Download document:
Hyperloop-alpha - .PDF file.
Features editor
Stuart joins the musing over Elon Musk’s Hyperloop proposal, and wonders whether Musk and his ilk are the Brunels or Edisons of our age.
It’s extremely tempting when you work on a publication devoted to new technologies to use science fiction analogies. It’s got to the point where I’m extremely tempted to put a ban on all mentions of Minority Report in our style guide (although I have to admit I did reference it myself last month). But when a concept comes along that’s so clearly science fiction-y, it’s almost impossible to avoid it.
When Elon Musk made his long-awaited announcement of his Hyperloop concept last week, all those science fiction comparisons came out. For those readers who’ve been out of the loop, Hyperloop is a high-speed medium-to-long distance travel concept where passengers ride in carriages or ‘pods’ contained within a sealed tube with low air pressure to minimise resistance to the pod’s forward motion. To minimise it even further, the pods are propelled using a magnetic levitation (maglev) system, with linear motors placed at intervals along the floor of the tube providing the impulse.
It’s not a new idea. Vacuum trains (sometimes known as vactrains) were first dreamed up in the early 19th century, and London had a pneumatic railway in Crystal Palace which operated for a year in 1864. The ‘father of rocketry’, Robert Goddard, was also among the conceptual pioneers in the early 20th century. And, bringing out that sci-fi connection, they feature in the works of Ray Bradbury, Arthur C Clarke (who also proposed the space elevator), Robert Heinlein, and in films like Logan’s Run. If you were one of the people who managed to stay awake during the first Star Trek film, you might have seen one in future San Francisco.
Musk has come up with some clever additions to the idea. Unlike most vactrain concepts, his tube isn’t completely evacuated: it’s far too difficult to pull a perfect vacuum even in a relatively small tube, let alone one which stretches from Los Angeles to San Francisco and is big enough to enclose something the size of a bus. Instead, his tube is kept at 100Pa (about a thousandth of an atmosphere). Each pod is equipped with a compressor on the front which sucks the air out of the way and pumps it underneath the pod so that it acts as an air cushion, keeping the nickel-alloy skis on which the pod slides from making direct contact with the tube floor. With linear motors placed every 100km, this means that the pods will reach a speed of 1220km/hr — not far short of the current land-speed record — in about 35 seconds from a standing start, with the whole journey from Southern to Northern California taking 35min. That’s about half the time it currently takes to fly.
The whole system would be powered by solar panels on the roof of the tube, with energy to spare, according to Musk — the photovoltaics would generate some 57MW, which is three times as much as he says the system will consume. The tube would be carried on pylons, 6m tall, placed every 30m — and if you place them alongside an existing highway, it solves land-purchase problems. And the cost? Musk reckons about $7bn (£4.5bn).
This all sounds somewhat too good to be true, and we at Engineer Towers have joined in with everyone trying to pick holes in the plan. Is sealing technology up to making a leak-proof tube that long? How much energy will it take to keep those pumps operating all the time to maintain the partial vacuum? How will the pods be kept at a comfortable temperature, when you can’t pump in cool air from outside? Is current photovoltaic technology up to it? What about maintenance and emergency rescue? And can it really be that cheap?
We don’t have the answers anymore than any one else does — and we’re waiting with interest for the results of various studies. But a lot of the scepticism has been allayed by the fact that it’s Elon Musk who’s proposing it. Although not an engineer by training (he has degrees in physics and economics) Musk has a well-deserved reputation for making technology happen. You can’t ignore Tesla Motors, the world’s most prominent pure-electric car manufacturer, or SpaceX, the only private company to send spacecraft to the International Space Station. And as for photovoltaics, Musk is also a co-founder and chairman of the largest supplier of domestic solar power in the US, Solar City. It’s probably safe to say he knows his solar stuff. And, of course, he has the money, mainly from his first venture, the online financial service Paypal.
Some might say that none of these ventures break new ground technically, but then neither does Hyperloop, at least in the terms Musk is proposing. And with banks notoriously unwilling to invest in both low-yield infrastructure projects and risky new technologies, it might be that only someone with Musk’s billons could take such a project forward.
Musk put the idea forward in despair at the proposed cost of a high-speed train link between LA and San Francisco — a situation which is, of course, parallelled here in the UK. Could a Hyperloop replace HS2? It probably couldn’t run on solar power — the home counties are a far cry from sunny California, even in a good summer. But the same problem applies. Who’d pay for it? HS2 is predicted on proved technology — proved now, and not in the 30 years it’d take to build it. Even if you built the tube alongside the M1 and M6, it’s hard to see the Treasury going for it.

