NASA has delayed setting a return date for the Starliner capsule three times. Since its launch on June 5, the capsule has encountered five helium leaks, five failures of its maneuvering thrusters, and a propellant valve failure. Consequently, the crew on the International Space Station (ISS) and mission management in Houston have had to spend more time than expected solving problems mid-mission.
The original plans for Boeing's astronauts, Barry Wilmore and Sunita Williams, to return to Earth have been disrupted by issues with the Starliner spacecraft, which is still docked at the ISS. The mission is being prolonged due to last-minute repairs and tests.
According to NASA's commercial crew manager Steve Stich, Starliner can remain docked at the ISS for up to 45 days. However, it could stay docked for up to 72 days if necessary, based on a variety of backup systems. Reportedly, Starliner's most recent internal return goal date is July 6, making the mission, originally planned for eight days, last for about one month.
Starliner's service module, which includes its expendable propulsion system, is the focal point of the current problems. It is crucial for backing the capsule away from the ISS and positioning it to re-enter Earth's atmosphere. Stich mentioned that many of Starliner's thrusters have overheated when fired, and the leaks of helium used to pressurize the thrusters appear to be related to their usage frequency.
Once NASA approves the return, Starliner's thrusters will be used to undock the capsule from the ISS and begin the approximately six-hour journey home. During descent, the capsule will adjust its orbit before landing using airbags and parachutes in one of several possible locations in the southwestern United States.
In a worst-case scenario, it is possible that Wilmore and Williams could return home on Crew Dragon, which has the capacity to accommodate more people in an emergency. However, NASA and Boeing officials, as well as program-aware engineers, do not foresee this as necessary based on Starliner's existing issues. The severity of Starliner's technical problems would play a critical role in determining its fate in such a situation. The last time a NASA astronaut required a backup means of transportation home was in 2022, following the arrival of two cosmonauts and American astronaut Frank Rubio to the International Space Station when Russia's Soyuz spacecraft experienced a coolant leak.