The crew of Boeing Co.’s Starliner spacecraft said Wednesday they are confident the spacecraft will return them safely to Earth at the end of a long stay aboard the International Space Station, despite a helium leak from the spacecraft’s propulsion system and problems with its steering thrusters.
Starliner, which launched on June 5th, was originally scheduled to be piloted by Captain Barry “Batch” Wilmore and co-pilot Sunita Williams for about eight days in space to test the craft’s manned test flights.
But a helium leak and thruster problems led NASA to extend the space station’s stay indefinitely — it reached its 35th day in orbit on Wednesday — while engineers conduct tests and analysis to better understand what caused the problems and make sure the spacecraft can return Wilmore and Williams safely to Earth.
NASA, meanwhile, has insisted the crew is not “stranded” in space, and Wilmore and Williams appeared to agree with that assessment, speaking to reporters for the first time in more than a month.
“Given where we are now, what we know now, and what the flight will look like as the spacecraft approaches to dock, I’m confident that if there was a problem with the International Space Station, we’d be able to get in, undock, talk to our team and figure out the best way to get home,” Williams said.
“I have a really good feeling that this spacecraft will get us home safely,” she added. “We’re now learning how to optimize our particular situation and finding out all about it.”
Asked about his confidence in Starliner, Wilmore said, “We have absolute confidence.”
“We’re currently conducting thruster testing at White Sands, New Mexico, to try to replicate (the issues) we saw during Rendezvous,” he said. “We’re going to learn from that, and we’re going to have new processes, new procedures that we’ll employ as necessary.”
But Steve Stich, manager of NASA’s Commercial Crew Program, said that as a precaution, the team “reused” a plan first drawn up when the Russian Soyuz spacecraft that carried NASA astronaut Frank Rubio to the space station suffered a coolant leak.
A backup plan was made to land Rubio aboard SpaceX’s Crew Dragon spacecraft in case the worst-case scenario occurred, but that plan was unnecessary when Russia ultimately launched a replacement Soyuz spacecraft.
“We decided to use Dragon as a way to get Frank home in an emergency, to use it as a lifeboat,” Stich said. “The configuration was to have Frank on the middeck of the Dragon, and of course we took some of those things out to compare with the Starliner.
“But again, our main option is to return Butch to Suni on Starliner…. It’s a long way from where we got with the Soyuz. We want to understand the thrusters a bit better before we commit to the final undocking and return.”
Meanwhile, Williams said he and Wilmore are enjoying their free time in space.
“We’re having a lot of fun up on the ISS,” she said. “Butch and I have been here before, so it feels like we’re coming home. It feels good to be floating. It feels good to be in space and working with the team on the International Space Station.”
“So I’m really happy to be here,” she said, “so I’m not complaining and Butch isn’t complaining about us being here a few weeks longer.”
Starliner launched on June 5, four years behind schedule, a month later than planned because of a small issue with the crew’s Atlas 5 booster, trouble with the countdown computer, and a small helium leak in the capsule’s rear service module. Helium is used to pressurize Starliner’s propulsion system and fire its jets when needed.
After a thorough analysis, NASA and Boeing officials determined that the leak did not pose a safety threat, and Starliner was cleared to launch anyway.
But en route to the space station in orbit, four more helium leaks occurred, and Starliner’s flight computers took several rear-facing piloting jets offline after telemetry did not match pre-set operating parameters.
One thruster was deemed unusable going forward, but the others were subsequently successfully test fired. This “hot fire” test gave engineers confidence that the jets needed for post-undocking maneuvers, and to stabilize Starliner during the critical de-orbit rocket fire, would function as needed to prepare the spacecraft for atmospheric re-entry.
The thrusters in question were pointed toward the sun for long periods during Starliner’s approach to the space station, and engineers speculate the previous issues may have been related to high temperatures and fast firing during final approach, conditions they are trying to replicate in ground tests.
Regarding the helium leak, the propulsion system is not used while docked to the space station. The system has been pressurized for hot fire tests but otherwise the valves are closed as always planned to isolate the helium tanks and no further leaks have occurred.
The system will be repressurized upon undocking to allow for the maneuvers needed for return flight, but engineers say the tanks contain 10 times the amount of helium needed for the return journey, providing plenty of headroom if a known leak worsens.
“We’re going to do some testing before we undock, first by opening up the helium valves, and then after we undock to make sure everything is working properly, which is exactly what’s planned based on what we found in the thruster tests,” Williams said, “so both Butch and I are very confident.”
All of the hardware in question is housed in Starliner’s service module, which will detach just before re-entry, so engineers will never be able to inspect the equipment directly. Williams said it made sense to extend the mission to do as much testing as possible before returning home.
“If we just went back, we would lose the Service Module (SM) and wouldn’t be able to do all the testing and understand the spacecraft,” she said.
Stich did not say when the crew would be allowed to undock. Crew Dragon’s next crew change flight is scheduled to launch in mid-August, and “we need to get Butch and Suni home a few days before that launch” on Starliner, he said.
“So this is kind of the back end,” he said. “We’re working really hard to track the data and see when we can target undocking and landing. I think some of the data suggests that optimistically, it’s probably by the end of July. But we’re going to be tracking the data and seeing when the right opportunity for undocking is.”
