For a while now there have been tantalizing hints that Elon Musk is at it again. His usual way of approaching a problem is to look at an industry, find some fatal flaw in it, fix that flaw and then leave everybody else in the dust, wondering why they didn’t do what he did. He’s one of the most interesting people on the planet at the moment and there isn’t a week that I do not come across some bit of information that re-inforces that view. I’m not a person that will readily admit to being a ‘fan’ of someone but let’s leave it at that I find it hard to not be infected by his devil may care attitude towards all things holy in industry and convention. Recently there has been a lot of buzz regarding the ‘hyperloop’.

The Hyperloop is the code name for his plan to disrupt the transportation industry, and maybe to hedge his bets on Tesla (which attempts to do the same in a less revolutionary way), and because of the lack of details speculation runs rampant about what it could be.

I’ve seen the most fantastic interpretations of the hyperloop name, including space bound filaments kept aloft somehow that people carrying projectiles are fired into (doesn’t anybody think of the children, or the grandmothers) and other science fiction interpretations.

This is my attempt at putting together what it could be taking into account some of the common elements in Tesla, SpaceX and paypal.

One thing Elon Musk doesn’t dabble in is science fiction, he seems to be stuck solidly in the science and engineering departments so I’ll go with ‘make it as simple as possible, but no simpler’ principle. Airborne tunnels don’t have that simplicity component so I’ll happily discard them, they’re almost impossible to construct and they are terribly fragile once they’re up (and taking them down for maintenance would suck).

There are a few facts known from things that Elon has said on the subject:

“Cheaper than high speed rail”

“ground based”

“it leaves when you arrive”

“no rails required”

“It will revolutionize the transportation industry”

“It is not an evacuated tunnel”

That last one really piqued my interest. At first sight says very little, but that depends on how you interpret the sentence and I suspect that Elon may be playing a little practical joke on us here, let’s not forget he knows a thing or two about computers.

You can parse that sentence two ways to get a completely different meaning, depending on where you place your ‘brackets’, but in a spoken sentence these are invisible. So they’re a neat spot for a verbal trick:

It is not (an evacuated tunnel)

and

it is a (not evacuated) tunnel

So, in other words he may be putting the truth out there for everybody to see: it is a tunnel that is explicitly not evacuated.

Which I read to mean that he is saying that it is pressurized. Pressure is a lot easier to maintain than a vacuum is, especially if you’re building long stretches of tubing. A really good vacuum needs a considerable support structure because the atmosphere will happily crush your apparatus. There is also a low limit of how effective you can be (1 atmosphere, to be precise is the upper limit of diference that you can achieve by definition). Then there is the problem that to brace against that atmospheric pressure you have to push outward, which would be annoying because that is exactly where you want you vehicles to run, which means that if you want to make a high speed transportation device using a tunnel based on a vacuum that you’re going to have to make the tunnel double walled, which will greatly increase the cost. So clearly a vacuum would have all kinds of drawbacks and is a non-starter. Then there is the problem of convincing the general public to enter a cart in a tunnel that is evacuated, no way to refresh the air while it is moving and so on. Vacuum: bad idea.

So here is my vision for what ‘hyperloop’ stands for:

If you reverse the picture and you imagine a tunnel that is pressurized then there is a much easier way to make the whole thing work, in fact it would explain one of the two parts of the word ‘hyperloop’, the fact that it apparently is a loop, which means that it is going to recycle some critical component. (the other, the ‘hyper’ bit I assume refers to the maximum speeds attainable by such a system).

And that re-cyclable component may very well be the moving air inside the tunnel. If the pressure is supplied from the outside then it could leak away causing vehicles to have to work harder than they were designed for and the transit speed would suffer, but there is an elegant solution for this and it involves seeing the system as a whole rather than as bits and pieces.

A packet switched network of carriages that can be inserted and removed at various locations that are propelled into a slot on the ‘loop’ and taken back out again when they reach their destinations. Energy would be expended when accelerating a carriage to the speed of the loop, after that has been done on a parallel track the carriage is shunted into the loop, and energy expenditure drops rapidly. Such shunt points would exist every few thousand meters along the length of the loop, comparable to on-ramps on highways. The whole thing uses the carriages themselves as the impellers that cause the air to move through the tunnel system, effectively everybody is drafting with everybody else. So the pressurized air is pressurized by the combined motive force of all the carriages. The more carriages in the loop the lower the energy budget per carriage. Carriages would be electrically propelled, mostly seal the tunnel walls and use maglev principles or something similar to reach their speed. One hyperloop could be the ramp up to the next by keeping ‘packets’ for the same destination together, shunting them out to an intermediary phase and speeding up again for the next level. Downshifting would be the same but in reverse.

So this system would actually be cheaper and more energy efficient as usage goes up, compared with ordinary roads where congestion and fuel consumption goes up with usage.

There would be a fair amount of redundancy in the system, since if a carriage would for some reason slow down or if it would be really busy they could be made to move in such a way that a rearward carriage would start to help push the one in front of it, effectively reducing aeronamic drag on the rearward carriage to near 0, using the air between the carriages as a buffer medium and shock absorber. Pumping the remaining air between two carraiges out would effectively lock them together for the duration of the trip. Instant train formation, with some maximum length based on the radius of the loop, and even if the carriages would not be locked together from an energy consumption point of view if they get close enough the effect is much the same.

Loops around a city would be joined to other loops around other cities by long stretches of tubing, with the occasional spot for egress in case of emergencies. The whole thing resembles the internet loosely, both are packet switched, where the electrical wiring needs a return path for the electrons the tube system needs a return path to keep the moving air in the system. If traffic is light dummy carriages can be inserted into the system to keep the air moving, and as traffic increases more and more of these can be circulated out. That way the system would work even when there is only very little payload.

No vacuum (with associated risks and technical issues), simple, reasonably cheap to set up and maintain with all the active components in the carriage and with good economies of scale and redundancy. It would still cost a bundle to install such a system but compared to todays roads it will probably come in cheaper, especially in the long run asphalt is terribly costly to maintain. No traffic jams, just a fixed maximum capacity that can be expanded by installing parallel tubes.

I’m not sure what the end-points of such a system should look like, I’m imagining something akin to what I saw in a mailroom where they used pneumatic tube mail. And effectively, that is what this is, a scaled up version of pneumatic tube mail with some elegant tricks thrown in to make it energy efficient.

So, that’s what I think the ‘hyperloop’ concept stands for. Time will tell if I was right or not, I wished I had some drawing skills so I could give you an artists impression of the words above.