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.
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