Two astronauts stuck on ISS as Boeing capsule faces technical woes

WASHINGTON: Problems with Boeing's Starliner capsule, still docked at the International Space Station, have upended the original plans for its return of its two astronauts - Sunita Williams and Barry Wilmore - to Earth, as last-minute fixes and tests draw out a mission crucial to the future of Boeing's space division. Nasa has rescheduled the planned return three times, and now has no date set for it.Since its June 5 lift-off, the capsule has had five helium leaks, five manoeuvring thrusters go dead and a propellant valve fail to close completely, prompting crew in space and managers in Houston to spend more time than expected pursuing fixes.
The current situation
Starliner can stay docked at the ISS for up to 45 days, according to Nasa's commercial crew manager Steve Stich. But if absolutely necessary, it could stay docked for up to 72 days, relying on various backup systems, according to a source. Internally at Nasa, Starliner's latest targeted return date is July 6, according to this source. Such a return date would mean that the mission, originally planned for eight days, instead would last a month.
Starliner's expendable propulsion system is part of the craft's service module. The current problems centre on this system, which is needed to back the capsule away from the ISS and position it to dive through Earth's atmosphere. Many of Starliner's thrusters have overheated when fired, and the leaks of helium - used to pressurise the thrusters - appear to be connected to how frequently they are used. Stich said recent test-firings of the thrusters gave mission teams confidence in a safe return. The mission team in Houston, made up of Nasa and Boeing personnel, is scrutinising data on the propulsion issues and considering how to fix them, such as by updating software or changing how the hardware is used. Once Nasa officials give the team a go-ahead for a return, Starliner's thrusters would be used to undock the capsule from the ISS and begin a roughly six-hour journey home. This is Starliner's first mission to orbit carrying astronauts - the final test needed for Nasa to certify it as its second ride to ISS along with SpaceX's Crew Dragon.
If the unexpected happens
Even with the propulsion system issues, Nasa has said Starliner still would be capable of returning the astronauts to Earth if absolutely necessary - that is, if the capsule must serve as an escape pod from the ISS in an emergency or if any of Starliner's perishable items - such as solar panels - show signs of expiring earlier than planned.
If Starliner cannot be used
If Starliner is deemed incapable of safely returning Wilmore and Williams to Earth, one option would be sending them home aboard Crew Dragon, which ferried four astronauts to the ISS in March and is able to fit more people in an emergency. That scenario, considered unlikely, would be embarrassing for Boeing. The last time a Nasa astronaut needed an alternative ride home came in 2022, when Russia's Soyuz capsule sprang a coolant leak after delivering to the station two cosmonauts and US astronaut Frank Rubio. He used an empty Soyuz capsule that Russia launched as a rescue craft. His mission was extended from 6 months to 371 days - a record-breaking duration for an American in space.