How the human body handles space travel

“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.