"We need an off-ramp for reliance on the SLS," said Scott Pace, director of the Space Policy Institute at George Washington University, in written testimony. He issued the statement in advance of a hearing about US space policy, and the future of NASA's Artemis Moon program, before a subcommittee of the House Committee on Science, Space, and Technology.

A physicist and influential policy expert, Pace has decades of experience researching and writing space policy. He has served in multiple Republican administrations, most recently as executive secretary of the National Space Council from 2017 to 2020. He strongly advocated for the SLS rocket after Congress directed NASA to develop it in 2011.

"Ideally, NASA should be able to buy heavy lift services to send payloads to the Moon—up to about 45 metric tons to 'trans-lunar injection' which is about the same performance as the SLS Block 2," Pace wrote. "I was a supporter of SLS when it was created as NASA required heavy-lift vehicles to send humans to the Moon and Mars. At the time, it did not appear (to me) that a private sector heavy-lift vehicle would be feasible within two decades. Today, the situation is different, with heavy-lift options from SpaceX, Blue Origin, and United Launch Alliance."