Senior NASA and Boeing executives told reporters Friday that they plan to launch the first test flight with the crew of the Starliner spacecraft as early as June 1, after several weeks of detailed analysis of a helium leak and a “design vulnerability” with the propulsion of the ship. system.
Extensive data searches over the past two and a half weeks have identified a likely source of the leak, which officials described as small and stable. During these assessments, engineers also built confidence that even if the leak were to worsen, it would not pose an unacceptable risk to the Starliner test flight to the International Space Station, officials said.
But engineers also found that an unlikely combination 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 causing a deorbit burn at the end of the mission.
“While we were studying the helium leak, we were also looking at the rest of the propulsion system to make sure we didn’t have anything else to worry about,” said Steve Stich, manager of NASA’s commercial crew program. which awarded a $4.2 billion contract to Boeing in 2014 to develop the Starliner spacecraft.
“We have found a design vulnerability… in the prop [propulsion] system when we analyzed this particular helium leak, where for certain fault cases that were very remote, we did not have the ability to do the deorbit burn with redundancy,” Stich said at a press conference on Friday.
These two problems, which came to light one after the other, caused the Starliner test flight to be grounded, giving engineers time to find solutions. This is the first time astronauts will fly into orbit on a Starliner spacecraft, following two uncrewed demonstration missions in 2019 and 2022.
The Starliner program is years behind schedule, mainly due to problems with the spacecraft’s software, parachutes and propulsion system, supplied by Aerojet Rocketdyne. Software problems ended Starliner’s first test flight in 2019 before it could dock with the International Space Station, and they forced Boeing to make an unplanned second test flight to gain confidence that the spacecraft is safe enough for astronauts. NASA and Boeing have postponed the second unmanned test flight for almost a year to fix a problem with corroded valves in the ship’s propulsion system.
Last year, just a few months before the capsule was scheduled to launch on the crew’s test flight, officials discovered a design problem with Starliner’s parachutes and discovered that Boeing had installed flammable tape in the capsule’s cockpit. Boeing’s star-crossed Starliner finally appeared ready to fly on the crew’s long-delayed test flight from Cape Canaveral Space Force Station, Florida.
NASA commander Butch Wilmore and pilot Suni Williams were strapped into their seats in Starliner on May 6 when officials stopped the countdown due to a faulty valve on the spacecraft’s United Launch Alliance Atlas V rocket. ULA rolled the rocket back to its hangar to replace the valve, with an eye on another launch attempt in mid-May.
But ground teams discovered the helium leak in Starliner’s service module in the aftermath of the countdown. After some initial troubleshooting, the leak rate grew to about 70 psi per minute. Since then, the leak rate has stabilized.
“That gave us pause as the leak rate grew, and we wanted to understand what was causing that leak,” Stich said.