art with code


Quick thought on Hyperloop

Hyperloop basics (or my understanding)

A lightweight car resting on an air cushion, propelled along a low-pressure tube by track-mounted linear motors. The car counteracts the air piling up in front of the vehicle by pumping it to the rear with a compressor

Low air pressure and air cushion make for low friction, so one linear motor can slingshot the vehicle for a hundred klick glide. The vehicle has batteries and electric motors to pump air, power the cabin and control the air bearing to maintain distance from the tube walls.

Thought experiment

Speed of sound in air is primarily determined by the square root of air temperature. If you fill the tube with hot air, the speed of sound inside the tube goes up. In 1000 C air you can do subsonic travel at 750 m/s. Go for 2200 C and it's 1000 m/s, or Mach 3 in normal atmosphere.

The thermal conductivity of air has a linear relation to its density: at 0.1% density thermal conductivity is also 0.1%. So, if you can cool the tube material and the vehicle to counter a 1 C temperature increase at normal air density, that cooling would suffice to counter 1000 C at 0.1% density.

But heat moves from cold to hot. If the air temperature is 1000 C, you can cool the vehicle by heating a part of it above 1000 C. Alternatively, you could use a thermal buffer to soak up the heat during brief hot air stints, and release the heat when transferring to a slow & cold part of the loop.

No comments:

Blog Archive

About Me

My photo

Built art installations, web sites, graphics libraries, web browsers, mobile apps, desktop apps, media player themes, many nutty prototypes