Guest Post by Willis Eschenbach
A recent article has discussed how Elon Musk’s “Boring Company” has raised $113 million dollars in startup capital. This is the company Musk formed to drill the tunnels for his proposed “Hyperloop” transportation system. It has encouraged me to discuss some of the engineering and practical problems with his LA-to-San Francisco Hyperloop proposal. The Hyperloop concept involves a windowless “pod” traveling at just below the speed of sound in a tube with all the air evacuated from it. There’s a reasonable description of the Hyperloop at Wikipedia and a much more hyper description at their website. It all sounds so good and so 21st Century, what’s not to like?
In no particular order, the problems with the Hyperloop include:
Vacuum: The Hyperloop requires a near-perfect vacuum to run at the proposed speeds. It has been tested with a one-kilometer long test track. The test track was billed as the “second largest vacuum chamber in the world”, after the vacuum chamber of the Large Hadron Collider.
But the LA-to-SF route is 615 km. This is a huge, almost unimaginable step up in size and problems. Consider that although the LHC is carefully internally braced to keep the pressure from collapsing it, they’ve said the Hyperloop tube will be a 1″ thick steel pipe supported on pillars. There’s no way to brace it internally, the pod has to run through the middle. The day/night expansion on that much steel would be very large, and the expansion joints for that use have never been built. In addition, atmospheric pressure on the tube would be about ten tonnes per square metre … and there’s a 15-tonne “pod” running through it, putting large stresses on all bends and joints.
This means that if the vacuum is breached for any reason, say a car runs into one of the pillars, or some fool shoots an high-powered rifle round at an expansion joint, or terrorists place even a small bomb anywhere along the length of the route, or a small thermally driven “kink” in the pipe develops, or heck, a ubiquitous California earthquake, everyone in the tube would die from the instantaneous deceleration. Here’s what happens to a railroad tank car with ~ 1/2 inch (12 mm) steel walls when it is not properly vented … it collapses from nothing more than the atmospheric pressure, and that is without a near-perfect vacuum inside.
Ooogh … you don’t want to be inside if that happens.
Thermal Expansion II: A difference of only 3°C from the top to the bottom of the tube will cause differential expansion of about 25 metres from top to bottom of the pipe over the length of the SF-to-LA run … very no bueno. The pipe will tend to either lift out of its supports or bend at the expansion joints … joints with a 15-tonne pod going through them at 750 mph.
Energy: The pumps necessary to keep the tube evacuated will be quite large. Remember that each pod has to be air-locked in and out at every station. The energy cost of this constant pumping at each station is unknown, but definitely not small.
Pod Integrity: The pod will be in near total vacuum. Airplanes fly at about 33,000 feet (10,000 m). The pods will be traveling at the equivalent of 50,000 feet (15,000 m). This means that if there is the slightest leak, there will be catastrophic decompression and everyone in the pod will likely die.
Passenger Throughput: This is likely the biggest problem with the Hyperloop—for all of its speed, it is remarkably slow at actually moving people. Consider the competing technologies. Freeways typically carry 2,000 cars per hour per lane, that’s maybe 3,000 people per lane per hour. So a four-lane freeway of the type common in California will carry about 12,000 people per hour.
A subway with three-minute headways between cars will carry about 36,000 passengers per hour. The proposed and insanely expensive high-speed “Bullet Train To Nowhere”, which Governor Moonbeam is trying to build fro LA to San Francisco will carry on the order of 12,000 people per hour.
Now, Musk claims that a pod will depart SF-to-LA and LA-to-SF every 30 seconds carrying 28 people per pod. That’s the best case, and it’s only 3,300 passengers per hour.
But wait, as they say on TV, there’s more. In general, you don’t want to run cars, trains, subway cars, or Hyperloop pods so close together that they can’t stop safely in case of an emergency to the car ahead. Humans can only sustain about half the force of gravity, called “0.5 G”, for safe deceleration. Musk says the cars will be traveling about 760 mph (1225 km per hour). At that speed, it will take around 75 seconds at 0.5 G to decelerate to a stop. So the inter-pod time has to be at least 80 seconds … and that means passenger throughput drops to 1,260 passengers per hour.
And the bad news doesn’t end there. The whole system can only run as fast as the slowest segment of the Hyperloop, and that’s the stations. Remember, at every station, the pods need to be depressurized. Then passengers need to get on and get off, and the pods need to be repressurized. Musk says that up to three pods will be in the stations at once. So that means that depressurization, passenger unloading and reloading, and re-pressurization need to take place in about two and a half to three minutes … and you better hope that nobody forgets anything on a pod and has to go back to get it, or the entire system slows down.
Net result? The Hyperloop will make less than half the difference in passengers transported, and likely much less than half the difference, that would be made by adding a single lane to the LA to SF freeway …
In Short: The Hyperloop is extremely dangerous to passengers, vulnerable to a host of problems, will kill everyone inside if even a small failure happens, moves a very small number of people, and oh, I forgot to mention … what happens if the power fails, as happens these days in California all the time because of our insane renewable mandates pushed by our less-than-genius Governor, Jerry Brown. Care to think about being stuck inside a windowless pod inside a steel pipe on a hot day in the California desert, with no way to escape?
And all of that for less gain than adding a single lane to the freeway … but there is one thing we can be sure of.
Elon Musk will get even richer from government subsidies for his latest whiz-bang proposal … truly, the man is a subsidy artist. Where most of us can see nothing but government boondoggle and waste, he sees personal wealth.
My best to all,
w.
THE USUAL: When you comment please quote the exact words you are discussing, so that we can all understand your subject. In addition, rather than telling me or anyone that we are doing something wrong, please demonstrate the right way to do it.
Well so long as tax payers money is not involved!
Cheers
Roger
http://www.thedemiseofchristchurch.com
Willis,
May I add a comment?
Copy & Paste:
“Consider that although the LHC is carefully internally braced to keep the pressure from collapsing it, they’ve said the Hyperloop tube will be a 1″ thick steel pipe supported on pillars. There’s no way to brace it internally, the pod has to run through the middle. The day/night expansion on that much steel would be very large, and the expansion joints for that use have never been built. ”
Thoughts –
a 1″ wall-thickness pipe looks insufficient. Granted and agreed.
What about a 3″ wall thickness pipe? Or more
More costs – sure, but if the taxpayer is paying – I fail to see a real objection . . . . .
Joints – oil tankers have used – for more than fifty years, P/E Joints.
Again, to upgrade to <2 millibars up to Californian pressures and temperatures might add to the cost. A bit.
Thermal expansion.
Surely shading [with the shades painted white], and then enclosing and air conditioning the whole LOOP – no HYPE here! – will prevent much of the obvious problem that you highlight – here: –
Copy & Paste – again:
"Thermal Expansion II: A difference of only 3°C from the top to the bottom of the tube will cause differential expansion of about 25 metres from top to bottom of the pipe over the length of the SF-to-LA run … very no bueno. The pipe will tend to either lift out of its supports or bend at the expansion joints … joints with a 15-tonne pod going through them at 750 mph."
Anyway – as long as the Californian taxpayers stump up, I suggest many of the problems will be solved.
May be not the throughput or safety ones – but even St. Elon [is he to be our next Pope?] cannot expect the impossible.
Can he?
Auto – not /SARC this time [albeit a tad doubtful of one or two of the Papabile's claims}
Not an argument. The TGV has derailed at (commercial) high speed. It is safe.
(The case of the Eckwersheim accident is different.)
St. Elon, or as I call I.T. Barnum the 21st century conman…
“The earthquakes and terrorism are more like arguments. But are they more arguments than on ordinary rails?”
I’d say yes because trains on ‘ordinary’ rails don’t travel at 760mph in a complete vacuum
Thermal expansion can be traded with longitudinal pressure / drag, as is done on modern railways.
Thermal expansion turns into some thermal pressure. The earthquakes and terrorism are more like arguments. But are they more arguments than on ordinary rails?
“What about a 3″ wall thickness pipe?”
External ring reinforcement on the 1″ thick wall pipe (lotsa welding). But it’s still not gonna work.
Auto,
I am well aware of the impossibilities that are apparent in this project.
The most compelling reason when I express hope that tax payer funds will not be involved, is that, if this remains a private venture, it will likely die a natural death when the money runs dry and investors see the light – preferably before anyone gets hurt.
However, if governments using tax payers money get involved, the project will linger on, not only bleeding the tax payer and the economy dry, but very likely progress will be made to the point where people will actually get hurt.
Cheers
Roger
http://rogerfromnewzealand.wordpress.com
Thrillionaire.
The more I learn about Musk the less I like (from a business perspective). How does someone with so many bad ideas get $5B of US taxpayer money and become a cult tech icon figure?
Thanks for the good read Willis.
William
As much as I think the hyperloop is a really bad idea, mostly because it is not cost effective given the monumental engineer feats that must be accomplished (…and then a miracle occurs) several of the points made are not correct.
A human can survive very high g’s for several minutes. The Russian cosmonauts have endured over 23 g’s for several minutes when they make ballistic reentries while sustaining only chipped teeth (from the vibration). Of course they are in fitted seats and partially reclined. The orientation of the loading is important. We refer to the crew loading as “Eyeballs -in” when the force is pushing on their backs, or “Eyeballs-out” when the force is pushing on their fronts. The nomenclature refers to the direction you feel your eyes being pulled. Eyeballs-in is preferred.
If the pod is pressurized at 1 atmosphere (14.7 psi, 1 bar) and the tube is 0 bar then the pressure differential cannot exceed 1 bar. This would produce large stress on the shell of the pod, which is why it will probably only be pressurized to about .7 bar (11 psi) the standard cabin pressure of commercial airliners.
Aircraft have experienced rapid cabin depressurization without killing everyone instantly. Furthermore rapid depressurization will take more than a minor leak.
How long would people be able to survive in a stopped pod? Rescue could be long in coming.
should be possible to allow air in the tube on one side of the pod to move it along.
Like Brunel’s atmospheric railway. Problem there was rats eating the greased leather seals.
http://www.ikbrunel.org.uk/atmospheric-railway
Well thought out, and the fools errand well destroyed. Thanks Willis.
Obsurd. Would you put your pet hamsters in the pneumatic tube at the bank? Why the need to go so fast anyhow? A bullet train would make way more sense economically, logically, and realistically. Would be interesting to be in a quake in that contraption also.
But… but… but… this would be so COOL!
That appears to be Elon’s reaction to any “investment” opportunity.
Slightly off topic, but the Tesla 3 line is shut down again. Supposedly “planned” – funny, the employees knew nothing about it. Maybe because they are going to go unpaid yet again.
I thought the plan was to have everyone drive their cars onto a ferry, which then is closed and the ferries move very close together through the loop. What’s the need for a vacuum?
This thing has to be level or the horizontal and vertical curves need the same turning radius as a jet doing 580mph. Otherwise the inside of the car will look like the vomit comet.
The insanity is infinite.
Exactly. Slow train tracks are essentially 2D + height (with a limit on ramp angle); but fast tracks are 3D: acceleration on the vertical direction becomes relevant.
Hint: Elon Musk’s “Boring Company”. The track on pillars is a h0ax. These tracks would be almost always subterranean.
This is just the next level of
Tony Stark’s Iron Man suitElon Musk’s Ponzi Scheme.The Ponzi family kindly requests that you refrain from using our good name in reference to Mr Musk.
If it doesn’t work….they can always turn it into this….
They used to call those ‘toast racks’ in the UK. Trams pulled by horses, and you had to get out and push if the hill was too steep.
so horsepower and human power.
a hybrid 🙂
Willow Grove park?
That was the last wooden frame roller coaster that I know about; admittedly a very limited knowledge level.
I don’t remember one called cyclone there though.
Thanks. I didn’t know (or remember) that. I’ve ridden the 6-flags over Georgia coaster, admittedly several decades ago.
I had understood that insurance costs for the wooden frame roller coasters had driven them out of operation.
An obviously flawed understanding that I read in a paper published near Willow Grove.
6-Flags over Georgia still has one.
Ah, yes. Of course!
Coney Island’s older larger and much grander rides.
Coney Island
The Hyperloop almost makes Jerry Brown’s toy train look good.
