The idea grew out of our Battlebot, one of our sponsors was Festo which makes pneumatic actuators. They had a new actuator which was a short throw 6" diameter cylinder and offered us one for our 'bot. The idea was that if we mounted it into the front of our wedge, and then fired it when an opposing robot was on the front, it would knock them off. Doing the calculations (150 PSI, 4L expansion tank) showed that we could develop an initial thrust of 2,100lbs with a working distance of 2". That calculation had the opposing 220 lb robot experiencing an acceleration of something like 1000 ft/sec^2 for .004 seconds. The end result was that we were in danger of tossing the opponent out of the 'battle box' by launching it over the top (in practice this wouldn't happen because the chance of firing the weapon under the exact center of mass was infinitesimally small) but it got us thinking about the hopper idea for the DARPA challenge (we already knew our robot could withstand the force of falling onto concrete from a height of 20').

Providing the gas pressure however is an issue. You can use solid CO2 recharge (drop in some dry ice, seal, and warm) but for the challenge it had to go a looooong way. And that would require a fuel, a generator, and a compressor. Weight went up, survivability went down, and some early tests on what was essentially a pogo stick pointed that it wasn't practical at those mass levels.

Gliding would have been an interesting choice. With something light like a parafoil wing even more so. If I dig up my notes I'll put up something on my web site about it.