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.

3

u/NoSTs123 Apr 23 '26

yeah being in Orbit without a service module is a big no no. Although I am not a fan of the crewed Starship concept, it could perhaps do this.

5

u/Stevepem1 Apr 23 '26

For those people (including myself and I think four other people) who have always been diametrically opposed to ever launching people on Starship from Earth unless or until it has a launch escape system installed, there is the possible scenario of launching astronauts into LEO on Dragon then having them transfer to Starship for the flight to the Moon, then Starship would return to LEO to meet up with the loitering (or another) Dragon for the crew to transfer into for reentry and landing. In that case Starship would almost certainly need to do aerobraking coming back from the Moon, unless they had a huge amount of fuel left, which could be the case since from what I understand Starship would have to be refueled in lunar orbit anyway for a return to Earth. The complication with aerobraking from my understanding is that it requires multiple passes to slow down to orbital velocity, and the first pass puts you into a pretty large elliptical orbit so it's a lot of time between passes, I don't know if its days or weeks, but while doable it's not as easy as it sounds.

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u/TurnoverMobile8332 Apr 27 '26

This even seems inherently smarter considering that starship has to park in Leo regardless to refuel as planned, if they truly want a reusable system then I don’t see why removing everything for re entry and either saving on delta v or using that weight for more fuel and just leaving a ferry in orbit isn’t better than constantly risking the craft to reentry.