Boeing’s Starliner overcomes malfunctioning thrusters to land on the space station

There was a malfunction in its propulsion system, but Boeing’s Starliner spacecraft and the two NASA astronauts it carried successfully docked at the International Space Station on Thursday afternoon.

The docking took place at 1:34 PM ET, more than an hour later than planned, after troubleshooting several malfunctioning propulsion devices.

“The team handled the surprise test really well,” Steve Stich, director of NASA’s Commercial Crew Program, said during a news conference Thursday after docking. “And they got all the answers right.”

The Starliner’s arrival came one day after the vehicle was launched from Cape Canaveral Space Force Station in Florida. The docking was a major milestone for the test flight, which is intended to provide a final check that Starliner is ready to begin once-a-year operational flights to carry NASA crews for a six-month stay on the space station.

NASA hired Boeing, along with SpaceX, to build the spacecraft as a replacement for its retired space shuttles. SpaceX succeeded in transporting astronauts to the space station in 2020, while Boeing faced costly technical problems and delays.

Now, the efforts are close to bearing fruit. The SpaceX Crew Dragon capsule docked in a different port on the space station. “When Starliner is certified, the United States will have two unique human transportation systems for the International Space Station that no other country in the world has,” said NASA Associate Administrator Jim Frye.

The work remains. The engineers expected to encounter problems during this flight, and they actually happened.

Even before launch, a small helium leak was discovered in the Starliner’s propulsion system. This led to several weeks of investigation.

Helium, an inert gas, is used to push propellant into the spacecraft’s thrusters. If you lose too much, the payment devices may not work properly.

Engineers determined that the leak appeared to be limited to a single seal, but then discovered a “design vulnerability.” If a series of unexpected propulsion system failures occurred after separation, Mr. Wilmore and Ms. Williams could have been stranded in orbit.

Boeing developed a backup procedure for the Starliner’s return to Earth in the event of unexpected malfunctions. Officials at Boeing and NASA decided that the helium leak did not need to be fixed and that the spacecraft could be launched.

However, last night, two more helium leaks emerged.

Helium flows to leaking parts of the propulsion system were stopped, and engineers analyzed the problem while Mr. Wilmore and Ms. Williams slept. In the morning, mission managers decided to continue the docking process. Helium flow was restarted for docking maneuvers.

Although a fourth leak was discovered after docking, there is still plenty of helium for the rest of the mission, Stitch said.

Another problem occurred when the Starliner approached the space station. Five of Starliner’s 28 maneuvering planes, all on the bottom of the spacecraft, appear to not be working properly. The thruster problem was not related to helium leaks, but was similar to what occurred during a previous uncrewed Starliner flight.

“There’s something causing the thrusters to fail, and we don’t know exactly why,” Stitch said.

He said that four of the five propulsion devices were found to be working properly and had been reactivated.

The fifth motive seems to behave differently. “We left that propulsion device off for the rest of the trip,” Mr. Stitch said.

With additional troubleshooting, the Starliner missed its first opportunity to dock. The spacecraft and astronauts waited for the next flight, then made their slow approach without further difficulty.

“We’ve accomplished a lot more than we really expected,” said Mark Nappi, program manager responsible for Starliner at Boeing. “We had a bunch of planned work that we had to do, and then some unplanned work happened.”

“We learned from both,” Mr. Nabi added.

In other respects, the Starliner’s performance was flawless. The spacecraft flies mostly autonomously with its own computers. But astronauts can take over the mission in an emergency, and they have tested this ability.

“Sonny and I did some manual maneuvers, and they were accurate, much more so than even on the simulator,” Mr. Wilmore said last night.

After docking, careful checks to ensure a tight seal between the Starliner and the space station took a few hours before the hatch was opened. At approximately 3:45 p.m. ET, Ms. Williams and Mr. Wilmore exited Starliner, and were greeted with hugs from the other astronauts.

“Whatever you ask us to do, we are ready,” Mr. Wilmore said during a brief welcome ceremony.