 100% holdings there, so if anything he has more
business interest in seeing high speed rail come about.
trose - 6 hours ago
Interesting idea. In Denver, they're partnering with our regional
transportation district to evaluate a hyperloop system here.
Unfortunately RTD has been completely incompetent with existing
rail programs to date so there isn't much confidence in their
ability to pull this off. Could potentially be designed to fail.
monocasa - 5 hours ago
Yeah, Denver being chosen just convinced me that this whole
thing is pump and dump cash grab.CDOT has this thing for
"public/private partnerships" which are just thinly veiled
schemes siphoning off taxpayer money. The whole US36 debacle
proved to me that they aren't capable of negotiating a good
deal on the part of the taxpayers.
icebraining - 2 hours ago
What whole thing? The Denver partnership was made by
Hyperloop One, which is just one of the companies trying to
build it, and is not affiliated with Elon Musk.
monocasa - 35 minutes ago
Sure, 'the whole thing' being Hyperloop One in this case.
rando444 - 6 hours ago
It's a good thought experiment, and not without precedent..
however the main problem holding high-speed rail back in the
United States is that freight trains have priority over passenger
trains.Without changing this, high-speed rail in the US will
never be a reality without building an entirely separate rail
network.
GuB-42 - 6 hours ago
Are they?AFAIK, passenger trains have priority. However, if the
passenger company rents a specific timeslot from the railway
and isn't on time, it isn't surprising if there is traffic
along the way.And high speed trains usually require dedicated
tracks to operate at full speed anyways.
NegativeLatency - 5 hours ago
And straight track runs for really high speed. Which means
that you need to acquire land to build through.
dvanduzer - 5 hours ago
I was also under the impression that freight trains had
priority, so I looked and found this
article:http://www.sfgate.com/opinion/article/Amtrak-has-
priority-ov...I've experienced these delays many times riding
the California Zephyr, and the conductors always say
something about the freight trains having priority. According
to the article this is because Amtrak is persistently ceding
priority, despite federal regulations prioritizing passenger
trains.edit: According to the WaPo article linked by jey in
this thread, this ended up overturned in federal court, so I
guess as of 2017, freight does have priority over passenger
trains in the U.S.
daemin - 6 hours ago
Isn't that because the freight companies are the ones that
actually built, own, and operate the tracks? If Amtrak or
another passenger company owned the tracks, their trains would
get priority.
pstuart - 6 hours ago
On land gifted to them by the government.
jcranmer - 1 minutes ago
The land grants weren't for the land that the railroads ran
on. It was for adjacent property that they could develop or
sell. And not all the transcontinentals relied on land
grants (e.g., Great Northern).
mseebach - 5 hours ago
Given the key function railroads had in opening up the
west, I think you'll struggle to argue that that was even
close to a bad deal.Indeed, that, if anything, is exactly
the kind of investments that a government should be making.
dnautics - 3 hours ago
nongovernment investments tend to be more sustainable,
because they are driven by observed demand, instead of
cronyism or politics. This was one of the few railways
to survive the great railway crash, it's still operated t
oday:https://en.wikipedia.org/wiki/Great_Northern_Railway
_(U.S.)
icebraining - 2 hours ago
Non-governmental investment - except for the 3 million
acres in Federal land grants.
jychang - 2 hours ago
> This was one of the few railways to survive the great
railway crashThe government well made its money back
before the great railway crash.Let's say the Internet
suffers a crash in a few decades. Few would argue that
any previous investment into the Internet was not worth
it.
dnautics - 31 minutes ago
you're cherry picking an example that succeeded. Let's
say DARPA's investment in ESP doesn't turn out in a few
decades. Few would argue that any previous investment
into ESP was not worth it. (disclaimer: I'm being paid
on a stupid darpa grant now)
bufordsharkley - 32 minutes ago
If in the mid-19th century these were gifted to the
railroad companies as 99 year leases, the value to the
companies wouldn't have been very different, but we
wouldn't be in thrall to them today.
jey - 5 hours ago
No, Amtrak supposedly has priority by law: https://www.washin
gtonpost.com/news/powerpost/wp/2016/04/29/...
mseebach - 5 hours ago
Yes, and that law didn't come out of the blue. More
pertinently, a purpose built passenger rail line will have
priority for passengers.
dvanduzer - 5 hours ago
Based on this article, I'm under the impression that the
law was overturned. The most recent article I can find
about the status of adjudication suggests that Amtrak will
have a very difficult time upholding that law:
http://lyldenlawnews.com/2016/09/22/u-s-faces-a-choice-on-
am...
goialoq - 6 hours ago
or they see that trains are the future and they want to own those
trains.
mc32 - 6 hours ago
Why would Elon have sparked the idea in the fist place, then?It
wasn't entirely novel, but he gave the idea legitimacy beyond the
normal fantastic imaginary future one is wont to see from time to
time.So I don't think this was an attempt to head the tech off at
the pass or some alternate reality like that.I think it was
genuine and continues to be.
[deleted]
microcolonel - 6 hours ago
I think it would be a good idea to make sure the California "high
speed" rail program is never funded. It is a terrible idea. As it
stands, it would be as slow as conventional rail, redundant with
AmTrak, and the most expensive rail line ever built. It would be
absolutely devastating for the government's relationship with at
least tens of thousands of land owners, hundreds of thousands of
home owners, who would see depreciation or outright loss of use
of their land (which may hold sentimental or historic value not
accounted for, or impossible to account for, in eminent domain
assessments).
valas - 5 hours ago
"it would be as slow as conventional rail" - citation?Even
Reason Foundation (which is as biased as it gets - it's funded
by Koch brothers and ideological critic of almost any
government investment) claim SF to LA times will be 3:30 to
4:40, which is faster than any train today.
nradov - 5 hours ago
That's barely faster than driving, once you account for the
time spent moving between your origin/destination and the
train station as well as transferring luggage.
baldfat - 4 hours ago
In the near age of driverless cars I think this might be
its biggest demise. If cars are automated people wouldn't
need a train. It will be cheaper and less confining to a
schedule and to a destination.I think air travel for short
to medium flights will fall off. By the time I leave my
house and get to someplace that is 8 hours by car it would
take 5 hours to check in and check out and you still need
to rent a car.
Frondo - 2 hours ago
3 and a half hours is way faster than driving. And for the
comfort of being on a train? Worth it!
kbenson - 4 hours ago
And taking the light rail north of SF to the ferry and then
the Embarcadero in SF takes longer than driving when my
brother commutes, but he still chooses that method.
