Boeing's Starliner spacecraft is set to spend a little longer attached to the International Space Station (ISS) as engineers on the ground work to recreate the oddities seen in orbit.

During a briefing on July 10, mission managers admitted that engineers had not been able to recreate the conditions that caused problems for the vehicle's Reaction Control System (RCS) thrusters during docking.

During its docking with the ISS, Starliner lost five thrusters. Four were recovered, but the cause has left engineers scratching their heads as they attempt to reproduce the problem in ground tests before signing off Starliner for a nominal return to Earth. According to NASA and Boeing, Starliner could be used in the event of an emergency, but engineers want to maximize the time available for testing before the service module, where the thrusters are housed, is discarded ahead of re-entry.

In an earlier briefing with the Boeing Starliner Crew Flight Test astronauts, Butch Wilmore and Suni Williams, the duo reported being more than happy about getting some bonus time onboard the ISS.

However, while praising the spacecraft's performance, Wilmore noted that the thrust degradation was detectable during the docking process. The duo also stopped short of wholeheartedly endorsing Starliner for future missions. Wilmore said: "There have been multiple issues with every spacecraft that's ever been designed."

"We did have some degradation in our thrusters ... and that's why we're staying: because we're going to test it ... we are going to get the data that we need to help inform our decisions so we make the right decisions."

As it stands, a definitive return date for the crew remains elusive. Managers said that testing on the thrusters and helium leaks, which have also caused engineers headaches, should be complete by next week, meaning a nominal undocking is potentially on the cards for the end of July.

Although managers have become comfortable with going beyond the initial 45-day limit set by the lifetime of batteries onboard Starliner, describing them as healthy and showing no sign of performance anomalies, getting the spacecraft away by the end of July is important to avoid a potential conflict with a Crew Dragon handover in August.

Should Starliner's stay be extended further, then managers will likely have to move from their preferred method of crew handover, where both crews are onboard at the same time, to the indirect method first used in the Crew Dragon program when the Crew-2 astronauts were returned before the Crew-3 astronauts launched. ®

https://www.theregister.com//2024/07/11/boeings_starliner/