Boeing’s Starliner safely departed the International Space Station on the night of Friday, Sept. 6 — albeit without its crew — and made a soft landing at White Sands Space Harbor in New Mexico at 12:01 a.m. EDT the following morning.

The reentry and landing concluded a test flight to the International Space Station that was unexpectedly extended after Starliner experienced helium leaks and thruster malfunctions on June 6, shortly after its launch.

The two astronauts aboard Starliner, Barry “Butch” Wilmore and Sunita “Suni” Williams have since been staying on the ISS alongside the Expedition 71 crew. After weeks of on-orbit and ground testing, technical meetings, and agency reviews, NASA announced in August that Wilmore and Williams would be returning to Earth via the SpaceX Dragon spacecraft next February.

A news release from NASA on Friday stated that its “Commercial Crew Program requires a spacecraft to fly a crewed test flight to prove the system is ready for regular flights to and from the orbiting laboratory.” But the agency was noncommittal as to whether this flight — which began with a crew and ended without one — would count. “Following Starliner’s return, the agency will review all mission-related data,” NASA’s statement said. That raises the prospect that another crewed test could be necessary before NASA signs off on regular Starliner operations.

Ken Bowersox, the associate administrator for the space operations mission directorate at NASA headquarters in Washington, D.C., said in the release that he was “extremely proud” of his team’s work during the flight test and “pleased to see Starliner’s safe return. … Even though it was necessary to return the spacecraft uncrewed, NASA and Boeing learned an incredible amount about Starliner in the most extreme environment possible. NASA looks forward to our continued work with the Boeing team to proceed toward certification of Starliner for crew rotation missions to the space station.”

The flight on June 5 was the first time astronauts launched aboard Boeing’s Starliner. It previously made two uncrewed test flights, including one to the orbiting laboratory and back. The Starliner capsule will now ship to NASA’s Kennedy Space Center in Florida for inspection and processing.

“We are excited to have Starliner home safely,” said Steve Stich, manager of NASA’s Commercial Crew Program, in the release. “This was an important test flight for NASA in setting us up for future missions on the Starliner system. There was a lot of valuable learning that will enable our long-term success. I want to commend the entire team for their hard work and dedication over the past three months.”

Bringing Starliner home

As scheduled, Starliner departed from the ISS at 6:04 p.m. EDT Friday evening. 

The spacecraft’s 59-second deorbit burn went off without a hitch just over five hours later at 11:17 p.m. EDT. Despite initial concerns around the much-scrutinized aft-facing thrusters, telemetry visualization on NASA’s broadcast showed they appeared to fire as needed.

The service module separated and performed its disposal burn, and Starliner was then set to reenter the atmosphere and touch down around midnight. 

Live video taken from the ISS and two NASA chase planes showed the craft streaking through the atmosphere less than an hour before the ship touched down at White Sands Space Harbor at 12:01 a.m. EDT. Landing and recovery teams followed NASA’s previously published mission timeline plans, and the spacecraft was then on its way to Kennedy Space Center.

In an early morning post-landing press conference, Stitch said that in departing the ISS, Starliner had performed a “breakout” sequence. “[It’s] the first time we’ve used that to back away from the station,” he said. “We backed out to about 5 meters and then did a series of about 12 burns using the service module forward jets. After that sequence of maneuvers, we ended up opening at about 22 kilometers per [orbit] away from the space station. All those thrusters did really well through that SEP [Solar Electric Propulsion] sequence, no problems at all. [There were] no fail-offs or any problems at all.”

He further stated that all eight of the Starliner’s forward thrusters and the two aft thrusters worked well during a hot fire.

“We had great performance from the GNC system, the guidance navigation control, [and] the VESTA [navigation and docking] system,” Stich said. “Last flight on [Orbital Flight Test-2], we had a little bit of trouble with what we call a ‘calibration maneuver’ to really make sure that the attitude is good for this Space Integrated GPS INS (SIGI) system, and that went really well. We had a deorbit burn that executed on time at 11:17 p.m. Central. It was about 130 meters per second, a 58-second burn. It was a really good burn and the service module thrusters performed well for that burn [and] the OMACs [engines] performed well.”

During the deorbit burn, Stich stated that the team noticed temperatures being a little higher in the starboard “doghouse” — the name for the external housings where clusters of thrusters are mounted. He said that one thruster in each of the starboard and top doghouses had “a little higher temperature than expected,” though neither shut down.

Stich said that Starliner performed great during entry, but one of the 12 thrusters on the crew module — an up-firing thruster — did not perform at all during a hot fire before entry. He also said that the third of the triple-redundant SIGI navigation systems failed off temporarily during landing. The second SIGI system also had a couple of hiccups during entry that Stich said his team would be looking into.

What’s next for NASA and Boeing?

Despite the change in mission plans over the last several months, Mantalbano said he would not describe this test flight as a failure — not even a “successful failure,” as Apollo 13 has often been called.

“We knew going in this was going to be a test mission,” Mantalbano said. “We learned a lot. The teams worked together, both the Boeing and the NASA team to understand the systems of the spacecraft and how they operated. … To me, [this was] a success. Clearly we [have] some work to do. The teams will understand that work and move forward.”

When asked if the next flight would be fully certified or another test flight, Stich said that it was too early to say.

Stich said that one of the first things NASA will do when the Starliner is taken back to Kennedy Space Center is analyzing the onboard data records, which are more detailed than the live telemetry streamed to the ground.

“With the test flight, we have a number of sensors across the systems that record data,” Stich said. “We’ll want to downlink all that high-rate data and take a look at that data. … So it will take a couple of weeks to get it back and a week or so to get the data off the spacecraft.”

Stich said that NASA and Boeing’s next steps will focus on understanding why the doghouses overheated and what modifications can be made to prevent that in the future. That includes possible physical modifications like removing thermal insulation and also software modifications to how the thrusters operate.

Several journalists present at NASA’s press conference asked why Boeing wasn’t in attendance to answer questions. Joel Mantalbano, NASA’s deputy associate administrator for its space operations mission directorate, answered that Boeing deferred to NASA because it represents the mission.

“I will tell you that Boeing has critical work that they do for NASA in the International Space Station Program, the Commercial Crew Program, and the Space Launch Systems Program,” Mantalbano said. “Their work is critical to our success, and we fully expect Boeing to continue all three of those programs.”

When asked again if the relationship between NASA and Boeing had been damaged, Mantalbano reaffirmed his previous statement.

“I think from a human perspective, all of us feel happy about the successful landing, but then there’s a piece of us, all of us, that we wish it would have been the way we had planned it,” Stich added. “We had planned to have the mission land with Butch and Suni on board. I think there’s, depending on who you are on the team, different emotions associated with that. And I think it’s going to take a little time to work through that. For me, a little bit, and then for everybody else on the Boeing and NASA team.”