Perhaps there are factors other than time that go into his
calculation.People would take HSR even if it took the same
time as driving. They would likely take it if it took an
extra 20%, as the time has more utility to them when used
for a train ride. That it's actually faster than driving
just makes it more attractive.
doingmything - 1 hours ago
Agreed. Many people underestimate the aversion of a large
swath of the population to driving. Driving basically
monopolizes your time and focus and exposes you to
accidents. I don?t know if I know anyone who would rather
drive if they could get to their destination in the same
relative time, unless they?d need a car on the other end.
chipotle_coyote - 5 hours ago
An under-four-hour train trip still sounds like a win over
a six-hour-with-good-traffic drive. Especially for people
who don't really like making that drive, which I suspect is
a substantial subset of the population. (I like driving,
personally, but that trip is decidedly less than a thrill.)
kbenson - 4 hours ago
> I think it would be a good idea to make sure the California
"high speed" rail program is never funded.Never funded? It's
already under construction[1]. Although it's likely pre-pre-
pre-construction, as they grade items and fix obstacles for the
actual railway construction, which I doubt will happen within a
decade, if ever.1: https://www.buildhsr.com/interactive_map/
jcranmer - 2 minutes ago
> Although it's likely pre-pre-pre-constructionThey're
building the bridges right now, that's not exactly pre-pre-
pre-construction.
Frondo - 2 hours ago
It's a great idea and I can't wait to see more high speed rail
built all across the country.We've already criss-crossed
uncountable acres of historic, sentimental (what?? really??)
land with roads, both local the state/federal highway system.
HSR would be so much better use of land than roads, for moving
a lot of people quickly and comfortably. Not at all redundant
with Amtrak.Happily, the California project is funded and is
already underway, and I think there's one or two others being
talked about/planned.
dkersten - 1 hours ago
On top of that, my experience of (southern) Californian roads
is that they are muuuuuch wider and take up much more space
than the coaster/amtrak train tracks take up, so roads have
been much more damaging to historic sentimental land than
rail is or would be.
Frondo - 3 minutes ago
What really irks me with that particular sentiment (the
land is historic/already in use) is how the federal highway
system absolutely decimated communities of color in a lot
of major cities.They'd put a highway right through where
the black folk live, and who cares? Well, all the people
in that neighborhood care, but they're poor minorities--
they have no political power, no ability to push back.If
you want to start talking about land being taken from
people, don't fucking start with farmers in rural
California and HSR, start with the inner city neighborhoods
the highway system destroyed.
mhermher - 5 hours ago
It's not redundant with amtrak. There's no way to get from LA
to SD on passenger rail without transferring through busses.
k_sh - 4 hours ago
The Coastal Starlight runs from Union Station in DTLA to Jack
London Square in Oakland. From there, it's a quick walk to
BART to get into San Francisco - no bus required.That being
said, the trip takes 13 hours and some change, depending
where in SF you're trying to go - which would be blown out of
the water by HSR.
mhermher - 4 hours ago
That must be new. That wasn't available as of like we years
ago or so.
ac29 - 2 hours ago
That rail route has ran continuously since 1971:
https://en.wikipedia.org/wiki/Coast_Starlight. The
transbay tube connecting Oakland to San Francisco via
BART opened in 1974.
rrix2 - 38 minutes ago
it's worth noting that coast starlight's once-a-day-each-
way schedule sort of makes it limited as a commuter rail
option.
mhermher - 5 hours ago
That should be SF, not SD.
jaredhansen - 6 hours ago
Of all the problems facing construction of "viable high speed
rail" in the US (they already exist in many other places), I
don't think Hyperloop competition is among ... the top
50.Practically anything could be "a clever political ploy", but
where's the evidence for this? Any in the absence of such
evidence, why speculate?Just as a thought experiment, could HN
user daemin's comments be part of a clever ploy to invent a fake
persona to distract from a SECRET AGENDA? ;)
Brakenshire - 6 hours ago
We're just building a new major high speed line in the UK, and
you'd be surprised how often you hear people say that it
shouldn't be built because the technology will be superseded by
the hyperloop, or autonomous cars, or whichever. It's one of
the major talking points, even if it isn't one of the major
blocks.
dionidium - 4 hours ago
Yes, I think this is it. I don't buy into any "clever
political ploy" theory, but this type of stuff does get into
people's heads. The rise of Uber and Lyft are already being
used in arguments against mass transit.
mseebach - 5 hours ago
Meh. The imminency of "Major New Technology Just Around The
Corner" has always been a favourite argument for the anti-
progress crowd.EDIT to add: Before Hyperloop, it was
Maglev.And frankly, a significantly better argument against
HS2 is that it's an impossibly expensive boondoggle.
Brakenshire - 4 hours ago
> a significantly better argument against HS2 is that it's
an impossibly expensive boondoggle.Nah, it connects most of
England's largest cities, and will be 2/3rds of the network
which will connect all of the cities of the North of
England into something approaching a single labour market.
Liverpool, Leeds, Sheffield, Manchester, Birmingham will be
all be within 30-50 minutes of each other, with London
within an hour and a half, with trains running between
destinations 2 or 3 times an hour. The value of that is
enormous.
twic - 50 minutes ago
The main point of HS2 is that it will relieve congestion
on the existing tracks, and allow more commuter services
to run:https://www.railengineer.uk/2014/01/03/the-
capacity-
benefits...http://www.citymetric.com/transport/hs2-isnt-
about-north-eng...The idea that it will turn a load of
separate cities into one big city is basically fantasy,
as i understand it - this is about HS3, but the analysis
is much the same:http://www.citymetric.com/transport
/crossrail-north-really-b...And yes, i do get all my
information from CityMetric, since you ask. It's
basically Buzzfeed for transport policy, i love it.
gaius - 3 hours ago
It would have been politically a LOT easier of they'd
built a Birmingham-Newcastle leg first
sgt101 - 3 hours ago
and probably better for the long term economy as well;
the last thing Birmingham needs is a reason why London is
a good base for doing business in Birmingham.
gsnedders - 3 hours ago
Perhaps. There would also have been political costs
incurred due to the overcrowding on the southern end of
the WCML and that then being apparently a lower priority
than providing a quicker link between two cities.And yes,
I realise the XC trains around Birmingham (inc. to
Newcastle) are frequently overcrowded, but there's a
comparatively cheap solution to this: buy more trains.
karmapolic - 6 hours ago
its things like these which make it seem like a clever ploy.
However cool a technology hyperloop seems like. it is nothing
more than a research project with a great marketing stunt.
aerovistae - 2 hours ago
Exactly.
tdb7893 - 2 hours ago
High speed rail already was not going to happen in the US for
large political and practical reasons. Having a master plan to
kill American rail travel just sounds like a waste of time
[deleted]
drawnwren - 6 hours ago
More likely, it's Elon worrying about how to colonize Mars than
anything else.
