WAILEA, Hawaii — Members of a House committee expressed skepticism about NASA’s reliance on commercial launch vehicles to carry out human lunar landings by 2024 rather than an upgraded version of the Space Launch System.

The Sept. 18 hearing by the House Science Committee’s space subcommittee on NASA’s exploration programs left members of both parties with doubts that with NASA’s current approach, and the cost and schedule problems programs like the Space Launch System and Orion have suffered, it could achieve the goal of returning humans to the surface of the moon by 2024.

The agency’s witness at the hearing, Ken Bowersox, the acting associate administrator for human exploration and operations, contributed to that skepticism. “How confident are you that we’ll have boots on the moon by 2024?” Rep. Bill Posey (R-Fla.) asked him during the hearing.

“How confident? I wouldn’t bet my oldest child’s upcoming birthday present or anything like that,” Bowersox responded. “We’re working towards it as hard as we can.”

NASA faced criticism from some members because of the architecture of the Artemis program. NASA plans to use commercial launch vehicles for elements of the lunar Gateway as well as lunar modules, largely reserving the SLS for Orion launches of crews with the entry-level Block 1 version of the rocket.

Doug Cooke, former associate administrator for exploration at NASA, argued in his testimony at the hearing that such an approach was inefficient. “A heavy-lift vehicle on the order of 100 to 130 metric tons or more, with a large payload volume, is needed for the large, heavy elements. Anything less overconstrains landers and habitats,” he said. “The fewer launches and critical operations per mission, the higher the probability of mission success.”

While the Block 1 version of SLS falls short of the 100 metric ton capacity recommended by Cooke, the Block 1B version, which uses the more powerful Exploration Upper Stage (EUS), would have a capacity of about 105 metric tons. “If NASA focuses on investment on the ongoing SLS with the EUS, Orion and ground system developments, there’s a better chance of making an earlier date,” he said.

Rep. Mo Brooks (R-Ala.) quoted an op-ed Cooke recently wrote that claimed that NASA’s plan was the result of “pressure from commercial launch providers who need additional launches to fill their manifests.”

“They appear to suggest that profit motive, i.e., the desire of some individuals for personal gain, may be driving NASA decision making at much greater risk to our astronauts,” Brooks said. Cooke didn’t address the profit motive claim, but said the “pressure to get to commercial capabilities and drive that objective is causing us to do things that are higher risk.”

“Nobody’s driving us,” countered Bowersox. “We actually came to these conclusions on our own.” A major factor in the agency’s approach is flexibility, giving NASA backup plans if one provider encounters problems.

Rep. Kendra Horn (D-Okla.), chair of the subcommittee, asked Bowersox if NASA had done an assessment comparing cost, risk, and safety issues of using commercial vehicles versus the SLS Block 1B. Bowersox said NASA considered that approach, but was not aware of a specific analysis.

She showed some frustration about the lack of specifics as the nearly two-hour hearing drew to a close. “What we need to see is an analysis of this: why these decisions were being made, what is driving them,” she said. “If there is not an analysis to back it up, why are these decisions being made?”

The hearing didn’t examine what it would cost to accelerate development of the SLS Block 1B so that it would be ready in time for a 2024 human lunar landing, or if that would even be possible given the extensive delays suffered by the program that pushed back the first SLS launch from 2017 to now no earlier than the end of 2020.

In addition, Cooke, identified during the hearing as a former NASA official, is now a consultant who works for, among other companies, Boeing. A “Truth in Testimony” filing accompanying his prepared remarks showed that he’s earned more than $465,000 since the beginning of 2017 for his work with Boeing. That work isn’t described in the document other than being described as “sometimes related to the subject” of the hearing. Boeing is the prime contractor for the SLS core stage and EUS.

Exactly when SLS will launch remains uncertain. Beyond a no-earlier-than date of the end of 2020, Bowersox did not provide a specific targeted launch date for the first SLS mission, Artemis-1, saying that job would left to the individual NASA selects to take over the job Bowersox has been holding on an interim basis for more than two months. “Within a month or two, that person would have time to come up with a date that they can be ready to commit to Congress on,” he said.

For all the urgency that NASA has said it’s placing on the Artemis program, Bowersox suggested a decision on an associate administrator was not imminent. “They’re working really hard, talking to candidates,” he said of agency leadership. “I think they’ve got a goal to actually be through with that process by the end of the year.”

“We want to give them all the time they need because we want them to find the right candidate,” he added. “We could be in a lot worse situation if we got the wrong candidate into the job.”