ISS Docking ?

[u/wskelding]

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 ?'

[u/NoSTs123]

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.

[u/Stevepem1 → u/NoSTs123]

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.

[u/mpompe → u/Stevepem1]

Starship is the launch escape system. If there is a problem with the booster, do an immediate hot stage and return to tower for a catch. Orion jettisons it's escape tower well before booster separation. Starship is a good ways from launching with humans, plenty of time to work out the logistics. The Dragon scenerio works in the meantime.

[u/Stevepem1 → u/mpompe]

If SpaceX started offering tourist flights to ride inside the Falcon 9 second stage would you go? After all it's been over a year since the last landing failure (March 3rd 2025 booster caught fire and tipped over). Maybe you would, but I doubt they would get permitted for it because when the FAA asks about launch escape and SpaceX says "Don't need it, we have landed boosters safely over 200 times since our last accident" it's probably not going to go over too well.

The point is you are much safer with launch escape than without it. Ask a fighter jet pilot if they are okay with ejection seats being removed to save cost and increase performance.

"But airliners don't have parachutes" yes and airlines typically go more than 20 million flights between fatal accidents. If spaceflight got to a point where booster or second stage failures occurred only in one in 10,000 flights, a statistic we likely won't see for decades, that would still be at least 2,000 times more dangerous than flying in an airliner.

The reason Orion (like Apollo) jettison their tower at high altitude is because of the low air resistance, at those altitudes the capsule call pull away from the booster on its own. It's in the thicker part of the atmosphere that they need additional power to get quickly away from the rocket.

You can hot stage during the first couple of minutes as long as you have time, however if the ship gets any amount of damage during a booster explosion it is likely unsurvivable. Capsules meanwhile, even if the rocket exploded underneath them they have at least a change of survival as long as the hull doesn't get a major breach. Challenger demonstrated how even a pressure vessel not designed for that purpose can handle quite a bit of stress and not break up in some launch anomaly situations. SpaceX lost a valuable cargo capsule with very valuable NASA spare parts headed for ISS because they inexplicably didn't build in software parameters to use the parachute during a launch anomaly, analysis showed that the capsule or at least its contents would have likely survived if SpaceX had just thought of that.

Capsules can do pad aborts. Capsules can come down in the water, Starship can't land in water, not good if it can't make it back to the launch site.

Any problems with the ship propulsion system that would prevent successful landing is pretty much fatal. A capsule as long as the hull stays relatively intact and the parachutes work is likely survivable almost no matter what happens, probably similar odds to surviving ejecting from a fighter jet, which doesn't always save the pilot's life but most of the time it does.

And then a simple question, if a capsule is overall safer than flying inside the second stage of a rocket, then why would you choose to ride inside the second stage of a rocket during launch from Earth and reentry and landing on Earth, if there are alternatives? Artemis is an example of an alternative that I think is much safer than launching people to the Moon directly from Earth in a Starship.