NASA update on Starliner thruster issues: This is fine

Boeing's Starliner spacecraft made its final landing on the International Space Station last month.
Enlarge / Boeing’s Starliner spacecraft made its final landing on the International Space Station last month.

Before Boeing’s Starliner crew capsule is allowed to leave the International Space Station and head back to Earth, NASA managers want to make sure the spacecraft’s troubled control engines can guide the two-person crew home.

The two astronauts who flew the Starliner spacecraft’s first test flight on June 5 agree with managers, but said Wednesday they have no problem sending the capsule back to Earth if an emergency occurs that requires evacuating the space station.

Five of the 28 reaction control system thrusters on Starliner’s service module went offline as the spacecraft approached the space station last month. Starliner’s flight software disabled the five control jets when they overheated and lost thrust. Four of the thrusters were later recovered, though some failed to reach full power levels when Starliner arrived for docking. By mid-June, the Starliner astronauts were firing the thrusters again, and their thrust levels were closer to normal.

“What we want to know is that the thrusters can perform; whatever their percentage of thrust, we can put it in a package that will give us a deorbit burn,” said Suni Williams, a NASA astronaut serving as Starliner’s pilot. “That’s the main goal that we need [for] the service module: to give us a good deorbit burn so we can come back.”

These small thrusters aren’t needed for the deorbit burn itself, which will use a different set of engines to slow Starliner enough to deorbit and head for landing. But Starliner will need enough of the control jets to maneuver into the proper orientation for the deorbit firing.

The test flight will mark the first time astronauts have flown into space aboard Boeing’s Starliner spacecraft, after years of delays and setbacks. Starliner is NASA’s second human-rated commercial crew capsule and is set to join SpaceX’s Crew Dragon in a rotation of missions ferrying astronauts to and from the space station throughout the rest of the decade.

But first, Boeing and NASA must safely complete the Starliner test flight and resolve the thrust issues and helium leaks that have plagued the spacecraft before they can move forward with operational crew rotation missions. A Crew Dragon spacecraft is currently docked at the space station, but Steve Stich, NASA’s commercial crew program manager, told reporters Wednesday that Williams and Starliner commander Butch Wilmore are currently planning to come home on Starliner.

“The beauty of the commercial crew program is that we have two vehicles, two different systems, that we can use to send the crew back,” Stich said. “So we have a little bit more time to go through the data and then make a decision whether we need to do something different. But the best option today is to send Butch and Suni back to Starliner. At this point, we don’t see any reason why that wouldn’t be the case.”

Mark Nappi, Boeing’s Starliner program manager, said officials have identified more than 30 actions to investigate five “minor” helium leaks and thruster problems on Starliner’s service module. “All of these items should be completed by the end of next week,” Nappi said.

“It’s a test flight and the first with a crew. We want to make sure we understand everything before we go into space,” Stich said.

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