This former pipeline engineer agrees fully with Willis.
If you like pretty pictures this YouTube video is good: https://youtu.be/RNFesa01llk
I find it amazing that so many smart engineers are working on Hyperloop in Nevada. They must know it isn’t practical.
Sad really…the concept is pure…the dream is admirable…but the engineering realities make it a fail at this point.
Until their pay checks bounce, why stop working on the project?
“so many smart engineers”!? You would be surprised at how recent engineering grads are woefully deficient in fundamentals. and common sense. I know several
I’ll double that!
The power of air pressure reminds me of Von Guericke’s Magdeburg Hemispheres. These were two iron hemispheres which were fitted together and then the air inside extracted to create a vacuum. The experiment, performed before Frederick the Great if I remember rightly, demonstrated that two horses could not pull apart the two hemispheres which were held together by no more than atmospheric pressure.
First demonstration was in 1654, before Holy Roman Emperor Ferdinand III in Regensburg. Some years later, the experiment was repeated for Frederick William, Elector of Brandenburg and Duke of Prussia, great-grandfather of Frederick the Great.
Within 15 years, autonomous vehicles will be able to pick you up at your home in LA and deposit you in anywhere in the SF Bay Area in 3 or 4 hours, likely at an adjusted cost of less 75 of “today” dollars.
Brown’s, brown bullet train will never be completed. Neither will the hyperloop. The economics of autonomous vehicles will change everything. It takes the same amount of time to drive to airport, fly, and leave airport.
Within 15 years California will have changed in a progressive sh.thole.
Viva Calizuela!!
Calizuela! Catchy!
15 years? Lot less me thinks
Autonomous private planes (drones with people inside) will give the FAA and other organs of the national security state fits.
And supply organ donors frequently as well?
The benefits go on and on, Pop.
Safer than cars.
Autonomous drones have a good “safety” record in the US military. Soon they’ll be used in fire fighting.
http://www.uavexpertnews.com/2018/01/autonomous-air-tanker-to-aid-in-firefighting/
But they will eliminate global warming; a reflective top surface, and we can welcome the next ice age.
RPT,
Yes, if the world’s 1.3 billion ground vehicles are replaced by an equal number of private, autonomous aircraft, then they might well enhance the planet’s albedo.
75 dollars says that won’t happen in 15 years, not even almost in 15 years.
Add a couple of decades to that estimate.
Autonomous driving is a bad joke. Like Tesla’s Autopilot, which loves to run into parked fire trucks
and crash barriers at 65MPH, followed by a battery explosion and fire.
Autonomous aircraft are the way to go for medium to long hauls, IMO. Granted, most of the world’s drones are still remotely piloted, but more and more of them are autonomous.
http://www.jpost.com/Business-and-Innovation/Tech/Israeli-firm-creates-autonomous-aircraft-that-goes-where-no-helicopter-dares-477334
To you, that is a bug. To terrorists, that’s a feature.
In fifteen years, you’ll rent a VR drone at your destination and visit from home. Not much need to move your body around when you can rent a body anywhere in the world.
Hey, you stole that idea right out of my virtual mind.
Just a note to the Bullet Train To Nowhere”, proposed for LA to San Francisco.
Bet you did not see this one coming:
To get the money Gov. Moonbeam has to make deals with other politicians. (Surprise!)
The price these pols want is for this super high tech, high speed wonder to serve their community along the way.
So we have now ended up with a high speed train which stops at every town along the way. In other words, it’s not high speed anymore.
It is a super expensive reinvention of Amtrak.
TonyL April 18, 2018 at 1:22 pm
No, I didn’t know that. As a kid I used to take the “Milk Run” train from Redding, CA, down to Sacramento. Stopped at every tiny burg along the way. It was great fun.
The good news is, now I won’t have to be nostalgic for that time …
Thanks, Tony,
w.
W. E.: ” It was great fun.”
I rode the Erie Lackawanna Railway from western PA, across Ohio and Indiana, into Chicago where, in the morning, I was catching the Santa Fe Chief.
Not much sleep time.
This was before Steve Goodman’s “City of New Orleans” song about the Illinois Central. When the song became popular via Arlo Guthrie, I felt the sadness.
Best few words: rhythm of the rails
and best line: This train’s got the disappearin’ railroad blues.
Steve Goodman was an incredible songsmith and performer.
Saw him at the Philadelphia Folk Festival before leukemia took him.
Willis, unless the passengers are expected to only travel one way in the morning and reverse direction in the afternoon, then I think two tubes should be considered. Either way, Musk’s income depends upon regular announcements of “cool” futuristic designs. Works for him.
“Good morning America how are you? Don’t you know me I’m your native son…” God that’s beautiful.
The graphic in the article shows twin tubes.
“So we have now ended up with a high speed train which stops at every town along the way.”
We call that a “Local” on the railroads I’ve worked on. 🙂
I just call it “loco.”
In places with functioning passenger rail, there are express trains that stop at major towns. If you want to go to a smaller town, you take an express to the nearest big town, walk across the platform, hang out for a while until a local shows up then take that to your final destination. Yes, that’s slow. But so is sitting in a monumental traffic jam at one of the I5-I405 merges.
The TGV makes a lot of stops between Marseilles and Lyon, but fewer from there to Paris. The distance is about 100 miles longer than LA-SF./CarteReseauTGV.jpg-page-001-5788b4353df78c09e99a19c8.jpg)
TGV is just a regular electric train (overhead) that can go fast on some segments. In the UK, a different model of TGV goes to third rail tracks too (not at high speed obviously).
ST,
Yes, it reaches top speed only on some runs, on its special tracks. But the train of Gov. Brown’s dreams will in effect be little different. Dunno if he plans a tunnel through the Tehachapis.
Willis, an aspect you haven’t mentioned is the need for linear accuracy. At the planned speed even a minor wiggle in the direction of travel will result in significant lateral (or vertical) forces as the pod makes an almost instantaneous change in direction. This raises problems for both pod guidance and passenger restraint. The structural discontinuities at expansion joints will be particularly difficult to handle. Manufacturing and putting in place the tube will be like no other pipeline job on the planet.
Further, in the event that the wall of the tube is damaged by any sort of accident or malfunction inside, it is possible that that the shape of the tube will no longer to be able to support the external pressure with the result that the tube will collapse. Without external stiffening rings or similar the collapse is likely to expand for the whole of the length of the tube at close to the speed of sound. There is no need to comment on what will happen to the passengers in the pods in the event that such a failure occurs.
If a crack starts in the pipe, the crack propagates at the speed of sound in the metal, but the pressure only drops at the speed of sound in air. That means the crack will extend to the nearest joint, which could be miles, and destroy any pods in that section.
dan, that’s true for internal pressure but failure due to external pressure is by buckling, as shown in Willis’s examp[les of the tank cars. Buckling from external pressure spreads at the rate at which the atmosphere can follow it up and for practical purposes that is the speed of sound in air. Stiffening rings at intervals will limit the buckling and will limit the distortion between rings. Longitudinal stiffeners have almost no value from the point of view of collapse under vacuum.
My original comment was based on the thought of a car running amok at high sped in which case it could inflict damage ovr a considerable length of the tube. It could also damage stiffening rings in the vicinity. This could be better or worse than a simple plane crash, according to how many cars became involved. Unlike a plane crash it would take out the whole system for a significant period of time.
‘Crack’ and ‘pipe’ seem to be the operative words for this project…..
“At the planned speed even a minor wiggle in the direction of travel will result in significant lateral (or vertical) forces as the pod makes an almost instantaneous change in direction.”
Do you reckon that crossing a number of active earthquake faults — including the San Andreas — might be a problem?
I think all of Musk’s best engineers went to SpaceX and his car company. This is what’s left.
Bankwupt…
http://www.india.com/wp-content/uploads/2018/04/Tesla-Elon-Musk.jpg
And if a compressor disk fails and pieces breech the containment vessel and one pierces the fuselage killing a passenger and de-pressurizing the aircraft it will fall out of the sky, crash and kill all on board destroying the whole crazy industry.
Or maybe some smart people will, given enough time and money, figure out how to make it work. As long as it isn’t my money, I’m fine with that.
My first thought was who in their right mind wants to be sealed inside a windowless 1-inch-thick-walled metal tube? I’m not particularly claustrophobic, but, really, … this in itself is like being buried alive within a round of ammunition that you pray will not misfire.
No, the hell, thanks!
They could put “windows” on the cars that are actually video display and project on them the illusion of looking out a window with scenery going by to help reduce the claustrophobia problem.
It would never work for me, who is very claustrophobic. I NEED to be convinced that I am NOT enclosed at all to function.
I had to be put on conscious sedation to be able to handle a MRI scan.
In August 2008, physicist Michio Kaku predicted in Discovery Channel Magazine that a teleportation device similar to those in Star Trek would be invented within 100 years.
(Physics students at University of Leicester calculated that to “beam up” just the genetic information a single human cell, not the positions of the atoms, just the gene sequences, together with a “brain state” would take 4,850 trillion years assuming a 30 gigahertz microwave bandwidth)
https://en.wikipedia.org/wiki/Transporter_(Star_Trek)
Any idea how many passengers per hour it can handle ?
And with the transporter, there’s no guarantee that the “you” that appears in the destination transporter is the same “you” that left. It may look like you and act like you; it may even think it is you. But it isn’t you. You have been disintegrated permanento. You’re dead, D.E.D.
The engineering of this matters not, it’s all about the greens, the hype and the NGO lobbyists – pay NO attention to the man behind the curtain …
Mitch Clapp, George Herbert and I have kicked around an idea that seems superior to Hyperloop and may be able to address all the concerns above. Mitch first described it on Rand Simberg’s Transterrestrial Musings last year:
Mitchell Burnside Clapp
April 18, 2017 At 5:13 PM
I believe Hyperloop has made some grave technical assumptions and errors that render the system profoundly infeasible.
Specifically, I think the evacuated tube idea is an error. As an alternative, fill the tube with hydrogen at standard temperature and pressure. Several things happen when this is done:
1: The drag drops by a factor of fifteen with respect to air at standard temperature and pressure. Yes, functional vacuum has lower drag still, but seriously, is it enough lower to compensate for the hassle of maintaining an evacuated tube?
2: Mach effects are comfortably remote – the speed of sound rises by a factor of nearly four. Travel at what would be Mach 0.95 in air becomes travel at about Mach 0.25. That’s comfortably in the incompressible flow range.
3: The passenger cars become substantially simpler – they don’t even have to be pressurized in a structurally significant way, just reasonably airtight with a CO2 scrubber and other climate controls. You might pressurize the car to a tenth of a psi over the tube pressure, and the tube by a similar amount over the atmosphere, but that’s not a significant structural burden.
4: Note that the tube may now be constructed from acrylic or polycarbonate or something appealingly transparent, since it isn’t structurally loaded in the same way any more.
5: I would recommend driving the passenger cars by external means, and using an onboard magnetic levitation system. There are ways to do this simply in two axes with permanent magnets. But this could be traded around. Steel rails aren’t out of the question as long as there’s a reasonable contactless power connection by an inductive mechanism.
6: The above observation moots most of the complicated hardware on Hyperloop’s passenger cars.
7: It’s technically possible to generate the power with onboard air for the passengers and a fuel cell reacting with the hydrogen working fluid, dripping the water exhaust into a catch basin on the car as you go along, I suppose. I think that is all a little too cute for the room in my opinion and would require a supply of makeup hydrogen on a per trip basis rather than to compensate for the inevitable leakage.
8: I am astonished at myself for advocating a transportation technology that requires hydrogen. This would of course work nearly as well with helium, but I don’t think there is that much helium on the planet.
9: I am mindful of the hazards of hydrogen, of course. I will point out that the Hindenburg mishap in 1937 had 36 fatalities and 62 survivors. Most of the fatalities were *crew* – who stayed at their posts helping the passengers escape, and in an era where that was not a key portion of the job description for cabin attendants. Also, of course, the fatalities were from falling and burning diesel or fabric. The hydrogen all went upwards and no one was harmed by it.
10: A minute in vacuum will kill you faster than a minute in 1 atm, 70 F hydrogen.
