Nasa to decide fate of Boeing astronauts stranded on ISS in hours but spacesuit quirk means they may be stuck until 2025

NASA is set to determine the fate of two stranded astronauts tomorrow, after their ride home aboard Boeing's Starliner was deemed too risky.

Butch Wilmore, 61, and Suni Williams, 58, flew to the International Space Station (ISS) for an eight-day mission in early June.

But the pair are currently unlikely to return to Earth before Christmas, Nasa announced earlier this month, and may be stuck there until February 2025.

Nasa boss Bill Nelson will hold an internal Agency Test Flight Readiness Review on Saturday (August 24) for the stranded crew.

The meeting will be followed by a live news conference soon after from the Johnson Space Centre in Houston, Texas, which is hoped to offer an update on their length of stay.

During a briefing on last week, Nasa officials said no return flight had been confirmed, but that Starliner would be the astronauts' emergency plan B.

The $1.5billion spacecraft was marred by setbacks before and after the launch, such as issues with the oxygen valve and helium leaks.

Wilmore and Williams are reportedly unable to hitch a lift with a SpaceX Dragon spacecraft, which regularly transports humans and cargo to the orbital outpost.

The spacesuits Wilmore and Williams arrived in are only suitable for Boeing's Starliner spacecraft, and will not work with the Dragon vessel.

The Dragon spacecraft has its own range of spacesuits that it can operate with.

'Bonus time'

Both astronauts are "very familiar" with the ISS, according to Russ DeLoach, Nasa’s chief of safety and mission assurance.

The Starliner launch, it's first crewed test flight, marked the third mission to the ISS for each of them.

The UK's newest astronaut, Rosemary Coogan, told The Sun in July that the waiting game Wilmore and Williams are currently being subject to is simply "bonus time" in space.

The average career astronaut flies to space just three to four times.

While some only fly once or twice - others can go their entire careers without ever being assigned a space-based mission.

With both Wilmore and Williams currently on their third mission, Coogan, it may well be their last.

'Old bones'

However, extended periods in space can wreak havoc on the human body.

Astronauts lose between 1% and 2% of bone density for every month spent in space, according to previous research by Canada’s University of Calgary, which can have devastating knock-on effects.

Kyle Zagrodzky, founder of OsteoStrong, a company that treats osteoporosis, warned the pair "could have the bones of a 75 to 80-year-old person when they land and that could be very detrimental to them if they end up having a spine or hip fracture".

This is due to the lack of gravity taking the pressure off their legs when it comes to standing and walking.

How does space affect the body?

Space takes a significant toll on the human body, such as:

• Redistribution of fluid around body due to long periods of weightlessness
• Bone density loss in critical areas such as lower limbs and spine
• Muscle atrophy

Although ISS astronauts spend an average of two hours a day exercising, muscle loss is unavoidable in space.

It takes several years to recover from a six-month spaceflight.

There can be ongoing health concerns long after astronauts have returned to Earth, including: