Congress/NASA killed it by not funding the Ares/SLS adequately. Michoud can only hold STS or SLS assemblies, but not both. So to build the new(er) rockets, NASA had to kill the STS to have room at Michoud. Hard to believe that they could spend so much money on paper and starting/stopping SLS efforts and they couldn’t find enough money to build another huge empty building. That was a shovel ready program.
Reminds me of when they killed the SR71 for the Keyholes.
We have some shuttle engines available but looks like we’re gonna be dependent on Russian engines for the most part. How come elon hasn’t come up with some solar engines yet? :>)