Boeing’s Starliner overcomes failed boosters to dock with space station

There were problems with the propulsion system, but Boeing’s Starliner spacecraft and the two NASA astronauts aboard it successfully docked with the International Space Station on Thursday afternoon.

The docking, at 1:34 p.m. Eastern Time, came more than an hour later than planned after several faulty thrusters were repaired.

“The team did a really good job on the pop quiz,” Steve Stich, NASA’s commercial crew program manager, said during a news conference Thursday after the docking. “And they got all the answers right.”

Starliner arrived a day after it launched from Cape Canaveral Space Force Station in Florida. The docking was a major milestone for the test flight, which will provide a final check on Starliner’s readiness to launch operational flights once a year to carry NASA crews for six-month stays on the space station.

NASA hired Boeing, along with SpaceX, to build the spacecraft to replace its retired space shuttles. SpaceX successfully flew astronauts to the space station in 2020, while Boeing struggled with costly technical issues and delays.

Now the efforts are starting to pay off. A SpaceX Crew Dragon capsule docked at another port on the space station. “Once Starliner is certified, the United States will have two unique human transport systems for the ISS that no other country in the world has,” said Jim Free, NASA Associate Administrator.

There is still work to be done. The engineers expected to encounter problems during this flight, and they did.

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

Helium, an inert gas, is used to push propellants to the spacecraft’s thrusters. If too much is lost, the thrusters may not work properly.

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

Boeing developed a backup procedure for Starliner to return to Earth if the unlikely failure occurred. Officials at Boeing and NASA decided that the helium leak did not need to be repaired and that the spacecraft could be launched.

However, two more helium leaks surfaced last night.

Helium flows to the leaking parts of the propulsion system were turned off and engineers analyzed the problem while Mr. Wilmore and Mrs. Williams slept. In the morning, mission managers decided to proceed with the docking. Helium flow was turned back on for the docking maneuvers.

Although a fourth leak was discovered after docking, there remains enough helium for the remainder of the mission, Mr. Stich said.

Another problem arose as Starliner approached the space station. Five of Starliner’s 28 maneuver jets, all on the underside of the spacecraft, appeared to malfunction. The thruster problem had nothing to do with the helium leaks, but it was similar to what happened during a previous Starliner unmanned flight.

“Something is causing the thrusters to fail, and we don’t know exactly why,” Mr. Stich said.

He said four of the five boosters appeared to be working properly and were reactivated.

The fifth thruster seemed to act differently. “We left that thruster turned off for the rest of the flight,” Mr. Stich said.

With the additional troubleshooting, Starliner missed its first docking opportunity. The spacecraft and astronauts waited for the next one and then made their slow approach without further incident.

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

Mr Nappi added: “We have learned from both.”

In other respects, Starliner performed flawlessly. The spacecraft flies largely autonomously with its computers at the helm. But the astronauts can take over in an emergency, and they’ve tested that capability.

“Suni and I have both done some manual maneuvering, and it is accurate,” Mr. Wilmore said last night, “much more so than the simulator.”

After docking, it took several hours for the hatch to be opened due to meticulous checks to ensure an airtight seal between Starliner and the space station. At approximately 3:45 p.m. Eastern Time, Mrs. Williams and Mr. Wilmore emerged from Starliner, greeted with hugs from the other astronauts.

“Whatever you give us to do, we’re ready for it,” Mr. Wilmore said during a brief welcome ceremony.