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Heaven Help Me, But I Sort of Love Elon Musk’s New Hyperloop Idea. (Well, at Least in Theory…)
The sci-fi buff and futurist in me just loves, loves, loves Elon Musk’s idea of building an underground hyperloop between Washington and New York. Heck, I would love the idea even if the vacuum tube connected LA and San Francisco or Houston and Dallas or Chicago and St. Louis. Even Dubai to Abu Dhabi.
Now since I live in the greater Washington DC area, I find the idea even cooler. I would love to be able to zip to Manhattan in 30 minutes. Plus, I would imagine, real-estate prices within driving distance of the stops would get quite a boost. And when there are hyperloops from coast to coast, time to get started on a space elevator.
But, but, but … the technology does not yet exist. The regulatory path to approval does not yet exist. The business case does not yet exist. The commitment for public financing does not yet exist. If we were a country that could build a project like this, I imagine we would already have a continent-spanning, high-speed rail network. And about the cost. Probably north of $300 billion. It is hard to see public financing on that scale to fund better transportation for the Acela corridor. (Oh, and it seems likely there would be additional stops, such as in Wilmington and Newark.) Didn’t the POTUS get elected by promising to help the left-behind communities in the Rust Belt and Appalachia? Musk’s idea for a city on Mars might be more realistic. (The Economist offers some conceptual problems as well as some boring, non-Boring Company transportation ideas.)
Then again, this is hardly the worst idea I’ve heard lately. (Using protectionism to “bring back” manufacturing jobs, travel bans, a solar border wall immediately pop to mind.) And I love that someone is trying to push forward rather than look backward. Anyway, Wired offers a pretty good take on the Musk hyperloop:
First, you have to get the OK from all the states and cities and municipalities involved…. To give you a sense of how big a deal getting everyone on board with a hyperloop would be, consider that just New York and New Jersey have struggled for over 20 years to reach an agreement to build a single tunnel under the Hudson River — a tunnel the region needs desperately…. Even if the feds could somehow take the lead on this one and ram a hyperloop through localities, it’s not clear who’s in charge. The Federal Railroad Administration, which handles high-speed rail? The Federal Highway Administration, which manages the roads? Who determines safety standards and holds the Boring Company accountable?…
And then there’s the little problem of moolah. Just updating the current Northeast corridor railroad — you know, the one run by Amtrak — to high-speed rail standards would cost an estimated $123 billion. Tunneling will be even more expensive…. Carving less than two miles of tunnel under New York for the Second Avenue Subway took $4.5 billion. Even if this hyperloop were entirely privately financed, it would take lots of zeroes…. Environmental effects can also strangle projects indefinitely. An extension of Washington, DC’s metro has been in the works since 1994, but was hamstrung by lawsuits alleging the project would destroy wetlands and other wildlife habitats…. Then there’s the little trouble of perfecting a technology that doesn’t exist yet. Hyperloop One, one of the many companies competing to build the first hyperloop, ran a successful test out in the Nevada desert last week. Just a few small problems: The track was 315 feet, the “train” a sled, and that sled reached just 70 miles per hour. (A completed hyperloop should hit 700.)
It’s a long way from here to there, even with “verbal government approval.”
Published in Economics, Technology
First used at the Crystal Palace Park in London, 1864.
Later, there was Beach Pneumatic Transit.
Thank you Chuck and I’m with you! I have to say that scrolling down these comments was depressing me terribly until I got to yours. As the song said in La La Land: “Here’s to the ones who dream; foolish as they may seem…” And even “here’s to the mess they make”. I still want to think of America as a place that dreams big.
Thank you @chuckenfield and I’m with you! I have to say that scrolling down these comments was depressing me terribly until I got to yours. As the song said in La La Land: “Here’s to the ones who dream; foolish as they may seem…” And even “here’s to the mess they make”. I still want to think of America as a place that dreams big.
Not at all like a subway. In a subway should it run out of electrons you can get out and walk up the tracks to an emergency exit. In this system the tracks are in near vacuum so you cannot. The Tunnel under the English Channel is only 20 odd miles long (the english channel is only 22 miles wide) – This would be a tunnel system 250 – 300 miles long. (or much longer if you’re going to do the entire Boston to Philadelphia network) The challenges presented by a project like this are at least an order of magnitude larger than the English Channel tunnel.
Crazy.
The technology of star trek, is meant to be a tool to tell stories – not actually forecast workable technologies. That doesn’t mean that some ideas – like communicators that became cell phones or data pads that became tablets – couldn’t in some form be workable ideas.
No.
Because 1 end would have to be open in order for your payload to leave – it would no longer be a vacuum.
