The first crewed mission of Boeing’s Starliner capsule has been in orbit for more than a month now, and it still has no return date.
The Starliner capsule launched on June 5 for a crewed flight test (CFT), carrying NASA astronauts Butch Wilmore and Suni Williams to the International Space Station (ISS) for a weeklong stay. However, the capsule experienced helium leaks and propellant problems during the trip, and engineers are still trying to determine the cause. Which means the Starliner capsule has not yet been cleared for liftoff.
“We’re taking our time on the ground to review all the data before deciding whether to return,” Steve Stich, NASA’s commercial crew program manager, said at a news conference Wednesday (July 10).
NASA, Boeing and the two CFT astronauts still have confidence in Starliner, however. At a separate news conference Wednesday, Wilmore praised the capsule’s capabilities in orbit during operational checkouts. “The spacecraft performed incredibly well,” he said.
Wilmore also discussed issues with Starliner’s reaction control system (RCS) thrusters during its pursuit of the ISS, and how the mission addressed them.
“We lost one RCS aircraft, then another, and then we could see that the thrust, the control and the capabilities were degraded,” he explained. “Luckily, we had trained and had been certified for manual control, so we took manual control for over an hour.”
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After arriving at the ISS on June 6, Wilmore and Williams joined the station’s Expedition 71 crew, which Williams said is now unofficially called “Expedition 71+.” Wilmore and Williams took on day-to-day maintenance responsibilities and science experiments, and they were able to catch up on a handful of overdue station tasks. Throughout their mission, the duo also continued to check Starliner’s many systems and any anomalies they encountered, which are also being investigated by Boeing engineers on Earth to determine their cause.
Stich highlighted the meticulous approach taken to analyzing data and reproducing the spacecraft’s thruster issues during testing 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 undocking.
In addition to the propellant issues, several helium leaks have been identified in the Starliner capsule. “There have been several specific actions identified both because of the helium and propellant anomalies,” Mark Nappi, Boeing’s vice president and head of the commercial crew program, said Wednesday. “There are a little over 30 (actions), more than half of which are closed at this time.”
“Regarding the helium leak, we hope to be able to discuss this with the Starliner mission management team for final resolution later this week,” Stich said. Despite the issues, agency officials have said the spacecraft is designed to leave the ISS in an emergency, with all but one of its RCS thrusters cleared for use during reentry into Earth’s atmosphere.
The decision to extend Starliner’s mission also gave ground crews extra time they didn’t expect. Amy Decker of Starliner’s chief engineer office said the extra data they’re getting is “AWESOME, in capital letters,” Nappi said.
“The more time you have to get more data,” Nappi said, “the more excited the engineers are.”
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The last Starliner that could return with Wilmore and Williams, according to Stich, would be mid-August.
“The main driver is the handover that’s coming up from Crew-8 to Crew-9, which is going to happen in mid-August,” Stich said, referring to two SpaceX astronaut missions to the ISS. “So … a few days before Crew-9 launches, we’re going to have to get Butch and Suni back on the Starliner.”
Ideally, they should return home sooner. “We’re really working to track the data and determine the earliest possible time for undocking and landing,” Stich said. “I think some data suggests, optimistically, that it might be by the end of July, but we’ll just track the data step by step and determine when the time is right for undocking.”
“We have great confidence in the thrusters as they are today,” Nappi said, citing an on-orbit thruster ignition test conducted by Starliner while docked with the ISS.
“What we’re doing is just taking the time to make sure that we’ve looked under every rock and stone, and making sure there’s nothing else that might surprise us,” Stich added in response.
The CFT mission follows two previous uncrewed Starliner missions to the ISS. The first, in December 2019, failed to reach the orbiting laboratory after experiencing a number of problems. The second, in May 2022, successfully docked but also experienced thruster issues.
“We knew this flight test would provide us with lessons learned,” Nappi said. “We learned a lot about how the equipment works, how our processes work and how we can improve.”
For now, “there’s one thruster that’s producing very little thrust that we’re going to turn off for the remainder of the flight,” Stich said. The extended stay on the ISS also helps teams prepare the spacecraft for future operational astronaut missions, which are expected to last up to six months, starting with Starliner-1 in 2025.
Testing at White Sands during the CFT helped planners anticipate this first operational mission and prevent similar thruster problems from recurring.
According to Stich, the Starliner’s thruster pulses fired more frequently than engineers expected this time.
“What we’re trying to do at White Sands,” he said, “is to replicate exactly what those pulses were perceived by the thrusters, and then understand the heating effects of those pulses, and just make sure that there are no unintended consequences of those pulses.”
Stich said he believes there is a way to take what teams observed with the thrusters during the CFT into account to modify 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 the safe return of Wilmore and Williams. “Starliner is prepared to return in the event of an emergency,” Stich confirmed. The team is working through the process, including a return flight readiness review, to prepare for Starliner’s eventual undocking and landing.