Tiktaalik - 5 hours ago
Of course it is. Organizations that benefit from road
infrastructure expansion actively work to discredit and defund
government transit initiatives.Historically there is the example
of 1920s era GM funding initiatives to convert tram lines into
bus lines, which required further investment in road networks,
which benefited their private car ownership business as transit
was defunded and discredited.
jgamman - 1 hours ago
Transpower in nz used this argument to drastically cut its
maintenance budget in the 90s using "distributed generation will
strand the assets" type reasoning. Nz suffered the consequences.
Who pays taxes and who booked imaginary accounting profits is
left as an exercise for the reader. So yeah, it's not obviously
wrong as a concern.
jankotek - 6 hours ago
There is some public support for high speed trains?Hyperloop at
least started a discussion. Once it fails, there might be some
actual public support.
JumpCrisscross - 6 hours ago
The original Hyperloop paper quotes its design pressure as ?about
1/6 the pressure of the atmosphere on Mars? [1]. Martian
atmospheric pressure is ?about 0.6% of Earth's mean sea level
pressure? [2]. So 0.1% of Earth?s surface pressure, or a 1,000:1
pressure change.To put that in perspective, the Boeing 787?s GEnx-
2B67, the most powerful GEnx engine variant, generates a 43:1
pressure ratio [3]. To get a sense of the engineering differences
between 6:1 and 1,000:1, look at NASA?s Space Power Facility
[4].The Hyperloop?s thermal issues are a hard enough problem that
they alone put this in the domain of materials science. That?s the
same category of problems separating us from a space elevator.The
Hyperloop always seemed like a transportation system not for this
planet. The thermal issues, too, become trivial to solve on Mars:
bury the tube. Mars does not appear to be too seismically active
[5] and has no existing property rights to take into account
[citation needed]. (The lack of water also makes steel more
viable.)[1]
http://www.spacex.com/sites/spacex/files/hyperloop_alpha-201...[2]
https://en.m.wikipedia.org/wiki/Atmosphere_of_Mars[3]
https://en.m.wikipedia.org/wiki/General_Electric_GEnx[4]
https://en.m.wikipedia.org/wiki/Space_Power_Facility[5]
https://www.space.com/418-marsquakes-red-planet-rumble.html
manigandham - 3 hours ago
We have oil pipelines stretching thousands of miles that are
under far more stress. We can build a low-pressure tunnel that
stretches without a problem. Nothing in the hyperloop is
impossible - it's just incredibly expensive and
unprofitable.Solve the mass-scale construction and maintenance
efficiency problem and we can get all kinds of cool things like
hyperloops, space elevators, and fancy megacities.
hwillis - 5 hours ago
> The Hyperloop?s thermal issues are a hard enough problem that
they alone put this in the domain of materials science. That?s
the same category of problems separating us from a space
elevator.What? What are you even talking about?? That's a
completely ridiculous statement. The pressure inside and outside
the lunar landing module was 1,000,000,000,000,000x. 100 kPa to
10^-10 Pa. It makes zero sense to apply this kind of ridiculous
relative measurement to pressures because it has no relation to
how pressure works. The structural challenge in building a tube
that works to .001 atmospheres is only 25% harder than building a
tube that works to .2 atmospheres (same as an airplane). And it
isn't any more dangerous.The only challenge that occurs is
sealing in that atmosphere without any leaks and that part isn't
hard either. 100 Pa is achievable by a $50 pump.I also have yet
to see any compelling argument that there will be thermal issues.
Floating mounts and expansion joints are hardly untested
technology.
JumpCrisscross - 4 hours ago
> The pressure inside and outside the lunar landing module was
1,000,000,000,000,000x. 100 kPa to 10^-10 PaWe didn't pump air
into the lunar module from the Moon. We carried it from Earth
pre-pressurized. Unless you're proposing we build and seal the
Hyperloop tubes in space before bringing them down, the analogy
isn't appropriate.Also, consider a soda can. It's stronger when
pressurized from the inside. Modern nuclear attack submarines
collapse around 730m [1]. Since for "every 33 feet (10.06
meters) you go down, the pressure increases by 14.5 psi," we're
talking about water pressure of about 1,000 psi or about 72
atm.[1]
https://en.wikipedia.org/wiki/Submarine_depth_ratings[2]
https://oceanservice.noaa.gov/facts/pressure.html
the8472 - 4 hours ago
The force exerted by the atmosphere on an evacuated tube is
the same as the force exerted on a standard-atmosphere filled
submarine diving 10m beneath the surface. A 100kPa
difference.And since they explicitly do not want a high
vacuum - some residual air inside the tube is necessary for
the hyperloop concept! - they don't have to deal with
advanced tech like turbomolecular pumps. Simple displacement
pumps will do.
schiffern - 4 hours ago
Note that downthread, they've already moved the goalpost
from "these pumps are technologically impossible" to "but
they'll need a lot of
them!"https://news.ycombinator.com/item?id=15459820
JumpCrisscross - 4 hours ago
> Note that downthread they've already moved the goalpost
from "these pumps are technologically impossible" to "but
they'll need a lot of them!"I never said vacuum pumps are
"technologically impossible". My original comment
references the Space Power Facility [1] and categorises
the vacuum problem as an engineering problem. A hard one,
but engineering nonetheless.The comment you link to [2]
replies to someone claiming the original white paper
calls for a 22:1 atmosphere:tube pressure ratio. I
pointed out that the figure they're referencing, Figure
11, discusses the capsule and not the tube.I'm skeptical
about the economics of de-pressurising the tube, but
that's an engineering problem and I've always held it as
such. The materials problem is the thermal expansion of
the top of the tube relative to the bottom.[1]
https://en.m.wikipedia.org/wiki/Space_Power_Facility[2]
https://news.ycombinator.com/item?id=15459820
schiffern - 2 hours ago
>The comment you link to [2] replies to someone claiming
the original white paper calls for a 22:1 atmosphere:tube
pressure ratio. I pointed out that the figure they're
referencing, Figure 11, discusses the capsule and not the
tube.I happen to be that someone. :) You were talking
about state-of-the-art axial compressors (the GEnx-2B67),
so I assumed you were talking about the axial compressor
on the front of the pod. Mea culpa. But then you drew an
analogy to the pressures in the SPS ("To get a sense of
the engineering differences between 6:1 and 1,000:1..."),
as if the Hyperloop people were trying to make a 1000:1
axial compressor. As I pointed out in my reply,[1] rotary
vane compressors can easily maintain those pressures.>The
materials problem is the thermal expansion of the top of
the tube relative to the bottom.If that were really a
problem, no pipelines of any kind could be built. Again
thermal expansion joints are the solution, since with the
abandonment of air-ski levitation the pod walls no longer
have a requirement to be ultra-smooth. Tiny leakage on
these joints is fine, since it will be made up for by the
pumps located along the track.[1]
https://news.ycombinator.com/item?id=15460061
JumpCrisscross - 2 hours ago
> If that were really a problem, no pipelines of any kind
could be builtThe Trans-Alaska Pipeline system, which I
believe is the largest at least in the United States, is
1.2m in diameter [1]. We're talking about a pipe almost 3
times wider that needs to hold itself against the
atmosphere and keep capsules neatly contained.Side note:
long pipelines zig-zag to allow for thermal expansion and
contraction [2]. You can't do that with the Hyperloop.
