WASHINGTON — NASA estimated it would have to cancel up to four commercial lunar lander missions and delay up to four more to fly a rover mission the agency announced in July it planned to cancel.

NASA announced in July its intent to cancel the Volatiles Investigating Polar Exploration Rover (VIPER) mission, citing cost and schedule overruns and concerns of additional costs and delays in its launch, which was scheduled for September 2025. The agency said at the time that if it continued VIPER, the additional costs would have affected other missions in the agency’s Commercial Lunar Payload Services (CLPS) program.

“The projected remaining expenses for VIPER would have resulted in either having to cancel or disrupt many other missions in our Commercial Lunar Payload Services line,” Nicky Fox, NASA associate administrator for science, said in a media briefing to announce the cancellation. However, the agency didn’t specify how many missions would be affected if VIPER continued, either in that announcement or subsequent public events.

NASA, though, did quantify the impacts on the CLPS program in a response to a letter from the leadership of the House Science Committee in September about the VIPER cancellation. The members write in the Sept. 6 letter that the cancellation “raises serious questions” and asked NASA to respond to 17 specific questions about VIPER.

In its Oct. 11 response to the committee, obtained by SpaceNews through a Freedom of Information Act request, NASA outlined three scenarios for when and how VIPER would launch that the agency said would result in canceling between one and four CLPS missions.

In one scenario, NASA assumed VIPER would launch on Astrobotic’s Griffin lander as previously planned in September 2025. The agency estimated it would need to spend $104 million to prepare VIPER itself, $20 million of which had already been allocated for activities in fiscal year 2024, along with $20 million in “additional risk mitigation activities” for Griffin. “NASA estimated that these additional funding requirements would lead to cancellation of one CLPS delivery and delay of another delivery by a year,” it stated.

A second scenario anticipated a one-year slip in VIPER’s launch to September 2026. NASA projected an additional $50 million in costs for VIPER and $40 million for Griffin. That would have resulted in two canceled CLPS task orders and a one-year delay to two others.

NASA also revealed it considered “alternative delivery means” for VIPER other than Griffin. NASA did not disclose details about those alternatives, calling them “highly proprietary” but which would have delayed the launch of VIPER beyond 2026 “and would still include significant uncertainty about the reliability of delivery success.” NASA projected total costs of $350 million to $550 million with this scenario, resulting in the cancellation of four CLPS task orders and delaying three to four more by two years.

NASA elected to cancel VIPER than pursue any of those alternatives, in part because the agency appeared skeptical that VIPER could be ready for launch by September 2025. “Based on delayed progress from design through rover assembly, programmatic analysis projects significant cost, schedule, and technical risk to finishing development,” the agency stated in its response to Congress.

The rover, though, has completed environmental tests, which were ongoing at the time of the cancellation decision, without any serious issues. “I’ve been a part of a number of flight thermal-vac test campaigns, and this one was just absolutely incredible in how well it went,” said Anthony Colaprete, VIPER project scientist, at an Oct. 29 meeting of the Lunar Exploration Analysis Group (LEAG). “Everything looks great so far.”

NASA is instead pursuing plans to offer VIPER to commercial or industry partners. In its response to Congress, NASA said it received 52 responses to a call for “expressions of interest” made when it announced the cancellation decision. The responses, NASA stated, “ranged from domestic companies and international agencies to backyard/garage enthusiasts,” with the agency concluding that 23 of the respondents had “enough spaceflight experience and technical abilities to conduct the VIPER mission.”

NASA subsequently issued a more formal request for information, receiving 11 responses. A NASA spokesperson said Oct. 30 that the agency was evaluating those responses and would “propose next steps by early 2025.”

The agency told Congress it also heard from 11 international partners interested in VIPER. “NASA reached out to each to gauge interest in partnering with NASA on completion of the VIPER mission. Four space agencies responded, and NASA expects to enter into one-on-one discussions with the agencies to determine feasibility,” it stated. Those space agencies were the Australian Space Agency, German Aerospace Center, Israel Space Agency and Japan Aerospace Exploration Agency (JAXA).

NASA also stated it would consider flying VIPER’s instruments on the Lunar Terrain Vehicle (LTV) that it is working with industry to develop for use on future Artemis missions as well as the larger pressurized rover that JAXA is providing. The LTV, though, won’t be ready until at least late this decade, while the JAXA rover is projected to launch no earlier than fiscal year 2032.

NASA’s decision to cancel VIPER has been sharply criticized by both scientists and advocates of space commercialization, arguing that the rover offered the best near-term chance to identify and characterize water ice deposits thought to exist in permanently shadowed regions of craters at the lunar poles. Such deposits, if present and accessible, could benefit planetary science research and also support commercial activities at the moon.

VIPER “was our only opportunity to start learning whether the foundation of all of our excitement about the south polar region of the moon has merit or not,” said Brent Sherwood, space domain lead at the American Institute of Aeronautics and Astronautics, during a Nov. 12 panel discussion at the Beyond Earth Symposium on cislunar infrastructure.

“Let’s go find out what it is that we think makes the moon worthwhile at all,” he said. “Let’s get the data. Until we have the data, everything else is just talk.”

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...