Two NASA icons raised questions about the feasibility of the space agency’s plan to return to the Moon by 2024 and eventually set foot on Mars during a House subcommittee hearing Wednesday.

The testimony from Lt. Gen. Thomas Stafford, a retired astronaut who flew on two Gemini and two Apollo space missions, and Thomas Young, a former director of NASA Goddard Space Flight Center, carries significant weight as Congressional leaders seek guidance on how best to structure successful future Moon and Mars missions.

Young, who also managed NASA’s Viking program, the first two U.S. spacecrafts to land on Mars, told members of the House Subcommittee on Space and Aeronautics that a Moon-Mars program will be “the most challenging and difficult civil space program ever undertaken.” He listed several questions in his opening statement that NASA would have to answer in developing such a program.

“Is the lunar part of the program to support success at Mars or is it to achieve sustained lunar presence?” Young asked. “Does the Mars part of the program have specific objectives such as a Mars orbital mission followed by boots on the ground or is it a long-range objective? Answers to these questions will have a profound impact on schedule, cost and a reasonable timeline for humans to Mars.”

NASA has been scrambling to meet an expedited 2024 timeline for a return to the lunar surface in the wake of March comments by Vice President Mike Pence directing the agency to meet that date using “any means necessary.”

Though NASA has not yet provided a budget plan to Congress and such a plan will not be ready until 2020, agency Administrator Jim Bridenstine has said the Artemis moon program could cost as much as $30 billion. More recently, a Congressional budget leader dismissed the 2024 date as unreasonable, citing cost and safety concerns.

To that end, Young made an explicit appeal for the agency to identify “the most probable cost” of a Moon and Mars program, breaking down projected spending in detail for each year. Young advised NASA to adopt a “bell-shaped” budget profile with higher budgets for fiscal years requiring development, manufacturing and testing of the necessary infrastructure for Moon and Mars missions.

“Flat budgets with a relatively equal funding level each fiscal year is the least efficient program management approach,” Young said. “A flat-budget approach can result in years of scheduling delay and potentially the doubling of projected costs.”

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Young added NASA would likely have to significantly reduce its human spaceflight portfolio in order to prioritize and plan for the Moon and Mars missions.

“I personally think the (NASA) leadership is going to have to, number one, prioritize, and number two, probably eliminate some of the things that are currently being done that will interrupt any opportunity of (returning to the Moon in) 2024 or even 2028,” he said.

Stafford, in his opening remarks, boosted NASA’s long-delayed Space Launch System rocket as essential for the Moon and Mars missions because of its payload capacity and ability to lift the Orion spacecraft. Orion will be used for Artemis’ uncrewed and human flights.

“If you don’t have a big booster, you’re not going to make it. But also what’s so important, besides just weight, is the size,” Stafford said. “You need a big payload shroud to carry the rovers, the habitats, the infrastructure.”

The sheer cost of building and launching the SLS rocket has become a thorny subject. A recent letter from a White House budget official said the SLS costs as much as $2 billion per launch. A NASA Inspector General report released Wednesday revealed NASA will have spent roughly $34 billion on the SLS, Orion, and Exploration Ground Systems programs through 2019, a sum projected to increase to over $50 billion by 2024.

There were also areas of notable disagreement between Young and Stafford. Young spoke in support of simplifying the agency’s focus to getting to Mars. Stafford favored returning to the Moon first and foremost.

“I may be a little dumb but I’m not stupid,” Stafford said. “The moon is only three days away.”

Young countered that he is leery of getting “bogged down” with another lunar mission and that the “most compelling” aspiration for NASA was humans setting foot on Mars.

Both, however, agreed NASA would have to expand its workforce and augment its leadership in order to fulfill its Moon and Mars goals. Young noted that during NASA’s Apollo days, the agency recruited Samuel Phillips, a four-star Air Force general, to run its lunar landing program; and George Mueller from the private sector to run its Office of Manned Spaceflight.

“Additional senior, experienced leadership from other government organizations, industry and academia will be needed, as was the case was for Apollo,” Young said.

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