How to survive in space

The toll that space takes on body and mind...
30 April 2024
Presented by Will Tingle
Production by Will Tingle.


Space flight


This episode of The Naked Scientists: as mankind seeks to colonise the Moon, Mars and beyond, we’ll examine the impact of cosmic voyages on body and mind, and what we can do to keep spacefarers healthy and happy...

In this episode

this is a picture of an astronaut doing a space walk

00:52 - How the human body handles space travel

Helen Sharman shares her 'out of this world' experience

How the human body handles space travel
Helen Sharman

“Exploration is in our nature. We began as wanderers, and we are wanderers still. We have lingered long enough on the shores of the cosmic ocean. We are ready at last to set sail for the stars.”

Carl Sagan’s book, Cosmos, was first published in 1980. And his sentiment echoed the collective primal urge to push our species out into space. In the 11 years before this quote, we had put men on the Moon, we had landed on Mars, collected soil samples from Venus, and had flown probes past every major planet in our solar system. Humanity was truly casting off into the cosmic ocean. Nowadays, we are using telescopes to peer back into the origins of the universe, and our probes are sending back information from 15 billion miles away. But, the evolution of the physical body cannot keep pace with our ingenuity. Getting a human being up into space, and keeping them there, is still a monumental task. The entire Moon landing, one giant leap for mankind, only lasted for just over 8 days. The average occupant of the ISS is only up there for 6 months. We have spent millions of years evolving to be comfortable on our planet, and so, to our fragile human form, space is still an unflinchingly hostile environment. So if we truly seek to expand out to the Moon, Mars and beyond, what are the challenges involved?

At a base level, we need to keep anyone exploring space alive, and in good health. So what does space do to the human body? Unsurprisingly, I can’t answer that. But I do know someone very special that can.

Helen Sharman became the first British person to go to space on the 18th May, 1991. She took me through her experience after liftoff…

Helen - Immediately it was just the most amazing feeling because although I was still strapped into my seat, I was a little bit floating away from my back. And so the ventilation, the air, could get behind my back and dry off some of that sweat. It took about two and a half more hours until I could unstuck from my seat and then actually float out. And that's when you really start to feel it for your own body. But of course up until then, every movement I made, I moved my little finger, I lifted up my instruction manual and there were signals going back to my brain all the time that everything felt weightless. So actually it just became a very natural kind of feeling.

Will - It feels like what you're describing is in stark contrast to what I imagine would be an innate, almost ape brain response that a human would have given they've spent their entire lives on this 1g hunk of rock and then to be fired into space and suddenly none of the rules apply. I feel like that would activate my fight or flight response. But you're telling me that wasn't the case.

Helen - I think that human bodies are just so adaptable and I suppose I wasn't scared because my brain had learned, I knew in my training, that this was something to expect, not that I'd ever really done any long duration weightless training. But yeah, I think we are just adaptable and we react to our situation. Our legs are pretty useless in space really. We use our arms to pull ourselves along with ropes along the sides of the modules and just we learn how to push off from one wall and very accurately actually just float exactly where we need to be to the other wall. So yeah, it's it's, it's a very adaptive process, I think.

Will - Whilst it's very reassuring that the human mind and the behaviours therein is very adaptable to zero G and being up in space, it's probably less sure to say that the body itself is the same. It feels like the team that sent you up probably didn't just stick you into a tin can, light the fuse and go, 'yeah, you'll probably be fine'. You were presumably told to watch out for certain health things whilst you're up there.

Helen - Yeah, sure. I mean, I knew that there was going to be a fluid shift and that's the first thing that you really notice inside yourself. So no longer body fluids are pulled towards the lower part of your body. These fluids kind of shift around and accumulate more in the upper chest and head than they do normally on Earth. Our noses, you know, we feel this sort of congestion and it does feel very much like that. The high pressure that you get in your head if you've got a heavy cold, that kind of thing. And it takes a few days, well really weeks I suppose, completely to finish, but I felt normal after a few days when this fluid, I think some of it might be actually excreted as urine, but a lot of it is just redistributed in the body. We think a lot of it goes from our blood vessels into other parts of the tissues of the body, for instance. But it redistributes and we feel much more normal again. But yes, it has this, this huge knock on effect. So I was aware of some of those things, but we've learned so much more in recent times. Muscle and bone loss is often due to the fact that we're not stressing our muscles and bones. Space radiation is another thing that I was warned about. And certainly I'd read that some of the early astronauts had sensed little sort of light flashes in their retinas, and I saw those too. We're protected on the Earth by our own atmosphere and also the Earth's magnetic field. But once outside of the atmosphere, we don't get that protection anymore. So yes, we get a lot more radiation through the spacecraft. And in Soyuz, the spacecraft I used to get to the space station, that was much less shielded by all the equipment and so on around us. And so that radiation could actually come through the walls.

