Tuesday, August 13, 2013


Pods would be mounted on thin skis made out of inconel, a trusted alloy of SpaceX that can withstand high pressure and heat. Air gets pumped through little holes in the skis make an air cushion. The front of the pod would have a pair of air jet inlets—sort of like the Concorde. An electric turbo compressor would compress the air from the nose and route it to the skis and to the cabin. Magnets on the skis, plus an electromagnetic pulse, would give the pod its initial thrust; reboosting motors along the route would keep the pod moving. In theory, the pods would be propelled at high speeds just below the sound barrier, and the set-up would be powered by solar panels running along the top of the system.

Pods, with skis on the bottom zip through tunnels put under low pressure.  The pods will ride on air bearings. The pod produces air, and it’s pumped out of little holes on these skis.  You can move huge, heavy objects with very low friction, using air bearings. In the consumer sense, people would be familiar with air hockey tables, except in this case the air bearings are being generated by the pod itself, as opposed to the tube.

You don’t want the tube to be expensive. Because the tube is so long, you want the expensive stuff to be in the pod.

Some people believe it is impossible because it would require too much energy to get something through a tube at such high speeds and long distances.  Some are questioning the energy that would be required to move the air and the pod. But it is not the air that is moving the pod. The pod is accelerated to velocity by a linear accelerator, which is basically a rolled-out electric motor. The air in the pod is going maybe 200 to 300 miles an hour, and it is low-density. So some were thinking: ‘Oh, the air is sea-level density, and the air itself will be the thing that pushes the pod.’ But that is not the case.

You do want to have a continuously circulating loop of air so that you are not losing energy by letting the air slow down. But it is more efficient to have the pod go faster than the air. If you just try to pump air—particularly at sea-level pressure—through what is effectively a 700 mile loop, the energy required would be extremely high if you wanted that air to go fast because of friction against the side walls of the tube.


How would the linear accelerator work that gets the pods going?  It’s actually a linear electric motor. It’s a very basic thing. They have been around for a very long time. The air skis in the pod would have a thin row of magnets—you don’t need much. The linear motor would electromagnetically accelerate the pod. It would be just below where the skis are. It just creates an electromagnetic pulse that travels along the tube and pushes the pod to that initial velocity of 800 miles per hour.  About half a dozen re-boosts would be needed between San Francisco and L.A., but the linear induction motor size needed for re-boosts is much smaller than the initial one.

How would you slow down?  When you arrive at the destination, there would be another linear electric motor that absorbs your kinetic energy. As it slows you down, you put that energy back into a battery pack, which then provides the source energy for accelerating the next pod and for storing energy for overnight transport.

The solar panels would be laid on top of the tubes. You would store excess energy in battery packs at each station, so you could run 24-7.  (Bloomberg Business Week, 8/12/2013, Wash Post, 8/12/2013))

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