(Bridges handle this with various ingenious methods, most
of which will work for the Hyperloop's longitudinal
expansion.)> thermal expansion joints are the
solutionScaling pipe expansion joints where they maintain
the near vacuum and deal with the structural stress of a
capsule whizzing by will be difficult. By "difficult" I
mean these are problems NASA (for the ISS) and
Schlumberger (for pipes) have been grappling with for
years and with billions of dollars in R&D.[1]
https://en.wikipedia.org/wiki/Trans-
Alaska_Pipeline_System#/...[2] https://www.quora.com/Why-
do-oil-pipelines-that-transfer-oil...
kbenson - 3 hours ago
> The materials problem is the thermal expansion of the
top of the tube relative to the bottom.What exactly is
the problem here? Is it because the top of the tube is
exposed to direct sunlight? I thought it was supposed to
be covered in solar panels anyway. Is it still a
materials science problem if the tubes are shaded,
because providing a structure that shades something with
expansion from direct sunlight exposure seems quite a bit
easier than to do so while trying to keep vacuum to a
particular level.
wbl - 3 hours ago
An evacuated tube on earth needs to sustain 1 atm.
sbierwagen - 4 hours ago
>Unless you're proposing we build and seal the Hyperloop
tubes in space before bringing them down, the analogy isn't
appropriate.I am not sure what your objection is here. Are
you saying vacuum chambers can't be built on Earth? There are
quite a few examples of large vacuum chambers, like the NASA
Space Power Facility (23,400 m^3) or the Large Hadron
Collider (9,000 m^3)
https://scap.hq.nasa.gov/docs/Glenn_SpacePower.pdf https
://lhc-machine-outreach.web.cern.ch/lhc-machine-
outreac...Both are pumped down to very high vacuum, not
required for the Musk Hyperloop, (low pressure electric jet
in a tube) but probably needed for the Hyperloop One. (maglev
vactrain) And, obviously, both chambers were built
terrestrially, and evacuated using conventional vacuum pumps.
JumpCrisscross - 4 hours ago
> I am not sure what your objection is here. Are you saying
vacuum chambers can't be built on Earth?No, I specifically
linked to the Space Power Facility in my original comment!
The "materials science" problem I call out is in the tube's
lateral thermal expansion.The best solution I've come up
with for that is to take a regenerative rocket engine [1]
and make it a tube. Pumping fluid in spirals along
kilometers of a vacuum tube isn't easy, but it isn't as
hard as trying to invent a material that won't deform when
the top gets hotter than the bottom, or the east side gets
hotter than the west.[1]
https://en.wikipedia.org/wiki/Regenerative_cooling_(rocket)
sbierwagen - 3 hours ago
>The "materials science" problem I call out is in the
tube's lateral thermal expansion.I admire your method of
argumentation.The comment I replied to said nothing at
all about thermal expansion. Your original comment, which
I wasn't replying to, was mostly strange references to
pressure ratios, and a single line about thermal
problems, with no numbers cited. In that comment you did
link to the Space Power Facility... as an argument
against Hyperloop One! You did something similar
downthread: https://news.ycombinator.com/item?id=15459777
But by asserting that you addressed the problem in your
original comment, you make the person you're arguing with
look like a bully, without having to actually address
their points. Very efficient.>The best solution I've come
up with for that is to take a regenerative rocket engine
[1] and make it a tube. Pumping fluid in spirals along
kilometers of a vacuum tube isn't easy, but it isn't as
hard as trying to invent a material that won't deform
when the top gets hotter than the bottom, or the east
side gets hotter than the west.Using the phrase
"regenerative cooling" in this context is another
headscratcher. Regenerative cooling in rocketry is
running propellant through channels in the nozzle, then
either dumping it overboard, using it to power a gas
generator, or burning it in the rocket. It's a great way
to get rid of megawatts of heat.None of these things
would be useful for a hyperloop tube? You don't want to
run kerosene/liquid oxygen/hydrazine/whatever through a
cooling jacket then dump it on the ground, you don't need
a gas generator for anything, and there's no way to feed
the heated propellant to the actual hyperloop car. And if
you could, you wouldn't want to, since if you combusted
it in the car it would just dump the exhaust in the tube,
killing the vacuum.Presumably active cooling of a
hyperloop tube would use a closed refrigerant cycle,
which has little to do with regenerative cooling, besides
the idea of cooling channels.Talking about regenerative
cooling in this context isn't wrong, exactly, it just
betrays a rather shallow understanding of the problem at
hand, as seen in your first comment.
JumpCrisscross - 3 hours ago
> Regenerative cooling in rocketry is running propellant
through channels in the nozzle, then either dumping it
overboard, using it to power a gas generator, or burning
it in the rocket"Regenerative cooling" is a rocket term.
It came to mind because I used to be an aerospace
engineer. There's no requirement in the definition of
regenerative cooling for the coolant to be dumped.>
Presumably active cooling of a hyperloop tube would use a
closed refrigerant cycleI don't think one can just
presume that. You've already got lots of pumps for
pumping air. Given (a) the seal on the tube will be
periodically broken (for entry, exit and maintenance) and
(b) a safety factor, you'll have more pump capacity than
you'll need. Filtering and then compressing atmosphere,
running it through a heat exchanger, and then letting it
expand through the cooling channels before dumping it
doesn't seem obviously worse than having kilometers of
refrigerant running around.> which has little to do with
regenerative cooling, besides the idea of cooling
channelsSee above. Also, I assumed if you did this you'd
use it to boost SpaceX's nozzles' economies of scale.
sbierwagen - 2 hours ago
>"Regenerative cooling" is a rocket term. It came to mind
because I used to be an aerospace engineer. There's no
requirement in the definition of regenerative cooling for
the coolant to be dumped.?Regenerative cooling in
rocketry uses propellant. Propellant is always dumped
overboard, because it's propellant.Please show me a
rocket that uses closed loop cooling of the rocket
nozzle.>Filtering and then compressing atmosphere,
running it through a heat exchanger, and then letting it
expand through the cooling channels before dumping it
doesn't seem obviously worse than having kilometers of
refrigerant running around.My turn to be pedantic about
definitions: this sure sounds like closed loop cooling to
me! The working fluid is air, you draw it from a big
reservoir, (the atmosphere) cool something with it, then
return it to the reservoir. (Something you can't do with
open-loop regenerative cooling of a rocket nozzle, since
the coolant gets burned at the end of the cycle)However,
maintaining the air dryers and replacing the filters
sounds like it wouldn't be any cheaper than conventional
phase-change cooling, and having to build custom
vacuum/compressor pumps for the hyperloop project is
going to be more expensive than buying COTS vacuum pumps.