Will - In terms of what you're describing then, it seems like you were made aware of all of these things, these gravitational changes to your body and these cosmic radiations, but there wasn't so much a plan or a treatment, it was just keep an eye out for it and if it gets bad, do we have to send you back to Earth?

Helen - Well, the fluid shift, yes. I mean your body does adapt to that, but we had these thick elastic straps around the tops of our legs, to help us feel a bit better about it. Radiation, we had monitors, but yes, of course that's not actually helping you. There are some things that we were semi prepared for. So things like gut microflora. I was aware it was going to be different. We didn't know much about it then. I don't think we know a huge amount about it now really in terms of how it changes in space. But I knew that I was going to be eating sterile food, for instance. It's a long life kind of food. There's going to be a different microflora around in the spacecraft itself in terms of making sure that we didn't take extra bugs with us into space. It was one of the reasons why our skin was washed in alcohol. So yeah, we were aware of a lot of this stuff, but yes, how to actually improve our health. We're still really, I think, quite at the beginning stages of helping astronauts.

Will - And so that kind of leads us to the future then. If we are going to spend so much more time in space, if we're hoping to mine the moon and colonise Mars, it seems like we're going to have to have a lot more attention paid towards treating space-based problems with the body. Because if you're stuck midway between here and Mars, you can't just nip back down to Earth to treat something.

Helen - Absolutely right. And as we have more people in space for longer periods, we're working out that there's also other factors that we hadn't considered before. So for instance, the extra pressure in our brains might affect all sorts of neurological issues. But also we know astronauts' eyes, the shape of astronauts, eyes changes in space can affect the way they focus. If you send an astronaut into space and then they can't see what they need to do later on, that can certainly be an issue and we're finding out more and more about that. But yes, I think that the big thing is that I think we need to be aware that these different gravity environments, whether they're Mars or the Moon, or you know, in transit feeling weightless, there may be different requirements and it might be a different normality and that new normal might be quite healthy in that environment. Let's say, if your bone loss in space, in microgravity is not a big deal until you want to come back to Earth. So yes, I think what we've really got to do is make sure that we do a lot more monitoring in the early stages to detect what astronauts are going through so that we might not be able to fix their health problems once they become a real problem. But if we can be alert to things that might be going, and I'll say 'wrong' in this instance, let's assume that we have worked out that this would be a negative for them, that we can stop things from getting too bad. Because of course we won't have whole body MRI scanners on Mars for the first few astronauts who go up there. We may have some kind of diagnostic equipment and artificial intelligence may well help quite a lot, but they're going to have to be really very, very self-sufficient with very little instrumentation, very little consumables to replace. IV fluids, for instance. What should those IV fluids be made of? What are the relative constituents? But that might be different because our blood volume changes in space, depending on what gravity environment we happen to be in. So yeah, so there's a lot of work still to do, but I think in the first few stages, the team's going to be very self-sufficient. They're going to have to be very tolerant of each other, tolerant of changes, physically and mentally really robust. And I think that selection of those astronauts is going to be particularly important. The further away we go from Earth and that isolation that we get, and the more that we send astronauts up, the more we will need that healthcare. What sort of pain relief? How do those drugs transfer across lipid membranes within the body? It'll be a different mechanism. So as certain that mechanism may be changed somewhat. Are we going to ever give anaesthesia in space? And how will that be different? So yeah, a whole load of things we need to start to get to grips with, I think, before many people go to Mars.

