Boeing’s Starliner is preparing for an uncrewed return to the International Space Station after propulsion problems delayed crewed missions and extended Sunita Williams’ 2024 spaceflight.
Boeing's Starliner spacecraft is expected to return to the International Space Station (ISS) on an uncrewed test mission as NASA and Boeing work to address technical issues identified during its first crewed flight.
The upcoming Starliner-1 mission is intended to test improvements to the spacecraft before NASA considers sending astronauts aboard it again.
The mission could launch as early as December 2026 or January 2027, depending on testing, certification and readiness requirements.
NASA and Boeing plan to operate Starliner-1 without a crew. The spacecraft will travel to the ISS and provide an opportunity to evaluate modifications made following problems encountered during its 2024 crewed mission.
NASA plans to use the flight to collect additional performance data and determine whether the spacecraft is ready to transport astronauts safely.
NASA Administrator Jared Isaacman said the uncrewed mission would help validate improvements and provide the flight data required before another crewed flight.
If the testing and certification process progresses as planned, NASA currently expects astronauts to return to Starliner on a subsequent Starliner-2 mission in 2028.
The approach allows NASA and Boeing to assess the spacecraft under actual flight conditions before putting astronauts back on board.
Starliner's major problems emerged during its first crewed mission, which began in June 2024.
Astronauts Sunita Williams and Butch Wilmore travelled to the ISS aboard Starliner for what was initially expected to be a short mission lasting roughly eight days.
However, problems involving the spacecraft's reaction control system thrusters raised concerns about its ability to safely complete the return journey.
NASA subsequently decided that Starliner should return to Earth without its crew.
Starliner landed without astronauts in September 2024. Williams and Wilmore remained aboard the ISS and eventually returned to Earth in March 2025 on a SpaceX Crew Dragon spacecraft.
Their unexpectedly extended stay turned the Starliner mission into one of the most closely watched crewed spacecraft tests in NASA's recent programme.
Following the mission, NASA conducted an investigation into the spacecraft's problems. The review produced 61 recommendations addressing technical and programme-management issues associated with the Starliner mission.
The investigation found that the spacecraft's service-module thrusters had operated beyond their engineering qualification limits. Thermal conditions and design-related factors were identified as contributors to the propulsion system's performance problems.
These findings have guided the modifications Boeing is now making before Starliner returns to flight.
Boeing is introducing several changes to improve Starliner's reliability before the next mission. One of the key areas of work involves the spacecraft's service module and propulsion system.
Boeing has made thermal changes to the service module to address conditions that affected the thrusters during the 2024 mission.
NASA plans to evaluate these modifications during the uncrewed Starliner-1 flight.
The company is also modifying thruster valves to address problems involving seal extrusion, which affected propulsion performance.
The changes are intended to improve the reliability of the system during future missions.
Other planned upgrades include:
New thrusters for the crew module
Improved spacecraft batteries
Changes to the parachute system
Additional testing and certification activities
Together, these modifications are intended to address technical concerns identified during Starliner's first crewed flight.
Starliner's return to crewed missions will also depend on NASA's certification of the rocket used to launch it.
NASA plans to certify United Launch Alliance's Vulcan rocket for crewed Starliner missions following the retirement of the Atlas V rocket.
This certification is another important step before astronauts can return to the spacecraft.
NASA's continued investment in Starliner is also linked to its broader goal of maintaining more than one system capable of transporting astronauts to low Earth orbit.
The agency currently relies heavily on SpaceX's Crew Dragon for crew transportation to the ISS.
NASA intends to exercise options for a fifth and sixth Starliner mission, helping maintain an alternative crew transportation system.
Having two operational crew spacecraft would provide NASA with greater flexibility for future ISS missions.
The upcoming uncrewed mission will be an important test for Boeing's spacecraft programme.
Rather than immediately returning astronauts to Starliner, NASA plans to first examine how the upgraded spacecraft performs in orbit and during its journey to and from the ISS.
The results will help determine whether additional modifications or testing are required before the next crewed mission.
Conclusion
Boeing's Starliner is preparing for an important uncrewed test flight following the propulsion problems encountered during its 2024 crewed mission. The Starliner-1 mission, potentially launching in late 2026 or early 2027, will test major hardware and software improvements before NASA considers returning astronauts to the spacecraft.