'Is having two legs useful' in space?: Astronaut John McFall explains what life in orbit might be like for the first physically disabled person in space

At age 19, John McFall thought he might never walk again after his right leg was amputated above the knee following a motorcycle accident. Fast-forward more than two decades, and he is now on the verge of becoming the first physically disabled person in space.

McFall, 45, is a British surgeon and former Paralympic athlete who won multiple medals as a T42-class sprinter. In 2022, he joined the European Space Agency's (ESA) Fly! program, which aimed to see if a person with a physical disability could live and work in low Earth orbit. And in February 2025, he became the first member of the program to be cleared for a potential future mission to space.

More recently, on June 2, the U.K. government announced that McFall had been selected as a prospective member of the first crew to live on Haven-1, an upcoming commercial space station from U.S. company Vast that is scheduled to be the first of its kind in low Earth orbit, if it launches on time early next year.

If everything goes according to plan, the roughly 30-day mission will help answer a series of interesting questions about how living in space might be both challenging and advantageous for people with physical disabilities.

Live Science spoke with McFall about what it would mean to break new ground, wearing a prosthesis in space and how microgravity might uniquely affect him.

Harry Baker: How did it feel to get the news that you might be going to space next year?

John McFall: Awesome. Very awesome, very exciting. And it feels like we're one step closer to realizing this amazing opportunity and achieving this very exciting milestone in human space exploration.

HB: What would it mean to you personally to become the first physically disabled astronaut in space?

JM: To me personally, it doesn't make a difference. In terms of "what an achievement for me," I don't tend to think of it like that. However, I am very aware that the broader message that it sends to wider society about what people are capable of — whether they have a disability or not — is very interesting and powerful. So I'm proud to be a very small part of that movement, if you like, and the journey of making society a more tolerant and inclusive place.

HB: What advantages do you think your disability might give you in space compared with other astronauts?

JM: It's a good question because we don't actually know. We can hypothesize, but until we actually get into space and conduct some science that's specifically relevant to my disability, we won't know. But there are some theoretical benefits.

One is that when you live in microgravity, you get a shift of fluid from the lower part of your body up into the upper part of your body and your cranium. This can cause swelling of the optic disk, which can temporarily affect vision. It's called spaceflight-associated neuro-ocular syndrome (SANS), and it affects around 70-75% of astronauts. I would hypothesize that, having a reduced lower limb volume to start with, you're going to get a proportionally smaller fluid shift in microgravity, relative to your physiological capacity to process it, reducing the risk of things like SANS.

Another is that in microgravity, because you're weightless, you're not using your bones as much, and your body naturally resorbs them. So your bones get weaker and thinner. And one of the byproducts of this is that you have to excrete a lot of calcium, and you do this via peeing it out. As it [calcium] passes through your renal system, or kidneys, this causes an increased risk of kidney stones in microgravity. So again, having lower bone mass to start with — but retaining the same physiological capacity to metabolically process calcium — there is potentially a lower risk of kidney stones.

So those are two small-but-hypothetical benefits of my particular disability in space. But the real answer is, we don't know until we do the science (i.e., urine samples, blood samples and eye examinations in orbit).

HB: How might space be more challenging for you than for other astronauts?

JM: Again, we don't know. The question is, do you really need both your lower limbs to help you stabilize and support yourself whilst your hands are doing tasks? And is having two legs useful in what we would call normal intravehicular operations [conducted inside the spacecraft], whether it be cargo operations, maintenance, this sort of stuff?

When we went through the feasibility initiative, trying to think of and work out all these scenarios, we couldn't really think of a disadvantage other than maybe having to work slightly harder.

HB: Will you be wearing a prosthesis in space?

JM: The plan is to wear a prosthesis. We deemed quite early on that wearing a prosthesis in a spacecraft would be a necessity, mainly at launch time. If there was an emergency that required me to get out of the spacecraft and get off the crew access arm and away from the launch site, it would be ideal wearing a prosthesis to do that.

But in space, we don't know whether it's going to be an advantage or be required for these intravehicular activities. Where I would definitely need to use one is on a long-duration mission where I need to exercise lots. I use a prosthesis to exercise on Earth, and I would use a prosthesis to exercise in orbit. However, short-duration missions [like this one] do not.

The prosthetics I use are modular, so I wear a socket — that's what's left of my leg goes inside — and then the hardware, what we call the terminal device, is attached to the socket. What I would envisage doing is always wearing the socket, because that way, you maintain consistency. But [for] the terminal device itself, I have a quick-change adapter that you can just unplug the device, and you can take it off and, likewise, put it back in again.

It's "plug and play," if you like, and [it will allow me to] make assessments of whether it's useful or not.

HB: Will your prosthesis need to be specially made for the trip?

JM: Not really. We are certifying a number of prosthetic hardware items to fly, but they're all what we call "commercial, off-the-shelf items." So they're products that are widely available.

However, there are some very small changes that we need to make to make them compliant with the safety requirements of the space station environment and the spacecraft, such as fireproof tape around certain parts of the device or changing the hydraulic fluid so it's less toxic in case there is a leak.

We're also doing a small amount of redesigning to the shape of the foot to make it more ergonomic to interface with things like rails and straps inside the space station, because you often slip your foot under rails and straps.

HB: Could anything you learn from your mission help physically disabled people back on Earth?

JM: Yeah, I think so, certainly from a prosthetics point of view. There are prosthetic developments that we have made that will benefit other prosthetic users in the future.

I mentioned this quick-change adapter. We have revised or reengineered this particular device to perform in a certain way, which I think will have advantages for a whole range of lower-limb amputees. The socket technology ‪—‬ the interface between my stump and the prosthesis ‪—‬ is [also] going to be redesigned and potentially has very beneficial applications for lower-limb amputees again.

HB: Are you hoping to be selected for more missions in the future? And would you like to become the first physically disabled person on the International Space Station (ISS) or the moon?

JM: Yeah, absolutely. I hope that we use this opportunity to demonstrate that it is very feasible, and I hope that that would put me in line for selection of missions in the future.

I would love to, in the future, potentially spend longer in space, demonstrating that it's possible for someone with a disability to live and work in space and cope with everything that comes with that.

And absolutely, I would love to go to the moon. You know, someone with a lower-limb disability, when you propose that against walking on the moon, it's quite a powerful statement, and I would love to do that.

Editor's note: This interview has been condensed and edited for clarity.