Neil Armstrong's face as he gazes at the Moon

10:46 - Space travel and the body clock

And why it might not actually be an issue on Mars

Space travel and the body clock
Matt Bothwell, University of Cambridge

The current medical limitations on spacecraft means that, much like on Earth, an ounce of prevention is worth a pound of cure. So keeping spacefarers in tip top condition will prolong their ability to function. And a huge part of that is maintaining circadian rhythm. Humans function best on a strict regimen, our bodies have evolved to perform certain functions based on their innate sense of the time of day. But the 24hr day that we’ve evolved to sync to doesn’t exist in space, or on the Moon, or Mars. So how much will not being on Earth affect our human bodies?  Cambridge University’s public astronomer Matt Bothwell...

Matt - It depends where we are really. The human body has obviously evolved to live on this 24 hour cycle. And really what we have to do is just do our best to simulate that 24 hour cycle because if you get too far away from that, our bodies get pretty unhappy. So astronauts on the International Space Station, for example, they zip around the Earth every 90 minutes. They have something like 16 sunrises every single day. The way they stay sane is to simulate artificially a 24 hour cycle. And so they stay on GMT, the lights get bright at six in the morning, the lights dim and get orange at night. And so even though they have 16 sunrises a day, they still get this 24 hour cycle that their brains need.

Will - With that being the case then if we are going to move further afield to the Moon and to Mars, which have time of days being longer or shorter than ours, are we going to have to put in some interesting kind of hacking our own biology in order to be able to still function in those places?

Matt - The answer is definitely yes for the Moon. I think interestingly for Mars we might be fine. There are studies of circadian rhythms; when you put humans in isolated environments and don't give them cues about what the light is doing, circadian rhythms tend to settle down onto a roughly 24 and a half hour cycle. Obviously evolution hasn't bothered to give us an exactly 24 hour circadian rhythm cycle. You get it close enough and then the cues from the sunrise and the sunset just sort of nudges us onto the schedule. So our natural circadian rhythm of a whisker longer than 24 hours is probably perfect for the Martian day, which is about 24 hours and 40 minutes. So I think we can function on Mars absolutely fine with no hacking needed.

Will - It feels like that there is a case of this kind of being trialled on earth already because we have people operating machinery on Mars that obviously have to attenuate to the Mars cycle already. That's

Matt - Exactly right. The NASA engineers that operate the Mars rovers have to live on Martian time, which is about 24 hours and 40 minutes. And so if you're living on Mars, that's fine. The sunrises and the sunsets on Mars would nudge your circadian rhythm back into schedule. But on Earth, living on a 24 hour, 40 minute period means you slowly drift out of sink with Earth. And then yeah, you blink and a couple of weeks have gone by and suddenly you are working the night shift. I think people only do this for a couple of months because I think it would drive you crazy after too long.

Will - Is the case then of finding the people with that slightly elongated circadian rhythm and shipping them off to the red planet?

Matt - Right, exactly. There was one study that came out of Harvard a few years ago that suggested that morning people have slightly shorter circadian rhythms and evening people have slightly longer circadian rhythms. So we just need to find all those people that like lying in and they'll make the perfect Martians.

Will - Delightful to have found a calling. But that's in terms of the internal human body clock. But when it comes to syncing up communications and satellites like that, are we going to have to end up creating time zones for different planets, do you think?

Matt - We absolutely will. We need time zones on earth because the earth rotates around and the Moon and Mars and anywhere we can conceivably go is all going to be spinning around in the future. So we will definitely need different time zones. I think one of the really interesting challenges that's gonna need to be solved is the fact that time doesn't behave the same on all planets. One of the big takeaways from Einstein's theory of relativity is that time goes a bit faster or slower depending on what your local gravitational field is like. And on the moon where gravity is only about a sixth of the Earth's gravity on the surface time is going to go ever so slightly faster. Not that in a way that humans would notice, but if we want any future satellites doing GPS positioning on the moon, we're going to have to take that into account.

Will - Do you think it would be better to keep people in these places so that they can fully get used to this circadian rhythm we create or keeping them there for a couple of months and then shipping them back home? Because it seems like if you're doing that, you're kind of constantly throwing people between these two things and that could potentially be worse.

Matt - That's a very good point, but I do wonder if maybe the answer is it's only about the same as being jet lagged or something. It might have the same effect of if you fly to the states or if you fly to Australia. Yeah, you feel a bit rough for a few days while your circadian rhythm catches up and then you're fine. So yeah, maybe in the future we just have to deal with Moon lag for a few days.