Okay, is there anything fundamentally unsound about this idea, apart from calling it HydroLoop?
Interesting concept, Doug, I hadn’t heard of that.
w.
Hydrogen brings to mind the hindenburg effect.
Why not just use a train and a simple acrylic-style tunnel and have fans blowing wind down it at whatever speed you want the train to move at?
This way you can run a regular bullet train at almost double the speed. All current technology. Should the tunnel be breached and windflow interrupted, the deceleration would not be catastrophic since the mass of the train itself (orders of magnitude larger than a pod) would regulate the deceleration process.
How do you provide electric power to that “bullet train”?
That might work. Which is something fundamentally unsound about the idea.
If it might work you might be asked to make it.
That’s no way to make money.
The global supply of He is likely to increase with the onset of advanced fusion reactors.
How would changing the gas from Hydrogen to Nitrogen affect the build considerations?
N2 is almost as massive as air, of which it comprises 78%. O2 and Ar are a little more massive, but make up only about 22% of air. Other trace gases, such as CO2 and H20 can be disregarded.
“A minute in vacuum will kill you faster than a minute in 1 atm, 70 F hydrogen.” More likely to kill you in a minute? Not really having a dig at you but surprised that such a half-arsed idea is better than something that found $113 million in funding.
Sounds ;like a very big cannon with people carrying bullets.
Put it on ocean and be 20 meter below ocean surface. Giving near constant temperature, with earthquakes not problem, but how to get out of it, if all goes wrong? Could have vacuum or H2 pipe within outer shell. Outer shell deals water pressure and way to leave it and intertube is the hyperloop.
I’d by inclined to put a turbojet engine and carry oxygen for passengers and the engine and make the car self-propelled. A direct hydrogen generator from a refinery could then be used with the turbine able to consume impurities. Cryo-pumps could accumulate water vapor. But we already have very fast tubes that move through very thin air.
Burning paint exterior fabric is not the same as igniting hydrogen in a metal container.
Any oxygen contamination in the hydrogen turns the hydrogen ignition into a powerful explosion.
Couple of comments regarding using hydrogen as the working fluid.
Make sure the steel tube is properly coated so the hydrogen doesn’t embrittle it.
While it burns very quickly it also burns hot (about 3000F) so we won’t have to worry about saving passengers if there is a fire.
you don’t need steel tube, as there is no pressure difference between inside and outside. You don’t need to make it round, either; for the same reason. a triangle or diamond or whatever fits best for other purpose would be just as fine.
You can double the hydrogen tube into another inert gas tube with few more hassle. Azote would be fine.
@ Doug
” … Okay, is there anything fundamentally unsound about this idea, apart from calling it HydroLoop? …”
—–
Fill party balloon with hydrgen, attach filled balloon to end of long stick, pass skin of balloon over lit candle.
Use ear plugs.
Not actually a big pop. You need oxygen for that and quite a bit of air to get a bang. Minimum of just under 30% air. A pretty big leak.
Planes are efficient because they cruise at reduced pressure ( ~20% of sea level).
Law of diminished return apply: you have to make much more effort to diminish the pressure from this 20% level to, say, 10%, for a much lesser gain on drag.
nice idea.
4. the tube need not even need to be round, solid, nor stiff. Could be anything reasonably non-flammable, provided it doesn’t leak (too much) hydrogen. joints won’t be a trouble.
And it could have variable size, larger for train crossing and station, for instance. Station could be has big as needed with minimal trouble
9. To cope with hydrogen fire hazard, just in-close the working tube into another tube filled with inert gas. azote would be fine.
10. Don’t bother, planes are more risky. They travel in 20% sea level pressure, -40°C temperature. And they are safe enough, so your idea is, too.
Now, I am still not convince that the game is worth the hassle.
why not hoist passengers to the stratosphere in a balloon and drop them?
2o minutes to get up, 5 minutes to get down.
nearly half the globe is the range.
too simple?
Interesting adjustments, but how do you get the hydrogen from in front of the moving pod in a tube to behind the moving pod in a tube? Even that is probably solvable, but at what cost? This has been the experience of my entire engineering career, a rarely encountered an unsolvable problem, but at least 50% of the time the client was unwilling to pay for my solution.
“Humans can only sustain about half the force of gravity, called “0.5 G”, for safe deceleration. Musk says the cars will be traveling about 760 mph (1225 km per hour). At that speed, it will take around 75 seconds at 0.5 G to decelerate to a stop. So the inter-pod time has to be at least 80 seconds … and that means passenger throughput drops to 1,260 passengers per hour.”
I don’t disagree with your premise that the engineering issues for this are gargantuan, and likely not worth the time and money. But, I thought I’d wade in a bit to correct this bit about deceleration rates and time.
Typical passenger car deceleration rates for casual braking (0.1g), typical stops (0.15g) and hard no skid (0.35g) are comfortable levels we have all experienced. Hard maximum effort braking on dry pavement, at a tire on pavement “skid-level”, regularly yields 0.70g to 0.90g rates. Such levels are uncomfortable more for the sudden ramp up to maximum and are not hazardous. Duration is clearly an issue, but I think the 0.5 g you applied here is a bit low.
Also, I think your math went off a bit. 760 mph is 1115 feet/sec. t = V/a =1115/(0.50*32.174) = 69 sec.
With a 0.75 g rate, the time about 46 seconds.
Thanks, Crash Expert. You’re correct. I’ve used conservative figures of 0.5 G and “around 75 seconds” instead of 69 … as a crash expert, surely you’d want a bit of a safety factor, no? In particular, you are assuming that the braking starts the instant the leading car stops.
In any case, thanks for checking my figures. It’s the first thing I do when I read someone else’s work, and I’m always happy when folks do it for my work. In fact, it’s one of my favorite things about the web—I’ve been prevented from wasting weeks or months on some blind alley by someone saying, “Umm … Willis … “.
All the best, keep checking,
w.
You used this bit of analysis to critique the time gap between cars with regard to the throughput of the system. Low balling the emergency stopping criteria just doesn’t seem like a necessary step to take.
The 30 second gap would require an average decel g-load of about 1.2g. Aggressive to be sure, but not outside of available techniques and not outside of the bounds of human tolerance. Particularly if you are in a rear-facing seat to distribute the load and a few seconds are used to ramp to the necessary peak rate.
30 seconds at 1.2g might be OK for you, but probably not for your eighty-year-old granny. Nor will you be in a rear-facing seat, unless they plan to turn the seats around after the pod reaches peak speed.
Yeah, killing one or two passengers will be better than killing them all, but you can’t base your normal business operations on killing a few passengers when something goes wrong.
No, wait, I did that wrong. This is one of those cases where the critical parameter in the calculation changes. The gap between the cars is defined by a time, so it’s natural to do the decel calculations with time. But, that’s wrong. That gap time is just a means to define a distance traveled at some speed, and the deceleration that follows in an emergency stop is for that distance, the length of the gap–it doesn’t matter how long it takes, so long as the car stops in that distance. Further, the deceleration time will necessarily be greater than the car’s nominal travel time at speed over that distance.
The assumed 30 second gap between cars at 760 mph (1115 ft/sec) constant speed is 33,448 feet.
a = V^2/(2D), So 1115^2 /( 2* 33448) yields 18.58 ft/s^2 or 0.58g.
Nothing particularly outrageous about that, similar to skidding your car on wet concrete pavement. Granny and the baby need to be in their seats with the belt on, but that’s not the failing criteria for the program.
Crashex April 18, 2018 at 9:02 pm
Oh, very well spotted. I’d made that mistake as well, thanks for catching it.
So now, instead of it being equivalent to half a freeway lane of passengers, it’s equivalent to a whole freeway lane full of passengers … probably just as well, it’s hard to fit cars in half a lane anyhow …
And this, folks, is why I encourage people to not trust calculations until you do them yourself … and sometimes, not even then—I did it myself and it was wrong. As my beloved grandma used to say …
Kudos to you, Crashex …
w.
Extreme roller coasters accelerate 3 to 6 g. Formula 1 cars brake at 6 g deceleration
How can roller coasters have 6 g when it’s powered by gravity that’s only 1 g? It’s the centripetal force in tight curves and loops
Willis,
I’m curious what kind of control system would reliably and instantaneously recognize a possible problem and begin full deceleration of a capsule. Position and velocity monitoring and communications would have to be very fast and sophisticated. Whatever delay detection and communications involves must be added to stopping distances. False problem detection with resultant deceleration triggering could be nearly as bad as a real fault. False trigger of a single capsules braking system could be catastrophic. And on that subject, what would the linear forces on a working tube when the high deceleration brakes activate in all the capsules in its segment. Just saying… calculating capsule timing based upon simple braking deceleration and distance is far short of necessary system safety requirements.
Assuming reasonable section lengths between stations, will there be provisions for handling and offloading capsules stranded in transit? Three capsule capacity at a station might be a little low for evacuation purposes. I can’t help but imagine sitting in one of those stopped capsules out somewhere in the tube. I doubt I’d be soothed by overhead speakers playing soft music and voice announcements that the problem was being worked on. At least in on trains and subways, there are provisions for evacuating on foot.
… that means passenger throughput drops to 1,260 passengers per hour.
Current and in-development single aisle jets (Boeing 737 MAX 10 and Airbus A321neo) have around 200 seats in single class configuration. This means that five aircraft flying 12 minutes apart would have the same capacity as the hyperloop.
The acceleration and deceleration rates mentioned here means that passengers would have to be seated and seat-belted for departure and arrival.
extremely dangerous to passengers, vulnerable to a host of problems, will kill everyone inside …
=========
Sounds perfect for California.
Seriously. You get a reduction in air resistance but what else? A huge capital expense along with a very demanding operating environment.
Combines the worst of air travel and rail travel. Since the system cannot overcome the speed of sound it isn’t a step up for long distance travel.
extremely dangerous to passengers, vulnerable to a host of problems, will kill everyone inside …
=========
Sounds perfect for California.
Seriously. You get a reduction in air resistance but what else? A huge capital expense along with a very demanding operating environment.
Combines the worst of air travel and rail travel. Since the system cannot overcome the speed of sound it isn’t a step up for long distance travel.
Men are not getting better… Lol
Oops, link to the original discussion here:
http://www.transterrestrial.com/?p=67555
Smaller engineering issues can be handled- thermal expansion is controlled by expansion joints, and seismic events can be detected before the s-waves arrive and command an emergency stop. Emergency stops can be done at two gees- that’s what seat belts are for- and the hydrogen-filled tube is entered and exited with a section of nitrogen-filled tube to prevent mixing with air. When not moving at maximum speed, the cars can simply run in air, and fan out to multiple stations at either end (in the extreme, driving autonomously they take you door-to-door). The loading and unloading of individual cars is thus decoupled from the high speed tube scheduling.
“Emergency stops can be done at two gees”
So you’re going to require passengers to take a medical before they get on board?
Only one quibble… the pods would be at atmospheric pressure at the stations so when sealed they would not need to be pressurized. However, the station would need to be resealed and depressurized before the airlocks could be opened, so no difference in terms of time required.
Musk has shown the ability to find some amazing engineers – eg. landing Space-X rockets – and great engineers can solve some really hard problems. But great engineers should also recognize that even if they can deal with technical issues, issues of economics and safety sometimes make an idea impractical. The Hyperloop idea seems to me to be one that could not be justified on economic grounds alone. It would most likely never be built unless massive subsidies are involved.
While, I do still see all sorts of other problems, In regards to the need to vacuum out a chamber, to insert the pod into the tube, I can see one solution. How about if there is an intermediate pod older, that can rotate out from the vacuum chamber, like a revolver gun. This intermediate pod, could be designed to hold the passenger pod, with any extra space filled with solid material.
This arrangement can, theoretically allow for passenger pod insertion/removal without pumping at all.
Some of the other technical issues may also be solvable. But, of course, the question if if it worth the cost.
Let him work it out. A similar critique of his proposal to land and reuse booster rockets on floating barges could have easily been made. Right until they did it. Also, this whole analysis presupposes that the entire loop needs to be a vacuum. That’s not true. Only the air in front of the pod needs removal and then it becomes a rate equation of how fast air can be moved and what does the work to remove it. That simplifies the initial conditions, stresses and margins.
