Independent Review Confirms Bad Valve Doomed Astrobotic’s Peregrine-1 Mission

An independent review of the January failure of Astrobotic’s Peregrine-1 lunar lander has confirmed that a single bad valve doomed the mission. While designated a risk before launch because of problems with its twin, the company concluded it would be even more risky to tear the lander apart and replace it. The outside reviewers agreed and simply chalked the failure up to a hardware failure, not to the lander’s design or lapse in company decision-making. Changes are being made so the valves are more robust.

The first of NASA’s Commercial Lunar Payload Services (CLPS) missions, Peregrine-1 got off to a perfect start on the first launch of the United Launch Alliance’s Vulcan rocket on January 8, 2024 from Cape Canaveral Space Force Station.

LIFTOFF of the first United Launch Alliance #VulcanRocket! pic.twitter.com/wZMlPxWr4l

— ULA (@ulalaunch) January 8, 2024

The rocket performed perfectly, but shortly after the spacecraft separated from the rocket, a valve in Peregrine’s propulsion system failed, allowing massive amounts of helium to flow into the oxidizer tank, rupturing it.

Pittsburgh-based Astrobotic knew immediately something was wrong. Attempts to mitigate the problem were unsuccessful and they were not able to put Peregrine-1 into orbit around the Moon or land. The spacecraft was on a trajectory that brought it back toward Earth and they used remaining fuel in the thrusters to aim it into Earth’s atmosphere where it disintegrated over the Pacific Ocean.  Peregrine-1 operated for a total of 10.5 days.

Through the CLPS program, NASA purchases commercial lunar landing services from several companies. The companies design, build and own the spacecraft and purchase launch services from providers like ULA and SpaceX. They are expected to find non-NASA customers to close the business case.

NASA and Astrobotic heralded Peregrine-1 as a success even though it did not achieve its primary objective to land on the Moon.

Astrobotic convened an independent review board to look at what went wrong. Chaired by John Horack, Professor and Neil Armstrong Chair at Ohio State University, the report was released today.

During a media telecon this morning, Horack told reporters the review confirmed the valve was the root cause of the failure. Asked what could have been done to prevent it, Horack pointed out that otherwise the spacecraft performed well and he only wished they “had a more robust design of the valve. Sometimes hardware just fails.”

Basically a threaded component inside the valve loosened due to vibrations, allowing tiny helium molecules to pass through. “It’s pretty much no different than when you’re in your kitchen. Water gets through the seal and comes out the other side. In this case it’s helium and it’s high pressure so it’s much harder to confine,” he explained.

In this case it was Pressure Control Valve 2 (PCV2) located deep inside the spacecraft. Its twin, PCV1, failed during pre-launch testing and was replaced, but changing out PCV2 would have meant taking the spacecraft apart, invalidating all the testing done already and setting the project back.

Astrobotic identified PCV2 as a risk, but a low risk, and proceeded.

Horack said his team concurred with Astrobotic’s decision-making. Choosing not to do “major surgery on the spacecraft” was a “very sound decision.”

“I can’t see any decisions that were made in-flow leading up to launch where I would have said, hey, you know I think we should have done this differently.  … I think the decision making of the team was very good.  … I think this is a situation where you had a pretty unfortunate piece of hardware that failed in the valve.” — John Horack

Two changes are being made for future Astrobotic lunar landers, both Peregrine and the larger Griffin. Pressure regulators and latch valves will be installed upstream of the valves so if there is a helium leak, it will not be able to enter the oxidizer tank. Astrobotic declined to say what company supplies the valves or specifics of the design because it is proprietary.

Astrobotic founder and CEO John Thornton stressed this was the first flight of the lander and problems are not unexpected on first flights of rockets and spacecraft.  In addition, CLPS is designed as a comparatively low-cost approach to lunar landings.

From his point of view, the mission otherwise was quite successful, increasing the Technology Readiness Levels (TRLs) of many technologies and training the mission control team on how to resolve other anomalies that occurred. Not including PCV2, there were 24 in-flight anomalies, eight of which were mission critical and potentially mission-ending, but were resolved by flight controllers in real-time.

Thornton is bullish on Peregrine’s future, but the focus now is the larger Griffin lander.  The company’s second CLPS contract was to send NASA’s half-billion dollar VIPER rover to the Moon, but because of cost increases and delays caused by Peregrine’s problems, NASA intends to cancel the mission.  It will still pay Astrobotic $323 million to send Griffin to the Moon, but without VIPER on board. The company has non-NASA customers already and is seeking more.

NASA has already invested $450 million in VIPER itself, apart from the Astrobotic contract, and expects to save only $84 million by cancelling it. The agency is inviting commercial and international partners to step up and take over the rover as long as it does not cost NASA any more money. Responses to a Request for Information are due September 2.

The decision is very controversial and not final until Congress weighs in. The Planetary Society is advocating to save VIPER and Sen. Shelley Moore Capito (R-WV) called on her Senate Appropriations Committee colleagues to help find ways to “repurpose the lander.”  West Virginia is part of the tri-state Keystone Space Collaborative that includes Ohio and Astrobotic’s home state of Pennsylvania to support the space industry in those states.

VIPER was supposed to launch in 2023, but slipped to 2024, and after the Peregrine failure, to September 2025 with consequent cost increases from $433.5 million to $505.4 million and now $609.6 million if launch actually took place in September 2025. NASA’s decision to cancel was based in part on concern that Griffin will not be ready then either and the costs will keep growing.

Thornton said several times today, however, they are working to launch Griffin by the end of 2025. It will carry whatever commercial payloads Astrobotic can acquire. NASA has offered to provide a mass simulator to take the place of VIPER, but it is not clear if Astrobotic wants it. The lander belongs to the company, not to NASA.

Astrobotic is just one of several companies with CLPS contracts. Intuitive Machine’s Odysseus enjoyed a more successful outcome in February. A second IM lander is expected to launch this year with more in the future along with landers from Firefly and Draper.  Intuitive Machines has publicly expressed interest in taking over VIPER.