NASA Confirms 5th Helium Leak on Boeing Starliner Spacecraft

NASA has confirmed that Boeing’s CST-100 Starliner spacecraft has experienced a fifth helium leak in its propulsion system while docked to the ISS. The "minor leak", was detected post-docking, and adds to the growing list of issues the spacecraft has encountered during its crewed flight test mission. The fifth leak was detected around the time as the post-docking briefing.

On June 10th NASA released a statement saying "five small leaks in the service module helium manifolds on the remainder of the mission."

This statement marked the first public acknowledgment of five leaks, as previous briefings only mentioned four leaks following the spacecraft’s June 6 docking with the International Space Station (ISS).

“The leak is considerably smaller than the others and has been recorded at 1.7 psi [pounds per square inch] per minute,” - Josh Finch, NASA Spokesperson Josh Finch

The saga of the helium leaks began before Starliner’s launch. NASA was aware of one leak detected shortly after a scrubbed launch attempt on May 6. When the spacecraft finally launched on June 5, NASA and Boeing officials deemed this an isolated issue, likely caused by a defect in a seal.

However, hours after the launch, controllers identified two more leaks, including a significant one at 395 psi per minute, as disclosed by Steve Stich, NASA commercial crew program manager, during a briefing. A fourth, smaller leak at 7.5 psi per minute was discovered after docking.

“What we need to do over the next few days is take a look at the leak rate there and figure out what we go do relative to the rest of the mission,” - Steve Stich, NASA Commercial Crew Program Manager

To halt the leaks, NASA closed the helium manifolds in the propulsion system post-docking. However, these manifolds will need to be reopened for the spacecraft’s undocking and deorbit maneuvers.

NASA engineers estimated that Starliner has sufficient helium for 70 hours of flight operations, although only seven hours are required for the return journey to Earth.

In addition to the helium leaks, engineers are examining other issues, including a reaction control system (RCS) thruster that shut down during the flight to the ISS. While four other thrusters were temporarily turned off by flight software, they were later reenabled. Additionally, an RCS oxidizer isolation valve in Starliner’s service module has not properly closed.

“We have the commercial crew program, Boeing, ISS teams all integrated, working very well together in order to come up with a forward plan for getting us in the best posture for that undock and reentry...The teams are still working through what are the best ways to go about testing and preparing for undock and reentry.” - Dina Contella, NASA ISS Deputy Program Manager

With some time to resolve these issues, NASA rescheduled Starliner's undocking from June 14 to no earlier than June 18, to avoid conflicting with a June 13 ISS spacewalk by NASA astronauts Tracy Dyson and Matt Dominick.

“To have it back to back, where we had an EVA followed by undock, was not the most convenient,” - Dina Contella, NASA ISS Deputy Program Manager

Undocking opportunities are available every few days, dictated by orbital mechanics for landing in the southwestern United States.

NASA astronauts Butch Wilmore and Suni Williams, who flew Starliner to the ISS, have been engaged in testing the spacecraft and conducting other tasks, including scientific experiments.

“Butch and Suni are an extra set of hands...Having Butch and Suni available to perform some key critical science has been outstanding.” - Dina Contella, NASA ISS Deputy Program Manager

Both astronauts have expressed high praise for Starliner’s performance.

“The spacecraft was precise, more so than I would have expected. We could stop on a dime, so to speak,” - Butch Wilmore, Starliner CFT Commander

“Our experienced test pilots have been overwhelmingly positive of their flight on Starliner, and we can’t wait to learn more from them and the flight data to continue improving the vehicle.” - Mark Nappi, Boeing Vice President and Commercial Crew Program Manager

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