That’s a specious strawman.
Nor is criticism about recovering boosters anything similar to the litany of safety, production and operating concerns that have been raised in Willis’s article and this thread.
Especially since both Russia and America regularly recovered and reused boosters used for space launches.
Criticism regarding recovering and reusing rocket components ignored common practice for space launches.
Let Musk build the tube. Without any use of tax payer funds!
Given Musk’s pretentiousness, Musk should build and operate the beastly thing using only renewable energy, including manufacturing the steel pipe.
“Also, this whole analysis presupposes that the entire loop needs to be a vacuum”
NO
It’s what the proposal says. (Proposals actually. There are many possible variants.)
We can only discussed what Elon Musk is suggesting. If YOU want to propose another design, than go for it. (Any change to fix one issue introduces many other issues.)
The density of 0.084 kg/m3 for H2 at STP is equivalent to air at 20.2 km, or roughly 66,000 feet, so the drag on a car in the tube would be far less than for an airliner at 35,000 feet or so.
So bottom line, I agree that a vacuum tunnel is a bad idea, but a hydrogen tube could be a good idea and may be useful if someone less busy than I am can do a serious first-order design.
The entertaining part is that fossil fuels are the only economical method for extracting hydrogen.
“tube would be far less than for an airliner at 35,000 feet”
But nobody proposed “an airliner at 35,000 feet”, AFAIK.
The proposals mention 100 Pa. That’s almost empty space.
How could ANYONE spend even a dollar on this nutty idea?
California. Nuff said.
Anybody that thinks they need to move that fast:
1) Should move closer to the hive.
2) Consider Skype, or those new video chat platforms I’m way behind on.
3) Maybe you take one trip thru the tube, just to say you felt what a 10 g acceleration felt like, and it didn’t even spill your coffee.
Within 15 years, autonomous vehicles
≠============
Not sure about the date, but it is most certainly a game changer for public transit in all forms that will eliminate entire industries.
What it does mean is that roads will remain the primary means of moving people. Mass transit systems on fixed rails will make no sense when private vehicles can go out and make money for their owners. Instead of paying for parking while at work your car will be out making money to pay for fuel, insurance, maintenance, etc. End of the day after making a few hundred $ in fares it drives up to the office to pick you up and take you home.
As an engineer I find myself intrigued by the possibilities of the hyperloop and its various technological difficulties.
I do believe it is prohibitively expensive and the cost of construction and running the system would make the price of using the system…astronomical.
This is an example of identifying a problem and creating a solution without acknowledging the constraints that the solution must meet.
On a side note, it is quite humorous to read all the negative commentary about the Hyperloop. I am certainly not a fan, but if you were to replace the word hyperloop with airplane with all these negative comments you would assuredly be entertained.
Self-flying aircraft will make this scheme and high-speed trains unnecessary.
Every industrial and commercial park, or large campus like Apple’s, will have its own landing strip. The planes might even be tilt-wing, so as to land and take off like helicopters, obviating the need for strips.
Yeah,as soon as we change physics. I mean flying is sooo energy efficient. /sarcasm
Look up the MPG for a small plane or helicopter
My thoughts exactly. “Imagine a tube moving near the speed of sound. to achieve this, we’re going to elevate the tube to 35,000 ft to reduce drag. We will pressurize the tube to keep passengers comfortable.” Oh wait, you mean it actually works, is used everyday by millions and changed the world?
It works well within constraints.
1. Cost benefit for passengers, they’re the ones paying for the service.
2. Destination, the destination has to be useful to the passengers.
3. Speed Vs safety, there are other forms of transport out there, at competitive prices.
Planes work well, but the Concord was dumped simply because it’s particular need (cost-benefit) wasn’t viable.
An earlier go “Atmospheric Railway”
http://www.ikbrunel.org.uk/atmospheric-railway
At least you could look out the window
Pure subversion.
All the charm and risks of traveling in a submarine submerged at a depth of x-hundred feet, only a lot faster, and what’s left of you when a failure occurs can be scooped up on dry land.
Don’t forget the nifty, the-power-is-free solar panels on top of the tube sections (see 1st drawing). Surely they will have a major effect of reducing operating costs (but are really there to get government subsidies).
So after an earthquake BART inspects tracks, an example here took around two or three hours, using trains: https://patch.com/california/piedmont/bart-inspects-tracks-following-earthquake
BART has 112 miles of track, though not sure if that’s distance of the routes or the actual tracks (e.g. a route typically has two sets of tracks for each direction). It also has a maximum speed of 80mph.
I wonder how much checking hyperloop would need after an earthquake & how it would be done, sensors only or running inspection cars at a lower speed through the tubes?
Elon Musk’s answer to everything: “track” (tube) inspection will be done by robots.
The crushed rail car is a poor example.
A tube with external steel braces (circumferential and/or longitudinal) or simply selecting a longitudinally crimped tube would be sufficient to bear the vacuum induced compressive stresses. Other engineer issues can also be solved as long as someone sprinkles money all around, a la Moon Project.
Certainly, no private investor will put money for this project which will never be a cash flow positive. Hence Musk wants government (the taxpayer) to subsidize this project.
Why should this be our government’s priority?
“Other engineer issues can also be solved as long as someone sprinkles money all around”
Probably not. You need to make the system mass transport system-safe. Not just mission to the Moon-safe.
But the project was presented with a budget. The sketchy project presented was based on existing, proven technologies. This is obviously a crook.
Before I knew anything about the technicalproblesms, I was aghast at the idea of being stuck inone of those pods, unable to escape. And the likelihood of a terrorist planting an explosive on the tube.
The elite need speed and chic and tax credits. Let the others eat carbon tax cake.
A more in-depth look at the concept was published here about 5 years ago, and it addresses each of the challenges listed above. The least of these, IMHO would be tube buckling due to atmospheric pressure. The tube radius is 65 inches, and the pressure load 14.7 psi. That’s a buckling stress of only 956 psi. Preventing buckling is simply a matter of adding external stiffening rings ever 10 feet. It’s the other loads that would dominate.
As for a cabin depressurization, this is not a much different problem from the Concorde, which cruised at 60,000 feet. Oxygen masks would be useless at that altitude, so the designers made the windows much smaller than on other jets. The pilots would go into a maximum angle dive at the first sign of cabin depressurization. If caused by a window blowout, the area was small enough to keep pressure in the livable range until the air packs could keep up with the bleed. Loss of a door, however, would have been un-survivable. The hyperloop cabin has no windows, which eliminates a lot of the problem. Elon has had a great deal of experience, no, flying a habitable cabin in space, and even with big windows and doors, Dragon has never had a problem.
The acceleration limit of 0.5 g is puzzling. Here is a list of the 9 fastest launch acceleration roller coasters in the world. Ninth is the Takabisha, at a modest 1.4 g. I’ve been on both the Xceleerator and Storm Runner (both a blast at 1.6 g). Number 1 is Japan’s Do-Dodonpa, which goes from 0 to 111.9 mph in a blazing 1.8 seconds (3.27 g). Stopping is just the inverse of starting, and I’m sure that 12.2 seconds at 3.27 g would be more acceptable to passengers than an instant stop from 760 mph.
Anyway, it’s an interesting read from the perspective of an engineer. Enjoy.
(PS: That tank car collapse was gnarly!)
Thanks for the thoughts on how to improve the concept, Michael, much appreciated. I was writing about the concept as it has been pushed by Musk. Yes, there are possible changes that could make it work better. My point was that what is being sold at the present time is not feasible.
I would add a couple of points. First, you say “Dragon has never had a problem” … in how many hours of operation in space? A few days worth? A week? We’re talking about something we expect to run 24/7/365 …
Second, the Dragon in a vacuum is not doing 750 MPH in an evacuated tube … it’s basically drifting in space. Nor does it possibly have suicide-minded bombers on board, or idiots with rifles taking pot-shots at it …
Finally, yes, I’m sure a young strong man like Colonel John Stapp can withstand over 40 G deceleration, and it sounds like you’re happy at 1.5 Gs … but we’re talking about infants that may not be strapped in, and old people with cardiac problems, and 300-pound folks with breathing issues, not you or Colonel Stapp. I wouldn’t advise strapping any of those classes of folks into the Do-Dongpa … but they will definitely want to ride a Hyperloop.
w.
There have been 13 Dragon commercial cargo resupply missions to the International Space Station (CRS-7 was a launch failure, CRS-14 is currently berthed at ISS), and they last an average of 30 days. Dragon goes through environments during powered flight, atmospheric entry, and landing that dwarf anything seen by a land vehicle. And CRS-14’s Dragon is on its second trip into space, the first having been CRS-8. It’s the second CRS mission to use a previously flown Dragon. All told, Dragons have chalked up around 377 days in orbit. It’s a testament to SpaceX that NASA allows Dragon to be part of the pressurized volume of the ISS for weeks at a time, and is going to fly astronauts into space in it beginning next year.
One other thing about the environments. Space isn’t all that benign. On top of such things as huge, rapid temperature swings and large temperature gradients, there is the growing problem of micrometeoroid and orbital debris (MMOD) strikes. At velocities that can be in the tens of thousands of feet per second, even a paint fleck can do a lot of damage. Before the first test flight of the Orion capsule, the NASA MMOD analysts were putting the odds of a mission failure at between 0.01 and 0.001. The problem was that the Delta IV upper stage (required for the entry burn) has high pressure helium tanks on the aft end, and they aren’t shielded. The vehicle was only up for 4 1/2 hours. To have such a high probability of failure in so short a time illustrates how severe the environment is. Dragon is a pretty big target, but is designed to handle strikes up to a certain size.
Sorry to go on like that – I do this for a living, and like it. I have to keep reminding myself that most people don’t find it as cool as I do.
I was thinking the same thing as well…..also having ridden many rollercoasters, including some of the launched ones like Storm Runner. There are also some that have some pretty hard stops as well (depending upon how the trains are blocked and how many can run the circuit at a time). But then again, those kinds of rollercoasters also have sophisticated restraint systems designed to keep passengers from being thrashed about too much. On public transit no one is going to want to strap in like a fighter pilot…..Probably the most that passengers would be willing to do would be to put on a seatbelt like in an airplane. That, and as the author of this article has mentioned, some people will be unwilling (or unable) to be subjected to such forces.
Also rollercoasters have a set of criteria on who can envoy the ride (“you must be that tall”).
A mass transit system cannot afford these restrictions. No public body is going to subsidize a transport system that severely restrict who can travel, especially is “protected groups” cannot use it. It’s just a non starter, from the point alone.
Whatever one thinks about the economic prospects of Musk’s other companies, his cars do at least work, his spaceships do reach orbit, and solar city can generate some electricity on a sunny day. This hyper-loopy thing can only detract from general confidence in them, and from confidence in the person at the helm. Man will walk on Mars before this works. It would be frightening if it wasn’t so funny.
Take that back. It is frightening, despite it being so hilarious.
All of his successes require one thing, subsidies from the government. The one true thing he is really good at is making himself rich with other people’s money.
If we assume 1” wall thickness, 11 ft diameter, how many miles could be layed given current world steel production?
The quantity of resources needed for this is staggering.
A 500 km tube, unreinforced, would weigh 1 million tonnes. The US produced 85 million tonnes of steel in 2014, and has produced as much as 140 million tonnes in a single year (1970). I really don’t think resources would be a problem. Currently we’re utilizing 75% of our capacity, and the remaining 25% is more than enough to build the hyperloop in just one year.
And this Willis,
“And all of that for less gain than adding a single lane to the freeway … but there is one thing we can be sure of.”
is the hammer on the nail.
Thank You for encapsulating the insanity of this state in one sentence.
I do travel up and down I-5 and !-99 a few times a year, an extra lane or two would be nice.
But
I live at the junction of I-395 and I-14 at the north end of the Mojave desert. I-395 is a notorious highway of death. 2 lanes for 65 miles, and it is a major highway used by Socal to head to Mammoth etc. And a major truck road. Just last week another local couple were killed in a headon on 395. I-14 isn’t as bad but it STILL has 2 lane sections.
This idiot governor can’t be bothered about bringing the state highways into the modern age but pulls all the stops out for his stupid train.
