More than six months after its first crewed mission came to a disappointing end, the future is still murky for Boeing's Starliner astronaut capsule.
That mission, called Crew Flight Test (CFT), extended CFT repeatedly to study the issues.
Finally, on Aug. 24, the agency decided to bring Starliner home uncrewed, which splashdown of SpaceX's Crew Dragon capsule "Freedom."
The Crew-10 arrived at the ISS on Sunday (March 16) to relieve the Crew-9 astronauts, and Crew-11 is scheduled to launch this summer, perhaps as early as July. Elon Musk's company may even send Crew-12 skyward before Starliner carries astronauts again, because NASA and Boeing are still mapping out the new capsule's next steps.
"We're certainly looking at Starliner very carefully," Steve Stich, manager of NASA's Commercial Crew Program, said on Tuesday during a press conference after Crew-9's splashdown.
"We're in the process of looking at that vehicle, looking at the helium system," he added. "We've got some candidate seals that we're going to replace. We'll get into some testing here over the summer timeframe with what we call an 'integrated doghouse' at White Sands [a NASA test facility in New Mexico]."
"Doghouse" is the term NASA and Boeing use for the thruster pods on Starliner's service module. The module sports four such pods, each of which houses 12 thrusters — five of the relatively powerful "orbital maneuvering and control" (OMAC) class and seven "reaction control system" (RCS) thrusters, which are used for finer adjustments, such as those needed during docking.
The thruster problems Starliner experienced during CFT concerned the RCS hardware: Five of the 28 RCS thrusters conked out during Starliner's approach to the ISS, though the mission team eventually brought four of the five affected ones back online.
Ground testing has linked the RCS thruster issue to overheating: Repeated thruster firings can apparently warm up the doghouses so much that some of their Teflon seals bulge, affecting propellant flow.
This theory is informing adjustments to Starliner's design and operations going forward, according to Stich.
"I think we have some changes we need to make to the way we heat those thrusters, the way we fire those thrusters, and then we can test that on the next flight," he said.
Indeed, testing will be a big part of the next Starliner flight, whenever it lifts off.
"We need to make sure we can eliminate the helium leaks; eliminate the service module thruster issues that we had on docking," Stich said.
NASA has not yet decided whether the coming Starliner flight will carry astronauts or not, he added. But even if the mission is uncrewed, the agency wants it to be crew-capable — "to have all the systems in place that we could fly a crew with," Stich said.
"As I think about it, it might be there for a contingency situation, as we prepare for whatever events could happen," he added. "One of the things that I've learned in my time at NASA is, always be prepared for the unexpected."
NASA plans to certify Starliner for operational, long-duration astronaut missions shortly after this next flight, if all goes well.
"We really need to get Boeing into a crewed rotation," Stich said. "Butch and Suni's return on Dragon, to me, shows how important it is to have two different crew transportation systems, the importance of Starliner and the redundancy that we're building into human spaceflight for our low Earth orbit economy."