JumpCrisscross - 2 hours ago
> Please show me a rocket that uses closed loop cooling
of the rocket nozzleThe most famous one is the under-
development SABRE [1], which includes a closed-loop
helium cycle. For cryogenic rockets, closed-loop cooling
of the nozzle has been explored [2] to avoid hydrogen
embrittlement and oxidation of the nozzle channels, as
well as to simplify plumbing.In any case, we've devolved
into arguing semantics.> My turn to be pedantic about
definitions: this sure sounds like closed loop cooling to
me!I was figuring on dumping the air once done versus
worrying about a reservoir. That said, I haven't done any
math on the benefits of saving the return piping (and
reservoir cost and maintenance) versus using something
traditional.> maintaining the air dryers and replacing
the filters sounds like it wouldn't be any cheaper than
conventional phase-change cooling, and having to build
custom vacuum/compressor pumps for the hyperloop project
is going to be more expensive than buying COTS vacuum
pumpsFair enough. As you observe, it's a problem I
haven't seen a suitable solution to (apart from burying,
which trades the thermal problem for, in my view, the
better water management problem and the scarier land-use
problem.)[1]
https://en.wikipedia.org/wiki/SABRE_(rocket_engine)[2] ht
tps://www.google.com/patents/US3516254?dq=closed+loop+roc
k...
sbierwagen - 2 hours ago
>The most famous one is the under-development SABRE [1],
which includes a closed-loop helium cycle.From the linked
article:>>The 'hot' helium from the air precooler is
recycled by cooling it in a heat exchanger with the
liquid hydrogen fuel.It's open-loop regenerative cooling,
with helium as an intermediate coolant. The heat still
ends up in the propellant, which gets dumped overboard.
Not closed-loop.That patent also specifies a heat
exchanger to the propellant tank.>I was figuring on
dumping the air once done versus worrying about a
reservoir.A poorly telegraphed joke. The atmosphere,
here, is the reservoir. I have edited my comment.
hwillis - 3 hours ago
How about wrapping the tube in insulating foam and using
peltier modules to regulate temperature. Or even using
double walled tubes. It would not be challenging to
regulate the temperature, but nobody talks about it
because it doesn't even seem necessary.
JumpCrisscross - 3 hours ago
> How about wrapping the tube in insulating foamAt that
point why not just bury it? It swaps the thermal problem
for the water problem, but we know how to build tunnels.
schiffern - 2 hours ago
>At that point why not just bury it?Because foam is
cheaper? A nice K.I.S.S. solution.Having seemingly solved
this thermal expansion problem "in the same category of
problems separating us from a space elevator," I'll be
expecting The Fountains of Paradise to come true soon. ;)
JumpCrisscross - 2 hours ago
> We seem to have solved this thermal expansion problemI
guess I'll have to telegraph my buddies in Hawthorne and
at NASA :).Joking aside, no, foam doesn't solve the
problem. You'll still have flexing. This is one of the
limits on how long you can have a launch tank on the pad.
Imperceptibly small flexing, but of the kind that weakens
every metal we know.
hwillis - 4 hours ago
> We didn't pump air into the lunar module from the Moon. We
carried it from Earth pre-pressurized. Unless you're
proposing we build and seal the Hyperloop tubes in space
before bringing them down, the analogy isn't appropriate.It
absolutely is appropriate, since the module was emptied and
filled each time the astronauts left.> Modern nuclear attack
submarines collapse around 730m. Since for "every 33 feet
(10.06 meters) you go down, the pressure increases by 14.5
psi," we're talking about water pressure of about 1,000 psi
or about 72 atm.Yeah- so building a hyperloop is structurally
as complicated as building a tube that sits 33 feet under
water. Hardly sounds complicated when put like that.
thearn4 - 5 hours ago
Some colleagues of mine also did a short feasibility assessment
of the original white paper, and came to some similar
conclusions. The propulsion system also made some assumptions
about compressor performance that seemed too optimistic compared
to existing turbomachinery.That said, I have not followed closely
enough to know if the hyperloop startups out there are following
the original conception or if it has significantly evolved or
not. I hear that they've ditched the compressor altogether, but
that's got to have a pretty big impact on expected speeds.
JumpCrisscross - 5 hours ago
> Some colleagues of mine also did a short feasibility
assessment of the original white paper, and came to some
similar conclusionsLikewise. It sounds like above-surface (on
Earth) is probably unfeasible given (a) security and (b)
thermal concerns.For security, we just contemplated debris from
the track (or a bullet from an errant rifle) puncturing the
tube. Hyperloop One is testing an 3.3m diameter and 500m long
track [1]. That's 4,276 cubic meters [a]. "At sea level and at
15 ?C air has a density of approximately 1.225 kg/m3" [2]. The
air in the Hyperloop One test track thus weighs about 5,200
kg.If we use the Hyperloop's original design spec [3], a
puncture means air on one side at 1 atm expanding into the
space on the other at 1/1,000 atm. This simplifies to a wall of
air moving at just below the speed of sound. Since the speed of
sound is about 330 m/s [4], the end of the tunnel will could
hit with a pulse with about 140 megajoules of energy [b].
That's the energy in about 30 kg of TNT [5][c].> I hear that
they've ditched the compressor altogether, but that's got to
have a pretty big impact on expected speedsIt currently sounds
like a vactrain [1] with magnetic levitation [2].[1]
https://arstechnica.com/cars/2017/03/hyperloop-one-shows-
pho...[a] pi * (3.3 / 2) ^ 2 * 500[2]
https://en.wikipedia.org/wiki/Density_of_air[3] http://www.spac
ex.com/sites/spacex/files/hyperloop_alpha-201...[4]
https://en.wikipedia.org/wiki/Speed_of_sound[b] (1/2) * (5200 /
2) * 330 ^ 2[5] https://en.wikipedia.org/wiki/TNT_equivalent[c]
(140 * 10^6 / 4.184 * 10^9) * 10^3[1]
https://en.wikipedia.org/wiki/Vactrain[2]
https://en.wikipedia.org/wiki/Maglev
dnautics - 4 hours ago
"a wall of air moving at the speed of sound"What? Particles
moving in through a hole against vacuum will usually be
travelling at a distribution of speeds dependent on ambient
temperature, usually a boltzmann distribution. It will not
be a wall, but rather a gradient.It's also not so much a
maglev as an inductrack, which has only really become
possible recently since it's come off-patent.
