John McFall Is Breaking Barriers as the World’s First Parastronaut

John McFall, a Paralympic sprinter who later became an orthopedic and trauma surgeon, has had an esteemed career fueled by his intense drive and curiosity. Now he’s adding yet another acclaimed career to the mix: astronaut.

Following a serious motorcycle accident when he was 19, doctors amputated McFall’s right leg above the knee. With the use of a prosthetic leg, which he has worn ever since, he won a bronze medal in the 100-meter sprint event at the 2008 Paralympic Games, where he represented the U.K. In 2022, after a competitive selection process, the European Space Agency (ESA) inducted McFall into its astronaut corps, making him its first physically disabled member, or parastronaut. McFall was specifically chosen to participate in ESA’s groundbreaking “Fly!” feasibility study, which aims to systematically assess the barriers that exist in spaceflight for individuals with physical disabilities. The Fly! study is set to conclude this autumn. McFall has yet to fly in space, let alone to be assigned a slot on any upcoming mission, but that could soon change.

He now awaits his chance to launch and continues his training. Scientific American spoke with McFall about the process of becoming an astronaut and the unique physiological challenges uncovered in the latest feasibility study.

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[An edited transcript of the interview follows.]

Why did you apply to participate in this study? What aspects of your background made you feel particularly suited for this project?

What was interesting about the application for this study was that there was never any guarantee of a flight to space. The notice was just for a candidate with a physical disability to participate in a feasibility study, with ESA’s goal being to hopefully create an opportunity to fly someone with such a disability to space. For me, it was like, “What have I got to lose?” I didn’t have going to space on my radar at all, but a friend of mine sent me a message suggesting that I look into it. I saw it as a bold and innovative opportunity, and it’s commendable that ESA is the first space agency to take on such a brave initiative. In the back of my mind, I thought that if I could get selected, this would tick all the boxes for things I love doing in my life: being curious while challenging myself academically, physically and emotionally.

In terms of my background: As an amputee and surgeon, I know a lot about medicine and my disability specifically—especially what is and isn’t feasible with my condition. As an athlete, I know that I’m fit and physically capable—probably an ideal person to demonstrate how capable people with physical disabilities can be. I thought I might be an ideal candidate to help answer this question.

It’s somewhat surprising that we haven’t had someone with a physical disability in space yet. Before doing this study, why do you think other groups hadn’t tried to do this?

I don’t think there is a definitive answer. If you look at the history of human spaceflight, especially in the last 20 years, the space station has been inhabited with a constant human presence since the year 2000. In the first decade [after 2000], essentially until the end of the shuttle era, the space station was still being built. We were also learning a lot about long-term human habitation in orbit. Around 2014 or 2015 we started gathering good long-term data on the effects of living in low-Earth orbit with microgravity on astronauts. Since then, the idea of whether this would be possible for someone with a physical disability has been floating around. Dave Parker, then director of human and robotic space exploration for ESA, went to all the ESA member states to get approval for selecting someone with a physical disability in 2021. It takes time, but I think the idea has been there for a while. Now that we’ve learned more about human spaceflight and how the body responds to prolonged microgravity, we’re ready to move to the next step.

What was your immediate reaction to being selected?

When I was selected from the final few candidates, I felt privileged. I was just very proud to be selected to represent ESA and the U.K. Space Agency and also the population of people with physical disabilities. Now I have this platform and responsibility to demonstrate our capabilities.

What does the Fly! study hope to demonstrate with this feasibility testing?

There are some activities in spaceflight operations that we take for granted that able-bodied people can do because, well, why wouldn’t they? Emergency procedures such as getting out of the spacecraft or medical procedures in microgravity, preflight training activities on the ground, being able to use the equipment from an ergonomic point of view—all of this has been designed around able-bodied people. If you look at those requirements and ask, “Well, astronauts are required to do this—can John with his disability and prosthesis still do that?” Some of it’s like, “Well, yeah, of course I can!”

But there’s no harm in asking the question anyway. It’s very fair because some people don’t have experience with physical disabilities, and this is where my background as a medic with a disability comes in. It’s not until you pick apart the requirements for flying to space that you look at how my disability and prosthesis might impact meeting them. The goal was to find out what we need to demonstrate to prove that they can be met.

Living in the microgravity of low-Earth orbit leads to internal fluid shift and muscle atrophy, among many other effects. How exactly did the study investigate how those factors might impact you and your prosthesis specifically?

Until you actually do it, there are limited ways to replicate the conditions of low-Earth orbit. There’s no substitute for being in orbit and doing it. The best we can do is come up with analog variants to simulate factors from spaceflight and then try to mitigate them as much as possible. You have to ask as many questions as you can to try to understand what the potential problems could be.

For example, yes, you would expect fluid shifts in microgravity. Generally, fluid moves from the legs up into the abdomen and thorax—so, theoretically, your lower limbs would have less volume. There will be acute and chronic fluid shifts, as well as chronic atrophy, because while you’re still exercising on the station, you’re not going to be able to achieve the same muscle strength and bulk as on Earth. We did analog fluid shift tests here on Earth to discern if there were any significant changes in stump volume that might affect my prosthesis fit and comfort. But we actually found there wasn’t anything significant. As I said, it’s impossible to replicate chronic changes without doing a longer-term bed study, in which you’re laying down for weeks or months on end to simulate the muscle loss from microgravity. So we did feel it was necessary that the prosthesis I would wear have some volume adaptability in the socket. My stump is probably going to get smaller in space, so it’s important to have some adjustability.

The actual spectrum of physical disabilities that this study covers is naturally limited—the testing is restricted to a single-leg amputation specifically. How much do these results generalize to the much broader spectrum of physical disabilities?

The study we’ve done is very specific to my disability—a single-leg amputation above the knee. You can probably extrapolate to a population of similar lower limb disabilities, but bear in mind that individual assessments would still be needed for each person.

What’s interesting is when you look at a person’s disability and how they would live and work in space, you need to consider where assistive devices play a role. If someone is dependent on assistive technology to undertake their tasks, as I am with my prosthesis, you have to make sure that this device works and is suitable for spaceflight.

There are several other disabilities [that merit microgravity studies], such as in the case of someone who can’t use their lower limbs and is a wheelchair user. In this case, lower limb muscle atrophy or fluid shift is not really an issue because they don’t walk or put weight on their lower body. They’d still need assistive devices to meet the emergency requirements at launch, but when you’re up in space, getting about and doing tasks is straightforward. Yes, they may have to demonstrate that they can stabilize themselves, and we can develop technology to help. But they are actually less dependent on assistive devices in space for their physical health. We also know that astronauts in space only see a reduction in bone density in their lower limbs—so if you don’t use those limbs, it doesn’t matter.

There are still open questions for wheelchair users regarding bladder and bowel function and the risks associated with microgravity, which are quite interesting. Essentially, there is a lot to understand and learn about. That’s what I think will be the legacy of this study.

You mentioned that in the selection process, there was no promise of being sent on a space mission and that this was purely a feasibility test. Whether you or someone else does become the first parastronaut in space, what message do you hope to convey to those who previously thought spaceflight was out of reach for people with physical disabilities?

ESA and the U.K. Space Agency are world leaders in challenging people’s intuitions and perceptions of what an astronaut looks like. I don’t think that human space exploration should be the only place where this happens. I hope that as a result of this, people will continue to challenge the idea of what certain professionals look like. This is another example of challenging that narrative, and I hope to spread that message.