3 ms·

Probably worse. Raw steam has an ISP of around 100s. There was an experimental ion thruster from U Michigan a few years ago that got that up to nearly 700s. Som

Probably worse. Raw steam has an ISP of around 100s. There was an experimental ion thruster from U Michigan a few years ago that got that up to nearly 700s. Some of the more efficient ion thrusters are like 20,000s (although they're operating at a different scale so idk if that's an apples to apples comparison) Edit- I looked at the Momentus paper linked above and apparently their ISP is 800s

walrus01 6y ago
It's my understanding that current state of the art very low kN, but high ISP efficiency hall effect/ion grid thrusters can achieve 6000-8000 specific impulse without an absolutely ridiculous amount of electricity. There are designs that have been ground tested but not flown which could achieve 15000-20000 ISP but would also require immense photovoltaic arrays, or a small nuclear reactor. Once in orbit unless you need to achieve a lot of delta-v in a relatively short period of time, I'm not sure why an engine/fuel combo with only 800 ISP would be a logical choice. It's certainly a whole lot more efficient than a bipropellant chemical rocket engine, which maxes out around 385-400 ISP. Although it's never flown I believe the theoretical efficiency of a NERVA would be around 800.