"I am concerned that the decisions are not being driven by what is most efficient." //

Bridenstine has decided that it is best to focus efforts on getting the core stage flying as soon as possible. Three SLS rocket flights by 2024 are probably all that Boeing can handle due to "performance issues" cited several times by Bowersox during Wednesday's hearing. This third flight would culminate in the Moon landing at the lunar south pole.

The NASA chief has also defended development of the Gateway as a critical component of a "sustainable" return to the Moon. Instead of emulating Apollo's "flags and footprints" missions from half a century ago, NASA would instead like to return to the Moon to stay and eventually send humans to Mars, using the Gateway as a staging point. //

added, "I am concerned that the decisions are not being driven by what is most efficient or effective and what is most cost efficient.”

This is an interesting viewpoint given that commercial rockets cost $100 to $200 million, at most, versus the $1 billion to $2 billion cost of a single SLS rocket—not including the hundreds of millions of dollars, at a minimum, the agency would have to invest in Exploration Upper Stage development contracts with Boeing. Moreover, one of the commercial rockets—the Falcon Heavy—already exists and has flown three successful missions. //

An SLS rocket with the better upper stage almost certainly wouldn't be ready by 2024, and NASA knows this.

"At this point, there is no path by which the Exploration Upper Stage will be ready for Artemis 3 in 2024," the NASA administration source told Ars. "Hence, it is not in the critical path (for the Moon landing)."