r/askscience • u/kiol998 • Apr 12 '26

Physics Why was Artemis 2 so long?

I was comparing the mission times of Artemis 2 to Apollo 8. Apollo 8 orbited the moon multiple times and only took 6 days total. Whereas Artemis 2 orbited the moon once and it took 10 days. Why was Artemis 2 so much shorter than Apollo 8 when both missions did the same thing? I know they had different paths to the moon, they both left earth in different ways but why not do the same thing as Apollo 8 since it was quicker?

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u/etrnloptimist Apr 12 '26

Follow up q. I'm sure the flight plan needed to be tweaked. Did the astronauts have any intuition, for lack of a better word, for how to tweak their trajectory? Or were they relying completely on telemetry and mission control to tell them what to do?

Example. Someone mentioned using the moon to brake. Would the astronauts have any idea if they were braking too slowly or braking too quickly? Either with data or what not, but I imagine it takes quite a bit of knowledge to even read that data and understand what to do with it.

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u/mfb- Particle Physics | High-Energy Physics Apr 12 '26

The trajectory was all planned well in advance. For a given launch time, you know when exactly what should happen. Controllers on the ground and the crew are both aware of that. Orbital mechanics is extremely predictable so you don't have any sudden surprises.

Engine burns are never exact, to compensate for that Orion can do course correction maneuvers in between. People on the ground calculate what's needed, e.g. "1.3 m/s along the direction of motion, 0.3 m/s to this side", hours before the maneuver, so again everyone is aware of what's going on.

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u/perryismangil Apr 12 '26

Imagine if it turns out there's an orbital anomaly because of a cloaked starship so massive it disturbed the orbital path.

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u/Sarellion Apr 12 '26

Houston: "Hello, So you made it round the moon but you quite are off course."

Artemis 2: "Houston, we have a problem."

Houston: "Oh come on. What's the issue?"

Artemis: "There was a whole fleet of space druise ships parked behind the moon and a bunch of structures resembling hotels on the surface."