The CST-100 Starliner spacecraft on top of its Atlas 5 rocket, being prepared for a launch scheduled for July 30, weather permitting. Credit: Boeing/John Grant

WASHINGTON — A test flight of Boeing’s CST-100 Starliner commercial crew vehicle, delayed by a valve problem in August, is unlikely to take place before some time next year, NASA official said Sept. 21.

In a call with reporters about organizational changes at NASA, Kathy Lueders, associate administrator for the new Space Operations Mission Directorate, said engineers were still trying to determine why valves in the propulsion system of the Starliner spacecraft were stuck shut, postponing an uncrewed test flight that had been scheduled for early August.

Boeing gave up on performing that test flight, called Orbital Flight Test (OFT) 2, in its August window, standing down Aug. 13. The company removed the Starliner spacecraft from its Atlas 5 rocket and returned it to its production facility at the Kennedy Space Center to further investigate the problem.

“The team is still going through its troubleshooting,” Lueders said. Boeing officials said last month that nitrogen tetroxide propellant leaked through Teflon seals on the valves and interacted with moisture on the “dry” side of the valve, creating nitric acid that corroded the valves and caused them to stick shut.

Lueders said workers have studied the dry side of the valves and was now considering removing valves to inspect the “wet” side. A “decision point” is coming in the next few weeks, she said, regarding whether to repair this service module or use a new service module for the OFT-2 mission.

She doubted that the OFT-2 mission could take place before the end of this year. “The timeline and the manifest through the end of the year is pretty right now,” she said. “My gut is that it would probably be more likely to be next year, but we’re still working through that timeline.”

The launch of the mission will depend on not just the readiness of the vehicle but availability of docking ports on the station. Commercial crew vehicles like Starliner can dock at one of two ports at the station. Both ports are currently in use, one by the Crew Dragon spacecraft for the Crew-2 mission and the other by a cargo Dragon spacecraft.

The Crew-2 spacecraft will be replaced by a new Crew Dragon, flying the Crew-3 mission, in November. The OFT-2 mission would have to fly when the other docking port is not in use by a cargo Dragon or a Crew Dragon flying the commercial Ax-1 mission to the station, currently scheduled for early 2022.

Continued delays in the OFT-2 mission will push back the Crew Flight Test mission, which will carry three NASA astronauts to the station, and later operational missions.

“I don’t think we’re ready to formally address when exactly the OFT-2 mission is,” Lueders said. “I think the team is making great progress on further troubleshooting and I absolutely know we’re going to fix this problem before we fly crew.”

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...