Senior managers from NASA and Boeing told reporters on Friday that they plan to launch the first crew test flight of the Starliner spacecraft as soon as June 1, following several weeks of detailed analysis of a helium leak and a "design vulnerability" with the ship's propulsion system.
Extensive data reviews over the last two-and-a-half weeks settled on a likely cause of the leak, which officials described as small and stable. During these reviews, engineers also built confidence that even if the leak worsened, it would not add any unacceptable risk for the Starliner test flight to the International Space Station, officials said.
But engineers also found that an unlikely mix of technical failures in Starliner's propulsion system—representing 0.77 percent of all possible failure modes, according to Boeing's program manager—could prevent the spacecraft from conducting a deorbit burn at the end of the mission.
"As we studied the helium leak, we also looked across the rest of the propulsion system, just to make sure we didn't have any other things that we should be concerned about," said Steve Stich, manager of NASA's commercial crew program, which awarded a $4.2 billion contract to Boeing in 2014 for development of the Starliner spacecraft.
"We found a design vulnerability... in the prop [propulsion] system as we analyzed this particular helium leak, where for certain failure cases that are very remote, we didn't have the capability to execute the deorbit burn with redundancy," Stich said in a press conference Friday.
These two problems, uncovered one after the other, have kept the Starliner test flight grounded to allow time for engineers to find workarounds. This is the first time astronauts will fly into orbit on a Starliner spacecraft, following two unpiloted demonstration missions in 2019 and 2022.