The head of NASA’s space operations division said this week an unpiloted test flight of Boeing’s Starliner crew capsule to the International Space Station, delayed from August by valve problems, will likely not launch until next year.
Officials may swap out the spacecraft’s service module, which contains the balky propulsion system valves, for a new one, said Kathy Lueders, associate administrator of NASA’s Space Operations Mission Directorate.
In a conference call with reporters Tuesday, Lueders said Boeing engineers continue troubleshooting valves on the Starliner service module. Boeing’s Starliner test flight, called Orbital Flight Test-2, was supposed to launch last month to the International Space Station on a final demonstration of the crew capsule before it flies with astronauts.
But managers scrubbed a launch attempt Aug. 3 after some of the valves inside the Starliner service module failed to open during a pre-flight checkout.
An initial round of troubleshooting with the Starliner spacecraft on top of its United Launch Alliance Atlas 5 rocket at Cape Canaveral Space Force Station did not fully resolve the problem. Managers decided to remove the Starliner spacecraft from the Atlas 5 rocket and transfer it back to Boeing’s factory at nearby Kennedy Space Center for more work.
The crew capsule returned to the Boeing factory Aug. 19.
The decision indefinitely delayed the OFT-2 mission, itself a re-do of an orbital test flight in December 2019 that was plagued by software woes. The software problems prevented the Starliner spacecraft from docking with the space station and triggered a premature end to the mission with a successful landing in New Mexico.
Boeing officials said last month that nitrogen tetroxide, an oxidizer consumed by Starliner maneuvering thrusters in combination with hydrazine fuel, leaked through Teflon seals in the valves. That is normal, Boeing officials said, but the nitrogen tetroxide reacted with water vapor that somehow made its way into the service module, creating nitric acid that corroded the valves and caused them to stick.
In space, where there is no ambient moisture, any nitrogen tetroxide that seeps through the Teflon seals can be vented without any issues, Boeing officials said.
Lueders said Tuesday engineers have looked at the “dry side” of the valves, the side opposite of the spacecraft’s propellant tanks. Boeing will soon decide whether to remove the valves to look at the “wet side.”
Twenty-four regulate the flow of oxidizer to the Starliner spacecraft’s thrusters used for in-space maneuvers. Boeing initially detected problems with 13 of the 24 oxidizer valves.
Officials will decide in a few weeks whether to repair the valves in the service module, or use a new service module for the OFT-2 mission. If Boeing goes with a new service module, the current service module might be repaired and used on a future mission, Lueders said.
Boeing officials said last month it was too early to know whether the valves might need to be redesigned, or whether ground teams could take more steps to ensure moisture does not get into the valves.
Lueders said the Starliner troubleshooting schedule and the list of other missions launching to the space station in the coming months is “pretty tight” to find an opportunity to launch the OFT-2 mission before the end of the year.
“So my gut is it would be probably more likely to be next year, but we’re still working through that timeline,” Lueders said. “I don’t think we’re ready to formally address when exactly the OFT-2 missions is, but 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.”
There are two docking ports on the International Space Station that can receive the Starliner spacecraft. Both are currently occupied, one with a SpaceX Crew Dragon spacecraft, and another with a Cargo Dragon supply ship.
The Cargo Dragon is scheduled to depart the station Sept. 30, and another Crew Dragon is set for launch to the station Oct. 30 with a four-person crew beginning a six-month expedition in orbit.
The Crew Dragon spacecraft currently docked to the station will return to Earth in early-to-mid November with its four-person crew. Another Cargo Dragon resupply mission is slated to launch in early December for a month-long stay at the space station, when both docking ports will again be occupied.
A private crew mission on a Crew Dragon capsule is scheduled for launch to the space station in early 2022, again occupying the second docking port.
Not only do Boeing and NASA managers have to find an opening in the space station schedule, but they also must work with ULA to secure a slot in the company’s Atlas 5 launch manifest.
An Atlas 5 launch is scheduled for Oct. 16 from Cape Canaveral with NASA’s robotic Lucy asteroid mission, followed by a launch for the U.S. military in November.
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