Senior NASA and Boeing executives told reporters on Friday that the company plans to launch the first crewed test flight of its Starliner spacecraft as early as June 1, following weeks of detailed analysis of the helium leak and “design vulnerabilities” in the spacecraft’s propulsion system.
Extensive data reviews over the past two and a half weeks have concluded that the source of the leak is likely small and stable. During those reviews, engineers also developed confidence that even if the leak worsened, it would not add an unacceptable risk to Starliner test flights to the International Space Station, officials said.
But engineers also discovered that a combination of unlikely technical failures in Starliner’s propulsion system — accounting for 0.77 percent of all possible failure modes, according to Boeing program managers — could prevent the spacecraft from performing a de-orbit burn at the end of the mission.
“While we were looking at the helium leak, we also looked at the rest of the propulsion system to make sure there weren’t any other issues of concern,” said Steve Stich, manager of NASA’s commercial crew program, which awarded Boeing a $4.2 billion contract in 2014 to develop the Starliner spacecraft.
“We discovered a design vulnerability in the prop. [propulsion] “When we analyzed this particular helium leak, we found that we had a system that did not have the capability to perform a deorbit burn with redundancy for that particular, very rare failure case,” Stich said at a press conference on Friday.
The two problems, which emerged one after the other, led to the suspension of Starliner test flights to give engineers time to find a workaround. This will be the first time that astronauts will fly into orbit aboard the Starliner spacecraft, following two uncrewed demonstration flights in 2019 and 2022.
The Starliner program is years behind schedule, due in large part to problems with the software, parachutes and propulsion systems of the spacecraft, supplied by Aerojet Rocketdyne. Software problems halted Starliner’s first test flight before it docked with the International Space Station in 2019, forcing Boeing to conduct an unscheduled second test flight to gain confidence that the spacecraft was safe enough for astronauts. NASA and Boeing delayed the second uncrewed test flight by nearly a year to overcome problems with corroded valves in the spacecraft’s propulsion system.
Just two months before it was due to depart for its crewed test flight last year, officials discovered a design problem with Starliner’s parachutes and discovered that Boeing had installed flammable tape inside the capsule’s cockpit. Boeing’s ill-fated Starliner appeared to finally be ready to take off on its long-delayed crewed test flight from Cape Canaveral Space Force Station in Florida.
NASA Commander Butch Wilmore and pilot Suni Williams remained seated in the Starliner on May 6 when officials halted the countdown due to a valve malfunction on the spacecraft’s United Launch Alliance Atlas V rocket. ULA returned the rocket to its hangar to replace the valve, with a view to attempting another launch in mid-May.
However, ground teams discovered a helium leak in Starliner’s service module in the aftermath of the aborted countdown. After initial troubleshooting, the leak rate increased to about 70 psi per minute. Since then, the leak rate has stabilized.
“The rate of leakage increased, which made us want to stop and understand what was causing the leakage,” Stich said.