British astronaut’s prosthetic leg could poison ISS crew

Sarah Knapton
Fri, 24 November 2023

John McFall is assisting with tests to find out whether it is possible to send disabled astronauts into space - ESA/NOVESPACE

When former Paralympian John McFall was selected to be the European Space Agency’s (ESA) first disabled astronaut last November, he knew there would be testing times ahead.

But nobody could have guessed one stumbling block would be that his prosthetic leg might poison the air on board the International Space Station (ISS).

The leg is made from a mixture of carbon fibres, resin and high-density foam and so may give off toxic gas that could build up over time and prove dangerous to astronauts on board.

Experts at the ESA are testing the leg to make sure it complies with Nasa standards. In 2015, the crew of the ISS were forced to evacuate the US part of the satellite following a rise in ammonia levels.

“It’s stuff you don’t necessarily think of,” Mr McFall told The Telegraph. “The socket is carbon fibre and it’s got like a high-density foam on the inside. The carbon fibre socket is impregnated with a resin. The foam is made with polymers.

“Those materials will continue to give off gases to one degree or another and in an environment like the ISS where the air is constantly recycled, any significant amount of gases that are produced from a material will be amplified over a period of time because they’re not filtered out.”

It is one of a number of revelations that Mr McFall has helped ESA uncover as part of the feasibility project to find out whether it is possible to send disabled astronauts into space.

There are nearly 100 requirements that astronauts must pass to be able to fly, including moving safely around the ISS and SpaceX Crew Dragon module, being able to carry out emergency procedures and experiments, fitting into space suits and maintaining good health in orbit.

Ensuring that Mr McFall's prosthetic leg is safe and continues to fit correctly in microgravity is proving challenging - Tony Jolliffe/BBC

Although the team originally thought that wearing a prosthesis in space may not be necessary, tests have shown it is likely to prove crucial for maintaining good fitness, balance, and for being able to evacuate quickly in an emergency.

But making sure it is safe and continues to fit correctly in microgravity is proving challenging. Astronauts’ bodies change in space because of microgravity, meaning Mr McFall’s legs could shrink or expand, and his prosthetic no longer fit.

To determine what might happen in space, he is undergoing experiments in Cologne on tilt tables in which he is tipped at an angle with his head lower than his feet, to mimic the effect of fluid rising up the body in microgravity.

“Most of the evidence so far suggests that fluid shifts up to your centre up to your trunk, and actually you lose some volume from a fluid point of view and your lower limbs,” he said.

“But we just need to prove that because a reduction in stump volume is easier to manage by padding it out a little bit with some extra material, but with an increase in stump volume you would need to make a socket that actually gets bigger.

“The commonest question I get asked is ‘do you need legs in space?’ and for floating around, maybe not necessarily, but it is useful in stabilising yourself so that you free up your hands for experiments.

“But we’ve found out I would need to wear a prosthesis on orbit to undertake the exercise countermeasures to maintain bone density and muscle mass.”

Mr McFall, 43, who was born in Surrey and grew up in Somerset, had his right leg amputated when he was 19 after a motorbike accident. But after learning to run again, he became a professional athlete, winning bronze in the 2008 Beijing Paralympics in the 100 metres T42 event.

Mr McFall (left) represented Great Britain at the 2008 Paralympics in Beijing, winning a bronze metal for the 100 metres T42 event - Andrew Wong/Getty Images

He also retrained as a doctor, working in the NHS for several years, and has recently completed his final exams specialising as an orthopaedic surgeon.

The astronaut feasibility study is due to end in 2025, when the ESA will present a case to European ministers, who will decide whether to fund a mission.

“It will be at that point when they make a decision about whether they want to support a flight for me or someone with an equivalent disability. Hopefully me,” he said.

“There are no red flags or no showstoppers at any level so far. I think a long duration mission to the space station is a fantastic opportunity for us to learn about someone with a physical disability living and working in space.

“Astronauts don’t get a lot of choice in when or where they fly but I would absolutely love to go to the Moon.”

The married father of three has recently moved his family to Germany to support his training. In fact, the only stumbling block to his spaceflight may come from something more mundane. He is missing being a doctor.

“I think the change of direction has been psychologically hard, rather than the astronaut training itself,” he said.

“I do miss the day-to-day hands-on of operating. I’m a very practical guy and this phase of the feasibility study is slightly less hands-on.”