The hyper loop consists of a pair of steel tubes, normally elevated, which are evacuated to 0.015 psi. This not quite a hard vacuum but "soft" enough that relatively ordinary equipment can be used to maintain it, and some tiny leaks can be tolerated. This is about the same pressure as a spacecraft flying at about 30 miles would feel. Pretty low drag, but far from zero, especially at the proposed 760mph, approximately 1/1000th of sea-level drag. The vehicle is substantially smaller than the tube (roughly 30%) and has on the front a big fan, which sucks in air. Most of this is spat out the back, helping to keep it going, but a little is squeezed out the bottom through what they call "Skis", which ride on the floor and sides of the tube, generating a cushion of air to ride on. This is familiar to people who play air hockey, and it's been used in lower speed transit before, such as the people mover in the Detroit Airport. The low pressure in the tube means that it doesn't take a lot of power to overcome air friction and can be sustained by on board batteries (using numbers gleaned from their work with the Tesla S), and the big power drain from acceleration is accommodated by Linear Induction Motors (many existing transit designs use LIMs, such as the Vancouver Sky train). These are mounted in the tube and the vehicle itself is passive. They are also used to decelerate the vehicle, recovering a large fraction of the energy used. They propose mounting solar panels on the guide way and calculate that those and a rather minimal amount of battery storage will fully power the thing.
They've actually done quite a bit of engineering on the support columns, concerned (it being proposed for California) about earthquakes. They allow the tube to shift freely a little bit relative to the support in three axes and have the ability to make more permanent adjustments to accommodate shifting terrain. The propose most of the route down the center...
Please join StudyMode to read the full document