Come on. This has been gone through before in the thread. I suggest you start reading.bongostaple » April 2nd, 2018, 3:55 pm wrote:Assuming it's water pumping down the hose, I guess so, but I'd prefer self-oxidising fuel that's on fire at the nozzle. Really the main bit about rockets working in the atmosphere (i.e. not in space) that I don't feel fits reality is that the NASA rocket thrust equations seem to ignore the density of whatever matter/air/etc is already sitting there when the burning fuel comes out of the nozzle. Are we expected to believe that a rocket on a launchpad and a rocket already in the air produce exactly the same thrust? That certainly appears to be the gist of the rocket thrust equations - I can't see why there wouldn't be a huge difference. But obviously if we extend that thinking from solid ground - air, and compare air - vacuum, then it starts looking rather unthrusty.dblitz » April 2nd, 2018, 11:07 am wrote:If I understood your question bongostaple; how about a wheeled chair and a high pressure hose?
Sitting on a wheel chair with a fire hose? Then you are constantly adding mass to the system. See any hoses that reach up to space attached to the "space" rockets?
And water has many hundred times the density of gas.
Why all these weird analogies when it's easy to conclude the non effect of gas expansion in vacuum? Release gas in a space where it can expand freely. No work. Case closed. Doesn't matter whatsoever how fast said expansion occurs.