WASHINGTON — NASA officials said May 8 the administration is still one to two weeks away from delivering a revised budget proposal to land humans on the moon by 2024, amid growing frustration from members of Congress.

During a hearing of the House Science Committee’s space subcommittee on NASA’s exploration plans, members pressed NASA officials for details about how much it will cost to carry out the goal announced by Vice President Mike Pence in a speech March 26. NASA Administrator Jim Bridenstine, testifying before the full committee a week after that speech, said he thought that the agency could “get really close” to delivering a revised budget request by April 15.

Five weeks later, that revised proposal has yet to be arrive on Capitol Hill. “What is the reason for the delay?” asked Rep. Kendra Horn (D-Okla.), chair of the subcommittee.

Bill Gerstenmaier, NASA associate administrator for human exploration and operations, said the agency was still working with the White House, including the Office of Management and Budget, to develop that detailed plan and budget estimate. “We recognize that this is a really serious challenge,” he said, “and we need a really solid plan.”

The administration has spent the last several weeks developing those plans while working with OMB on the budget. He estimated the administration was “maybe a week to two weeks away” from delivering a plan and budget.

Mark Sirangelo, a special assistant to the NASA administrator who joined the agency last month to work on the new exploration effort, said that as NASA finalizes those plans, “we also have an obligation to make sure that we work together with the budgeting process” at the White House. “From our perspective at NASA, we’re very close to doing that.”

Agency officials, though, declined to provide any specific budget numbers, including what they may have originally proposed to OMB. “Right now it’s under review and we can’t come up with a number,” Sirangelo said when asked about those estimates by Rep. Mo Brooks (R-Ala.) “It’s still under discussion with OMB and NASA.” He added those discussions have been “very positive and open.”

“We understand that the delay is frustrating, but this a big challenge and we want to get it right,” he said.

That frustration was clear, particularly among Democratic members of the committee. “The lack of planning evidenced so far is no way to run our nation’s space exploration program,” Horn said in her opening remarks at the hearing. “The 2024 missive left NASA in a tizzy, scrambling to develop a plan and hastening to pull together a budget amendment that still has not been delivered to Congress.”

Rep. Eddie Bernice Johnson (D-Texas), chair of the full committee, said she was concerned about the impact the additional cost would have either on other NASA programs or on other agencies, whose budgets could be raided to fund the new lunar plan.

“I hope that when NASA delivers that plan and revised budget to Congress, it will also provide a compelling rationale for the proposed crash program that justifies the additional resources that will be required,” she said. “As chair of the Science Committee, I cannot look at NASA’s proposal in isolation, nor can my colleagues on the Appropriations Committee.”

Republican members of the committee appeared more patient with the delays in the revised budget proposal. “While this hearing is very helpful, and I realize that NASA previously committed to delivering a plan to the committee by now, holding the hearing without new details does seem premature,” said Rep. Brian Babin (R-Texas), ranking member of the subcommittee.

Even Republicans, though, emphasized the need for adequate funding both in the upcoming revised budget request and future years’ budget proposals developed by OMB. Rep. Frank Lucas (R-Okla.), ranking member of the full committee, warned against “creative bookkeeping” to fund the lunar initiative. “If we don’t accomplish this this time, I don’t know when we’ll have a fourth opportunity” to return to the moon, he said.

Inadequate funding also posed a safety risk, argued Patricia Sanders, chair of the Aerospace Safety Advisory Panel and another witness at the hearing. She said the “can-do” approach of agency employees might lead them to find shortcuts to achieve the goal under constrained budgets. “It’s a huge risk,” she said. “It puts NASA in the position of trying to achieve something that’s not really achievable.”

Gerstenmaier, despite the budget uncertainty, was optimistic about the agency’s ability to get humans on the moon by 2024. He noted that all the technical elements needed to carry out that lunar landing mission, including modules for the lunar Gateway and a lunar lander, will either be under contract or study within the next two months.

“I think it’s very achievable,” he said, with the biggest issues involving the “political challenge” of lining up funding and other support. “Can we get united in this goal enough to move forward at the pace we’d like to go? That will be the biggest challenge.”