If you’re interested in non-rocket launch systems, you should look up the works of Gerald Bull. A designer of artillery systems who wanted to shoot small satellites into orbit with a cannon. However this kind of system would never work for people, as they’d die in the first second of flight when that 100+g force acceleration launched them down the barrel of the gun.
He ran an experiment back in the late 60’s – early 70’s called Project Harp. Where he welded 2 naval artillery gun barrels together, and was able to launch sensor packages out of the atmosphere. (because they didnt have orbital velocities – they would fall back to earth)
Hyperloop is hype until we see a plausible plan to deal with the massive engineering challenges they face.
For example, they have not begun to address the serious problem of thermal expansion. Musk’s concept involves a single welded steel tube hundreds of kilometers long. A steel tube that long will expand and contract over 1000 feet during the day. Musk has said that this will be solved at the terminal ends by having a terminal that adjusts to the moving endpoints of the tube. And each pylon will have bearings that allow the tube to slide back and forth.
This is not even remotely an adequate solution. For one thing, the hyperloop has curves in it. It is not built in a straight line. This means that every single arc in the system will be constantly changing in size and position, by hundreds of feet. This is an immense engineering challenge to solve.
Then there’s buckling from differential heating. The top of the hyperloop gets much hotter than the bottom. This puts a buckling force on the tube – a tube already under huge compression loads because of the vacuum inside it.
And whatever solution they come up with, it has to be able to do it while holding a near perfect vacuum in a tube hundreds of miles long. If you try to solve this problem with expansion joints, you will need hundreds of them – maybe thousands. If any one of them failed, it could destroy the entire loop.
Another engineering problem with Hyperloop is that it is not fault tolerant. Mass transit systems should fail safely when possible, and generally require multiple points of failure before an accident occurs. But if any portion of the hyperloop tube failed, it would cause a cascading collapse of the entire thing.
There are a number of other serious engineering challenges at a very basic level with hyperloop.
Maybe these problems aren’t insurmountable. But solving them will certainly drive cost estimates up, perhaps to the point where the whole thing is just completely infeasible financially.
But here’s what bothers me: If I were running an engineering company seriously trying to build this thing, the first thing I would do is make a list of the ‘showstopper’ technical problems, and all our early resources would be dedicated to proving those out and coming up with feasible solutions to them, before another nickel was spent on the project. Early feasibility is just responsible engineering practice. And yet, when I look at the players in the Hyperloop market, I see showmen, not serious engineering. Cute college design competitions to see who can come up with the ‘neatest’ pod, collaborations with design schools to design futuristic terminal buildings, ‘proof of concept’ demonstrations that amount to a toy train on a maglev track we’ve known how to build for 20 years… None of this breaks new ground, or answers any serious questions.
When a company seems to be investing more money and effort into promotion and 3D renderings as they are into trying to solve the problems that might prevent the project from working at all, hold on to your wallet. The business model in question might be more about extracting rents than building an actual functioning, commercial hyperloop system.
Did I mention we’re talking about politicians and bureaucrats?
That makes it a feature and not a bug.
Seawriter
Does Hyperloop fill a great need? Not even close. It is does matter one iota that it may be a technological marvel.
However, speaking of transportation in and around our cities, I think there are some great needs that badly need to be solved and filled in the near future.
I don’t know about other states but here in California, our State Transportation planners are purposely creating gridlock, creating hellacious commutes from the extremities of urban areas and thus trying to force people into our central cities to avoid those terrible commutes for inane and completely ill advised environmental reasons.
It is a war on the suburbs. Pure and Simple. The suburbs are to be crushed.
Only a few enormous problems with that.
First of all, suburbs on the periphery of our great cities are where land is cheapest and thus where mass produced housing can be built with by far the least expense. It is where new housing should be built and if it is not built there middle class housing needs likely will not be met. Urban infill housing will never compete on a price level with mass produced housing on the periphery- the cost difference is extreme. But nooooo! our planners and our betters have determined that building housing on the periphery is an environmental crime against Mother Gaia and thus simply verboten. So it shall not be done! And so all new housing must be much more expensive that it ought to be.
All major cities in California, as do many other cities around the country, have a huge housing crisis. Housing costs in rents already consume near or around 50% of many families incomes around the country. Fashionable urban planning and transportation policies have priced housing far beyond the reach of the young and much of the middle and lower classes. It is already a horrible social disaster, but the real effects of social decline are just now being felt. The next generation of workers may not have a place to live!
