Senior executives from NASA and Boeing told reporters on Friday that they plan to begin the first crewed test flight of the Starliner spacecraft as early as June 1, after weeks of detailed analysis of a helium leak and a “design vulnerability” in the ship’s propulsion system. System.
Extensive data reviews over the past two and a half weeks have ruled the likely cause of the leak, which officials have described as small and stable. During those checks, engineers also built confidence that even if the leak worsened, it would pose no unacceptable risk to the Starliner’s test flight to the International Space Station, officials said.
But engineers also found that an unlikely combination of technical failures in the Starliner’s propulsion system — representing 0.77 percent of all possible failure modes, according to Boeing’s program manager — could prevent the spacecraft from performing a deorbital burn at the end of the mission.
“When we studied the helium leak, we also looked at the rest of the propulsion system to make sure we didn’t have any other things to worry about,” said Steve Stich, NASA’s commercial crew program manager. which in 2014 awarded Boeing a $4.2 billion contract to develop the Starliner spacecraft.
“We found a design vulnerability… in the prop [propulsion] system when we analyzed this particular helium leak, where for certain failure cases that are very remote, we didn’t have the ability to do a deorbit burn with redundancy,” Stich said at a news conference Friday.
These two problems, discovered one after the other, kept the Starliner test flight grounded to give engineers time to find a solution. This is the first time astronauts will fly into orbit on a Starliner spacecraft after two unmanned demonstration missions in 2019 and 2022.
The Starliner program is running years behind schedule, largely due to problems with the spacecraft’s software, parachutes and propulsion system, which is supplied by Aerojet Rocketdyne. Software problems cut short the Starliner’s first test flight in 2019 before it could dock with the International Space Station and forced Boeing to conduct an unplanned second test flight to ensure the spacecraft was safe enough for astronauts. NASA and Boeing delayed the second unmanned test flight by nearly a year to overcome a problem with corroded valves in the ship’s propulsion system.
Last year, just months before it was due to be launched for a crewed test flight, officials discovered a design problem with the Starliner’s parachutes and discovered that Boeing had installed flammable tape in the capsule’s cockpit. Boeing’s star-studded Starliner has finally appeared ready to fly for a long-delayed crew test flight from the Cape Canaveral Space Force Station in Florida.
NASA Commander Butch Wilmore and pilot Suni Williams were strapped into their seats inside the Starliner on May 6 when officials halted the countdown due to a faulty valve on the spacecraft’s United Launch Alliance Atlas V rocket. ULA returned the rocket back to the hangar to replace the valve, with an eye toward another launch attempt in mid-May.
However, ground teams discovered a helium leak in the Starliner’s service module after the countdown was cleared. After initial troubleshooting, the leak rate increased to about 70 psi per minute. Since then, the leakage rate has stabilized.
“That gave us pause because the leak rate was going up, and we wanted to understand what was causing the leak,” Stich said.