NASA and Boeing planned the first manned test flight of the Starliner spacecraft to the International Space Station (ISS) on June 1. This decision was made after several weeks of detailed inspection, which revealed a helium leak and a structural weakness in the propulsion system. Engineers are confident that the risks of the crewed Starliner flight remain within acceptable limits.

An extensive data analysis was conducted over the past two and a half weeks to help determine the possible cause of the helium leak, which officials described as small and stable. Engineers confirmed that even if it broke down, it would not pose an unacceptable risk for the Starliner’s test flight to the ISS.

However, engineers also found that an unlikely combination of technical failures in the Starliner’s propulsion system with a probability of 0.77 percent of all possible failure modes could prevent the spacecraft from leaving Earth orbit at the end of the mission. This was announced by Steve Stich, head of NASA’s commercial flight program.

Studying We also checked the entire engine system to make sure there were no other issues we needed to worry about due to helium leaking. While analyzing this helium leak, we discovered a design weakness in the propulsion system; In some extremely rare failure cases, we were unable to perform a repeat deorbit braking maneuver.“, Stich said at a press conference on Friday.

These two problems, discovered one after the other, caused Starliner’s test flight to be postponed so that engineers could develop workarounds. This will be the astronauts’ first flight on the Starliner after two unmanned demonstration missions in 2019 and 2022.

The Starliner program fell several years behind schedule due to problems with the software (software), parachutes, and engine system provided by Aerojet Rocketdyne. Software problems disrupted Starliner’s first test flight in 2019, preventing it from docking with the ISS and prompting Boeing to conduct an additional test flight to prove the vehicle’s safety to astronauts. NASA and Boeing delayed the second unmanned test flight by about a year due to corrosion of valves in the engine system.

Last year, a problem with Starliner’s parachutes was discovered months before the planned manned test flight. It was also determined that flammable tape was used inside the capsule. Despite all these problems, the Starliner mission was finally ready for its long-awaited crewed test flight from the Cape Canaveral Space Station.

On May 6, Commander Barry “Butch” Wilmore and pilot Sunita Williams were in their seats aboard the Starliner when the launch was aborted due to a faulty valve in the booster of United Launch Alliance’s (ULA) Atlas V launch vehicle. Ground crews later discovered a helium leak in the Starliner service module after the countdown was aborted. As a result, the company returned the rocket to its hangar to replace the valve, with the intention of attempting another launch at a later date.