Secondly, relative to a subject that James writes a great deal about – productivity – new start ups are most often starving for capital and desperately need the cheapest cost environment to make a go of it. Historically, it is that cheap land on the periphery that allows for much cheaper rents that provide a place for new start-up to open and a place for them to grow which is not nearly as possible in the urban core. Furthermore, the urban core is not a place that really is desirable at all for manufacturing. There simply is not the land or the suitable infrastructure. On the periphery is where manufacturing needs to go. But here again, the War on the Suburbs denies the appropriate location for manufacturing to grow. I suspect that this lack of available and suitable manufacturing locations has had a serious effect on our nation’s ability to create new manufacturing businesses and jobs.
Dan,
This also describes 99% of the Green Energy projects. Once addicted to the government money & guaranteed green investment money these firms don’t care if they can beat the real problems so that their technology will ever be market viable. They are glad to stay on the green gravy train ad infinitum. We would have had far more viable renewable energy projects, probably of the niche type rather than total solutions, if we could have gotten rid of these green energy parasites.
Only the discipline of the real free market brings the real innovations that resolve the problems. Necessity is the mother of invention and the father too.
Regards,
Jim
I was reading about this last week, and I was astounded. It’s happening in plain view, and nobody’s paying attention.
Read this Tweetstorm. Start here and follow it down. It’s absolute craziness.
https://twitter.com/ThomasWictor/status/887838918753763328
Need is easy. Even morons like me can identify need. Our economy hasn’t grown on need for a long time. Opportunity is the driving force. Capitalizing on opportunity requires vision and drive, two qualities which are relatively scarce.
I liked Heinlein’s ideas of the Roads better than the hyperloop.
This is the main showstopper. I have struggled to find any proposal that makes hyperloop safe for passengers under off-nominal conditions.
Among the safety issues:
If you want to see what that looks like, have a look at what happened when the Mythbusters tried to pull a vacuum inside a rail tanker car:
That tank car crushed after the vacuum came down to 23″ of Mercury, or about 11.3 PSI. That’s only a 3.4 PSI differential against the atmosphere. Musk’s design requires going down to almost 0 PSI.
Now imagine a tube like that hundreds of kilometers long, collapsing under 3 times that much force.
Other than that, it’s a great idea, though? Worth a great big government subsidy? I mean we can hand wave away those minor problem issues you point out at the Congressional committee hearings to secure funding. Any presentations would be to politicians, not intelligent creatures after all.
Seawriter
If they really have extra money to spend on the Boston – DC corridor, improve I-95. Make it at least 8 lanes everywhere, with some limited access high speed lanes. At least that will improve the problem, and it will actually work.
In CT when they expanded just a couple of stretches north of exit 50 from 2 to 3 lanes they deliberately made all the new overpasses just big enough to hold the expansion and not big enough to accommodate any further expansion. Same with replacements along the stretch that stayed 2 lanes. No room to add a third lane.
We also need to build a couple of bridges between CT and eastern and central Long Island
Glorious!
Ah – hadn’t thought of that.
Although I’ll bet they could rebuild every overpass, rebuild every bridge, and make I-95 ten lanes wide start to finish for less money and in less time than the tube would require. And again, it would work.
Doesn’t mean it’s a good idea, though…
The same is true of I-beams, but we don’t refer to them as being weak in compression. Steel tubes are very strong in both compression and tension. They are less strong in compression because they only fail by buckling when in compression, but that doesn’t make them weak. Have fun trying to collapse that scuba tank by pulling a vacuum on it.
My nephew and I made a vacuum cannon out of schedule 40 PVC pipe (rated for about 120 psi working pressure) and two layers of aluminum foil to plug the ends. Our Vacuum pump would only pull 20″ Hg, but the pipe and aluminum foil were fine. That rail car was not a pressure vessel. It was made to hold liquids. It’s the steel equivalent of a milk jug.
The old steel soda cans were pressure vessels. They were orders of magnitude stronger in tension than compression. I think the point still stands.
So is a basketball. So what?
How do you think that SCUBA tank would fare if we pulled a vacuum on it, then put it in a 3000 PSI compression chamber? Especially after we hit it with a hammer to introduce a dent on the side (-:
It’s not the steel itself that is weaker in compression than tension – it’s the application. Pressure on the outside of the cylinder is applying a buckling force to every point. So long as the pressure is exactly equal all the way around, you might be fine. But introduce a stress riser or an asymmetry in force due to a dent, and you have an interesting day.
This must have been a small diameter pipe. It should not be surprising that 1″ ID pipe designed to handle 350 PSI internally is capable of handling 9.8 PSI externally. But look at the ratio of wall thickness to interior size. Schedule 40 has a .133″ wall thickness in a 1″ tube. But by the time you get to 2′ in diameter, you need a wall thickness of about 2/3 inches, and the pressure rating drops to 120 PSI.
