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Boeing’s Starliner capsule is on track to launch on the OFT-2 mission to the space station on May 19

Boeing’s CST-100 Starliner capsule remains on track for its crucial May 19 test launch, company officials and NASA officials said.

Starliner was to take off for an uncrewed mission to the international space station called Orbital Flight Test 2 (OFT-2) in August 2021. But standard pre-flight checks shortly before launch revealed that 13 of 24 oxidizer valves in Starliner’s service module propulsion system were stuck.

So Boeing and NASA pulled Starliner and its United Launch Alliance Atlas V rocket out of the pad for troubleshooting. Within months, investigators had found the probable cause of the valve problem: Oxidizer of nitrogen tetroxide (NTO) reacting with humidity in the air, generating nitric acid. The nitric acid then reacted with the aluminum housing of the valves, creating corrosion products that impeded the operation of the valves.

In picture : Boeing’s Starliner OFT-2 mission in pictures

That initial diagnosis was on the money, Boeing representatives and NASA officials said in a call with reporters today (May 3). And the mission team has since successfully resolved the issue, they added.

“Super proud of the Starliner team and the NASA team over the past eight months,” said NASA Commercial Crew Program Manager Steve Stich on today’s call. today. “It’s been a tough eight months, I would say, but very rewarding that we got the problem fixed with the oxidizer isolation valves and headed into launch.”

The valve patch is multi-layered. For example, technicians sealed “a potential moisture path” in the electrical connectors of the valves, said Michelle Parker, vice president and deputy general manager of Boeing Space and Launch, during today’s call. . The team also purges moisture from the valves using nitrogen gas, she said.

“And then, on top of that, we loaded the NTO later,” Parker said. “And we’ve added – operationally, we’ve added a cycle of the valves every two to five days after loading until launch time, to make sure the valves stay operational.”

Boeing also fitted the OFT-2 Starliner with a new service module, docking that component to the crew capsule on March 12.

If all goes as planned on OFT-2, Starliner will meet the ISS about a day after launch and spend five to 10 days docked at the station, NASA officials said.

As its name suggests, OFT-2 will be Starliner’s second crack on an uncrewed test mission to the ISS. The first attempt, which took place in December 2019, was cut short when Starliner suffered a number of software issues and could not reach the station.

Boeing has a contract with NASA to fly the agency’s astronauts to and from the ISS with Starliner. The capsule cannot begin carrying the crew until it has successfully completed an uncrewed test flight to the orbiting laboratory; the company also hopes to complete its crewed test flight before the end of the year.

SpaceX also holds a NASA commercial crew contract. Elon Musk’s company recently launched its fourth operational astronaut mission for the agency, known as the Crew-4. The four astronauts from SpaceX’s Crew-3 flight are currently aboard the station but will return to Earth early Friday morning (May 6), if all goes as planned.

Mike Wall is the author of “The low(Grand Central Publishing, 2018; illustrated by Karl Tate), a book about the search for extraterrestrial life. Follow him on Twitter @michaeldwall. Follow us on twitter @Spacedotcom Or on Facebook.