Boeing Starliner: New leak delays astronaut undocking from space station

NASA and Boeing's teams are working through several issues with the Starliner spacecraft before it can undock from the space station and return astronauts Butch Wilmore and Suni Williams back to Earth. 

Boeing’s Starliner launched on a United Launch Alliance Atlas V rocket on June 5, docking about 24 hours later. Wilmore and Williams were set to spend about eight days on the International Space Station (ISS) as part of the Crew Flight Test for Starliner, the final step to certify the spacecraft to fly astronauts under NASA’s Commercial Crew Program. Now, NASA is targeting no earlier than June 18 to undock the Starliner from the station.

The additional days in orbit for the astronauts are due to several issues NASA and Boeing's teams are troubleshooting with Starliner. 

Before launch, the spacecraft had one known helium leak. While en route to the ISS, at least three other leaks were discovered and isolated. This week, NASA managers said a fifth helium leak was found on Starliner. 

NASA said Starliner "has plenty of margin to support the return trip from station" because only seven hours of free-flight time is needed to return to Earth. Starliner has enough to support a 70-hour spaceflight after departing the ISS. While Starliner is docked, the manifolds are closed, preventing further helium loss.

ISS deputy program manager Dina Contella said Boeing, NASA and ISS teams are working on a "forward plan" to address some of Starliner's issues while in orbit.

Contella said the spacecraft's sublimator used more water than anticipated for the journey, and ISS teams are working out how to top off those water tanks.

Issues with at least four Reaction Control System (RCS) thrusters, part of the propulsion system, delayed the Starliner’s docking with the ISS.

In addition to the thruster issues and helium system leaks, Contella said an RCS oxidizer valve was "sticky" and did not properly close. Teams on the ground performed a population system valve check over the weekend, and the suspected problem valve would remain commanded closed for the rest of the mission.

"Mission managers are continuing to work through the return plan, which includes assessments of flight rationale, fault tolerance and potential operational mitigations for the remainder of the flight," NASA wrote on a blog.

NASA and Boeing managers will provide another update on the issues before Starliner undocks from the ISS.

Ahead of Williams and Wilmore’s departure, they will be on station for a busy week. Two spacewalks are planned for their fellow astronauts, and a third spacewalk is scheduled for early July.

During the first spacewalks on Thursday, NASA astronauts Tracy Dyson and Matt Dominick will swab samples outside the ISS to see what microbiomes survive outside the orbiting laboratory in the vacuum of space. The samples will then be brought back to Earth for analysis. The pair will also remove a faulty electronics box from a communications antenna on the space station.

When Williams and Wilmore depart the ISS, Starliner will complete a deorbit burn and land in the New Mexico desert using a parachute and airbag system.