NASA and Boeing plan to spend the next few weeks conducting tests on the ground in order to better understand issues with the Starliner spacecraft’s thrusters before giving its crew the go-ahead to fly back to Earth, officials said in a press conference Friday.
They’re not stranded because the part of the capsule that isn’t working has multiple redundancy and is intended to burn up on reentry anyway.
Starliner is perfectly capable of leaving the ISS whenever they want, but they would be unable to continue collecting data on the thruster shutoff (again, because it would burn up in the atmosphere).