The Human Body in Space

When you think about the true cost of space exploration, what do you think of? Maybe you think about the Challenger accident, or maybe you think about the Columbia disaster. Anything with a space shuttle blowing up really. Perhaps the numerous failed tests of the Apollo Missions that tend to go unnoticed in the grand scheme of things? These incidents are spectacular. They are explosive. They are heart-breaking. That’s why we remember them. But what about the more subtle cost of spaceflight and exploration? The cost of being in an environment we simply did not evolve to live in?

In a way it’s a tad surprising. For one, it’s not like space has a lot going on. There is quite literally nothing for most of it. And, yet space makes its presence felt to your body the moment you leave the nourishing confines of our own planet. So, what really happens to our bodies in space?

Well, to answer that question, let’s plan out a mission. To a planet. Any planet. Forget about the return journey. Let’s just consider the one-way trip for now. Based on the technology we have now that would take, let’s say, around a minimum of 10 months. So let’s get to the launch pad and blast off.

Lift off is the very first thing you feel in your space journey, and it’s not to be taken lightly. During a rocket launch, astronauts will ‘only’ experience around 3 g’s. I say only because while 3 times the force of gravity on your body is certainly not pleasant, most of us can handle it, certainly with some training. Some roller coasters can actually hit G-forces up to double that.

As the thrill ride slowly calms down, you stop being pushed into your seat and instead start being freed from it. The effect of weightlessness is perhaps the second visceral indication that you are in space. But now that the weight is literally off your shoulders, you have something else to worry about. You see, as strenuous as it may feel sometimes, our bodies need the force of gravity to remain healthy. Our bone density and muscle mass depend a lot on the daily loads of gravity. The daily wear and tear are reminders to our bodies that we need to maintain our sturdy frame with all its muscle. It’s essential for our survival. But up in space where you could basically lift anything without breaking a sweat, not so much. The closest thing you and I have felt here on earth is prolonged periods of bed rest.

Remember how even standing up and getting out of bed feels like a struggle after sleeping for way too long? In space, at least for now, it’s not so much that the astronauts are lying down and doing nothing, it’s quite the opposite actually. What’s different is that their frames are not under any stress most of the time, and as a result their bodies simply get rid of the ‘excess’ weight that doesn’t need to be carried around. This has meant that astronauts in the ISS have experienced bone density loss of around 1-2% a month, which may not sound like much before you put it into perspective. In comparison, the elderly lose bone density of around 1-2% not in a month, but in a year. Scientists have been trying to combat this, of course. They are doing this by creating exercise machines that replicate the resistance we feel here on earth. And for astronauts in the ISS, exercise is as important as any of their responsibilities as astronauts. It is paramount to the long-term wellbeing of the crew. But let’s continue with our journey.

A few hours after weightlessness sets in, you start to realize your head feels all stuffed. This is because the heart evolved to pump blood against the force of gravity, and without that force, the heart is suddenly pumping more blood to your head than necessary.

The effect is somewhat similar to having an allergic reaction, but not just in your nose, in your entire head. Your brain will actually swell up and the combined swelling in all of your face can lead to structural changes in your eyes, often leading to vision problems. If you’ve ever seen an astronaut, notice how most of them have poor vision.

If all that work on board does manage to tire you, it’s bad news. You see, sleep in space is not nearly as refreshing as it is on earth. We spend an entire day standing up against the force of gravity. So, when we lie down, we can finally relax to the withdrawal of resistance. That’s what makes sleeping so nice. In space, however, there is no real difference between lying down and standing up because there is no fluid shift inside your body, nor is there any change in the vestibular system that works with the rest of your body to tell you that you’re lying down. Basically, your brain doesn’t get that same relief you’d be getting on the surface of earth. In addition to that, our circadian rhythm, or sleep cycle, is messed up because there is no regular exposure to sunlight or darkness that would orient our sleep-wake cycle. Astronauts on board the ISS have to deal with the sun coming up every 90 minutes. On longer missions, depending on where you are as part of your mission, it could either be always sunny or always dark, and we can’t really be sure of the effects that will have on humans long term.

Since your heart doesn’t have to work as hard as it used to, your cardiovascular health declines. That’s why a lot of astronauts return from their mission with low blood pressure. Speaking of weak hearts, however, a mission to Mars is a long, long journey. Away from people, away from home, away from anything familiar. Beyond 300,000 km/s, even at light speed, communication will be delayed, and that delay will only get longer as you go along, driving home the message that you are just one lonely small human in the unending darkness of space. Psychology is an often under-rated aspect. Not just in space missions, but in reality in general. And in high-stakes missions like the ones astronauts go on, the inclination to leave out mental health to the latter pages of the agenda seems only human.

Yet, as our journeys become longer and longer, this has become more and more of a concern. To test this exact concern out, a few brave scientists self-isolated on a remote site in Hawaii for an entire year in 2016. And according to them, the most challenging aspect wasn’t acquiring food or water, it wasn’t their sleeping situation, it was the monotony, being in the same place, with the same people, eating the same thing. All day, every day. Overlooking the mental implications that something like that causes is pretty much setting yourself up for disaster from the start.

