The crew of Boeing's Starliner spacecraft said Wednesday they are confident the capsule will return them safely to Earth at the end of their extended stay aboard the International Space Station, despite helium leaks in the craft's propulsion system and problems maneuvering the thrusters.
Launched on June 5, Commander Barry “Butch” Wilmore and co-pilot Sunita Williams originally expected to spend about eight days in space, putting the Starliner through its paces on the craft's first piloted test flight.
But helium leaks and thruster problems prompted NASA to extend their stay aboard the space station indefinitely — Wednesday marked their 35th day in orbit — while engineers conduct tests and analysis to better understand what caused the problems and ensure the spacecraft can bring Wilmore and Williams home safely.
NASA, meanwhile, insists the crew is not “stranded” in space, and both Wilmore and Williams, speaking to reporters for the first time in more than a month, appeared to agree with that assessment.
“I think given where we are right now, what we know and how the spacecraft flew as it approached to dock, I’m confident that if we had to do it, if there was a problem with the International Space Station, we would be able to get in our spacecraft and undock, talk to our team and figure out the best way to get back home,” Williams said.
“I have a feeling that this spacecraft will bring us home without any problems,” he added. “We are now learning how to optimize our specific situation and make sure we know everything about it.”
Asked about his faith in the Starliner, Wilmore said: “We're absolutely confident.”
“We’re doing propulsion testing right now at White Sands, New Mexico, trying to replicate (the problems) that we saw when we got close,” he said. “And we’re going to learn from that. And we’re going to incorporate new processes, new procedures that we’ll employ if necessary.”
But to be on the safe side, Steve Stich, manager of NASA's Commercial Crew Program, said the team has “dusted off” plans originally developed when the Russian Soyuz spacecraft carrying NASA astronaut Frank Rubio to the station developed a coolant leak.
In that case, preliminary plans were made to possibly drop Rubio in a SpaceX Crew Dragon capsule if the situation worsened. It turned out that the Russians launched a replacement Soyuz and those plans were not necessary.
“We decided to use the Dragon as a contingency return option for Frank… to use as a lifeboat,” Stich said. “We had a Frank configuration on the middeck of the Dragon. I mean, we’ve certainly dusted off some of that stuff to look at in relation to Starliner, just to be prepared.”
“But again, our main option is to return Butch to Suni on Starliner… We’re pretty far from where we were with Soyuz. We just want to understand the thrusters a little bit more before we commit to the final undocking and return.”
Meanwhile, Williams said she and Wilmore were enjoying the extra time in space.
“We’re having a great time here on the International Space Station,” she said. “You know, Butch and I have been here before, and it feels like… coming home. It feels good to float. It feels good to be in space and working here with the International Space Station team.
“Yeah, it’s great to be here,” he said. “I’m not complaining, Butch isn’t complaining about us being here a couple more weeks.”
The Starliner, which was delayed by four years in its launch, launched on June 5, a month later than planned due to minor issues with the crew’s Atlas 5 rocket, problems with a countdown computer and a small helium leak in the capsule’s rear service module. Helium is used to pressurize the Starliner’s propulsion system so that jets can fire as needed.
After a thorough analysis, NASA and Boeing managers decided the leak was not a safety threat and Starliner was cleared for launch as was.
However, once in orbit and en route to the space station, four more helium leaks occurred. In addition, Starliner's flight computer shut down several rear-facing maneuvering engines when telemetry did not match pre-set operating parameters.
One booster was deemed unusable going forward, but the others were later successfully tested. That “hot burn” test gave engineers confidence that the boosters needed for post-undocking maneuvers and to keep Starliner stable during the critical deorbit rocket launch will perform as required to prepare the spacecraft for reentry.
The thrusters in question were pointed toward the sun for long stretches of Starliner's approach to the station, and engineers suspect the problems experienced earlier were related to the high temperatures and rapid burns during final approach. They are trying to replicate those conditions in ground tests.
As for the helium leaks, the propulsion system is not in use while docked to the space station. The system was pressurized for the fire test, but the valves were otherwise closed as always planned to isolate the helium tanks, eliminating additional leaks.
The system will be repressurized for undocking to allow the maneuvers needed to return home. But engineers have said there is ten times more helium in the tanks than is needed for the return trip, providing a comfortable buffer even if any of the known leaks were to worsen.
“I anticipate that we will continue to do testing before we undock, opening the helium valves first and then once we undock to make sure everything is working properly as intended from what they found during the thruster testing,” Williams said. “So I’m confident, Butch is confident.”
All of the hardware in question is housed in Starliner's service module, which is jettisoned just before atmospheric entry. As a result, engineers will never be able to examine the equipment firsthand. Williams said it made sense to extend the mission to do as much testing as possible before returning home.
“If we were to go back home, we would lose the SM (service module) and then we wouldn't be able to do all this testing and understand our spacecraft,” he said.
Stich did not say when the crew might be cleared to undock. Crew Dragon’s next crew rotation flight is scheduled for mid-August and “a few days before that launch opportunity, we would need to bring Butch and Suni home on Starliner.”
“So that’s kind of the final stage,” he said. “We’re really working to try to follow the data and see when is the earliest we could target to undock and land. I think some of the data suggests, maybe optimistically, that it’s by the end of July. But we’ll just follow the data (and) figure out when is the right opportunity to undock.”
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