A little more than a day after launching into space, Boeing's Starliner spacecraft flew up to the International Space Station and docked with the orbiting laboratory on Thursday.

The journey through space was not always easy. In the immediate hours after launch on Wednesday, the spacecraft was beset by two helium leaks in its propulsion system. Then, on Thursday, several of Starliner's spacecraft thrusters went offline for a time. Far more often than originally planned, spacecraft commander Butch Wilmore had to take manual control of Starliner while engineers on the ground worked on these and other issues.

However, at 1:34 pm ET on Thursday, Wilmore and the mission's other crew member, Suni Williams, successfully docked with the space station. A couple of hours later, they floated through the hatch, making a triumphant entry onto the station—and making history.

With Thursday's success, Boeing became only the second private company to build and fly a human orbital spacecraft, joining an elite club of just three nations: Russia, the United States, and China, alongside SpaceX. For the first time in history, three different crewed vehicles, Starliner, SpaceX's Dragon, and Russia's Soyuz, were all simultaneously docked at the station.

"We accomplished a lot, and really more than expected," said Mark Nappi, vice president and manager of Boeing's Commercial Crew Program, during a post-docking news conference. "We just had an outstanding day."

Helium leaks

Before Wednesday's launch, Boeing and NASA were already managing a helium leak in one of the eight manifolds that pressurize Starliner's propulsion system. However, several hours after launch, two more leaks were discovered. Then, another one was found after Starliner reached the space station.

During the news conference, officials were at pains to explain that Starliner still had a considerable excess of helium on board and that they were not concerned about these issues affecting Starliner's flight back to Earth. However, they acknowledged that these leaks appeared to be a more systemic problem than originally believed.

NASA and Boeing engineers, prior to launch, said the initial leak was likely due to a defective gasket and that changing a seal would fix it. Boeing opted not to do this because it would have delayed the launch for several weeks, and they worked to convince NASA it was a manageable issue.

Now, with four separate leaks, Nappi acknowledged that Boeing may not fully understand the root cause of the problem. "They’re very similar in the way that they’re behaving, so there’s a good reason to believe that they may be similar,” he said Thursday. The company has already begun investigating the issue with similar hardware on the ground.

Thruster issues

The flight's other significant problem developed on Thursday, just hours before Starliner was due to dock at the station. This was the failure of five of the vehicle's 28 reaction-control system thrusters at certain times. These small thrusters are used for fine pointing and maneuvering, especially close to the space station.

During a troubleshooting process, in which the thrusters were essentially reset and fired again, four of the five thrusters came back online. This gave NASA confidence to allow Starliner to approach and ultimately dock with the space station.

However, this is now the second consecutive mission in which a subset of these small thrusters failed to operate during a Starliner flight. During the vehicle's previous mission, Orbital Flight Test-2 in May 2022, some of these same thrusters failed to operate when called upon during the approach to the station. Although two small software fixes were applied after that flight, they appear not to have addressed the issue.

"I think we’re missing something fundamental that’s going on inside the thrusters," said Steve Stich, NASA's commercial crew program manager on Thursday. However, he and Nappi also said they believed that the failure of the thrusters was likely due to a "data issue" rather than the thruster hardware or software. 

Stich declined to speculate about how long it would take to study and resolve the thruster issue as part of the certification process necessary to clear Starliner for operational crewed missions to the International Space Station. Boeing is contracted to fly six of these missions, each carrying four astronauts for six-month increments on the station between now and 2030.

Coming home

NASA and Boeing want to spend the next couple of days assessing data collected during Starliner's flight to the station to determine whether any additional tests are needed before Starliner undocks and returns to Earth with Wilmore and Williams. This could happen as soon as June 14 but could also be delayed, Stich said.

Undocking, initiating a de-orbit burn, and surviving reentry through Earth's atmosphere will be one of the most challenging parts of the Starliner mission. Two sources told Ars on Thursday evening that NASA had a lot of issues to work through before Starliner would be cleared to fly home. Both helium supplies and the reaction-control thrusters are necessary for a successful departure from the station and entry into Earth's atmosphere.

However, the Boeing official speaking to reporters on Thursday, Nappi, sought to downplay the severity of the issues confronted by Starliner and its flight controllers. There are two primary problems, he said, the helium leak and the intermittent thruster problems.

"Those are pretty small, really, issues to deal with," he said. "We’ll figure them out for the next mission. I don’t see these as significant at all."