Will - So our ideal astronauts are businessmen that often fly between here and the states and also get up very late in the morning.

Matt - Exactly. They're, they're the future Martians, I think.

Will - Take that Matt Damon <laugh>.

Vertical Future farm

How do you grow food in space?
Jen Bromley, Vertical Future

The importance of circadian rhythm in keeping astronauts happy extends beyond the astronaut themselves. Because we all need to eat, and the food grown in space will be from plants that, again, are in no way used to having their internal clock and gravity thrown out of whack. So what’s the deal with space food? Jennifer Bromley is a fellow at Churchill College, Cambridge, and chief scientific officer at Vertical Future...

Jen - Vertical Future are an agritech technology and data company. And our mission is to improve planetary and human health by building a better food system. But the way how our technology has evolved means that it's now equally applicable off Earth as well as on Earth. And we are now leading a UK space agency funded project called Autonomous Agriculture for Space Exploration.

Will - What kind of crops are you finding work best up in space?

Jen - There's a variety of different crops that have been grown in space. So NASA has a very active crop science group who have two different growing facilities on the International Space Station. They're called Veggie and the Advanced Plant Habitat. And they've grown a number of different crops from things like lettuce through to peas. They've done radishes and I think my personal favourite is they've grown chilies and the astronauts particularly enjoyed eating those.

Will - When I think of growing plants as a humble earthling, I think of plants being buried deep in nice thick soil as a nutrient delivering mechanism. I assume that is probably a bit tricky.

Jen - Yeah. With no gravity, it's kind of difficult to deliver water and nutrients to plants in space, but it is completely possible and has been very much done already. So typically on Earth, when we're looking at vertical farming, we'll be typically using no soil, but we use substrates like jute. We use recycled matting, we use coco coir, but that all requires water and nutrients dissolved in the water to be delivered to them in liquid form, either by hydroponics or aeroponics. Now that's going to be a problem in space because the water will bubble up and float around the space station, which is really not what you want in an environment with a lot of electronics. And so what has been pioneered are these little plant growing pods that are known as pillows. And these pillows are essentially little watertight units that contain a water absorbent material. The plant grows through a small opening on the pillow, and then there is a port which if anybody's had any sort of interventions at hospital, you may recognise the sort of port that they will be injecting you with. And then what's happening at the moment is the astronauts who are running the experiments are manually injecting nutrients dissolved in water into the port, which then delivers it to the absorbent material around the plant root. So very much a soil like scenario, but the nutrients are provided externally through the water that's provided rather than it being sort of ingrained in the soil already.

Will - And as Matt Bothwell was speaking about just a moment ago, one of the biggest challenges about moving into space and onto other planetary bodies is going to be the shake up to our circadian system. Plants, very much the same and perhaps even more driven by the presence and position of light. How are you going to deal with that?

Jen - So the joy of growing in a controlled environment means that we can fully control when the lights turn on and when the lights turn off, the intensity of the light that we give them and the wavelength of the light that we give them. And so we can just play tunes with that to our heart's content. You can grow plants under a 24 hour constant light. They can start to look a bit funky. I'll be quite frank, they're not big fans of it. But it is possible to do it. But if you can essentially replicate the kind of conditions that you see on Earth, the sort of environment that the plant has evolved in, that's typically going to be the best environment and lighting condition that you can give to the plant in space. And so with the lights that we've developed at Vertical Future, we're able to do that and that's what we are putting on board the space station. We started to work on the ISS. The ISS works on GMT, it's working on a 24 hour cycle, so keep going on that. But you can start to shift plants away from the typical 24 hour cycle. There was some very interesting work that was carried out by Professor Alex Webb and his lab at Cambridge where they looked at what the optimum day length was for a variety of different accessions of one particular species. And they showed that most plants do not have a bang on 24 hour period. So you can shift away and you can make a plant more productive. If you do shift too much away from their optimal period, then they will start to reduce their yield volumes as well. So by being able to turn the lights on and off when we want to though, it means that we can keep the day to work for the plant and we can create the environment that the plant needs rather than try and sort of shift a plant onto the environment that we want to inhabit.