I’d respectfully submit that collapse of the tube isn’t as big of a deal as you make it out to be WE. The pressure loads are trivial compared to what subs endure. The tank car video, while entertaining, isn’t relevant since those cars are not designed for such a load.
External ring and stringer stiffeners would suffice – think of it as a standard airplane fuselage turned inside out, approximately. A simple shell “only” as the tank car video shows is wouldn’t be an ideal solution. Alternatively, an external pressure shell with internally placed ring frames and stringers as the structure, with an inner liner to define the tube way for the car might be another engineering solution. Note that I suspect submarines are built this way (certainly the WW2 vintage ones, not sure on the current types) – there is a pressure hull distinct from the external, hydrodynamic shell in WW2 boats, and there certainly could have been an inner liner hull distinct from the pressure hull just as easily.
I also don’t see the joints needed to handle thermal expansion / contraction or external imposed loads as being too big a deal. Note that simple fabric coated rubber core “P” and “Y” seals pressed into the adjoining fuselage structure are used to seal the doors of passenger airplanes to 8 PSI. Put 4 such seals (2 primary, each taking ~1/2 the load, 2 more as fail safe) in series at a “tube inside a tube” slip type joints and there you go – pressure sealed with flexibility as well. If you do this in the context of a tube-in-a-tube arrangement, the car will never encounter one of the pressure loaded slip joints, being isolated to the inner “liner” tube. Supports that impose proper section-to-section alignment across the tube section joint while allowing linear flexibility of the tube sections are trivial in concept (tube mounted rails, with interfacing support mounted rollers that constrain relative lateral displacement without constraining linear displacement).
Where I see the issue with this whole concept is simply the economics. Can the cap & running cost generate sufficient risk adjusted income to make it worth while? At this point, I’d be highly skeptical on that part.
No Name Guy April 18, 2018 at 3:42 pm
Thanks, Guy. I was analyzing the proposal as it has been put forth by Musk. Could it be improved? Sure. What can’t be improved? But that’s not the question.
The question is, can it be done safely and economically in such a way that it makes more sense than adding a single lane to the existing freeway?
To that, I’d say no.
w.
Doesn’t that depend on the goals?
Adding an extra freeway lane doesn’t get journey times to “35 minutes” which I would of thought is the main benefit of hyperloop.
Of course what the actual improvements in door to door time would be is another matter, the general claim that LASF time is almost a wash between driving and flying (given check-in etc.), even with hyperloop would there still be a four hour door to door time for a real journey?
climatebeagle April 18, 2018 at 5:10 pm
Per the current plan, basically yes, because the proposed Hyperloop run starts well north of LA and will end in the East Bay. So you’d have to add in car time at both ends.
w.
For a meaningful reduction in travel time, autonomous aircraft are the ticket. A helicopter from your house to your destination would be most convenient, but slower in transit. A fixed wing AA would fly faster, but unless you live on an airstrip, you’d have to drive before or after flying.
The software for an autonomous helicopter already exists:
http://heli.stanford.edu/
Range might be an issue for a fast light helicopter. It’s about 382 miles from LA to SF. But 150 mph should be possible, for flight time of ~2.5 hours, with convenience of taking off and landing precisely where desired.
Flight time could be really short for a small jet or twin engine prop plane, but the price tag might be too high for private use. A company however could own one or a fleet. Cruise speed of Mach 0.9 is possible, but cost and range could be an issue. A one-seater capable of 220 mph however might cost only 150 grand, and get good “mileage”.
http://www.dailymail.co.uk/sciencetech/article-3071919/Would-SELF-FLYING-JET-Google-boss-sets-sights-developing-autonomous-plane.html
All the vacuum Hyperloop will ever require can be generated by connecting one end of the tube to the Tesla cash-flow machine. Talk about some serious negative suck!
Is the hyperloop’s capacity really an issue?
The paper Michael Kelly linked to says has a much lower hourly capacity than you calculate and states: The capacity would be on average 840 passengers per hour which is more than sufficient to transport all of the 6 million passengers traveling between Los Angeles and San Francisco areas per year.
I’m not sure about that claim of all passengers travelling is only six million per year, but 840/hour gives around 20,000 per day assuming a 24 hour day. That seems to be comparable to Southwest’s daily capacity from the Bay Area to LA area, ~28,000 (198 flights x 143 passengers/737): https://www.southwest.com/thmpg/flights-from-SFO-to-LAX.html
Caltrans seems to give average daily traffic for I5 around 38,000 in Kern county (as an example of the middle two lane (each way) portion). http://www.dot.ca.gov/trafficops/census/volumes2016/Route5-6.html
So it’s seems its daily capacity is roughly in-line with existing transportation options.
Willis – re the collapsed tank car. I believe that was done by Mythbusters in their final season, and they had a heck of a time with it.. Their first try, they steam cleaned the car, sealed it up while hot, then sprayed it with water to simulate a rainstorm after a cleaning and ill advised sealing. The tanker didn’t collapse. The tried again with an older, rusted tanker. The tanker didn’t collapse. They finally dropped a five ton block of concrete to dent the tank. Only then were they able to collapse it. There’s a description at http://www.thetvaddict.com/2016/01/16/mythbusters-recap-tanker-implosion-crushed/
Maybe 1 inch steel for the tube is enough. (and maybe not).
yes the collapsed tanker is a horible red herring. They are built to hold up agaainst a positive internal pressure
Red herring? Not. The only difference between the Hyperloop tube and the tanker is the thickness of the steel.
The Hyperloop is 1″ thick and the tanker steel is about 12 mm thick, just under half. Other than that they are the same situation, a steel cylinder. Claiming the Hyperloop tube can’t collapse under atmospheric pressure? Because the steel is thicker, it won’t collapse just under atmospheric pressure alone … unless it is kinked, or bent, or damaged in some way. but there are lots of ways that it could get kinked or bent, and then, game over.
In addition, a tank car doesn’t have a fifteen-tonne pod moving through it at 760 mph …
Can all of this be accounted for and engineered for?
Some yes … others, no.
How do you plan to account for earthquakes, for example? Mosh, are you willing to bet your life that a 1″ steel tube won’t collapse under atmospheric pressure, ten tonnes per square metre over the entire pipe surface, in an earthquake?
Pod is going 760 mph, if the quake shifts a pylon an inch or two w.r.t. another pylon, you gonna guarantee the tube won’t fail? Me, I wouldn’t bet on that one … and in California the earthquake question isn’t IF, it is WHEN …
Best regards,
w.
looks like you didnt read.
pylons have xy dampers
and z dampers.
you can bet the engineers do more than speculate using tankers as models of what could happen.
and yes the internal structure of the tube is different. its not purely thickness.
This project will not be affordable for the middle class. The infrastructure cost is an order of magnitude higher than aviation infrastructure. He can’t move enough passengers through the system to spread the cost of the system, over millions of passengers per month, so the tickets will be higher than airfare. And he is still going to need the same TSA hassles that make flying a wait-in-line experience. It has no advantages over flying. You can’t put the terminals in the city, or you will gridlock the city streets, with passengers trying to get in and out of the terminal.
And the final nail could be an increase in speed limit for automated cars. An automated car could certainly drive safely at over 100mph in the left lane of an expressway. That brings the time to drive under 4 hours.
You can overcome a problem or two, when you have no competition in the space you are trying to fill. This project has a very limited customer base, and huge start-up cost. And the rest of the country will not be riding it, so we are all going to vote for not funding it. CA has a lot of voters, but they are not going to get support from the other 49 states. LA and SFO may not even be in the same state, in 15 years!
I don’t think the car speed limit is the issue on I5, there tend to be three problems on I5 in the middle 2-lane sections.
1) Trucks overtaking other trucks, causing the left lane to slow down to ~55mph
2) Drivers flying down the empty right line behind the truck being overtaken and cutting into the already compressed car traffic backed up behind the overtaking truck (from 1) causing others to break and slow even more.
3) Drivers that stick in the left lane, next to, and at the same (slow) speed as the vehicle in the right lane, thus blocking the freeway for everyone else wanting to go faster.
Maybe spending serious money on driver education and enforcement would actually allow a higher speed limit and cut the driving time.
The solution is to have the driving skills designed into the vehicle. The expressways could handle vastly more capacity than it does now, if the system was designed for max throughput. If we are willing to give up control, you will see a vastly different expressway system 20 years from now. Most of it is doable with today’s technology. It just needs to have a critical mass of vehicles that can take advantage of the system, and the desire to save time and money by not sitting in traffic jams.
Absolutely correct, and applies to almost all I-Slabs.
Keep the trucks in the far right lane, which is the rule in some parts of Europa. Capacity and safety would make step-change improvements.
Or, make two lanes for trucks and two others for not trucks.
The claim from the doc Michael Kelly linked is:
The total cost of Hyperloop is under $6 billion USD for two one-way tubes and 40 capsules. Amortizing this capital cost over 20 years and adding daily operational costs gives a total of $20 USD plus operating costs per one-way ticket on the passenger Hyperloop.
So only $20!! Easily affordable for the middle class.
As a cost comparison, the new east span of the Bay Bridge was $6.5 billion for 3km, so that $6 billion for a 500+km project looks somewhat optimistic.
If you want those structures to withstand a 7.0+ earthquake without collapsing it is going to cost 5x that much. Even at that cost there will be substantial damage, from the earthquake that is going to happen. There needs to be a footing dug out, and poured. Then an earthquake force distributing attachment to the ground for everyone of those structures Then they need to keep the tube level, over un-even ground for miles at a time. And we are talking CA labor prices. $6 billion might not even get out of LA county.
In today’s environment, building something so sensitive to manpad missiles with shaped charges is beyond foolish. I’m with Elon in thinking it neat and wonderful, but we aren’t in that Star Trek peaceful future yet.
Add a few new AIRPORTS and enlarge some of the others, The total land use will be less than hundreds of miles of right of way needed for tube or rail trains..
Have fleets of helicopters using helipads, like in LA in the 50’s..
For the future, file flight plans over the ocean for some supersonic flying..
Remember this is what liberals want to use trains for.Note also for crude oil, no pipelines.
sounds like you watched thunderfoot.
https://youtu.be/kx52A-v65Q8
https://youtu.be/Uh0uwJoNnhc
Robert Heinlein wrote a story, The Roads Must Roll. It features a network of parallel moving sidewalks. Passengers would load at the outside and move to progressively faster sidewalks. They would ultimately work up to a sidewalk moving at 100 mph.
After reading Willis’ article and the comments above, Heinlein’s idea seems eminently practical in comparison with Tesla’s idea. For sure it would move orders of magnitude more passengers.
Willis, You started off with the Boring Company, and sorted of segued into Hyperloop. My impression was and is that while the Boring Company could be used to ream out hyperloop tunnels, Musk really had something simpler and slower in mind. I’m not sold on urban tunneling. Huge permitting problems. And too much poorly documented infrastructure under cities. The latter turned out to be a huge problem in Seattle when a boring machine trying to dig a two mile tunnel to replace the aging Alaska Way Viaduct hit a steel pipe and was stuck for TWO YEARS. https://en.wikipedia.org/wiki/Alaskan_Way_Viaduct_replacement_tunnel.
But there seem to be cases where tunneling looks like the best of a bunch of bad choices. For example connecting downtown Chicago to O’hare airport. There aren’t a lot of companies that can manage a tunnel like that. It may be that the Boring Company (sans Hyperloop) is actually a viable business.
That’s an impressive TBM! The smaller twin tunnels under East London for UK HS1 worked out OK. 2 x 7.15m diameter 19km long. At least one back garden disappeared overnight but not the houses luckily!
https://www.arup.com/projects/high-speed-1
http://www.tunnelsonline.info/news/ground-collapse-above-ctrl
Hyperloop One Test:
I was curious so I assume others will also be curious. It’s from the movie ‘Contact’. link
I can’t be the only person who thinks that Elon Mush is a fantasist?
