# Could a spacecraft produce lift using sublimating material?

Following this question, could a spacecraft approaching upper atmosphere from very low circular Earth orbit, produce lift to soar propulsively, bleeding speed at constant apoapsis, by sublimating material on its lower surface until entry speed is low enough to avoid very high temperatures when entering more dense regions of atmosphere?

Could it also raise its orbit, or explore very low orbits for extended period of time, as long as there is material to sublimate, converting its mass into lift or downwash?

• I think you are not making something quite clear yet. At 373K the speed of a water molecule at $k_B T$ is almost 600 m/s. At heat shield temperatures the speeds of small molecules are way over 1,000 m/s. While the steam drifts slowly in air, it's because collisions that happen within microns cause the momentum to mix into the dense atmosphere, and that whole situation gets a little complicated to describe in one sentence. At very low pressures in space, that km/s is substantial thrust, and dismissing it with a kettle is misleading. It's not a good analogy. – uhoh Jan 9 '19 at 3:14