Space flight

Surviving the isolation of space travel
Kate Greene

The importance of good food cannot be understated when it comes to space exploration. Because a wholesome and hearty meal can, and I speak from experience here, make or break the quality of a day. And preserving your mental health when you are isolated in a cramped environment with the same group of people for months at a time is essential for successful and productive voyages. Kate Greene is the author of Once Upon a Time I Lived on Mars, inspired by a four-month stint inside a simulated Martian habitat as part of the HI-SEAS program, an isolation simulation which seeks to find out the effect that a spacecraft setting has on the individual and groups of spacefarers. Kate found herself involved with the program after becoming fascinated by a very unusual question…

Kate - Back in 2011, I was scrolling Twitter and I came across an article and the basic premise was, why do astronauts like to use a lot of Tabasco sauce on their food? Was this gravity, was this boredom? Did they need the spice to get something exciting in their senses? And as I read to the end of the article, I saw that there was a call for participants in a simulated Mars mission to actually study potential future food systems. This was a NASA funded study, and it would take place in a dome on Mauna Loa in Hawaii in the year 2013. And I thought, I have to apply to this.

Will - So when that was the case, when you applied and you're successful, and they said, we want you on board, what was your residence like?

Kate - It was a crew of six people total, and we spent four months in isolation mostly to test these potential future food systems. So for instance, we were looking at the question of, are you going to get bored with your food? And so we had two different food systems that we tried out, like the 'just add water and eat' meals, which is what astronauts on the ISS, the International Space Station eat, or could we make our own meals with preserved material? So preserved ingredients like dehydrated cheese or dehydrated vegetables, flour, and that we would just creatively cook up a new meal, like make a pizza, or make a cake to celebrate a birthday and this like sort of creative food system. Get rid of some of that boredom. So we were really looking at questions of food boredom as the fundamental study, but there were a tonne of other studies that participated in studies that we brought ourselves and also research that other researchers gave to us to be participants in and produce data for.

Will - So what was your preferred meal of choice then?

Kate - I would go down to the kitchen and I would make myself an omelette in the style of Julia Child the French omelette. I would use the somehow delicious powdered eggs. It was actually, these powdered eggs were kind of a miracle, the way that they're made, almost like slow batch dehydration of a mixed up egg. And I would rehydrate that and sprinkle rehydrated cheddar cheese and parsley on top, salt and pepper. I would have Earl Gray tea and finn crisps with a layer of rehydrated butter and a jam. And I loved this meal so much. I would sit there and I would look out the one and only window we had onto the red rocky vista of Mauna Loa, and imagine actually being back on Earth.

Will - It sounds like a genuinely positive experience and something that everyone handled really well. And so I don't want to sow any seeds of doubt here, but I do feel compelled to ask, do you think there is an upper limit? Do you think if you got to, say, a year, you'd be like, 'no, get me out.'

Kate - Well, the HI-SEAS project did increase the amount of time that crews were under isolation. So there was an eight month mission and then a year long mission. And that year long mission did endure a significant difficulty with the personality and crew cohesion, there was some breakdown. So it's kind of unclear if there is an upper limit or what sort of environment could be sort of engineered or designed to maybe increase the amount of time that people are in isolated environments. So in a productive and successful way, but also like how you select the people to do that. I mean, these are actually still open questions that are being looked at. NASA has studied human adaptation in space, and one of the things is humans have evolved to be adaptable to a changing environment. And when you're on a long space mission, you have an environment that more or less stays the same. And there are other ways, other experiences that also create something similar. I think many of us experienced this during the pandemic. While you had some ability to move about, there was a certain sameness to the day. And when you don't have an environment that's changing, that's constantly sort of like asking you to adapt and evolve, like a very serious kind of boredom can set in that maybe is difficult even for the people who think that they don't get bored to identify. And so one thing that is actually really important is to make sure that you can mix up your environment, change things up and find surprises, find those things that challenge you and make you want to change and adapt and grow. Because those are things that, as it is now, space living systems don't offer a tonne of that, but it might be a good idea to have those included in any space mission.

Will - So enrichment might be the key, we should get a coconut with some straw in it for the future astronauts.

