NASA has made the decision to bring Boeing’s Starliner spacecraft back to Earth without its crew, prioritizing safety after unresolved issues with the capsule's propulsion system.
In light of these concerns, the two astronauts currently aboard the International Space Station (ISS), Butch Wilmore and Sunita Williams, will return to Earth aboard a SpaceX Dragon capsule in February 2025.
This decision follows months of uncertainty regarding Starliner's performance, particularly after malfunctions in its reaction control thrusters raised concerns about the spacecraft's ability to safely complete its mission.
A Major Change in Plans for NASA's Crewed Spaceflights
Originally, Wilmore and Williams were expected to return aboard Starliner after their eight-day mission in space, but technical challenges extended their stay aboard the ISS to a total of eight months. The problems began during Starliner's docking procedure when five out of 28 thrusters malfunctioned, leading NASA and Boeing to question whether the spacecraft could safely bring the astronauts back to Earth. Faced with this uncertainty, NASA chose to prioritize astronaut safety by opting for an uncrewed return of the Starliner capsule.
“We are dealing with a very complex issue with the thrusters,” said Steve Stich, NASA's Commercial Crew Program manager. “It’s challenging to predict their performance; it’s challenging to predict the temperatures we’ll see.” Given these challenges, NASA concluded that the risks associated with attempting a crewed return in Starliner were too high.
NASA Administrator Bill Nelson emphasized the agency’s commitment to safety as the key factor behind this decision. “The decision to keep Butch and Suni aboard the International Space Station and bring the Boeing Starliner home uncrewed is a result of our commitment to safety: our core value and our North Star,” Nelson explained.
Instead of returning aboard Starliner, Wilmore and Williams will now make their way back to Earth aboard a SpaceX Dragon capsule, which will be part of the Crew-9 mission launching in September 2024. The capsule will be specially modified to accommodate the two astronauts, and NASA will reconfigure the spacecraft to carry additional cargo, personal items, and Dragon-specific spacesuits for Wilmore and Williams.
Technical Troubles Force NASA's Hand
The decision to bring Starliner back to Earth without its crew was not made lightly. The spacecraft had encountered a helium leak during its launch, and subsequent thruster malfunctions during docking prompted both NASA and Boeing to extend the astronauts' stay aboard the ISS while investigating the problems. The uncertainties surrounding the thrusters’ performance during the return trip—especially during the deorbit burn and separation sequence—were deemed too significant to risk a crewed descent.
“We are changing the separation sequence that we planned, and we will review those aspects at the Readiness Review,” Stich added. He explained that the spacecraft's separation technique will be simplified to ensure a safer detachment from the ISS, allowing Starliner to make a more controlled, uncrewed return to Earth.
In reviewing the situation, Ken Bowersox, NASA's Associate Administrator for Space Operations, expressed the agency's caution: “One of the really important factors is that we just don't know how much we can use the thrusters on the way back home before a problem.” He also noted that NASA's past experiences with space shuttle disasters influenced their decision-making. "NASA, ever since, has tried very hard to bring about an atmosphere in which people are encouraged to step forward and speak their mind," Bowersox said, emphasizing the importance of safety and transparency.
Despite the setbacks, NASA and Boeing remain optimistic about the Starliner program. Nelson affirmed his confidence in Boeing’s ability to address the spacecraft’s issues and eventually achieve success with crewed missions. “We want to further understand the root causes and understand the design improvements so that the Boeing Starliner will serve as an important part of our assured crew access to the ISS,” Nelson stated.
Preparing for the Future: Starliner’s Uncrewed Return
Starliner is expected to return to Earth without its crew in early September 2024. The spacecraft will autonomously detach from the ISS and land at White Sands Space Harbor in New Mexico. This uncrewed return will be categorized as a test flight, providing critical data that will help NASA and Boeing refine the spacecraft’s design and resolve the thruster issues before Starliner can be certified for future crewed missions.
NASA's decision to proceed with the uncrewed return of Starliner highlights the complexity and risks of spaceflight, particularly in the development and testing phases of new spacecraft.
While SpaceX’s Dragon capsule has become NASA’s go-to vehicle for crewed missions, Boeing's Starliner is still seen as an essential component of NASA’s long-term strategy for maintaining multiple options for crewed spaceflight to the ISS. “Competition is healthy in a lot of ways,” Bowersox noted. “It causes you to develop your technology, it causes you to get better pricing, and we would like to have that competition in the future.”