Moltenmetal: yeah, I calculate that I use a little more than a liter a minute walking, so I am looking at refueling every 7-10 min at the moment, which is bad, but better than compressed air, which only gets me about 5 min operation in equal weight, plus I need to swap tanks, rather than pour in...
Transient1: Commercial (anybots.com)
MintJulep: It seems that dry ice has much the same problems as LN2 just worse. It takes more heat to vaporize, still needs to be brought up to a temperature that won't frost, and Carbon Dioxide is heavier per mol than N2 so you get less Work per kg out of it.
The idea is to take some of the liquid Nitrogen and then heat it in a vessel so that the pressure increases as the nitrogen turns into gas.
Simplest version: Liquid Nitrogen is poured into a large boiler at atmospheric pressure. The boiler is sealed with a flame under it. The flame adds heat...
I am working on a project to develop a system that a pneumatic robot could carry that could supply it with pressurized gas. We are considering having a tank of liquid nitrogen, which we than take small amounts of and then heat with either ambient air or with fossil fuels to raise the pressure...