Kate - Right? And, you know, like celebrations, like look for ways to break up the calendar. Are you going to celebrate birthdays, half birthdays? What kind of anniversaries do you want to celebrate? And how are you going to celebrate them? What different ways are you going to celebrate them? I mean, if you think of the office party, it's kind of like how you go from one environment to another, but in the same space and with the same people. It's a real shift of energy. Maybe lighting, design, music. We on HI-SEAS had inflatable furniture, so we were able to move our furniture around and reconfigure our environment, and that was pretty important. We had movie nights, that sort of thing. So it's the enrichment. Enrichment in your environment and your activities. And with the Tabasco sauce enrichment in your food.

Space hotel

27:29 - Are we ready for space tourism?

Can those that can pay the toll, take the toll?

Are we ready for space tourism?
Jenifer Millard, Fifth Star Labs

Taking into consideration the healthcare, body clock, and psychological stressors, how much will the impact of space affect what is becoming a race to commercialise space? We have talks of civilian space flights, even space hotels, with the only current constraints on who is eligible to go being the size of the customers wallet. But what impacts will the mercilessly harsh conditions in space have on these endeavours? Astronomer at Fifth Star Labs, and co-host of the Awesome Astronomy podcast, Jeni Millard...

Jeni - I think it's really going to influence the type of adventures the average Joe goes on. Because I feel like for the short jaunt into space, the likes of Blue Origin and New Shepherd where it's an 11 minute flight, it's a parabolic flight, so you're just hopping up and then you're coming back down. You're in microgravity for three to four minutes. I feel like most people can handle that. And I feel like for a couple of days maybe you could cope in space for a couple of days, perhaps, you know, in orbit around the Earth, in a small capsule. But I think it's when we come to the longer journeys where you are maybe on a space station for a few weeks, you are on the surface of the Moon for a couple of weeks, that's then really where we're going to have to start thinking carefully about who can go and do these things. There's going to be physical limitations. I mean, how are people going to cope being on the Moon for more than two weeks and suddenly having two weeks of complete darkness, having no sight of their home planet. I think that might really play with people. And then of course, moving on to Mars. I mean Mars is, let's be honest, probably at least a century into the future, for like the average person to go. With Mars, it'll be seven to nine months to get there. At least three months on the surface because you've got to wait for everything, all the planets to realign to be able to get back. And so, it's a long time to be cooped up with the same people. And so I think it really is going to direct the kind of commercialised space that we see. I think we'll see a focus on the shorter journeys rather than the longer ones.

Will - If we are, as you say, accelerating towards a point where regular schmucks like me can get into space, do you think there may have to be some kind of governing ratifying body that can decide whether or not you are fit and able to do so?

Jeni - I think that there will have to be some kind of generally agreed upon rules, but then I think there are generally agreed upon rules when it comes to putting people on aeroplanes. You know, and while there's no global body that kind of medically tests people, there are these kinds of general rules that then the local health authorities can then enforce and you know, you can go and get your checks and so on like this. And so while I think there's going to have to be some kind of general body that will maybe come up with some general rules, it is going to have to be on an individual basis as well. And I think the psychological side is going to be the most interesting. Because I don't think the psychological side is going to come in too much for the short journeys. When we progress eventually. Not to just go into the Moon for a holiday, but when people are working on the Moon, you can almost imagine maybe they go to the moon for six months and then they come back for six months and then they go again. It's like extreme shift work, something like that. Then we are really going to have to consider all of the psychology there and then we start blurring the lines between commercialisation and professionalism. And I think the way the space sector's going to evolve over the next decades and centuries is going to be really interesting.

Will - And having heard all that you've heard about health, psychology, diet, how long do you think you could last in space?

Jeni - Oh my goodness. What a question. Do you know what, I feel like the little hops into space that you get with Blue Origin or Virgin Galactic? I reckon I could manage that. I reckon I could probably do a couple of days in orbit in a capsule or perhaps a couple of days on a space station. I think beyond that, because I think for a couple of days you're sort of, you'd be so excited, everything is so new and novel and you know, I've just come back from three weeks in the States and it was a lot of travelling. I did seven states in four days on an RV trip and I've been flying here, there and everywhere. And then by the end of those three weeks, I had a fantastic time but you know what, I was done. I was so done. I was like, I just need to go home. So based on that, I feel like I could do a few days, I'd really enjoy it. And then I think after that, that's when the problems might start coming in, be they physical health, be they mental health. That's my personal opinion.


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