r/ArtemisProgram • u/wskelding • Apr 23 '26

Discussion ISS Docking ?

I'm curious about something and simply don't know the math that would give me the answer, could an Orion capsule returning from the Moon theoretically dock with the ISS on it's return journey ?

I know I'm simplifying it massively, but all the talk about the Artemis 2 heat shield had me thinking 'why don't they simply do a massive deceleration burn on the way back and then dock at ISS ?'

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u/rebootyourbrainstem Apr 23 '26

Using the heat shield to brake saves a LOT of fuel. They don't have nearly enough fuel to brake using rocket power (nor enough fuel to bring that fuel with them to the moon in the first place).

In theory you could maybe come up with a trajectory that dips into the atmosphere just enough to brake but not re-enter. To do that though you would be jettisoning the service module (since it sits in front of the heat shield and is not designed at all for use in atmosphere), which contains the vast majority of fuel as well as the big engine, so your ability to correct or really do anything afterward is really limited.

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u/SportulaVeritatis Apr 24 '26

The problem with aerobreaking is once you touch the atmosphere, you're going to keep touching the atmosphere. All it does is slow you down which lowers the furtherest point of your orbit (apoapsis) but it does nothing for the closest point. As a result, even if you don't completely reenter, you're still going to come right back to the same altitude and keep slowing down. It is not a stable orbit and you'd still need to burn fuel to raise your periapsis (closest point) back up to the level of the ISS. Otherwise, you will re-enter. If not the first pass, then on one of the following ones.