A sort-of follow-up to What do the astronauts do whilst the air-lock cycles?

The ISS fact-sheet writes to say

Pressurized Volume: 32,333 cubic feet (916 cubic meters)

Elsewhere on the stack are mentions of ISS maneuver to avoid space debris. So I let my mind free-wheel and came up with this question.

If the crew on-station were to suit-up, and vent the station atmosphere ... how much velocity change could they achieve? Sort-of the way a sub-marine pumps fluid for buoyancy.

The answerer will necessarily have to make some assumptions like the vent rate ...


1 Answer 1


That amount of air has a mass of about $1000\,\mathrm{kg}$. The mass of ISS is about $400000\,\mathrm{kg}$. The theoretical best specific impulse you could hope for is around $60\,\mathrm{s}$ from a cold gas thruster designed for the purpose. So about $600\,\mathrm{m/s}\times 1000/400000=1.5\,\mathrm{m/s}$.

However to actually get $1.5\,\mathrm{m/s}$ would be very problematic. The time for most of the gas to leave would be extremely long due to the very low starting pressure. Water would freeze, clogging the thruster. Probably a myriad of other problems I'm not thinking of. You would not be able to just open the back door and expect to get that amount of $\Delta V$.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.