Before they clear Boeing’s Starliner crew capsule to leave the International Space Station and head for Earth, NASA managers want to make sure the spacecraft’s problematic control thrusters can help guiding the ship’s two-person crew home.
The two astronauts who launched June 5 on the first Starliner crew test flight agree with managers, though they said Wednesday they were comfortable flying the capsule back to Earth should there be an emergency that might require evacuating the space station.
NASA astronauts Butch Wilmore and Suni Williams were supposed to return to Earth weeks ago, but managers are keeping them on the station as engineers continue to investigate the propellant problems and helium leaks that have plagued the mission since its launch.
“This is a tough business we’re in,” Wilmore, the Starliner commander, told reporters Wednesday at a news conference from the space station. “Human spaceflight is not easy in any regime and there have been many problems with every spacecraft that has ever been designed and that is the nature of what we do.”
Five of the 28 thrusters of the feedback control system on the Starliner’s service module went offline as the spacecraft approached the space station last month. The Starliner’s flight software disabled the five control planes when they began to overheat and lose thrust. Four of the thrusters were later recovered, although some were unable to reach their full power levels as the Starliner came in for docking.
Wilmore, who took manual control for part of the Starliner’s approach to the space station, said he could feel the spacecraft’s handling qualities diminish as the thrusters temporarily fail. “You could say it was run down, but it was still impressive,” he said. The Starliner eventually docked at the station in autopilot mode.
In mid-June, the Starliner astronauts fired up the thrusters again and their thrust levels were closer to normal.
“What we want to know is that the thrusters can perform; whatever their thrust percentage is, we can put it in a package that will give us a deorbit burn,” said Williams, a NASA astronaut who serves as the Starliner pilot. “That’s the main goal that we is needed. [for] service module: to give us a good deorbit burn so we can get back.”
These small thrusters are not needed for the deorbit burn itself, which will use a different set of engines to slow the Starliner down enough for it to exit orbit and head for a landing. But the Starliner needs plenty of control planes working to maneuver into the right orientation for deorbit firing.
This test flight is the first time astronauts have flown into space on Boeing’s Starliner spacecraft, after years of delays and setbacks. Starliner is NASA’s second human-rated commercial crew capsule, and it is poised to join SpaceX’s Crew Dragon in a rotation of missions that transport astronauts to and from the space station over the rest of the decade.
But first, Boeing and NASA must safely complete the Starliner’s test flight and resolve the propellant problems and helium leaks plaguing the spacecraft before moving forward with operational crew rotation missions. There is currently a Crew Dragon spacecraft docked at the station, but Steve Stich, NASA’s commercial crew program manager, told reporters Wednesday that, right now, Wilmore and Williams still plan to return home on the Starliner.
“The nice thing about the commercial crew program is that we have two vehicles, two different systems, that we can use to return the crew,” Stich said. “So we have a little more time to review the data and then make a decision if we need to do something different. But the main option today is to get Butch and Suni back on the Starliner. Right now, we don’t see some reason that wouldn’t be the case.”
Mark Nappi, Boeing’s Starliner program manager, said officials identified more than 30 actions to investigate five “minor” helium leaks and propellant problems in the Starliner’s service module. “All these items are scheduled to be completed by the end of next week,” Nappi said.
“It’s a test flight, and the first with a crew, and we’re taking a little bit more to make sure we understand everything before we commit to deorbiting,” Stich said.