Two astronauts are waiting to come home while Boeing works to fix spacecraft problems. Here’s what’s at stake.

Boeing’s Starliner spacecraft was poised for a significant milestone this month: transporting two NASA astronauts to and from the International Space Station, demonstrating the capability of the long-delayed and over-budget capsule.

Starliner is halfway to achieving that goal.

However, the two experienced astronauts on this test flight are now in a precarious situation, having to extend their stay on the space station for a second time. Engineers on the ground are working urgently to understand the problems encountered during the first part of their mission.

Spaceflight veterans Sunita Williams and Butch Wilmore arrived at the space station on June 6 aboard the Starliner. Initially, NASA expected their stay to last about a week.

However, issues encountered during the trip, such as helium leaks and malfunctioning thrusters, have raised concerns about the remainder of the mission.

NASA announced Tuesday that Williams and Wilmore will now return no earlier than June 26, extending their mission to at least 20 days. Engineers are working to better understand the spacecraft’s problems while it remains safely attached to the space station.

Officials believe Starliner can still bring the astronauts home, but “we really want to work through the remainder of the data,” said Steve Stich, NASA’s Commercial Crew Program manager, at a Tuesday news conference.

Meanwhile, Boeing has described the mission as both a success and a learning opportunity, despite the challenges the Starliner team is facing with the “unplanned” aspects, as Mark Nappi, Boeing’s vice president and Starliner program manager, stated on Tuesday.

It’s not unusual for astronauts to have their stays on the space station extended unexpectedly, sometimes for days, weeks, or even months. NASA has indicated that the Starliner can remain at the orbiting laboratory for up to 45 days if necessary, according to Stich.

However, this situation adds to the uncertainty and embarrassment for the Boeing Starliner program, which is already years behind schedule and has faced numerous similar setbacks. It also contributes to the ongoing stream of unfavorable news surrounding Boeing as a company.

A Nail-Biting Finale

Boeing and NASA engineers have decided to keep Starliner, along with astronauts Williams and Wilmore, on the station longer than planned to conduct additional analysis. The helium leaks and thruster issues occurred in a section of the vehicle that is not designed to survive the return trip to Earth. Therefore, mission teams are postponing the spacecraft’s return to learn as much as possible about the issues.

The return from orbit is always a dangerous phase of any space mission, arguably the most perilous part.

The Starliner spacecraft on NASA’s Boeing Crew Flight Test is pictured docked to the Harmony module’s forward port on June 13 as the International Space Station orbited 262 miles above Egypt’s Mediterranean coast.NASA

The journey back will require Starliner to enter Earth’s dense atmosphere at over 22 times the speed of sound, heating the spacecraft’s exterior to about 3,000 degrees Fahrenheit.

Next, a set of parachutes—recently redesigned and tested by Boeing in January—must safely slow the capsule for its landing on solid ground, rather than an ocean splashdown. Starliner will be the first U.S.-made capsule to land this way, an approach Boeing hopes will simplify recovery and refurbishment for future flights.

A Series of Setbacks

Starliner’s path to this historic crewed test mission began in 2014 when NASA selected both Boeing and SpaceX to develop spacecraft capable of carrying astronauts to the International Space Station.

At the time, Boeing was considered the reliable aerospace giant expected to finish first, while SpaceX was the unpredictable newcomer.

However, over the past decade, the situation has changed.

SpaceX’s Crew Dragon successfully completed its first crewed mission in 2020 without any apparent issues and has since been regularly transporting astronauts and paying customers.

A SpaceX Falcon 9 rocket carrying the company’s Crew Dragon spacecraft launched NASA astronauts Robert Behnken and Douglas Hurley to the International Space Station, marking the spacecraft’s inaugural crewed flight, on May 30, 2020.Joel Kowsky/NASA

The two astronauts who piloted Crew Dragon’s inaugural flight, Bob Behnken and Doug Hurley, also stayed on the space station longer than planned, extending their mission to over 60 days instead of the brief stint initially expected for such test flights.

However, their extended stay was to assist with daily activities aboard the understaffed space station, not due to specific software or hardware issues with Crew Dragon.

In contrast, spacecraft issues have plagued Boeing’s Starliner program at nearly every turn. The vehicle has faced years of delays, setbacks, and added costs exceeding $1 billion, according to public financial records.

The first uncrewed Starliner test mission in late 2019 was marred by missteps, including a software error that set an internal clock off by 11 hours, causing the vehicle to misfire in orbit.

A second uncrewed test in 2022 revealed additional software issues and problems with some thrusters.

Steve Stich, NASA’s Commercial Crew Program manager, noted at a June 6 news conference that engineers might not have fully resolved the issues from 2022. “We thought we had fixed that problem,” Stich said, adding, “I think we’re missing something fundamental that’s going on inside the thruster.”

Michael Lembeck, an aerospace engineering associate professor at the University of Illinois Urbana-Champaign and a former consultant for Boeing’s spaceflight division, told CNN that it is challenging to determine if more ground tests could have caught the thruster issues.

Lembeck also emphasized that evaluating this test mission’s success is not as straightforward as directly comparing it to SpaceX’s Crew Dragon inaugural crewed test flight.

For instance, SpaceX’s Dragon cargo capsule, a direct predecessor of Crew Dragon, completed over a decade of uncrewed cargo missions to the space station before Crew Dragon’s first flight.

“SpaceX did have a head start with the cargo program,” Lembeck said. “They had an advantage that Boeing did not have. Boeing is essentially building a crew vehicle from scratch.”

If this Starliner test mission faces further setbacks, Boeing might have to rely on its competitor to bring Williams and Wilmore home.

“The embarrassing backup is that a Crew Dragon would have to go and retrieve the astronauts,” Lembeck explained. The spacecraft “could be sent up with two crew members and return with four—that would likely be the way home.”

Boeing executives have emphasized that the Starliner program operates independently from the company’s other units, including its commercial aircraft division, which has faced scandals.

“We take the responsibility of flying humans on this vehicle very seriously,” Nappi stated during an April news briefing before Starliner’s launch.

He also asserted then that the Starliner team was operating at its best and eagerly anticipating a safe mission. However, when questioned about this assertion on Tuesday, NASA’s Stich acknowledged that both Boeing and NASA had anticipated finding additional issues during this test flight.

Williams had also noted this expectation before the flight, saying, “We always find things, and we will continue to do so.”

Stich further conceded on Tuesday that Boeing and NASA might have been able to prevent some of the issues encountered by Starliner: “Perhaps we could have conducted different ground tests to better understand some of the thruster issues beforehand,” he remarked.

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