The first manned mission of Boeing’s Starliner capsule has been in orbit for more than a month, and there is still no date set for its return.
Starliner launched on June 5 on Crew Flight Test (CFT), carrying NASA astronauts Butch Wilmore and Suni Williams to the International Space Station (ISS) for a planned week-long stay. However, the capsule experienced helium leaks and thruster problems during the journey, and engineers are still investigating what caused them — meaning Starliner has not yet been cleared for departure.
“We’re taking our time on the ground to review all the data before we make a decision on whether to return,” Steve Stich, manager of NASA’s Commercial Crew Program, said during a news conference on Wednesday (July 10).
NASA, Boeing and the two CFT astronauts, however, still have confidence in Starliner. During a separate media event on Wednesday, for example, Wilmore praised the capsule’s on-orbit capabilities during operational checks. “The spacecraft performed incredibly well,” he said.
Wilmore also discussed the issues with Starliner’s Reaction Control System (RCS) thrusters during the chase to the ISS and how the mission handled them.
“We lost an RCS jet, and then another one, and then you could tell the thrust, the control, the power, was gone,” he explained. “Luckily, we had practiced and were certified for manual control, so we took over manual control for over an hour.”
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After arriving at the ISS on June 6, Wilmore and Williams integrated into the space station’s Expedition 71 crew, which Williams said is now unofficially called “Expedition 71+.” Wilmore and Williams have been handling daily maintenance responsibilities and science experiments, and they’ve been able to close the gap on a handful of overdue tasks on the station. During their mission, the duo has also continued their checks of the Starliner’s many systems and any anomalies they’ve encountered, which are also being investigated by Boeing engineers on Earth to determine the cause.
Stich emphasized the meticulous approach used to analyze data and replicate the spacecraft’s thrust issues during tests at NASA’s White Sands Test Facility in New Mexico. One advantage of the ISS, he said, is its ability to serve as a temporary orbital “hangar,” providing a unique opportunity to understand Starliner’s long-term performance in space before it undocks.
In addition to the thruster issues, several helium leaks have been identified in the Starliner capsule. “There were a number of specific actions that were identified by both the helium and thruster anomalies,” Mark Nappi, Boeing’s vice president and Commercial Crew Program manager, said Wednesday. “It’s just over 30 [actions]more than half of which are currently closed.”
“As for the helium leak, we hope to present that to the Starliner mission management team later this week for a final resolution,” Stich said. Despite the issues, agency officials said the spacecraft is classified to leave the ISS in the event of an emergency, with all but one of its 28 RCS thrusters cleared for use during re-entry.
The decision to extend Starliner’s mission has also given ground teams extra time they weren’t expecting. According to Nappi, Amy Decker, from Starliner’s chief engineering office, says the extra data they’re getting is “AMAZING, in all caps.”
“The more time you have to collect more data,” Nappi said, “the more excited [the engineers get].”
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According to Stich, the very last Starliner could return with Wilmore and Williams in mid-August.
“The big driver is the handoff that we have between Crew 8 and Crew 9, which is going to happen in mid-August,” Stich said, referring to two SpaceX astronaut missions to the ISS. “So… a couple of days before that [Crew-9] If we were given the opportunity to launch the spacecraft, we would have to get Butch and Suni home on the Starliner.”
Ideally, though, they’ll come home sooner. “We’re really working on following the data and seeing when the earliest we can aim for is undocking and landing,” Stich said. “I think some of the data is maybe late July, optimistically, but we’re following the data step by step and figuring out when the right undocking window is.”
“We have a lot of confidence in the thrusters as they stand right now,” Nappi said, referring to a test flight of a thruster Starliner conducted while docked with the ISS.
“What we do is take the time to make sure we look under every rock and every stone, and that there is nothing else that would surprise us,” Stich added.
CFT follows two previous unmanned Starliner missions to the ISS. The first, in December 2019, failed to reach the orbiting lab after a series of failures. The second, in May 2022, docked successfully but also encountered thruster problems.
“We knew we were going to learn something from this flight test,” Nappi said. “We learned a lot about how the hardware works, how our processes work, and how we can improve.”
“Right now, there’s one thruster that’s producing very low thrust that we would turn off for the rest of the flight,” Stich explained. The extended stay on the ISS also helps teams ready the spacecraft for future operational astronaut missions, which are expected to last up to six months, starting with Starliner-1 sometime in 2025.
Testing at White Sands during CFT has helped planners look ahead to that first operational mission and how to prevent similar problems with the boosters from happening again.
According to Stich, the Starliner’s thrusters were fired more often this time than engineers had expected.
“What we’re trying to do at White Sands,” he said, “is mimic exactly what the pulses were that the thrusters saw, and then understand the heating effects of those pulses, and just make sure there are no unintended consequences of those pulses.”
Stich said he thinks there’s a way to use what the teams observed with the thrusters during CFT to adjust their requirements for future rendezvous and docking maneuvers. “I think that’s the work that lies ahead for Starliner-1,” he said.
As the CFT mission continues, the focus remains on ensuring a safe return for Wilmore and Williams. “Starliner is ‘go’ to return in an emergency,” Stich confirmed. The team is working through the process, including a return flight readiness assessment, to prepare for Starliner’s eventual undocking and landing.