Before allowing the Boeing Starliner crew capsule to leave the International Space Station and head for Earth, NASA managers want to ensure the spacecraft’s troubled control thrusters can help guide the craft’s two-man crew home.
The two astronauts who launched the first crew test flight of the Starliner spacecraft on June 5 agreed with managers, although they said Wednesday they were comfortable flying the capsule back to Earth if there was an emergency that might require an evacuation on the space station.
NASA astronauts Butch Wilmore and Sonny Williams were supposed to return to Earth weeks ago, but managers are keeping them on the station while engineers continue to investigate the problems with thrusters 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. were ever designed and that is the nature of what we do.”
Five of the 28 thrusters on the Starliner’s Service Module Reaction Control System went offline when the spacecraft approached the space station last month. The Starliner’s flight software disabled the five control nozzles when they began to overheat and lose thrust. Four of the thrusters were later rebuilt, although some were unable to reach their full power levels when the Starliner came in for docking.
Wilmore, who took over manual controls for part of the Starliner’s approach to the space station, said he felt the spacecraft’s handling qualities diminish as the thrusters temporarily failed. “You could say it was degraded, but it was still impressive,” he said. Eventually, the Starliner docked at the station in autopilot mode.
In mid-June, the Starliner astronauts fired the thrusters again and their thrust levels were closer to normal.
“What we want to know is that thrusters can work; if whatever their thrust percentage is, we can put it in a package that will give us an orbital burn,” said Williams, a NASA astronaut serving as the Starliner pilot. “That’s the main target we need [for] the service module: to give us a good burn from orbit so we can go back.”
These small thrusters are not needed for deorbit 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 enough operational control jets to maneuver into the correct orientation for firing from orbit.
This test flight is the first time astronauts have flown into space on Boeing’s Starliner spacecraft, after years of delays and setbacks. The Starliner is NASA’s second commercial crew capsule to be evaluated by humans and is set to join SpaceX’s Crew Dragon in a rotation of missions carrying astronauts to and from the space station for the rest of the decade.
But first, Boeing and NASA must safely complete the Starliner test flight and resolve the thruster and helium leak issues plaguing the spacecraft before moving forward with operational crew rotation missions. There is currently a Crew Dragon spacecraft docked with the station, but Steve Stich, NASA’s commercial crew program manager, told reporters Wednesday that Wilmore and Williams still plan to return home on the Starliner for now.
“The beautiful thing about the commercial crew program is that we have two vehicles, two different systems that we can use to bring the crew back,” Stich said. “So we have a little more time to look at the data and then make a decision if we need to do something different.” But the main option today is to get Butch and Sunny back on the Starliner. We don’t at the moment, I see no reason not to.”
Mark Nappi, Boeing’s Starliner program manager, said officials have identified more than 30 actions to investigate five “minor” helium leaks and problems with the Starliner’s service module thrusters. “All of these items are scheduled to be completed by the end of next week,” Nappi said.
“This is a test flight and the first with a crew, and we’re just taking a little bit more to make sure we understand everything before we commit to deorbiting,” Stich said.