JumpCrisscross - 4 hours ago
> What? Particles moving in through a hole against vacuum
will usually be travelling at a distribution of speeds
dependent on ambient temperature, since T = v_rmsA proper
answer merits CFD. Barring that, sure, one can adjust for
the velocity distribution [1] and the fact that a vena
contracta [2] will reduce initial flow rates.I used 330
m/s, the speed at 0 ?C (which is generous since these
tracks will likely be operating in hotter conditions),
which one will observe is around the molecular velocity of
oxygen or nitrogen.[1] https://chem.libretexts.org/@api/dek
i/files/68415/BolzDist-M...[2]
https://en.wikipedia.org/wiki/Vena_contracta
schiffern - 4 hours ago
sigh another "deadly wall of air" theory ala Thunderf00t?
Hasn't this been debunked already?"A little bit of physics is
a dangerous thing."* A bullet or piece of debris would likely
leave a hole much smaller than the diameter of the tube. A
breach 1/10th the diameter of the tube will admit 1/100ths as
much the air.* Even if there was a whole-tube breach, the
"wall of air" will rapidly slow down and smear out into a
gradual pressure rise due to friction with the tube walls.
Pipes are not lossless! Within 5 km friction will have the
air moving at highway speeds. So if you're so close that you
can be killed by the air blast, you're so close that the pod
can't brake before hitting the whole-tube breach (bad). In
other words, "deadly pressure waves" don't increase your odds
of dying beyond that of a regular "derailment" event.* In the
event of a breach (whole-tube or otherwise), sensors in the
track will signal all the pods to stop and the tunnel to
undergo emergency re-pressurization. So any "wave" won't get
far.
JumpCrisscross - 4 hours ago
> ala Thunderf00tJust watched one of his videos on this--
interesting and thank you for the pointer. Agree with you
on his overstating the deadliness of pressure pulses. 30 kg
of TNT is a lot of energy, certainly enough to knock your
infrastructure out of commission for a couple days. The
"everyone dies if the tube is punctured" argument is
hyperbolic, though.The materials science problem is the
thermal expansion. And not the longitudinal one that
Thunderf00t mentions. It's the transverse expansion. If
these are above ground, the top will heat up relative to
the bottom. That's a nasty problem to solve while
maintaining the structural integrity to keep a giant vacuum
with speeding capsules in place.
hwillis - 3 hours ago
> It's the transverse expansion. If these are above
ground, the top will heat up relative to the bottom.
That's a nasty problem to solve while maintaining the
structural integrity to keep a giant vacuum with speeding
capsules in place.Right... you can probably solve that
with a bucket of white paint. Worst case you cover it
with an aluminum shield- aluminum does not absorb
infrared radiation and will reflect 99.9% of ambient
heat. Since the proposal included covering large
sections of the tube in solar panels that isn't even a
significant change.
JumpCrisscross - 3 hours ago
> you can probably solve that with a bucket of white
paint. Worst case you cover it with an aluminum shield-
aluminum does not absorb infrared radiation and will
reflect 99.9% of ambient heatIt's, unfortunately, harder
than this. It's a similar problem to the ones we dealt
with regarding rockets, standing fueled, on a pad. Both
methods you propose were tried. The solution is to (a)
paint it and (b) launch before the gradient becomes too
big.The stresses on the Hyperloop tube, when a capsule is
rushing through it while it's containing a near vacuum,
are comparable to those on a rocket nearing max Q [1].
The difference is with a rocket we take great care to
maintain symmetry. With the Hyperloop, that isn't an
option. That persistent asymmetry is what makes it a
difficult materials problem, particularly if we're using
any known metals (even wonderful light and thermally-
conductive aluminium).[1]
https://en.wikipedia.org/wiki/Max_Q
hwillis - 3 hours ago
Dude, what. That's bullshit, and the size difference
will be on the order of dozens or low hundreds of
microns. Not only that, but the distortion will be
spread evenly across the tube because it's a tube.
You're just asserting that putting the tube in shadow
will somehow not block heat from the sun.I'm also not
sure you understand what I'm saying about an aluminum
shield? Aluminum has an emissivity coefficient of .04.
Thermal conductivity has nothing to do with it since it
isn't touching the tube. It's purpose is just to not re-
radiate infrared onto the tube.
kbenson - 2 hours ago
I think what we have here is someone applying a known
problem and solution space for one industry (rocketry) to
another (civil engineering). A large vertical tube that
needs to move quickly and under great stress may not
allow for the same solutions that apply to a large
horizontal tube that is relatively static.Fixing a large
enough solar shield above a rocket hundreds of feet in
the air which has to get out of the way quickly before
the rocket launches has very different requirements than
fixing a shading structure above a vertical static
structure a few tens of feet in the air. I'm not sure
how this problem was solved in rocketry is necessarily
indicative of how hard it is to solve in other
circumstances.
JumpCrisscross - 1 hours ago
> I'm not sure how this problem was solved in rocketry is
necessarily indicative of how hard it is to solve in
other circumstancesVery fair. The advantage a rocket has
is you choose when it's rolled out. You don't have to
design for the worst weather because you can always
hide.You can't do that for a static structure. The
Hyperloop is an attempt to marry the challenges of
rocketry to the standards of civil engineering. The
advantage is you don't have to think about aerodynamics,
which is good, because air is the worst. (You also get
civil-engineering budgets.) The bad is you can't hide
from the edge cases.If you want to grapple with this
problem live, rent (or borrow) a thermal camera and make
a model. Aluminum or tin foil would probably work for
something on the window. I've only done this upright, to
simulate storing an unfuelled vehicle outdoors in "ready-
to-launch" mode, but you'll run into similar problems
with a horizonatal configuration. At first, the shade
works. Then thermals develop. You can foam it, and that
looks like it works for a few days. Then someone
instruments the inside and, lo and behold, hot spots.
Turns out foam doesn't really help with heat that recurs
in the same place, day after day. (Our solution: slowly
rotate it.) You could completely isolate the tube, which
is what NASA does in its vehicle assembly building [1],
but at that point you might as well (a) bury it or (b)
have a fleet of Concordes flying on loop, because either
will be cheaper.I'm not saying it's impossible. But it's
much harder than the pressure problem, which is itself
hard to get economical. If you want the tube above
ground, I don't think it works with existing materials.
My criticism of the Hyperloop One project is they didn't
bother solving these issues with models. (Note: this is
how Elon did it with the Falcon 1.) Instead, they decided
to build a maglev track.[1]
https://en.wikipedia.org/wiki/Vehicle_Assembly_Building
kbenson - 1 hours ago
So, to make sure I understand the problem correctly, you
expect thermals to develop under shaded portions that
still cause heat, and that to affect the structure's top
and bottom heat differential to a degree that it would
still cause problems? Is this different than oil
pipelines because of the low pressure and lack of a heat
transferring medium to even the temperature of the tube?