Well spotted with vacuums in cylinders and vacuous humans inside them but my Superlative Spherical Storage Company has the shortcomings licked with the appropriate seed capital to save the planet. As you know there’s a wee problem with unreliable wind for the turbines so Superlative Spherical Storage is desperately needed. With large enough spheres surrounded by a circle of wind turbines when the wind blows hard they would additionally drive vacuum pumps to evacuate the sphere and when the wind is low the valves would be opened for the inrush of air to drive the wind turbines again. As you know this is all settled science and just needs a few grants to sort out the best plumbing arrangements, etc but first up a meeting of the minds in the Maldives to get the balls really rolling.
This makes me think of the Schlitterbahn ride in KC.
Yeah, it kinda does, now that you mention that. And of course we know what became of that ride – and the men who designed it (well, OK, they’ve only been charged and haven’t yet gone to trial). However, neither of the two men who designed the ride had any background in engineering. One would hope that wouldn’t be the case for a hyperloop, should it ever be built!
I are a mechanical engineer. I think the problems are far smaller than you suggest and there is far too many people wading in on this who are consulting only their intuition rather than informed assessment.
-The tube can be easily constrained against thermal deflection by supports at 50-100m spacings, like high speed rails (it is like a wire 300000x longer than it is in diameter), slight longitudinal compression or expansion is not a big deal, +/-20°C gives only about +/-40MPa, an order of magnitude below the strength of the steel, and the curves are exceedingly gentle – probably >20km radius to reduce g-loads so that lateral buckling forces from these stresses are very very low. They can either be purely constrained by supports or accommodated by hermetically sealed welded metal bellows joints over overlapping steel tube expansion joints.
-Leakage will be almost non-existent, so vac pumping average power will be very low (outside of pump down events after maintenance), Air-locks can have cm-close fitting solid blocks around pods to reduce pumping, or be filled with low-vapour pressure vacuum oil in a 10m high u-tube type manometer arrangement to eliminate vacuum pumping entirely using hydrostatic pressure.
-Buckling failure is a non-issue, 1inch thick walls are rigid as hell, and rigidity scales with cube of thickness. If super paranoid add circumferential ribs, or spiral weld tube in situ from a pre-ribbed strip. I’ve used 2m dia vac industrial chambers constructed with 12mm walls for years.
-Steel is ridiculously cheap, $0.3/kg in bulk, so tubes are 20km radius curvature (holding lateral acceleration to <0.5g at Mach 1).
“the curves are exceedingly gentle – probably >20km radius”
Where do you find >20km radius-flat terrains?
“in a 10m high u-tube type manometer arrangement ”
I don’t see it. Could you please post a drawing?
“Self-flying aircraft will make this scheme and high-speed trains unnecessary.”
– Chimp
Not exactly a novel idea.
1988. – “This is the first fully automated plane, flown by a computer”:
It was a human who decided to make a demonstration at very low altitude, low power, high AoA!!!
(And yes there are certainly issues with the Airbus computer system, but the accident does not demonstrates that.)
It was the crew that persisted in ignoring the aircraft’s computer that was telling them to pull up – apply more power – they were going to crash. It was right and they were wrong.
No, they applied more power, and the computer did not immediately.
There is also a big “ideation” to exchange the recorders, obstruct justice, etc. to preserve Airbus reputation. This was a terrible scandal in France and proved that French authorities could only be trusted to obstruct justice and destroy evidence, as they still do.
AI software has gone through a number of generations in the past 30 years, evolved rapidly and now is at least as good as humans. There can always be a remote, joystick-equipped human in the loop if need be.
If software and sensors allow the USN’s MQ-25 Stingray stealthy autonomous tanker/attack drone to trap on a carrier deck, it can land on land without trouble. It’s catapulted off the carrier, but with a longer take off roll, it was tested on land.
Not to mention autonomous commuter drone tech from three years ago, air and ground:
Wasn’t there a Bond movie where he rides in a capsule inside a pipeline?
A partial vacuum. If 2/3s of the air was removed, it seems wind resistance would down to 1/3 of normal. Jetliners fly where this less air rather than using bigger engines.
see the white paper.
Dumb question from a non-engineer. Is there a problem with passenger movement within the hyper loop vehicle while it is “running”? Passengers standing, bouncing their legs, any of this a problem inside a vacuum? For some reason I’m thinking about when kids ride the elevators down and start jumping up and down (like the scene in Big).
“Is there a problem with passenger movement within the hyper loop vehicle”
Probably not; according to the article:
“there’s a 15-tonne “pod” running through it”
And then it’s guided – by some unspecified method. (Almost every technical detail is unspecified, or specified in contradicting ways, that’s my main criticism.)
For comparison, the ascent stage of the Apollo LM was only 4,700 kg according to https://en.wikipedia.org/wiki/Apollo_Lunar_Module#Ascent_stage
looks like you didnt read.
Hyperloop is the cold fusion of transportation ( and the hot fusion ) if people only believed enough we will see fantastic results in 20 years.
@Willis Eschenbach
@mods
“The pods will be traveling at the equivalent of 50,000 feet (15,000 m).”
I believe this is incorrect. Very, very wrong, actually.
https://hyperloop-one.com/facts-frequently-asked-questions says
This is a big difference!
Thanks, s-t. The two are measuring different things. One is the normal operating environment. The other is the maximum that the pods and tube are designed to withstand.
w.
For static behavior, it makes very little difference for either the tube or the pods, both will have pretty much 1 atm pressure difference. (The discussion of the difference of differentials is ridiculous, the difference in pressure between two difference days is much greater than that.)
The issue is supersonic air flow around the pod and the rapid variation of pressure implied. The buildup of air in front of the pod at that speed will be an issue.
That may be correct assessment, Willis; but I think “artist” is the wrong word there.
“There’s a reasonable description of the Hyperloop at Wikipedia and a much more hyper description at their website.”
The two big design proposed are:
– an air levitation design
– a magnetic levitation design
Not sure what counts as “Hyperloop”! There are many ideas thrown randomly with relatively few technical details in common. (“low pressure tube” is a vague hint, not a technical detail)
Two sources on Hyperloop design are given in the article: WP and Hyperloop One website.
According to the WP article:
According to Hyperloop One website:
What are we even discussing here?
“The Hyperloop concept involves a windowless “pod” traveling at just below the speed of sound in a tube with all the air evacuated from it.”
I just can’t get my head around that: how can people discuss that as a subsonic transportation when it is clear that the airflow around the pod will have to be supersonic? How does air behave in that case?
“glides at airline speeds for long distances due to ultra-low aerodynamic drag”
I wonder how that is going to be accomplished. Magnetic levitation does get rid of mechanic friction and since the vehicle has no wings or fins there will be no induced drag, but the parasitic drag moving at airline speed close to the ground will be very large. As a matter of fact it will be worse than for a low-flying aircraft because the vehicle will be only inches off the surface and there will be a lot of interference drag.
The speed of sound is related to air density. In an evacuated chamber like the Hyperloop is supposed to be in, the speed of sound and supersonic shockwaves will be dramtically reduced. What everyone keeps refering to as the speed of sound is the speed of sound at sea level, aprox. 700mph, which it definitely won’t be inside the tube.
No, the speed of sound in gases is determined only by the molecular weight and the temperature. Pressure is irrelevant.
What will be the temperature inside the tube when the air is pumped out the first time?
I think that Elon Musk is a modern day Charles Yerkes. He’s both capable of delivering very real results that far surpass what his critics think is possible and simultaneously perfectly comfortable flimflamming his way past competitors, both real and potential. I think you’re spotting the flimflam, kudos for that, but are distracted by it nonetheless so you’re not seeing what’s really going on. I’m not sure what’s going on either, but I think that I see some real situations where his Boring Company actually has a practical route to profitability.
Charles Yerkes pushed and prodded the city of Chicago into allowing the creation of the Chicago Loop.
http://www.chicagotribune.com/news/opinion/commentary/ct-perspec-flash-yerkes-elevated-train-loop-0910-story.html
He’s a charming scam artist, Solar City is a massive joke, Hyperloop is a massive joke and Tesla is asking for volunteers to help them meet production targets 😀
I think it’s actually intended for use on Mars.
Mathematics makes a mockery of this Hyperloop folks.
?
Atm Muskrat is stripping down a Tesla, and trying to make it go not quite as fast as a high speed train, but it’s just a Tesla stripped down to nuts and bolts with wheels and no driver 😀
Furthermore, the stripped down Tesla will be the equivalent of a truck doing 60mph and the rail inside the tube that this will run alone, looks rather flimsy for such a load.
Then there is the types, rusted, and so weak that they can’t even retain their shape under their own weight, and this test will run in a city
Then there is the “tubes”
Also, this can only go in a straight line 😀 LMAO
We already have those high speed trains, Musk reinventing the wheel, by putting expensive corners on it
expansion
https://youtu.be/BJa9tQyMXDc?t=6m50s
Claustrophobia could be a problem.
https://youtu.be/YtktNetGOKU?t=77
https://youtu.be/UpWeU2fvFGs
“Humans can only sustain about half the force of gravity, called “0.5 G”, for safe deceleration.”
At least one easily solved problem. Turn the chairs around. Humans can take about ten times as much deceleration backwards.
As a matter of fact aircraft chairs should be the other way around too for safety reasons (they are in some military transports). But people don’t want to fly backwards.
As for explosive decompression, note that emergency oxygen (like in aircraft) won’t work. It does in aircraft because the pressure at the altitude they fly is not low enough to be really dangerous, at least not for a short time as long as you get enough oxygen. Full vacuum requires more protection to be survivable (though not a full pressure suit as is often stated).
By the way Musk probably was a Heinlein fan in younger days. His hyperloop is a dead ringer for the “loop” described in chapter 1 of “Starman Jones”. Though Heinlein who knew his physics realized that the noise from a vehicle going at airline speed at ground level would be awesome.
Why limit to 0.5G acceleration or deceleration? Willis got it wrong big time. The human body can withstand 18Gs for brief periods of time with no discernible damage. (please google on your own look for Colonel Stapp)
At that limit, 18G, the pod can go from 360m/s to 0 in 2 seconds and has a stopping distance of 720 meters.
Try that with a senior citizen with brittle skeleton and weakened arteries and I guarantee the damage will be very discernable.
Yes, when you are strapped down in the proper position. What if you are standing, in the bathroom or the person in front of you has a book, a coffee cup or there are loose items near by such as luggage?
I’d call it a HamsterTube, but hamsters probably wouldn’t be allowed to board because of animal cruelty regulations.
Which just about sums up its usefulness.
“But the LA-to-SF route is 615 km. This is a huge, almost unimaginable step up in size and problems. Consider that although the LHC is carefully internally braced to keep the pressure from collapsing it, they’ve said the Hyperloop tube will be a 1″ thick steel pipe supported on pillars. There’s no way to brace it internally, the pod has to run through the middle. ”
Its funny you are making the same already debunked arguments that thunderfoot made.
https://youtu.be/UQPAzZX7Pp4?t=14m45s
The tubes are nothing like a tanker.
How about somebody actually makes a working tube with a full size passenger car that can can for more than 5 seconds, then we’ll see who was right about what. But no one seems to have made any progress towards this after 5 years of “work”.Even Musk himself won’t put any money in to it.
http://www.dailymail.co.uk/sciencetech/article-5620897/First-European-Hyperloop-track-propel-passengers-670mph-begins-construction-France.html
Next couple of years will tell. A lot of the doubts people have are not well grounded.
The doubts of it being built on time, on budget, without huge subsidies and being able to be operated at a profit are extremely well grounded. Much of the bunking, de-bunking and de-de-bunking revolve around wheter or not it can be built. Of course it can be built. The major problems deal with cost and profitability which somehow get handwaved away.
It “can” be built… WHAT can be built?
The magnetic sustentation thing? The air cushion thing?
In a tube maintained at 100 Pa? Please explain HOW it can be done. How EACH and EVERY technical difficulty can be managed. (At any cost.)
so explain in any terms how the effects of atmospheric pressure differ between the two?
Steven Mosher April 19, 2018 at 12:45 am
Thanks, Mosh. I have a simple rule of thumb. Any time someone says that something is “debunked” … it’s not.
I will bet you a thousand bucks today that we will not see a SF-to-LA hyperloop in the next quarter century, Anthony can hold the stakes … debunk that!
w.
I hope you’re still around to collect!
