A while ago, I asked on Twitter what people would like me to blog about. One person (you know who you are) said: the effect of space travel on human beings. I promised that I would write about it, but that I wanted to read one more book before I did so. That book is Packing for Mars by Mary Roach. I have now read it (highly recommended), so here we go: the effect of space travel on human beings, with an eye on the future and the science fiction writer.
As one might expect, there are two types of effects long-term space travel has on human beings: physiological and psychological effects. Each of these effects mentioned below is probably worthy of a separate blog post, but let’s start with the overall first.
The physiological effects themselves can be split into two sections: lack of gravity and what I shall call external threats.
External threats are simple: accidents and radiation. Both are managed at the space ship design level and crew training stages. Good design will limit radiation exposure. The risk is solar flares, but it is a known and theoretically manageable risk. Manned missions to—say—Mars will contain shielding (best material: water, since the ship will have to carry plenty of that anyway). There will be advanced warning for the crew to take shelter in a fortified part of the craft. Accidents are obviously less predictable, and can be expected to be serious and fatal. Space travel is not without risk. Nor is getting into a car.
By far the most serious and insidious effect of space travel on human beings is the bevy of problems caused by the lack of gravity. We have evolved to live with gravity. On the short term, its absence causes disorientation and nausea. Individuals vary in their responses to weightlessness and astronaut training famously involves weeding out those most seriously affected. People with abnormalities to the inner ear may be completely unaffected, but having a deaf crew member could pose challenges of its own. It’s interesting to note that all mammals can be made to suffer from motion sickness, except rabbits and guinea-pigs (thanks to Mary Roach for that tidbit of information).
Other short-term effects of the absence of gravity are the loss of taste and appetite, the disruption of the digestive system, the pooling of blood in the upper body and the inability to sleep. Most of these effects will disappear, or at least become less prominent, after a few days as the body adjusts.
Far more serious is the loss of bone and muscle mass. Exercise helps, but doesn’t completely prevent the decrease of bone density in long-term space-travellers. And that loss can be significant, comparable with that suffered by a sufferer of extreme osteoporosis.
That said, there is a fairly simple solution: artificial gravity through rotation. At the moment, it is beyond the engineering limits of current missions, but once people overcome problems associated with sending manned missions to Mars or further, giving the inhabited section of a ship or station a constant rotation should not be too hard.
The psychological effects of space travel are associated with the fact that you’re isolated in a tin can, a long way from anywhere, with people who, like partners in a stifling marriage, start to irritate you more and more.
This makes psychological screening important. The first chapter of Packing for Mars describes seemingly inane tests done by the Japanese Space Agency (JAXA) in order to select possible astronauts, and unravels some reasons for these tests. Most importantly: how do you react to boredom? How do you react when something unexpected happens? There are huge differences between people, and in an isolated group of people, these differences may make or break a mission.
An obvious partial remedy is to send larger missions in larger ships. The lack of privacy and the inability to get away from each other conspire to make any inter-personal problems worse. The human being is a curious type of herd animal. We want to be close, but not too close to each other. It seems that a larger mission will be the answer in the long term.