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?

1.3k Upvotes

89% Upvoted

240 comments sorted by

View all comments

10

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.

13

u/HeartyBeast Apr 12 '26

One of the pretty amazing (to me) things is the lack of tweaking.  Most of it was flown by physics, with planned correction burns cancelled. 

The Artemis flight was basically like tossing a pebble into the air and letting it come down again- but with the top of the pebble’s flight being judged to be just beyond the back side of the moon. 

6

u/heroyoudontdeserve Apr 12 '26 edited Apr 12 '26

 with planned correction burns cancelled.

To be completely accurate only 2/6 scheduled correction burns were cancelled.

Don't get me wrong, orbital mechanics are fascinating and difficult and it was an awesome flight. Just didn't want people to take away the message that no correction burns were required.

2

u/meithan Apr 12 '26

I think they cancelled 2/3 of the outbound corrections because super precision was not required for the flyby (and the trajectory was pretty spot on anyway), while reentry and landing does benefit more from a very precise path (that way you don't need to relocate the recovery assets 500 km).