Speaking of disaster, after the Columbia disaster in 2003, one of the first things that was done was to let the astronauts aboard the ISS know that their fellow astronauts did not survive the journey. In those weeks, all on board were mandated to check in with a psychiatrist. The stresses of being up in space are almost entirely physical. But the mental stress is perhaps just as big of a puzzle piece in the next chapter of human exploration. The path to exploration is a solitary one. 

But this data has all been derived from experiments conducted on scientists aboard the ISS. And as far as that is, the ISS still enjoys a lot of the protections of earth. Things like the magnetic shielding that protects us from almost all of the sun’s harmful radiation. Beyond a certain portion, we will have none of that protection, and as such, radiation is perhaps one of the things we are least prepared for. 

While the muscle atrophy can be countered by a rigorous exercise regiment, we have very few answers as yet to the radiation problem and the effects it has on the human body. One of the many effects this has had is DNA damage. Perhaps one of the more intriguing effects has been the lengthening of telomeres. Telomeres are structures at the end of a chromosome that help it divide. As we age, our telomeres shorten and lead to more mistakes during division. This causes further complications in our body as we get older. This is something we’ve actually studied on astronaut Scott Kelly, who as many know spent nearly an entire year aboard the ISS, and has spent over 520 days in space during his lifetime.

Surprisingly, Scott’s telomeres actually lengthened with the passage of time on the ISS. Now before you start planning your trip to space for your anti-aging therapy, it was temporary, as they slowly shrunk back to baseline levels soon after he came back to earth. Beyond that, the exposure to all that radiation increases the likelihood of astronauts to develop cancer. To add to the anti-aging effects of space, astronauts also experience an increased production of collagen, a protein that provides skin structure and prevents wrinkling. Again, this is not the type of anti-aging treatment you want to be going for, because while yes, their skin produces more collagen, it actually thins out more than before, actually leaving you with less protection. 

You also grow taller in space. Not by too much, about 2 to 3 inches, but it’s enough that your suit has to be built with the expansion in mind. This may be obvious by now considering how much we have talked about gravity and what its absence does to us, but the routine exertions of the day, like walking, grabbing something out of a cabinet, sitting and standing, and really any other movements actually help compress your spine and keep it in the shape that it's meant to be in. A sudden lack of that force can, over time, develop into back problems, making walking very difficult and even painful. You don’t even get to keep the couple of inches, you lose it all when you come back to the confines of gravity.

Despite all of this, most of these changes take place over a reasonably long period of time. That allows the body to adjust to it as well as it can. But what about the changes our bodies just cannot adapt to? What about the ones that are just too quick? What would happen, say, if you were to be left out there with no suit? Your body is given no time to react, is this the end?

Well, for one, the truth is both less spectacular and less dramatic. You don’t explode like the movies would want you to believe. You still die, don’t get me wrong. But you just won’t explode to death if that’s what you had in mind. You see, without a suit to maintain the air pressure that we need, any and all air left in our respiratory system will expand quickly in a dire need to equalize with its surroundings, which in the middle of outer space, is basically nothing. This means if you know you are going to be in space without a suit, just let go of your breath. You are actually better off that way. The absence of pressure will also turn the liquids in your body to gases. But again, your skin is elastic enough that it won’t cause you to explode. 

The temperature aspect is also something that is misrepresented. While it is true that the temperatures in space are capable of being extreme in certain situations, without an atmosphere, heat just won't transfer fast enough to kill you either by burning or by freezing. You will eventually freeze, as any and all leftover heat from your body will eventually radiate away. Next… well there isn’t a next. That’s about 60 seconds. You’re passed out, and for all intents and purposes, you’re gone forever. It’s not all bad though. Despite all the things that will happen to you, at least it will be over soon.

So much remains to be known. The longest someone has spent in space is 437 days, a little over 14 months straight. Now, not to understate the magnitude of the achievement, it was still done on the ISS with some of the protections that we won’t have on longer missions. The most comprehensive experiment on the influence of space on our bodies so far conducted has been the NASA twin study experiment, where 2 astronaut twins were the subject of a prolonged study. One of the twins sitting here on earth acting as a control, the other serving in the longest mission on the ISS any American has ever served. It’s a one-of-a-kind study, but that’s a remarkably small sample size. The subjects of this particular study were astronauts Mark and Scott Kelly who I mentioned earlier. Yes, there’s two of them.

What is to say the twins, astronauts Mark and Scott Kelly weren’t just naturally predisposed towards developing better mutations for space travel? We still don’t know enough on how our bodies react to the fractional gravity on Mars or the moon. The gravity on these planets is not as strong as that of the earth. However, they are there. And so, on the occasion that the relationship between gravity and the side-effects of being without it may not be linear. Meaning, it doesn't exactly mean that only having half the gravity makes it half as “good” for our human bodies.

Despite all of these risks and side-effects, including that of a reduced life-expectancy, most of an astronaut’s life returns to ‘normal’ after a long enough period of time on earth. The real question is, what would happen if they simply never returned? What would ‘normal’ look like then?

The harshness of space travel comes not from the things that exist out there, but from the things that don’t. Things like an atmosphere, gravity, and so on. These are things we take for granted everyday. We’ll probably never really know how truly important they are, until they’re no longer around.

- MA, MM