Can Humans Survive in Space Long Term?

Astronauts lend insight into the feasibility of humans becoming a space-faring species.

We are getting closer to sending humans on extended trips into space. SpaceX is planning on sending the first humans to Mars in 2024 and we will likely soon set our sights for destinations further than that. But can the human body withstand much time in space? Den of Geek recently had the opportunity to interview two of the U.S. astronauts who have spent the most time in space and ask them about the feasibility of humans becoming a space-faring species.Former Astronaut Scott Kelly spent 340 consecutive days in space. The longest time any U.S. astronaut has spent in space during a single mission. The nearly year-long trip was his fourth mission, making it 520 cumulative days Kelly has spent in space. No doubt, he is uniquely suited to answer questions about the viability of humans becoming a space-faring species.In a recent exclusive Den of Geek interview with Kelly at a science advocacy event held by 3M, we asked whether long space flights are realistic. 

“If we are talking about Mars, as an example, whether we go back to the Moon or not first, Mars is the next logical step as a species leaving the Earth,” Kelly said. “I think we have a lot of the technology we need to do that mission. I think over the course of the life of the space station we have learned a lot about humans living and working in space.”

Given that it is possible to send people to Mars, and organizations such as SpaceX seek to be ready to send humans there within the next 20 years, We asked if he felt the physical effects of the trip would be too severe.“Here is the deal with that,” Kelly explained. “I was in space for 340 days, and when I got back, I didn’t feel great. But if I had to perform a certain function, I would have been able to do it. I wouldn’t have been happy, but I would have been capable.”One thing it is important to remember at this point is that Kelly was also a fighter pilot in the Navy. He is used to taking his body to the extreme, and no doubt he did just that with his year in space.Kelly has written a book titled Endurance: A Year in Space, A Lifetime of Discovery. The Sydney Morning Herald posted an excerpt from the book titled, “Astronaut Scott Kelly on the devastating effects of a year in space.”In the excerpt, Kelly describes his difficulty having dinner with his family within 48 hours of returning to Earth. He had to leave dinner early and struggled to walk back to his room to lie down.“Every part of my body hurts,” Kelly described in the book. “All my joints and all of my muscles are protesting the crushing pressure of gravity.”Later in the excerpt he describes, “I spent 159 days on the ISS in 2010-11. I had a reaction to coming back from space that time, but it was nothing like this.”That night, Kelly woke up feeling feverish. As he struggled to stand up and go to the bathroom, he says he felt “as though all the blood in my body is rushing to my legs, like the sensation of the blood rushing to your head when you do a handstand, but in reverse.”When he got to the bathroom and flipped on the lights, he looked down and found his legs swollen. He described them as “alien stumps, not legs at all.” His fiancé, Amiko, came to help him and said she felt around and could not feel his ankle bones at all. As she squeezed, Kelly says his leg squished “like a water balloon.”He also had a rash that inflamed his skin.These extreme effects are what he had to endure when he got back to Earth. Imagine having to deal with a situation like this on Mars. But all is not lost for those looking forward to future Martian vacations. Kelly went on to explain a Mars mission would be much different than what he experienced after his year in space.“Going to Mars is going to take about 200 days,” Kelly explained. “There was a big difference between when I flew 159 days and 340 days. It didn’t seem linear. It seemed like a little bit of an asymptotic change in how I felt. So going to Mars is 200 days and you are on the surface of Mars for maybe a year, so you are operating in a lesser gravitational field.”Kelly concluded, “I think you can function after being in space for that long and going to Mars is not going to be as long. It’ll be shorter.”He admits, longer trips will prove to be a much more significant challenge in the future.“I think if someday we want to go to the moons of Jupiter or Saturn, that’s when we have to consider artificial gravity because when you get there, you are going to be a ball of jello,“ Kelly says.Peggy Whitson is the U.S. astronaut who currently holds the record for the most cumulative days in space. During three missions she spent over 150 days in space on each, the last was 289. National Geographic Channel’s series One Strange Rock looked at her last mission on their season finale.“I definitely think it’s feasible to do it, to live in space,” she told Den of Geek. “For long periods of time it’s not without risk, but it’s definitely feasible to do it. And I think that there are exploration reasons that make the risks worthwhile. So, I’m a big supporter.”She admits there is a lot to figure out and she says physical changes her bones went through from her time in space may still be affecting her.“We have a better understanding how to maintain bone density, but the devil’s in the details,” Whitson explained. “We’re still trying to figure the mechanisms for those changes and if the bone quality that we maintain from our exercise [in space is] the same as it would have been if we hadn’t been in space.”“So, that means, maybe, even though I might have maintained my bone density, the bone quality might not be as good,” Whitson continued. “And I might still be more susceptible to fractures. So, there’s still research going on to find these answers and to look at other drugs that might help us better prevent the loss in the first place.”Whitson also points out that there are physical effects caused by space travel that might take some time to understand.“I think there’s gonna be others [such as] radiation effects that we’re not going to understand necessarily because of the small subject population that we’re talking about, only a few hundred astronauts,” says Whitson. “It’s going to be hard to determine what was caused by being in space versus, you know, just a person’s genetics.”However, she is confident ongoing research will find answers and that the research will benefit more than just space travelers.“Anything that gets developed up there and tested up there has applications here on earth for us, [Earthbound] folks as well. So, it’s part of the process of learning more about what the risks are about being in space.”

Illustration by Samantha Güt.