I have never once read about abort-to-orbit capability as a concept, let alone a requirement for Artemis HLS.
Here’s a 4 year old video detailing past abort systems and why Starship won’t have one: https://m.youtube.com/watch?v=v6lPMFgZU5Q
Apollo 14 had a piece of loose solder in the button triggering abort-to-orbit, so it occassionally triggered itself. This wasn't a problem en route to the moon, but the second the descent phase started it would have been a Poisson-timed bomb that would prevent the landing.
There was a bit of memory that could be set to ignore the state of the abort button (this bit was the reason the abort sequence wasn't triggered en route). The problem was this ignore bit was reset by the landing sequence (to allow aborting once landing started), and they did not believe the astronauts would be quick enough to set the bit again before the button shorted out and triggered the abort.
(Ignoring the abort button was fine because an abort could be triggered in the computer instead. Takes a little longer but was determined a better option than scrapping the mission.)
Don Eyles came up with a clever hack. Setting the program state to 71 ("abort in progress") happened to both allow descent to start and prevented the abort button from being effective. So this program state was keyed in just before descent.
The drawback was that it obviously put the computer in an invalid state so some things were not scheduled correctly but Eyles and colleages had figured out which things and the astronauts could start those processes manually.
Then once the computer was in a reasonable state again the ignore abort bit could be set and the program mode set correctly and it was as if nothing had happened.
ATO was an abort mode [1] on the Shuttle program and is notably the only abort mode that was successfully used in the entire program, on STS-51f [2] . Challenger suffered an engine anomaly on liftoff that resulted in a lower orbit than was intended, but otherwise the mission went off without a hitch.
[1] https://en.wikipedia.org/wiki/Space_Shuttle_abort_modes#Abor... [2] https://en.wikipedia.org/wiki/STS-51-F
Per the links: “A particularly significant enhancement was bailout capability. Unlike the ejection seat in a fighter plane, the shuttle had an inflight crew escape system[12] (ICES). The vehicle was put in a stable glide on autopilot, the hatch was blown, and the crew slid out a pole to clear the orbiter's left wing. They would then parachute to earth or the sea. […] Before the Challenger disaster, this almost happened on STS-51-F, when a single SSME failed at about T+345 seconds. […] A second SSME almost failed because of a spurious temperature reading; however, the engine shutdown was inhibited by a quick-thinking flight controller. If the second SSME had failed within about 69 seconds of the first, there would have been insufficient energy to cross the Atlantic. Without bailout capability, the entire crew would have been killed.“
Why is the naming scheme of shuttle launches so bad
I always wished it at least included the orbiter name in it. But I suppose the orbiter choice could change closer to actual launch.
STS-41B-ATL2
Ouch, shortly after they get standardized and consistent flight numbers, the shuttle program gets cancelled. I guess computer science doesn’t have a monopoly over the difficulty of naming things.
This was basically a lawn-chair rocket for two which would utilise a disabled LEM's (lunar excursion module) fuel tanks, and would be hand-piloted without any guidance computer to an intercept orbit with the Apollo Command Module, with the hope that a rendezvous and crew transfer could occur within the four-hour window of space-suit oxygen supplies. Given that the CM's orbital period was two hours, this meant at best two chances for a successful intercept.
<https://en.wikipedia.org/wiki/Lunar_escape_systems>
(I'd run across this from the recently submitted MOOSE article, "Man out of space, easiest", a strap-a-foam-mattress-to-your-ass reentry concept: <https://en.wikipedia.org/wiki/MOOSE>.)
It does still leave the system without a means of aborting if the ship's main engines have trouble, although I suppose they do have a good bit of redundancy there.