I'm tired of dancing around this, so I'm just going to put all my cards on the table.
/u/rookisaacman alluded to this in his leaked email to the workforce. Specifically, here:
So if that means preserving an ICPS option while driving Centaur V in parallel, we will do so. If it means having ML‑1 pad modification hardware ready to move immediately after Artemis III launches, we will do that too.
The newest version I've heard is that this is almost completely ruled out now. They're going to have to start ML-1 mods right after Artemis III, so they can't fly it on Artemis IV.
Why are ML-1 mods necessary? Because of the kick stage and stretched Centaur. The kick stage is a bit fuzzy, but the current idea seems to be essentially a stripped-down ESM. I tried to hint at this with a post here a few days ago... but honestly, fuck subtlety. A kick stage to allow Orion insertion into LLO is the plan right now.
The stretched Centaur (official-ish name is "Exploration Centaur") is something I've covered here before, but I'm just going to outright say that the purpose of the stretch is to handle the kick stage. Again, I tried to be coy about it, but fuck it. Let me bring the transparency Administrator Isaacman promised.
Some of you more tuned into the history here might be a bit confused. Isn't this exactly the kind of mission EUS could handle? Wasn't ML-2 commissioned precisely because NASA’s Aerospace Safety Advisory Panel said the modifications to ML-1 for a new upper stage would take far too long (33 months estimated)? How does Administrator Isaacman plan to have all this hardware ready on a faster timeline than EUS and ML-2, which were projecting 2028/2029?
Your guess is as good as mine. The engineers just didn't believe hard enough back then, I guess. 🤷♂️
Anyway, those of you still doubting me can have that "mid-October" Artemis announcement to look forward to. For the rest of you, I want you to keep in mind that the coming flight gap is entirely one man's fault... and that once they start tearing into ML-1, it will not be possible to launch any Artemis missions until they are done. Including if they encounter any more serious, unforeseen difficulties.