Boeing's Starliner capsule has just returned to Earth without astronauts, marking the start of a new series of investigations by Agency.
Starliner lifted off from the International Space Station (ISS) on Friday night (September 6) and landed in New Mexico shortly after midnight on Saturday (September 7). The landing brought an end to the crewed flight test (CFT), Starliner’s first astronaut mission. But no astronauts came down with the capsule on Saturday; Starliner experienced problems with its reaction control system (RCS) thrusters shortly after liftoff from the CFT on June 5, and Agency decided not to risk putting Williams and Wilmore back aboard the capsule.
The duo have a solid plan for getting home: They’ll return to Earth in February 2025 aboard a SpaceX Crew Dragon capsule, which will fly the company’s Crew-9 mission, which launches toward the ISS on Sept. 24. But what’s next for the Starliner program is a bigger question.
In 2014, Agency tasked SpaceX and Boeing with sending astronauts to and from the ISS. Building on the knowledge gained from its Cargo Dragon spacecraft, SpaceX flew a Crew Dragon test mission to the station in 2019 without astronauts and passed all tests, allowing the company to launch its first test flight with astronauts the following year. That effort was successful, and SpaceX quickly transitioned to flying long-duration operational missions with astronauts to the ISS for Agency. It is in the midst of its eighth such flight and is preparing for its ninth (Crew-9).
Related: Agency astronauts can't wear Boeing's Starliner spacesuits on SpaceX's Dragon spacecraft. Here's why
Starliner, a new design, has required quite a bit of fine-tuning. Its first mission, an uncrewed test flight in December 2019, failed to reach the ISS due to software glitches. The capsule was successful on its second attempt to reach the ISS in May 2022, but experienced some issues with its propulsion system during that flight.
The CFT has also had its share of issues, including helium leaks and thruster problems (five of Starliner’s 28 RCS thrusters failed as it chased the ISS shortly after launch). The mission was only supposed to last about 10 days, but Agency kept Starliner at the ISS for three months while it looked into the thruster problems and what to do about them.
These problems appear to be related to overheating, perhaps a result of both the frequency of use of the thrusters and their placement inside heat-retaining shelters on the outside of the spacecraft, known as “doghouses.” Bulging seals and peeling insulation appear to restrict fuel flow to the RCS thrusters.
Agency and Boeing had hoped the CFT would pave the way for Starliner’s first operational crewed flight. That mission, known as Starliner-1, is tentatively planned for August 2025. But it’s too early to tell whether Starliner will meet that deadline.
“I think we'll see where we are in another month or so, and we'll have a little bit better idea of what the overall timeline is going to be,” Steve Stich, manager of Agency's Commercial Crew Program, said during a post-landing news conference Saturday morning.
That timeline could even include another test flight before Starliner is certified for operational missions with astronauts.
“I would say it's probably too early to think exactly what the next flight will look like. I think we want to take the next step and analyze all the data,” Stich said.
“We know we have to work on some things,” he added. “We'll do it and figure it out, and then we'll fly when we're ready.”
Much of this work will focus on the RCS thruster overheat problem and how to mitigate it.
“What we need to do now is go take a booster ride at White Sands. [Test Facility in New Mexico] “And making sure we understand the exact pulse sequences that cause the heating,” Stich said. “And then at the same time, in parallel, looking at software changes to reduce the amount of demands on the thrusters.”
The teams will also investigate the possibility of removing or altering thermal blankets inside the dog houses, to help keep the thrusters cooler, he added.
“So I would say there are really three different axes,” Stich said.
But Stich stressed that there are many positive aspects to the CFT. Starliner performed very well during its entry, descent and landing today, he said, describing the touchdown at the White Sands spaceport as a “knockout.” And he estimated that despite Starliner’s problems, Boeing was able to achieve 85% to 90% of the CFT mission objectives.
Joel Montalbano, deputy associate administrator for Agency's Space Operations Mission Directorate, also highlighted the positives and tried to put the CFT in proper perspective.
“It's important to remember: This was a test mission, right?” Montalbano said during the post-landing press conference. “We learned from this mission.”