NASA hasn't set a return date yet, having delayed it three times. Since its June 5 launch, the capsule has faced several issues, including five helium leaks, five thruster failures, and a propellant valve problem.
These issues have caused the crew and mission management in Houston to spend more time solving problems than expected.
The original plan was for Boeing astronauts Barry Wilmore and Sunita Williams to return to Earth, but problems with the Starliner spacecraft have delayed their departure.
According to NASA's commercial crew manager Steve Stich, Starliner can stay docked at the ISS for up to 45 days.
If needed, it could remain docked for up to 72 days, relying on backup systems, especially if new issues arise that mission authorities cannot promptly resolve.
The latest target return date is July 6, which would extend the mission from its planned eight days to about a month.
Starliner's issues are mainly with its propulsion system, part of the service module. This system is crucial for moving the capsule away from the ISS and guiding it back through Earth's atmosphere.
Several thrusters have overheated, and the helium leaks seem related to their usage frequency.
Once NASA approves the return, Starliner’s thrusters will detach the capsule from the ISS for the six-hour journey home.
During descent, the capsule will adjust its orbit before landing with airbags and parachutes in the southwestern United States.
If Starliner cannot safely bring the astronauts back, Wilmore and Williams might return on Crew Dragon, which arrived at the station in March and can carry extra passengers in an emergency.
Although this scenario is unlikely, it would be embarrassing for Boeing. However, NASA and Boeing officials, along with program engineers, believe Starliner's current problems don't necessitate this backup plan.
The severity of Starliner's technical issues will determine its fate. The last time NASA had to use a backup return method was in 2022, when two cosmonauts and American astronaut Frank Rubio returned on Russia’s Soyuz spacecraft after it experienced a coolant leak.