It reminds me of the argument between George(or was it Robert?) Stephenson and Brunell in the early days of rail development. Brunell envisioned carriages being pulled along by a vacuum in a tube laid between the tracks. Stephenson stuck with his Rocket based locomotive. We all know who won.
I have heard say that it was the rats that decided the issue; as they chomped away at the leather sealing strip in the tube.
But hey, he’s already got the branding going, lol. This is a testament to the idiocy of our elites. Perhaps I should pitch “Solar Roadways” to these same VCs and pick up 100 million or so…
HyperLoop is nothing more than 21st century version of The Gravity Train. Also required vacuum, and lots o’ engineering: and very, very great distances between Points A and B.
Very good critique Willis. I believe all of the possible problems you describe can be solved with 2 items ……money and time. Just as the Wright brothers solved their issues.
As for the expansion and contraction, as well as the heat and potential terrorist issues. These can possibly be solved with a double or even triple tube system. Of course this again brings up the primary situation in building this boondoggle. Money and time. I believe Elon can get his own financing.
I agree that the problems could be solved with more money … but as near as I can tell, it is only marginally profitable with current, likely underpriced cost estimates.
You refer to the Wright brothers. I’d say it is more similar to the SST airplane, the Concorde. Yes, all the problems were solved with a combination of money and time … but there are no Concordes flying now.
Why? Too much money for too few passengers made it uneconomical. Remember that the Hyperloop will not move lots of people. So if it is to turn a profit, it must charge each passenger more … and the time advantage won’t be that great.
Upthread I offered to bet Mosh that we wouldn’t see a working Hyperloop between SF and LA in 25 years. I hold to that. Yes, any technical problems can undoubtedly be solved … but at what cost?
w.
The Concorde was sunk by its rejection by the US. With few customers, it had no technical evolution (the first analog design was still used for the last flight).
(Also, there was this accident which was wrongly attributed to external factors, when all well informed people know the maintenance was defective.)
Quoting the author, to wit:
Maybe I overlooked it, but I don’t recall any estimated/calculated “time” required for accelerating each pod to attain its 760 mph (1225 km per hour) speed.
Is acceleration more, ….. less …..or bout the same, ….. “troubling” for the human body than deceleration?
“Less”, because it is directed backwards. I should think 2 g would be practicable with strapped-in average healthy passengers. That means 17 seconds and a distance of about 2 miles to accelerate to full speed.
Why does it have to be steel? Could it be some sort of more flexible carbon fiber composite material?
Cost. Carbon fiber composite is quite expensive and the limited size of curing autoclaves means that it has to be made in fairly small pieces.
And it isn’t really that much stronger than steel, just a lot lighter.
“if the vacuum is breached for any reason,.. everyone in the tube would die from the instantaneous deceleration”
If the hole is less than 0.5 cm diameter, air pressure will decrease due to friction. The Darcy friction factor for turbulent flow is around 0.01. The air pressure will decrease by 99% to 0.147 psi
Correction: that should be less than 2 cm diameter since the tube is 2.5 cm (1 inch) thick
Sorry the Darcy-Weisbach equation is for liquid flow, may not be true for air flow
You’re still going to need highways. And people will still prefer greater utility and flexibility. But yes, for argument’s sake, this may eventually be technically capable of providing expensive transportation for elites wishing to demonstrate to themselves and to society how advanced they are. With Musk, the expense will be covered by other people’s money – because “technology,” “infrastructure,” “environment” and other persuasive buzzwords. It seems a lot more expensive and a lot slower than tele-conferencing or skype to me.
Let the people who put up the $113 million put up the – cough – rest. Let the true believers do it themselves. That transportation system is for them anyway. They should be the first ones to die in the “just a few more bugs to work out, but …” phase anyway. If they’re right, then great. But that way, society won’t be forced into both restructuring and paying to accommodate their dream.
I spent much of my career flying about the USA for worthless meetings and worked in software development so my entire work and that of my collegues would have easily lent itself to virtual reality. The problem with going virtual was twofold.
1. Management lack of trust and evaluations based on ‘motion’ not results and
2. Lack of tools, culture and bandwidth to make virtual workspaces practical.
Spend the money on solving those things and you eliminate the need for hyper travel in the first place.
Railroad tracks have problems with expansion and contraction with temperature, but they are very thick and trains are designed to be pretty forgiving of some irregularities in the tracks-you can hear the clicking and feel the wobble/bumps but usually nothing bad happens. But a vacuum tube of this size if it distorts will cause the pod to hit the walls–no good.
In addition, no one has ever maintained a vacuum of such a size. It just seems insanely impossible. Did anyone even notice there is already a multi-billion $ boondoggle bullet train being built on the same SF to LA route? 2 trains needed for the same route? even one will never have enough passengers.
Willis mentioned decompression: the Southwest Airlines engine explosion that sucked a woman halfway out the window and killed here is what would happen if the pod hit the tunnel walls so the pod would need to be much stronger than an airplane which does not need to be resistent to things hitting it (in general).
When i was a young lad, probably early ’60s i was very taken by an article in Scientific American that proposed a high speed railway running in a continuous tunnel. I dont remember the details but the cars ran on steel rails (because, it claimed, the energy required to provide air or magnetic levitation would be of the same order as the energy required to overcome steel on steel friction). The cars ran in an inner tube within the outer tunnel walls. Pumps would operate continuously to maintain a vacuum in the inner tunnel and the cars would be propelled by releasing a burst of air behind them (as in the pnumatic tubes that used to be common in large stores for moving money and reciepts – and in Brunell’s atmospheric railway). I may be wrong but i think the article rejected linear induction motors as too expensive and in fact unnecessary. The tunnels would slope down from the stations, helping accelerate away from and deaccelerate approaching stops. I am sure they were not thinking speed of sound, and maybe it wouldnt be a replacement for mass transport, but it was intended as a high speed service. It seemed to have a simplicity about it (notwithstanding the huge cost of tunnelling, which it justified because surface structures would be too hard to fit into the built environment and too susceptable to vandalism etc) that seems to be lost in Musk’s version.
Hey if the thing is unsafe after spending billions of leveraged federal dollars and carbon tax revenue you could always hail it as the first solar highway…..to no where. The anti-car bias runs deep.
As a former F4 Weapons System Officer, I have experienced +8.5 g’s and around -2.0 g’s. One thing I do know is that the average person will become very uncomfortable when experiencing g forces (both in accelerating and decelerating) other than 1.0g. Many will become sick and that will spread to the other passengers (have you ever been on a plane when only one person used a barf bag?). There might be thousands who will be brave enough to travel it one time, but my bet is that most of them will opt to use another mode of transport (see Mark Twains description of a genuine Mexican plug in Roughing It: Chapter 24).
I don’t think people realize the energy of a 700 mph vehicle. If something goes wrong with a 200 mph train the result will be an awful crash and probably a number of fatalities.
If something goes wrong with a 700 mph vehicle the result will be confetti, some of it organic.
Yet Musk has other ways of sucking off the overly ample American public tit and feeding sloppily at our too generous trough:
http://www.latimes.com/local/lanow/la-me-elon-musk-tunnel-ceqa-20180418-story.html
Vs Hyperloop, what’s wrong with a plane? The trip to the airport and the hassle are what’s wrong with a plane and the hyperloop does nothing to relieve those problems. It’s a little faster than a plane and carries fewer passengers. Banish the TSA, make it walk on walk off and ticket sales at the gate, no, get rid of the gate too. No checked baggage either. Planes the way they used to be, no hyperloop required.
“Planes the way they used to be, no hyperloop required.”
In less than 20 years, computer-piloted vertical takeoff and landing (VTOL) passenger transport will be common. There will be far less need for large airports with large runways and multiple terminals…especially for flights under 500 miles. Instead, any fairly large parking lot in a small or medium-size city will be able to support an “airport.”
As I keep saying but many keep pooh-poohing.
To me, it’s a no-brainer. But the naysayers say that’s right, brains and guts all over the place.
If you liquefy the people first, all of these issues go away!
A human being is an incredibly inefficient device. Think intelligent squid. With eight arms and 2 really long arms, we could finally nail or screw correctly…
A squid in a liquid environment, can be easily transported in say ” an oil pipe line”. Usually, no waiting at a toilet to flush; as a matter of fact, if you were a squid, you would love to flush toilets.
Bones are old fashion; they are only needed for land. Think, more sea level rise, more water territory!!!
Now, don”t get me wrong, but look how intelligent those octopus are! And what big beautiful eyes!
We could eat fish, clams, etc., and not worry about CO2.
Our Einstein would probably theorize a vortex; lets call it a whirlpool. We could then used nuclear whirlpool weapons to drive our opponents away.
Lets get back on topic! LA to Vegas, one pipe line, no spacing, i.e. foot to head, 100 miles per hour, and gold fish to eat on the way….
Why does this remind of this?
https://en.wikipedia.org/wiki/Beach_Pneumatic_Transit
Nice demo but never used.
(Though a spin-off lasted awhile. https://en.wikipedia.org/wiki/Pneumatic_tube_mail_in_New_York_City)
PS “Boss Tweed” is mentioned. Thankful we don’t have a “Boss Hillary” in place to back Elon.)
“What Elon Musk tells us about the president who will follow Trump”
By David Von Drehle April 17 at 7:40 PM WaPo
“On the 28th day of June 1971, a baby was born in Pretoria, South Africa. If the last words of that sentence had been “Anytown, USA,” that baby might be on his way to the presidency.
………….
“President Trump 2.0, and versions beyond, will take the Trumpian tools of hype, novelty and shock that are so compelling on social media and deploy them with less frenzy, heat and bluster. They’ll resemble Elon Musk — with the proper birth certificate.”
https://www.washingtonpost.com/opinions/what-elon-musk-tells-us-about-the-president-who-will-follow-trump/2018/04/17/42e43486-4265-11e8-ad8f-27a8c409298b_story.html?utm_term=.419bf84b5a98&wpisrc=nl_rainbow&wpmm=1
To follow the daily Tesla drama (very dramatic during the last two weeks), click here:
https://seekingalpha.com/symbol/TSLA/analysis-and-news
Why would the inter-pod time increase to 80 seconds? Acceleration and deceleration time is part of travel time. At 615 km distance and speed of 1225 kph, travel time is 0.5 hour. 80 seconds x 2 is less than 3 minutes. So travel time will be 30 minutes + 3 minutes. Inter-pod time is still 30 seconds.
Why would passengers die if the tube gets pressurized to atmospheric pressure? If the tube is pressurized at the back of pod’s direction of motion, the pod will accelerate. If pressurized at front of pod, it will decelerate. Assume the tube is 3 meters in diameter.
Area = pi/4 x 3^2 = 7 m^2
atmospheric pressure = 100,000 N/m^2
Force on pod = 7 (100,000) = 700,000 N
Weight of pod = 15,000 kg
acceleration or deceleration = force/mass = 700,000/15,000 = 47 m/s^2
This is +/- 4.8 g. Like a roller coaster thrill ride but the pod has to brake before it crashes.
This is unlikely to happen because the air will lose pressure due to friction when it passes through a small hole in the tube. Turbulence will also dissipate the dynamic pressure of the air.
The supersonic pod will probably disintegrate.
“This is unlikely to happen because….”
———————-
I hate the likely part.
I calculated some simple numbers for travelling from my house in Oakland,CA to Disneyland, including items like parking, checkin, rental car etc. and came up with:
Driving: 7 hours (via In-n-Out 🙂
Flying: 4 hours 24 mins (OAK-LGB)
Hyperloop: 3 hours 6 minutes (based upon approximate station location in Hayward/Sylmar (though this location is vague in the tesla pdf)
I made some assumptions such as:
– Hyperloop terminals are smaller than an airport so parking/checkin/rental car time is faster
– Hyperloop does not require a specific departure time, you just get on the next available pod
It’s interesting that the LA terminal location means that you have to deal with the worst sections of LA traffic once you get off Hyperloop.
Because pods take passengers frequently, waiting time at the security gate should be trivial.
Just like it’s trivial in a big airport that has a plane takeoff every minute. /sarc
Well, it is less passengers, claim of 6M/year, while OAK has 13M/year and airports don’t operator 24 hours a day while the claim is the hyperloop would.
