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It wasn’t perfect, but the propulsion system that NASA worried about did its job today as Boeing’s Starliner space capsule made an uncrewed descent from the International Space Station back down to Earth.

The gumdrop-shaped spacecraft, christened Calypso, floated down to a parachute-assisted, airbag-cushioned touchdown at White Sands Space Harbor in New Mexico.

“Starliner is back on Earth,” Boeing commentator Lauren Brennecke said.

Starliner’s first crewed trip to the space station was supposed to last only about a week, but when the capsule made its approach for docking on June 6, five thrusters out of a set of 28 malfunctioned. Four of the thrusters were reactivated, and NASA astronauts Butch Wilmore and Sunita Williams executed a successful docking. But concerns about the thrusters — and about a string of helium leaks in the propulsion pressurization system — sparked weeks of troubleshooting by NASA and Boeing.

Engineers decided that they could cope with the helium leaks, but the thruster problem was a bigger concern. Tests determined that the propulsion system’s performance was degraded by overheating that exceeded design specifications.

Two weeks ago, NASA said the uncertainties surrounding the system’s performance were too great to risk having Williams and Wilmore ride back to Earth on Starliner. Instead, the astronauts were told to remain on the station for months longer than originally planned.

To accommodate the personnel shift, NASA reduced the size of the next scheduled crew, known as Crew-9, from four to two spacefliers. That crew is due to go into orbit in a SpaceX Crew Dragon capsule on Sept. 24. Williams and Wilmore will join Crew-9 and return to Earth in the SpaceX capsule next February.

The problems with the propulsion system couldn’t be totally resolved: One of the thrusters in the set of 28 on Starliner’s service module was taken offline, due to performance concerns that arose during testing. But the other 27 were in working order for Starliner’s departure at 6:04 p.m. ET (3:04 p.m. PT).

“She’s on her way home,” Williams said as the spacecraft cleared a 4-by-2-kilometer (2.5-by-1.2-mile) region around the space station known as the approach ellipsoid.

Orbital tests revealed that one of the 12 maneuvering thrusters on Starliner’s crew module didn’t fire when commanded to do so, but NASA commentator Brandi Dean said that resulted in only a “slight loss of redundancy” for Starliner’s maneuvers.

Under autonomous control, the spacecraft successfully executed the required rocket firings, including a deorbit burn that sent it screaming through the atmosphere. NASA said Starliner’s heat shield protected the hardware from temperatures in excess of 3,000 degrees Fahrenheit (1,650 degrees Celsius) as the craft decelerated.

Starliner’s three main parachutes deployed on cue, and the airbags inflated for a soft landing at 10:01 p.m. MT (9:01 p.m. PT). A beacon on the spacecraft helped guide the recovery team that drove out through the desert in the dark. Securing the spacecraft was expected to take hours.

“It was a good landing, pretty awesome,” Mission Control told Williams over a radio link with the space station.

“You guys are the best,” Williams replied.

Today’s relatively trouble-free landing was likely to come as a welcome turn for a program that has suffered through years of delays and about $1.6 billion in cost overruns — overruns that Boeing has had to absorb. An uncrewed Starliner test flight went awry in 2019, forcing a re-do in 2022.

Now that the end has come for what was to have been Starliner’s first crewed round trip, NASA and Boeing will be taking a close look at data from the test flight and determining the program’s future course.

“Today we saw the vehicle perform really well,” Steve Stich, program manager for NASA’s Commercial Crew Program, told reporters during a post-landing briefing. “We’ve got some things we know we’ve got to go work on, and we’ll go do that and fix those things, and go fly when we’re ready.”

He said he had no regrets about the decision to keep Williams and Wilmore on the space station and send Starliner home empty. “If we had a model that would have predicted what we saw tonight perfectly — yeah, it looks like an easy decision to go say we could have had a crewed flight,” Stich said. “But we didn’t have that.”

Mark Nappi, vice president and program manager of Boeing’s Commercial Crew Program, paid tribute to his teammates. “I want to recognize the work the Starliner teams did to ensure a successful and safe undocking, deorbit, re-entry and landing,” he said in an online update from Boeing. “We will review the data and determine the next steps for the program.”

SpaceX’s Crew Dragon has been successfully flying astronauts to and from the space station since 2020, but during a news briefing last month, NASA Administrator Bill Nelson said it was important to have Starliner as well.

“We need two [types of] spacecraft to have the redundancy in case one is not able to take crew to and from the International Space Station,” Nelson told reporters.

Ken Bowersox, NASA’s associate administrator for space operations, also signaled that the space agency would stick with Boeing. “We’ve had two good partners, Boeing and SpaceX, when it comes to commercial crew,” he said last month. “When they have problems, we don’t just throw rocks at them, or tell them that we don’t like them. We work with them to get through those problems.”