I'm trying to figure out how this would affect a proposed
hyperloop system, when it seems sufficiently solved for
other above ground pipeline systems.I can see relative
size, inside medium, building material differences,
shading structures and acceptable tolerances all
affecting the outcome one way or the other, but I'm not
sure to what degree each one would affect the outcome, so
I'm not sure if it's actually as hard as you make it
sound or whether a solution is known and achievable.
JumpCrisscross - 42 minutes ago
> Is this different than oil pipelines because of the low
pressure and lack of a heat transferring medium to even
the temperature of the tube?Most hydrocarbon pipelines
run HTHP: high temperature, high pressure. This keeps
their contents viscous. That, in turn, means heat
emanates relatively uniformly from inside the pipe. For
pipelines subjected to asymmetric expansion (e.g. when
starting up or shutting down), they "walk"."Walking
behaviour occurs as the pipeline is heated, and expands
asymmetrically, until the point when pipeline expansion
is fully mobilised. Expansion is ?fully mobilised? when a
virtual anchor forms near the centre of the pipeline. The
virtual anchor is then stationary, while pipe to each
side expands away from the anchor as the temperature
continues to rise. Once expansion is fully mobilised,
walking ceases for that cycle." [1] As long as it walks
laterally, pipeline owners tend to be fine with itThe
solution to walking is typically laissez faire (taking
care to ensure the deformation occurs laterally, i.e.
side to side, versus sticking a butt up into the water.)
Needless to say, this isn't an option for the
Hyperloop.Granted, the contents of these pipes operate at
130? to 170? C. They're also narrower, resist a smaller
pressure differential, face fewer such asymmetric events
and don't face the stress of capsules periodically
whizzing past inside them. Our tube won't displace by
meters. Its displacement, moreover, won't be problematic
on day one. But over time it will critically weaken known
materials. Big, dynamically mechanically stressed, close
to vacuum and above ground is hard.[1] https://www.resea
rchgate.net/profile/David_Bruton/publicatio...
dnautics - 3 hours ago
yeah Thunderf00t's hyperloop video is dumb, moreover, yes
a lot of pressure can cause a tiny metal bearing to
punch through a glass tube but the net force distributed
over a mass scales with the size of the object squared,
but the mass scales with the size of the object cubed.
So the effects of pressure on a tube 2 meters wide is
going to be far less dramatic than one 2 cm wide.
DiThi - 3 hours ago
> If these are above ground, the top will heat up
relative to the bottom.The heat will quickly conduct to
the other side. It's one of the main reasons for choosing
steel. Add white paint to that (or solar panels) and
you'll have reduced heat absorption to a minimum.
JumpCrisscross - 3 hours ago
> The heat will quickly conduct to the other sideI take
it you haven't had the pleasure of watching carefully
machined cylinders buckle in the Arizona sun :). White-
painted aluminum and shaded, mind you.Those were
structures on the order of meters. These problems become
nasty with scale.
matt4077 - 5 hours ago
Weren't there published papers by NASA scientists proving,
without a doubt, that it's impossible to construct a booster
rocket with the structural stability to return to earth?I'm
willing to give this guy the benefit of the doubt considering
his track record. It's also instructive to read the comments
when the original Hyperloop idea was published. Even the people
thinking Musk would fail were in the minority, because everyone
was certain he had no plans of even trying.
JumpCrisscross - 4 hours ago
> Weren't there published papers by NASA scientists proving,
without a doubt, that it's impossible to construct a booster
rocket with the structural stability to return to earth?No.
Going back to the 1960s, re-usable two-stage configurations
were being drafted [1].[1] http://papers.sae.org/640297/
yahna - 4 hours ago
But I thought this all came to our god king in a dream.
hwillis - 4 hours ago
oh stop. People are excited about reusable rockets, a
mainstay of science fiction since the beginning. Why do
you have to be a wet blanket? "Elon Musk didn't think of
reusing rockets, and he didn't personally build them, and
he doesn't have a degree in rocketry!" You're fighting a
Quixotic battle against a strawman.
yahna - 3 hours ago
I think reusable rockets are cool, and I think musk is
impressive.I'm just not a member of the cult of Elon. I
think he follows a path of aim impossibly high, be happy
with getting pretty far. People instead take it as "he's
literally going to do everything".
hwillis - 3 hours ago
I see many more people talking about "the cult of Elon"
than people who actually think he's literally going to do
everything.It reminds me way more of the nickelback is
terrible thing. It's more of a meme than the actual
subject. It's fun to feel like a member of the
enlightened in-group that doesn't follow Elon Musk like
sheep. All those dumb people that think GM will go
bankrupt next year.
kbenson - 4 hours ago
The worst thing about the Hyperloop concept is how it takes
different smart people with slightly different assumptions about
what is being described, how it should work, and how it does work
in the fields they are familiar with or experts in and the other
fields they are only conversant in, and turns those people into
rabid defenders of their own calculations that somehow lose the
ability to reassess where mistakes might have been made. I'm not
sure how or why this happens, because as far as I know none of
this is theoretical science, it's just a matter of applying the
principles accurately (which seems to be the sticking point).
For example, here's a whole playlist of people arguing over the
physics of it, which does devolve into name-calling at points.[1]
There appears to be good science involved in the assessments
though, but could be said for the most part about both parties.
The interesting parts are where people step outside their areas
of expertise and their unfamiliarity with the application of the
principles causes mistakes.1:
https://www.youtube.com/playlist?list=PLSPi1JFx4_-Gz0Fm0qq2K...
Robotbeat - 5 hours ago
Wait, who said that they need to compress the air all the way to
Earth pressure?None of your critique makes sense without that
assumption, and nowhere in your post do you say where that comes
from.
schiffern - 5 hours ago
> Wait, who said that they need to compress the air all the way
to Earth pressure?No one. The Hyperloop alpha paper explicitly
contradicts this assumption on page 18, where the flow diagram
gives the compressor input at 99 Pa and the output at 2.1 kPa
(a 21:1 pressure ratio).http://www.spacex.com/sites/spacex/file
s/hyperloop_alpha-201...
JumpCrisscross - 5 hours ago
> The Hyperloop alpha paper explicitly contradicts this
assumption on page 18, where the flow diagram gives the
compressor input at 99 Pa and the output at 2.1 kPa (a 21:1
pressure ratio)One standard atmosphere (atm) is defined at
over 100,000 Pa [1]. The 21:1 pressure ratio in Figure 11 on
page 18 is for the "passenger plus vehicle capsule" [2]. I'm
talking about the tube.Going from 99 to 2.1 isn't hard. Going
from 100,000 to 100 and then keeping it there is.[1]
https://en.wikipedia.org/wiki/Atmosphere_(unit)[2] http://www
.spacex.com/sites/spacex/files/hyperloop_alpha-201...
