Two astronauts who flew to the International Space Station for eight days and ended up staying months were aware of the risks and will be being kept busy, a retired astronaut who knows the pair says.
NASA astronauts Sunita "Suni" Williams and Barry "Butch" Wilmore crewed Boeing's Starliner which left earth on 5 June for what was meant to be an eight-day test mission.
They're now expected to return in February on a different spacecraft.
Retired astronaut Michael Fossum told Nine to Noon what happened to Wilmore and Williams was "pretty jarring" - to go from an eight day mission to months spent in space.
But this was a test flight, he said.
"This was the first human flight in the Boeing Starliner spacecraft, and both Butch and Suni have flight test backgrounds in the Navy. They're naval aviators and they were testers. And so this was always one of the possibilities - that something could go wrong."
Fossum said the pair probably started thinking about the possibility of being stuck while still in free flight after their launch when problems arose with the thruster systems.
'Crowded, functional, busy'
Fossum spent 19 years as a NASA astronaut, and helped design and build the International Space Station.
It was crowded, functional, and larger than one might expect, he said.
"It's about the size of 12 school buses or the internal volume of a 747. Of course it's not one big volume like an airliner. It's in these different modules and they're all built for different purposes."
It was also busy, with time scheduled down to five minutes by mission control back on earth.
The main function was science that can only be done at microgravity, such as combustion technology, Fossum said.
The space station crew were generally not scientists but acted as "laboratory technicians".
Fossum described it as living like a goldfish in a bowl, with cameras and control centres around the world watching your every move.
"Where everybody can see in, but your view out is limited and distorted."
Keeping busy
Wilmore and Williams were no doubt being kept busy with science and maintenance work, which there was always plenty of, Fossum said.
"In addition, we're always studying changes to the human body. It's been a few years since Butch and Suni have been up in space for a long period of time, so now we're getting another complete data set on them at an older age."
While there was always food on the space station, they didn't go with full kit and things had been couriered up to them, Fossum said.
"They had eight days worth of kit with them, so that was one of the practicalities, they got up there and they didn't have months worth of clothes.
"The things like your toothbrushes, all those kind of things, they had some, they did not have the full complement of exercise shoes and things that we would use for the long duration crew members."
Starliner's uncertain future
The future of the Starliner was a matter for Boeing, Fossum said.
But he hoped they continued with it and fixed the leaks in the propulsion system that resulted in the use of backup modes and reduced capability for manoeuvring the spacecraft.
"You learn from every flight and this was a test flight... And the fact that they had problems, to me as a professional flight tester for many years, it's not a surprise - you expect to have problems on a flight, especially a first human flight."
SpaceX return
The pair are due to return home on SpaceX's Dragon in February 2025.
That was the safest option, Fossum said. Although their Boeing Starliner did land safely.
"If they'd been on it, they would have been fine. But how lucky do we want to get? And we didn't have to."
There was disappointment for the two Dragon crew members pulled to make room for Wilmore and Williams, but it was the right thing to do, Fossum said.