Maybe since it would be a smaller facility there would be less security gates so the security clearance would be about the same.
How many people really want to travel at 3AM?
climatebeagle, I fail to see how any of that (number of passagers) is relevant.
If the frequency of departure is extremely high, then waiting times for security are very small. Do you disagree with that?
Why do people even accept to wait a lot of time in airports? Isn’t that one of the greatest mystery of mankind?
> If the frequency of departure is extremely high, then waiting times for security are very small.
I think they might be less than an airport but they can’t be very small as you probably can’t afford a single slowdown to lead to empty/delayed pods, so you have to build some buffer time in? Also will the terminal operator want to offer the passengers shopping, so want them as a captive audience after security? Isn’t that a good revenue stream for airports?
My point with the numbers is that OAK has twice as many passengers, but has two terminals and probably has four or five security setups (X-ray, metal-detector etc.) in each terminal. How many would security setups might a hyperloop station have? Less setups mean larger lines.
“Hyperloop Test Track Under Construction In [Toulouse] France”
https://seekingalpha.com/instablog/22912651-daniel-jennings/5148235-hyperloop-test-track-construction-france
“320-meter long full-scale tube”
Yeah… impressive. In a kind of practical joke way.
Relying on pressurization in a complex system can be an issue:
From the caption on the Youtube video:
Because complex systems often have mind-bogglingly simple failure modes, what you see happen in this video is all chalked up to the accidental introduction of a small gas bubble during fueling. Details are hard to come by, but there’s a good account of what happened here:
http://www.thespacereview.com/article/1326/1
How much trouble could a small gas bubble or some similar thing cause the Hyperloop.
I was looking for the 1987 failure of a similar vehicle where I remember a cool picture of a Centaur upper stage crumpled upon itself, but I couldn’t find the picture.
There are so many great articles and analyses on this website and WUWT is one of my favorite stops for rational commentary on issues. But I’m afraid the analysis in this OP doesn’t stack up.
I am fully in agreement that the California high speed rail project has been a disastrous boondoggle. Hopefully the project will be abandoned or significantly reworked before much more taxpayer money is wasted. I also agree that there is serious question whether Hyperloop would ever be economically feasible or commercially viable. But some of the engineering critiques raised in the OP are a little off.
Let’s start with the vacuum. Yes, there are challenges in scaling up. And yes there are challenges with structural stability. But these are hardly show stoppers. A perfect vacuum is not required, and minor leaks are easily dealt with. Furthermore, it is possible to add structure stability either outside or inside the tube, particularly if the tube is enlarged and less than the entire circular surface area used for the pod. As for the catastrophic implosion risk, it was strange for a paragraph to be devoted to the risk of a leak — i.e., air getting into the tube — and then, as an example, we are shown a video of a tanker car catastrophically imploding due to too much air being pulled out of a structure that was not designed to operate with structural integrity as a vacuum.
Passenger throughput is claimed as the biggest problem for Hyperloop. The question isn’t whether it is the most “efficient” way to move people. How many planes fly from LA to, say, SF every hour? The question is whether it is a viable commute option for people who want a faster trip than driving. Again, the Hyperloop may be utterly cost-ineffective and may be a terrible investment. But the fact that it doesn’t move as many people as a full lane of traffic is not, in and of itself, a reason to abandon the project. Willis questions the every 30 seconds departure, because that is only 3,300 passengers per hour. But again, how many people are we moving by air every hour?
Then there is the deceleration claim. As others have pointed out, a 0.5G deceleration is certainly not a limit. Decelerating from 760 mph to 0 mph in 30 seconds in an emergency situation is not going to be particularly problematic, and can be further accommodated by seating backs-forward. Even turning seats around after acceleration is a very doable option. Again, there might be minor inconveniences to deal with, but there are various options and these are pretty simple engineering issues to address.
Finally, Willis is concerned about the station loading and unloading timeframe. Yes pod throughput is an issue, but easily resolved. Disneyland solved it decades ago with lots of “pods” and multiple loading/unloading points. This is an entirely trivial engineering problem to solve.
Again, Hyperloop may be a financial boondoggle. It might make little economic sense. It might be commercially nonviable. But let’s be a lot more careful about level engineering problems that are readily solvable or, in some cases, completely trivial to deal with.
Thanks for the comments, Climatereason.
Can the technical problems inherent in the Hyperloop proposal be solved?
Generally, yes. Generally, any technical problems can be solved if you throw enough money at them. My point was that there are too many such problems for too little increase in either passenger throughput or travel time to make the system economically viable.
For example. You can indeed solve the station loading and unloading timeframe in the manner that you propose, multiple pods. But with a 30-second headspace between pods, if just one station in the entire loop has a loading problem from any cause, the whole system has to slow down.
Or you could just skip loading the pod from that station and keep the whole system running … but then where do you insert the missed pod back into the system? All the pod slots in the parade are filled.
Nor is there any great decrease in travel time. Including downtown-SF to the airport, checking baggage, getting through security, flight time, and LAX to downtown-LA, it’s not hard to spend nearly as much travel time on the ground as in the air … and the proposed Hyperloop stations are further from both city centers. Remember, the actual speed of the Hyperloop is only about 60% faster than a commercial jet airplane. Flight time LAX-SFO is an hour and a half. Hyperloop is CLAIMED to be 35 minutes flight time, but real-world performance could easily be 50% longer. So the difference is likely only 45 minutes or so, a chunk of which will be eaten up in longer downtown-to-station times at both ends. So total time saved is likely to be only 15 to 30 minutes out of three hours or so… hardly impressive.
Can the tube expansion problem be solved? That one is a bit tougher. If you look at oil pipelines, every so often they have an up-and-down kink in them to solve the expansion problem. The Hyperloop engineers are rather vague about this one, saying:
However, such a device has not yet been built, and the airport version doesn’t have to maintain a near-perfect vacuum.
Next, the terrorist question. The Hyperloop will be an incredibly tempting target to a terrorist. The impact would be far, far larger than say blowing up an airplane. This one is much tougher than the technical problems because it is a human problem. How do you plan to protect hundreds and hundreds of miles of vulnerable Hyperloop pipe? A cheap and simple shaped charge could easily blow a very large hole in the pipe … what is the technical solution for that?
Finally, earthquakes. Freeways are designed so that they can move a few inches in case of an earthquake … but a tube with a pod going 750 mph in it cannot sustain such a shift. Again, is it solvable? Possibly, perhaps even probably … but again, at what cost? I don’t know if you’ve ever been out to the park north of San Francisco, where the horizontal shift in the ground from the 1907 quake was about 13 feet (4 metres). Such a shift would, of course, destroy a freeway, and might cost a few lives, perhaps a dozen, before the traffic stopped … but the same shift would rip a Hyperloop tube in half, and probably cause hundreds and hundreds of deaths. The lawsuits to follow can only be imagined, and unlike the freeways which are publicly funded and thus relatively immune to lawsuits, the Hyperloop company will have to insure against such an occurrence … again, not cheap.
Initial claims from Musk were that the system could be built for $6 billion, which seemed way low to me. Leaked docs from the company now put it at somewhere between $9 billion and $13 billion, and that’s before the first shovel has gone into the ground. Considering the problems Musk has had keeping his car costs down, it’s not encouraging.
So I fear that your “it’s all solvable” point of view, while technically valid, is very likely to drive costs up far beyond the breakeven point. Yes, it’s easy to wave your hands and say that any technical hurdles can be overcome … but a number of these are not minor issues that are “readily solvable” or “completely trivial” as you claim. They are things which have never been attempted, and those things are generally not as easy as they might seem to overcome.
Best regards,
w.
Thanks, Willis. You’ve raised some valid points and concerns about the project. Many of them deserve careful scrutiny and weighing of pros and cons: from an engineering standpoint, from a cost standpoint, from a safety standpoint. My point was simply that the idea is far from a dead end from an engineering standpoint.
It may be, for example, that something like a Hyperloop is perfectly feasible in a kind and gentle world, but that the additional expense of hardening it against terrorist attack in our current geo-political climate makes the project infeasible. This kind of analysis has to be done all the time, and I can certainly see someone raising the same concern about the latest and greatest skyscraper that goes up.
It may be, for example, that something like a Hyperloop is perfectly feasible in a more stable region that is not prone to earthquakes, but that the additional expense of hardening it against tremors makes the project infeasible. I tend to think this one is pretty solvable, even in California, but it would require some hard analysis and numbers to make the decision.
At the end of the day, it seems most all the technical difficulties can be solved pretty readily, at least for the system to fulfill its functional purpose. Then the questions become: (a) how much would it cost for the base system, (b) how much would it cost to harden it against particular risks in the world we live in and in the particular geographical region, (c) how many riders would realistically ride and at what ticket price, and so on. Once we have better answers to those questions, a rational decision can be made about whether the project makes sense. But I just want to be cautious not to take the engineering criticisms a bridge too far, at least not on functional engineering grounds. The real nail in the coffin is more likely to be social and/or commercial.
Personally, I am skeptical that it could be constructed for a commercially-reasonable cost. The $6B pricetag you mentioned is a joke — I hadn’t heard that number. If that was really the claim, then they didn’t know what they were talking about. We’re not talking about a few % points in cost overruns. It isn’t even in the ballpark.
Even the bullet train, which in many ways is an easier project to build, has now ballooned to an estimated $70B or so, last I heard. There was so much misinformation surrounding the bullet train when presented to the voters years ago, it was a real travesty. As someone who voted firmly against it at the time, when the bullet train boondoggle comes up these days all I can do is mutter under my breath to family and neighbors and anyone who will listen, “I told you so.” And $70B isn’t even right. I have full confidence that the estimate will eventually exceed $100B before any serious work is even done. And even that number will still be too low.
As someone who has to estimate project costs for my work, I’m regularly astounded at the wildly inaccurate initial estimates that some of these large public works projects throw out. An order of magnitude off in some cases.
On that point, I am firmly in agreement with you.
Best,
Thanks, Climatereason. Here’s the text from the promoters::format(webp)/cdn.vox-cdn.com/uploads/chorus_asset/file/7352899/Screen%20Shot%202016-10-26%20at%203.20.18%20PM.png)
Like you, I just laughed when I saw that …
As to the question of earthquakes, here’s the shift in the earth I was mentioning yesterday. I’ve been there, it’s about thirty miles from my house, and it’s amazing. In one place it was a total of 24 feet of lateral movement, the San Andreas is a strike slip fault … and I doubt greatly whether you can engineer a Hyperloop tube to survive that …
Best regards,
w.
As I wrote, the whole tube will be in a tunnel anyway (less costly) so the external attacks are limited.
Maybe this is a solution to limit the rate of incoming air in case of a breach: a tube inside a tube.
Which creates other complications for evacuation, arrival of safety teams, etc.
s-t April 22, 2018 at 5:39 pm
I’m sorry, but that simply is not true. Take a look at the promoters’ budget up above. There is $600 million for tunnelling (through the Tehachapi Mountains) and $2.55 BILLION for pylons. Much of the proposed line is aboveground.
w.
For the pilons based project to be viable, you would need quasi flat terrain. But then, why bother with pilons?
Willis:
The $6B cost claim is such nonsense. Front page of the San Jose Mercury News this morning indicates that extending BART to San Jose is costing $4.8B. That is for 6.1 miles and related station stops.
Granted, over open land between cities each mile isn’t going to be that expensive, but it gives us some idea of what the cost is to build a rail system through existing city infrastructure. They’re going to have that problem at both ends in spades, plus several urban stops in between.
Hyperloop from SF to LA isn’t even going to make it as far as San Jose for $6B. Perhaps barely out of SF.
The number just isn’t even in the ballpark, and it is completely irresponsible for them to claim otherwise.
The tubes should be a composite made of structural concrete with a thin steel gas barrier on the outside in order to take the atmospheric compression forces and prevent air from passing through the porous concrete. A steel sliding expansion joint should be provided every 200 m fitted with bellows seals to exclude dirt from the machined sliding surfaces and double O ring seals.
Escape from such a structure in the event of pod failure would be difficult and might be the most difficult technical problem. Earthquakes in California would be another huge problem for such a structure.