Comment by romaaeterna
2 days ago
Amazing tech demo. I would have liked to see more discussion of the cold-gas thrusters in the earlier Hacker News article. Some people seemed confused and made claims that the demo was a separate "rocket" version that used a combustion technology.
Well it is a separate rocket version, it just doesn't take jet fuel. "Invite only" for the rocket version means probably less than 5 will ever be made, if that.
I strongly suspect that the invite-only version is the tech that was described in the demo, and differs from the $250K version by the size of the air tank and compression motor.
Cold gas or not, these are still rocket motors.
Without fuel or an oxidizer or combustion? Not really. It's compressed air, like an air rifle.
Motors don't need combustion, they just need to provide power. See electric motors or compressed air engines.
A rocket engine doesn't require combustion, it just requires expelling a gas to produce thrust, and that the engine not be air breathing. Most rocket engines use combustion to produce the high speed gases, but there are plenty that don't (water rockets, steam rockets, plasma rockets, and... cold gas thrusters as demonstrated by Tesla)
I doubt it is actual air. When compressing gas to 10,000+ psi and then running it through a rocket motor, clean/dry nitrogen is the way to go. Normal air has moisture, which can form ice, and oxygen which gets extremely reactive when heated.
And many a rocket scientist would be insulted by the comparison of a nozzled rocket motor to the simple pipe of an air rifle.
It takes genius to take rocket motors and cover them in cringe.