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Leaky valve issue forces Boeing to swap out Starliner’s service module

The very top of a rocket on a launch pad.
Enlarge / In early December 2019, the Starliner spacecraft is mated to its Atlas V rocket.

Trevor Mahlmann

Nearly two years have now come and gone since Boeing’s Starliner spacecraft made its unsuccessful debut test flight, launching on December 20, 2019. Now, finally, there is some clarity on when the vehicle may launch again and attempt to dock with the International Space Station.

NASA and Boeing said Monday that they were working toward a launch of Starliner in May 2022. To accommodate this launch date for the “Orbital Flight-2” or OFT mission, Boeing will swap out a faulty service module—which provides power and propulsion to the Starliner capsule in flight—with a new one.

Boeing initially tried to fly OFT-2 in August. However, with less than five hours remaining in the countdown to launch, during a routine procedure, 13 of the 24 valves that control the flow of dinitrogen tetroxide oxidizer through the service module of the spacecraft would not cycle between closed and open. The launch was aborted.

The decision announced Monday comes after months of troubleshooting a “leaky valve” issue on the Starliner spacecraft that was intended to fly the do-over test flight.

“NASA has been working side-by-side with Boeing on the service module valve investigation, including leveraging the agency’s materials and propellants expertise to better characterize the potential causes of the issue,” said Steve Stich, manager of NASA’s commercial crew program, in a news release. “Because of the combined work, we have a much better understanding of the contributors that led to the valve issues, and ways to prevent it from happening in the future.”

NASA and Boeing did not hold a media event to announce their findings, and unfortunately some key questions remain. For example, it appears that Boeing has not yet fully identified the root cause of the valve failure, which was believed to be related to high humidity at the Florida launch site, which caused corrosion.

“Ongoing investigation efforts continue to validate the most probable cause to be related to oxidizer and moisture interactions,” the news release states. “NASA and Boeing will continue the analysis and testing of the initial service module on which the issue was identified.”

The service module is ejected by the Starliner capsule near the end of its mission, prior to reentry into Earth’s atmosphere. It is not reused. To accommodate the OFT-2 mission, Boeing will bring forward the service module it had intended to use for the first crewed test flight. To ensure the corrosion problem does not recur, Boeing said its technicians and engineers would apply “preventative remediation efforts” to the new service module.

It was not clear from NASA’s and Boeing’s releases what fate awaits the service module with faulty valves, which would be a costly loss. Previously, Boeing took a $410 million charge on its fourth-quarter earnings in 2019 to pay for the OFT-2 mission. It was not part of the original scope of NASA and Boeing’s commercial crew contract, which pays a fixed price for flying astronauts to the International Space Station.

However, after myriad software issues nearly caused the first Starliner spaceflight to end in catastrophe, NASA and Boeing agreed that a second uncrewed test flight was necessary before astronauts launched into orbit.

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