SLS had an “engine conditioning problem” on engine four. They had cut the wet dress rehearsal short and missed some kind of issue with a pressurization valve, but they slightly misjudged those models and it was terminated at T+60 seconds out of an abundance of caution.

There was some flash observed near the gimbal right when the vehicle was beginning to test the engine gimbals. This triggered an abort.

There’s not enough information to know how to proceed at this point in time. If easily fixable they might ship it, if it’s a bigger issue, they’ll figure out what to do and how to progress forward.

@SciGuySpace asking about whether or not the engines could be swapped on site, they could pull from one of four engines there at Stennis! They could also swap at Kennedy Space Center. That’s a good thing for sure.