Robotbeat - 4 hours ago
But that's no challenge at all. You're just describing a
usual vacuum pump. And just a single-stage roughing pump
(Harbor Freight, anyone?) can get down to less than 1
Pascal, so 100Pa is a piece of cake. That's only needed for
slight leaks in the tube, not for the pod itself.Keep in
mind that the absolute pressure difference is far less for
Hyperloop than for a typical natural gas pipeline, and yet
the latter can keep leaks to an absolute minimum in spite
of thermal expansion, etc.
JumpCrisscross - 4 hours ago
> You're just describing a usual vacuum pumpScaling is
hard. The largest vacuum chamber we've built is a
fraction of the size of the proposed Hyperloop. It was a
very, very hard problem [1]. It's expensive, sucks up
loads and loads of power and needs lots of thermal
management, structural reinforcement and vacuum-off
maintenance.> Keep in mind that the absolute pressure
difference is far less for Hyperloop than for a typical
natural gas pipelinePipes are pressurized from the
inside. See my comment from elsewhere in the thread on
why vacuums are different [2].All this said, I generally
agree with you. I don't think building a giant vacuum is
beyond current technological capability. I do think
building one structurally sound and thermal-expansionwise
stable enough to carry passengers at high speeds is.[1] h
ttp://teamcorporation.com/images/technical_documents/Spac
e-...[2] https://news.ycombinator.com/item?id=15459873
schiffern - 3 hours ago
>The largest vacuum chamber we've built is a fraction of
the size of the proposed Hyperloop. It was a very, very
hard problem [1].Do we really have to say that a long
extruded tube that only has to maintain low vacuum is a
lot simpler than the SPS?SPS: big thing made up of many
custom one-off parts that runs at 1/380,000,000ths of an
atmosphere and can blast test articles with intense
simulated sunlight.Hyperloop tunnel: big thing made up of
many identical parts that runs at 1/1,000ths of an
atmosphere.>It's expensive, sucks up loads and loads of
powerI think they know that, don't you? There's no line-
by-line breakdown, but the paper allocates $260 million
for the station+pumps and 21 MW for electricity
consumption (pumping, accelerating pods, and charging pod
batteries).>needs lots of thermal managementI agree that
you need it, but what specific problem do you see?>Pipes
are pressurized from the inside. See my comment from
elsewhere in the thread on why vacuums are different
[2].You said a soda can is stronger when pressurized from
the inside. That's true, but the obvious solution is to
make it thicker than a soda can. :) The paper calls for
0.8-1.0 inch thick steel, which my math says is more than
adequate.
JumpCrisscross - 3 hours ago
> I think they know that, don't you?Who's they? Hyperloop
One? No--they've just punted the "hard" stuff to the end.
(Kind of like the Wright Brothers designing the seats of
their plane before getting it flying. Oh look! [1])Elon
Musk? Yes--I do. That's why he's waiting.> what specific
problem do you see?The top heats up and the bottom
doesn't.> The paper calls for 0.8-1.0 inch thick steel,
which my math says is more than adequateAdding mass adds
strength while increasing the time the structure takes to
reach thermal equilibrium. The thermal gradient isn't
itself a problem. But if you look at the forces necessary
for the materials in question to tear themselves apart,
and then consider their thermal coefficients of linear
thermal expansion, you can derive a maximum tolerable
thermal gradient given the size of each tube segment
(we'll assume the problem of reticulating vacuum seals is
solved).When you solve for strength, you get too much
material for the system to reach equilibrium before
inclement weather either causes (a) the structure to
buckle, laterally or (b) the outside of the tube to start
shearing itself from the cooler inside.When you solve for
thermal stresses, you lose your strength. Microbuckling
and microfracturing may not seem like a big deal, but it
is when you're talking about 1 standard atmosphere
bearing down from the outside with a capsule swinging
about on the inside.We need a strong material that either
(a) conducts heat really well or (b) doesn't change shape
when asymmetrically heated. We don't have something that
meets those requirements yet that we can manufacture at
scale.[1] http://www.stacksmag.net/2013/10/space-virgin-
galactics-rich...
schiffern - 2 hours ago
>No--they've just punted the "hard" stuff to the
end.Citation needed. The link provided gives no support.I
would be interested in seeing your calculations on the
thermal side. An ANSYS multiphysics simulation (the
software SpaceX uses) would show the problem, no?SpaceX
has already built and used a mile-long, 11' diameter
vacuum tube in Southern California, which would seem to
put this matter to rest (the proof is in the pudding,
after all).
JumpCrisscross - 1 hours ago
> An ANSYS multiphysics simulation (the software SpaceX
uses) would show the problem, no?Yes. But SpaceX !=
Hyperloop One.> SpaceX has already built and used a mile-
long, 11' diameter vacuum tube in Southern California,
which would seem to put this matter to rest (the proof is
in the pudding, after all)I'll go ahead and predict that
the strength of that tube will have materially decreased
after 1 year in the elements. I'll even posit that will
occur independent of rusting, which appears to have
unfortunately taken place, due to the formation of
microfractures within the metal due to repeated lateral
thermal flexing. That said, this was a demo track. It
wasn't designed to withstand one standard atmosphere
while whizzing fast, heavy capsules inside it for years
on end.
hwillis - 4 hours ago
That vacuum chamber has two sets of fifty foot tall
doors. The hyperloop is an inch-thick welded steel tube.
Pinholes are trivially detected by ultrasonic testers.
There are no leaks. Even hydrogen and helium would take
centuries to diffuse inside. The only problems are
sealing the ends, which are a couple meters wide.The
hyperloop as written was very challenging, but the
engineering aspects are not. The practical building
(grinding the inside, transporting the tubes, etc.) are
significant. The financing is insane. The theory is not
even particularly hard, much less at the level of a space
elevator.
schiffern - 4 hours ago
Axial compressors aren't the only compressor design. Rotary
vane compressors have no problem with those pressures.The
internal pressure was chosen explicitly because it was easy
to maintain with simple, single stage mechanical vacuum
pumps (see Figure 13 on page 22). Heck, the first result on
Amazon for "vacuum pump" goes down to 5 Pa.
https://www.amazon.com/dp/B012CFTYX4/Compare the Hyperloop
to true "vacuum train" designs, which need to run at
1/1,000,000th of an atmosphere to mitigate sonic booms (an
alternate way to get around the Kantrowitz limit). This
requires multi-stage pumping with mechanical roughing,
followed by turbomolecular pumps and cryopumping. That
1000x harder vacuum takes 1000x as much pumping power (not
because the differential pressure is meaningfully
different, but because you expel 1000x less air per
stroke).
kegan_myers_asy - 4 hours ago
VH1 rises again.
Apocryphon - 2 hours ago
I guess one of the silver linings of living in a "cyberpunk neo-
Gilded Age but with better UX than '80s cyberpunk" world is that
dueling tech magnates might accidentally craft something that could
help society.