Work on Boeing’s CST-100 Starliner commercial crew vehicle to correct minor problems during an uncrewed test flight in May will delay its first flight with astronauts to early 2023, NASA and Boeing said Aug. 25.

The Crew Flight Test (CFT) mission, with NASA astronauts Suni Williams and Butch Wilmore on board, is now scheduled to launch no earlier than February 2023. Boeing had been preparing to fly CFT as soon as this December immediately after completing the Orbital Flight Test (OFT) 2 test flight in May.

Mark Nappi, vice president and program manager for Starliner at Boeing, said during a media teleconference that a review of the data from the OFT-2 mission, which is now wrapping up, shows the need for a “minimal amount of changes” to the Starliner that will fly the CFT mission, a process he called “fine-tuning” and which he said the company expected from the earlier test flight.

That work, though, ruled out any chance of a CFT mission this year. “We had schedules that supported late ’22, the December timeframe, for CFT,” he said. “There were areas that we needed to go do a little bit more work on the systems. We plugged that into the plan and that’s what moved us out by a month, five weeks or so.”

That work addresses problems that came up during the OFT-2 flight, including Orbital Maneuvering and Attitude Control (OMAC) thrusters that shut down during the orbital insertion burn. Nappi said some “debris-related conditions” likely caused those thrusters to shut down, but later noted that is their best estimate since the OMAC thrusters are in a service module that burns up on reentry and is not recovered.

“We do not know where the debris may have come from,” he said. “The bottom line is that it looks to be the leading root cause, and we’ve eliminated that by looking at the CFT vehicle and making sure that there’s absolutely no debris in the system.”

Several reaction control thrusters also shut down during the mission, which Nappi said was likely due to low inlet pressures and can be addressed with a “tweak in timing and tolerances” in software. High pressures in a thermal control loop noticed in the mission were linked to filters that engineers determined are not needed and can be removed. A guidance system on the spacecraft called VESTA worked well but generated more data than the flight software could handle, requiring changes to the software.

Work on the Starliner vehicle that will fly CFT, which includes the same crew module that flew the original OFT mission in December 2019, is on track, Nappi said. That crew module will be mated to its service module in November, “and we have good plans to get us to support that date in February.”

Boeing is not planning to make major changes to the valves in the service module for CFT. Those valves suffered corrosion before an OFT-2 launch attempt in August 2021 when ambient moisture reacted with nitrogen tetroxide propellant that seeped through the valve, creating nitric acid that corroded aluminum elements of the valve. For the May OFT-2 launch, Boeing took steps to purge moisture from the valves and regularly open them to confirm they worked.

“We feel that we have a good short-term solution that we are enhancing slightly for CFT because it’s being implemented during the build and not after the vehicle was built,” he said. “We’re flying that same configuration on CFT.”

Boeing is continuing to study long-term changes that would involve sealing off the valves from moisture and replacing aluminum in them. “Our goal is to get it done as soon as possible,” he said, but added the schedule was tight to have it ready in time for the first operational Starliner mission, tentatively scheduled for the fall of 2023.

A CFT mission to the International Space Station, docked there for eight days, would have to work around an “incredibly busy” schedule there in the first half of the year, said Joel Montalbano, NASA ISS program manager. By early March there will be a Soyuz crew exchange, followed by the Crew-5/Crew-6 exchange of Crew Dragon missions. Also on the manifest are cargo Dragon, Cygnus and Progress missions and Axiom Space’s Ax-2 private astronaut mission.

He said, though, that flying CFT will be a priority so that the vehicle can be certified in time for its first operational mission in the fall. “CFT is a big deal for us,” he said. “When these guys are ready in February, we’ll be making sure there’s room for them, and they will be a high priority unless we’re working a major issue on board space station.”

Montalbano added that he expects to start discussions with the Russian space agency Roscosmos in the fall to update the existing “integrated crew” agreement signed in July to exchange seats between Soyuz and commercial crew vehicles. The current agreement covers one exchange a year between Soyuz and Crew Dragon in 2022, 2023 and 2024.

The modification, he said, would include Starliner and extend the agreement beyond 2024. “The goal is a long-term agreement where, every time we fly, we have a cosmonaut on either SpaceX or Boeing and then an astronaut on the Soyuz spacecraft.”

Boeing, in its second quarter financial results release July 27, said it recorded a $93 million charge in the quarter from its commercial crew program, “driven by launch manifest updates and additional costs associated with OFT-2.” Boeing has now recorded $688 million in charges related to development of Starliner dating back to early 2020.