@RogerBW@nyrath This is being a little disingenuous with not expanding "ICPS". It stands for "Interim Cryogenic Propulsion Stage". It was never intended to be the final upper stage.
I also feel that "NASA insists that astronauts fly SLS" is misrepresenting the situation. It'll be Congress that mandated this, political meddling.
But, yeah, SLS largely sucks.
And the whole SpaceX HLS scheme is just insane. So much riding on them magically developing not only in-orbit refuelling of cryogenic propellants, but being able to keep enough from boiling off before used. SpaceX and NASA are suspiciously not forthcoming with details about how the test during IFT3 of Starship went.
nyrath