There were problems with its propulsion system, but Boeing’s Starliner spacecraft and the two NASA astronauts it was carrying successfully docked with the International Space Station on Thursday afternoon.
The 1:34 p.m. ET docking was more than an hour behind schedule after several failed thrusters were repaired.
“The crew did really well on the quiz,” Steve Stich, NASA’s commercial crew program manager, 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 the Cape Canaveral Space Force Station in Florida. The docking was a major milestone for the test flight, which should provide a final check that the Starliner is ready to begin operational flights once a year 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 the retired space shuttles. SpaceX was able to send astronauts to the space station in 2020, while Boeing had costly technical problems and delays.
Now the effort is close to paying off. SpaceX’s Crew Dragon capsule docked at another port on the space station. “When Starliner is certified, the United States will have two unique human transportation systems for the ISS, and no other country in the world has that,” said Jim Free, NASA’s associate administrator.
The work remains. The engineers expected to encounter problems during this flight, and they did.
Even before launch, a small helium leak was detected in the Starliner’s propulsion system. This led to several weeks of investigation.
Helium, an inert gas, is used to push propellants to the spacecraft’s engines. If too much is lost, the thrusters may not work properly.
Engineers determined the leak appeared to be limited to a single seal, but then discovered a “design vulnerability.” If a series of unlikely failures had occurred to the propulsion system after undocking, Mr. Wilmore and Ms. Williams could likely have been stranded in orbit.
Boeing has developed a backup procedure for the Starliner to return to Earth if the unlikely failures occur. Boeing and NASA officials decided that the helium leak did not need to be fixed and that the spacecraft could be launched.
However, two more helium leaks appeared last night.
Helium flows to leaking parts of the propulsion system were turned off and engineers analyzed the problem while Mr. Wilmore and Ms. Williams slept. In the morning, the mission managers decided to go ahead with the docking. The helium flow was turned back on for the docking maneuvers.
Although a fourth leak was detected after docking, plenty of helium remained for the rest of the mission, Mr Stich said.
Another problem arose as the Starliner approached the space station. Five of the Starliner’s 28 maneuvering jets, all in the bottom of the spacecraft, appear to be malfunctioning. The thruster problem was unrelated to the helium leak, but was similar to what happened during an earlier unmanned Starliner flight.
“There’s something that causes the thrusters to fail and we don’t know exactly why,” Mr Stich said.
He said four of the five thrusters were found to be working properly and were reactivated.
The fifth engine seemed to act differently. “We left the thruster locked for the rest of the flight,” Mr Stich said.
With additional troubleshooting, the Starliner missed its first docking opportunity. The spacecraft and astronauts waited for the next one and then approached slowly without further difficulty.
“We accomplished a lot and really exceeded expectations,” said Mark Nappi, program manager for Starliner at Boeing. “We had a bunch of planned work to do, and then we had unplanned work that happened.”
Mr Nappi added: “We learned from both of them.”
In other respects, the Starliner performed flawlessly. The spacecraft mostly flies autonomously with its computers in charge. But astronauts can take over in an emergency, and they tested that capability.
“Sunny and I did some manual maneuvers and it’s precise,” Mr Wilmore said last night, “much more so than even the simulator.”
After docking, meticulous checks to ensure airtight seals between the Starliner and the space station took several hours before the hatch was opened. At about 3:45 p.m. ET, Ms. Williams and Mr. Wilmore exited the Starliner, greeted with hugs from the other astronauts.
“Whatever you ask us to do, we’re ready,” Mr Wilmore said during a brief welcoming ceremony.
