WASHINGTON — NASA Administrator Bill Nelson claims proposed spending reductions for fiscal year 2024 could have “devastating and potentially unrecoverable” effects on NASA programs, delaying or canceling many missions.

In a March 19 letter to Rep. Rosa DeLauro (D-Conn.), ranking member of the House Appropriations Committee, Nelson outlined the effects on NASA of two budget-cutting scenarios being considered by House Republican leadership. DeLauro published the letter this week along with similar letters she requested from other federal agencies.

One scenario considered rolling back discretionary spending across the board to fiscal year 2022 levels, which for NASA would mean $24 billion, $1.4 billion less than what NASA received in 2023. A second scenario proposed exempting defense spending from that cut, requiring deeper reductions for non-defense discretionary agencies. NASA estimated in that scenario its budget would be cut by 22% from 2023 levels to about $19.8 billion.

“To fund NASA at such a level in FY 2024,” Nelson wrote in the letter of the latter scenario, “would have devastating and potentially unrecoverable impacts upon the objectives that the President and Congress have set for NASA, and weaken our Nation’s position as a global leader in exploration, science, technology innovation, and discovery.”

That cut, according to documents provided in the letter, would “significantly restructure or terminate” various elements of Artemis 4, including the upgraded version of the Space Launch System and lunar Gateway elements. That would, NASA stated, “threaten [the] ability to fly Artemis IV and defer lunar exploration beyond Artemis IV.” [emphasis in original]

The cut in science would delay or cancel several missions in development, including Mars Sample Return, the DAVINCI mission to Venus and the Dragonfly mission to Saturn’s moon Titan. Up to three missions in the Earth System Observatory program of Earth science missions would be canceled, with delays to the Roman Space Telescope, future astrophysics missions and Interstellar Mapping and Acceleration Probe, among others.

Other changes would be a reduced number of International Space Station cargo missions and delays for both an ISS deorbit module and development of commercial successors to the station. The agency estimated that the cuts would require laying off 4,000 center and contractor personnel across the agency’s programs.

The other scenario, with NASA funding cut to 2022 levels, had less severe effects. It would “substantially delay” Artemis 4 and also cancel a procurement for a second Artemis lunar lander. It would delay Mars Sample Return, DAVINCI and Dragonfly and cancel one Earth System Observatory mission, while delaying three others. The ISS deorbit tug and commercial space stations would also be delayed, with at least 1,000 center and contractor personnel laid off.

The document did not state how NASA came with the proposed delays and cancellations or the individual value of each. The letter contains one notable error: in the scenario with the larger cuts, the letter lists the same amount for the budgets of science, space technology and space operations of $6.1 billion. Under that scenario, science would be cut to $6.1 billion but space technology would have only $935 million and space operations $3.3 billion.

DeLauro requested the spending cut plans from NASA and other federal agencies in January after comments by the new Republican leadership of the House that they would seek to cut spending to fiscal year 2022 letters. They disclosed few details about the plan, including uncertainty about whether defense spending would be included, prompting her to request both scenarios from the agencies.

House appropriators have just started hearings on fiscal year 2024 budget proposals from the agencies, but have not yet scheduled one for NASA.

Jeff Foust writes about space policy, commercial space, and related topics for SpaceNews. He earned a Ph.D. in planetary sciences from the Massachusetts Institute of Technology and a bachelor’s degree with honors in geophysics and planetary science...