It’s tempting to think that back in Victorian days, the system would be up and running by now. Entrepreneur-engineers such as Brunel, Boulton, Watt and the Stephensons weren’t put off by the risks of developing technology and drove the railways across the country by sheer force of will (and, crucially, deep pockets). Are technology billionaires like Musk the modern equivalent of these pioneers, or their US equivalents like Edison? And if so, do we have anyone similar in the UK? Names like Richard Branson and Herman Hauser spring to mind, but I have a nasty feeling that the closest equivalent is Simon Cowell, and I dread to think what the background music in a Syco Hyperloop would be.
At the moment, Hyperloop is — quite literally — a pipe dream, but Musk has recently stepped back slightly from his original statement that he wouldn’t develop the system himself, saying that he’d probably consider building a demonstration version. That would certainly dispel a lot of the doubts. It’s certainly part of the science fiction future I’d like to live in.
I think by far the most interesting thing about the proposal is that it doesn’t require some massive jump in technology or a new type of hyper efficient fuel source which doesn’t exist yet, there are some elements which would need to be development beyond their current state, but you could put together a demonstrator with stuff you can buy today.
I’d love to be part of any group that really wants to try and make it work .. anyone feel like starting a hyperloop company?
Friday afternoon…. winding up for the weekend…. then you press my button….
First, we need to break away from 4′ 8.5″; it sort-of still works, but there are some awkward features that never got resolved. Will this proposal overcome them? Basically it’s about safety/ redundancy, time saving, energy use and cost to implement and change….. amongst many more….
Yes, I’d love to put my twopence-worth in. It starts with calculation then the confidence that, when scaled to fit our landscape, we can afford to start. Followed by a wind tunnel test then a model….. and finally; something real.
It’s all about breaking a loop in my view!
From Elon Musk’s own presentation he states that a limit on speed exists if a lump is pushed down a tube as the gas trying to get past it will become choked at some point.
This is a correct comment but an incorrect conclusion as the result of choking the flow is that the pressure difference betweeen front and back of the lump will increase (resulting in a higher downstream Mach number) and a rising drag term. Nothing wrong with this but it is not, as he states it, that this is a “speed limit”.
Replacing the flow around the lump with a big blower in front ramming it through a duct within the lump does not make this go away as the choking now occurs in the duct, and possibly between the blades of the blower, instead. He simply moves the “problem” to another part of the system.
Something very like this was proposed in the early 19th century as a way of making waveless (and hence wave dragless) barges for use in narrow waterways.
Elon Musk is not a Brunel/Edison, he is an ideas enthusiast who is fortunatley rather wealthy. Good luck to him but (like most of us if we are honest) he needs to work on the self-education.
Not sure from whence I found this -possibly even the Engineer Journal, but it so beautifully sums up our work.
“I take the vision which comes from dreams and apply the magic and logic of science and mathematics, adding the heritage of my profession to create a design.
I organise the efforts and skills of my fellow workers employing the capital of the thrifty and the products of many industries, and together we work towards our goal undaunted by hazards and obstacles.
And when we have completed our task all can see that the dreams and plans have materialised for the comfort and welfare of all.
I am an Engineer.
I serve mankind by making dreams come true “.
( Found pinned to a site hut during the construction of the Konkan Railway )
Engineers do for 10p what any fool can do for £1.
N Shute -Engineer turned Author used this phrase in the dedication to each of his books.
As Jonathan Howes commented, the problem of flow choke may have just been moved to another system, the compressor. The devil will be in the details of the compressor design, since getting the aerodynamics and flow efficiency right would be key. Fail safeing a 300 mile long evacuated tube warrants a thorough review of technology options and their costs. So far , the 50 page proposal is only half baked and I hope a more thorough review will come out in the beta study.
Ron George, Dubai
http://www.georgeron.com
If it develops a leak what stops the cars crashing into each other at high speed?
How do you develop enough air volume to support an air bearing in a vacuum.
I can think of plenty more but I really don’t like people claiming that their system is cheaper and more reliable when they have never built one.
This is certainly an interesting idea with little theoretical reason why it cannot happen.
Keeping a long pipeline free of even tiny leaks is a lot more than possible, it has been done in the oil, gas and compressed air business for a long time ai much higher differentials in pressure than 1bar.
Getting power into the “train” might be less easy. This problem plagued the high speed train projects of the 80s and 90s and isn’t going to go away easily. If it is the track that provides the impuse, then that solves that.