On Monday, Elon Musk, entrepreneur, inventor, and amazingly rich guy, unveiled his vision for a new, super-fast transit system that, if it ever becomes reality, could revolutionize transportation. Among other things he released a set of plans in PDF format that include a huge amount of information. A lot to wade through, but the general consensus appears to be that the plan is very interesting and actually plausible.
Speculation had circulated for weeks regarding what the actual process for Hyperloop’s proposed super-high-speed transportation would be. The thought was that it would involve some sort of tubes, and would probably require the application of a vacuum in the tube in order to overcome the effects of air pressure and friction. Much of the hype likened the plans to the tubes seen in the opening sequence of Futurama or the old pneumatic tubes sometimes used at banks.
Musk’s actual plan for the Hyperloop is a little different, but a fairly clever combination of various technologies and physical principles. Passengers would ride in relatively small aluminum pods that would be shot through tubes. The pods would zip along at a top speed of 760 mph. In one of the proposed designs, the pods hold 28 people, but there is an alternative design which would allow for entire cars to be transported. The pods travel through two low-pressure steel tubes (one in each direction) welded together and stacked on top of each other. The tubes would be elevated and would rest on simple pylons, unlike railroads that require much more complicated foundations due to their immense weight. The tubes would also be covered in solar panels that would generate most of the power needed for the Hyperloop.
Musk proposes an initial route that follows the existing right-of-way path along Interstate 5 in California rather than carving out an entirely new, straight path. According to Musk’s studies, the primary advantage of this approach is that it is relatively easy to acquire or clear the land until right when you get to Los Angeles. It is also a relatively straight line, important for maintaining those high speeds.
Contrary to prior speculation, however, Musk does not think that the answer is to send the pods through the tunnel in a vacuum. Imagine the problems if something broke down and people were trapped inside a hard vacuum, or the cost associated with breaking the seal for maintenance and then pumping all of the air back out of the tubes.. Unfortunately, Musk also thinks that it is far too inefficient to use a fan to generate huge columns of air, as was previously proposed by Musk’s “best guess” designer John Gardi. Instead, the plan calls for each of the pods to come with a battery-powered air compressor on the front that actively transfers high pressure air from the front to the rear of the vessel, where it is stored in a compressed air reservoir. This prevents air from collecting in front of the pod as it accelerates, keeping simple air pressure from stopping Hyperloop dead in its high speed tube. “Why compress the air rather than just vent it out the back?” you might ask. Well, that is another interesting aspect of this design.
Just as air pressure in a tube is an issue, so too is friction between any vehicle and the surface over which it travels. Friction is one of the biggest limiting factors to speed. Hyperloop would not use magnetic levitation to keep the capsules off the ground, as had been widely assumed. Instead, it floats on air bearings, which work much like an air hockey table to keep the pods moving (almost) friction-free. This technology, according to Musk, has been demonstrated at speeds of up to Mach 1.1. Of course, the air bearings rely on a cushion of air being pumped out by the pod against the tube, which is derived from the compressed air collected by the car as it passes through the tubes.
The system will rely on an onboard battery aboard each pod that will power a linear electric motor, similar to that used in the Tesla Model S, to accelerate the pod down the tube.
Musk thinks the Hyperloop system can be built for $6-10 billion. That’s considerably less than the $70 billion high-speed rail proposal currently being floated in California. Most of this cost would be the construction of a track and acquisition of land. He thinks that using solar panels and some energy recapture, the system can be essentially self-powering, and, as you have read, the whole system has efficiency thoroughly baked into its design.
Unfortunately, Musk has also indicated that he is not interested in building the system himself. So, the only question remaining for Hyperloop is whether anyone with any authority will actually grab onto the idea and move it forward as a viable option for meeting America’s transportation needs or, at the very least, the needs of California.