The result of this is that as the diameter of the tube grows, the pressure it takes to collapse it drops faster than the interior pressure it takes to burst it. A 1″ diameter schedule 40 tube can handle 1200 PSI of internal pressure before it bursts, and 975 PSI of external pressure before it collapses. But by the time you get to an 8″ pipe, it can handle 500 PSI of interior pressure before bursting, but only 50 PSI of exterior pressure before collapsing. The ratio of exterior to interior pressure capability drops from roughly 1.2-1 for the small diameter, to 10-1 for a 8″ diameter.
This is why I emphasized the need for a dent or other stress riser. If the tube is perfectly round, the external pressure is evenly distributed around the cylinder. Put a dent in it, and suddenly the force is no longer symmetrical. When the Mythbusters first tried collapsing the tank car, they couldn’t do it. But once they put a dent in it, it collapsed easily.
The tank car Mythbusters used was most definitely a pressure vessel. DOT-112 and DOT-114 tank cars are specifically designed to carry gases under pressure, and are tested to an overpressure of 600 PSI. Even tanks that are not designed for pressurized transport have to be tested as pressure vessels, because liquid contents expand and contract due to temperature, and if they are volatile they can’t be vented. These types of cars have pressure relief valves set at around 350 psi.
So that actually makes the case I mentioned above. The Mythbusters took a tank that can handle 600 PSI when internally pressurized, and managed to collapse it and utterly destroy it with a mere 3 PSI pressure differential, once there was a dent in it.
For further proof of how weak such a cylinder is when the force is coming from outside, these tankers also have a vacuum relief valve, specifically to prevent the tank from collapsing. A common scenario is a tank that is completely emptied while sitting in the hot sun then sealed. Night comes along, the interior pressure drops as the air cools off, and foom! Therefore, they need a valve to let air in when the internal pressure drops, precisely to prevent collapse.
So how much negative pressure differential are they designed to handle? A typical vacuum relief valve will pop when the internal pressure lowers only 0.75 PSI compared to ambient. And remember, the Mythbusters managed to collapse one with just a 3 PSI difference.
BTW, the pressure vessels in those cars are made up of 7/16″ steel, almost the same as that of the Hyperloop, which specifies 1/2″ steel. They are also almost the same diameter, so the comparison is closer than you think.
Now imagining cutting the ends off of those, and welding tens of thousands of them together. Evacuate the whole thing down to almost zero pressure, then start running heavy cars through it at twice the speed of sound, while it’s expanding and contracting by about 1300 feet in length from night to day, every day. Just how long do you think that thing will survive?
Avoiding localized air compression would be hard, yes. Making it a loop would help, but there’s still the difficulty of inserting a capsule into the airstream smoothly.
Chuck Enfield (View Comment):
Seems like it’d be safer than evacuating the tube, though. But you’re right, it would use a lot more energy.
It would be if it was long enough… (-:
As Gerald Bull found out, such a gun can also be used to shoot at your enemies. Saddam Hussein wanted to do this, and Israel didn’t want him to. So now Gerald Bull is no more.
And that’s the real rub. Sub-orbital spaceflight is not hard. Orbital spaceflight is orders of magnitude more difficult.
The problem you have with shooting a projectile into orbit is that it needs to still be going 17,000 miles or more by the time it reaches orbital altitude. We simply have no technology that could launch a projectile so far in the atmosphere that it could do that. And if you did, what comes out of the barrel would be more like a bomb going off than a projectile headed for space, because at speeds in the hundreds of thousands of miles per hour, Interacting with the atmosphere would cause an immense release of heat energy.
There is a very cool non-rocket alternative to obit, through. It looks feasible in theory. Basically, you use an airship. A really, really big one, shaped like a giant ‘V’. An airship so big it never comes to earth, but docks with a floating ‘spaceport’ at 140,000 ft.
As the airship rises into thinner and thinner air, you start moving forward slowly under power, so the combination of displacement lift and aerodynamic lift causes you to go higher. Over a period of weeks you keep ascending/accelerating, until you are basically in low earth orbit. With a big enough airship going at orbital speed, there are still enough air molecules to maintain lift at orbital altitudes. Then you reverse the process to come back down. Actually, you just shut off the engines, and drag from the tenuous atmosphere will slowly bring you back down.
You get a lot less drag without the tube. Why have the tube at all if you’re going to keep it at ambient pressure?
Perhaps I misunderstood your argument. You seemed to say tank cars are flimsier in compression than they would be if they were designed as pressure vessels. Soda cans are pressure vessels and are also flimsy in compression (basketballs too). As Dan has laid out above, pressure vessels are often, if not always, weaker in compression than tension. Please tell me where I misunderstood you.