Lately space science has made a slightly disturbing discovery. Space travel makes you go blind. Really.
It’s a bit of a surprise, given that in other ways science has found solutions for most of the biomedical problems of free fall and, along the way, learned an awful lot about osteoporosis, which is a spinoff of incalculable benefit. The eyesight thing is also kind of ironic given that back before the space age began, when there was no experience of how humans might behave in free fall, aero-medical specialists had all kinds of worries about what might happen.
The fears of 1950s doctors were manifest. Maybe heart function would disrupt. Who knew? They didn’t even know whether humans could eat or drink in absence of being pulled down by gravity. One outcome was that aircraft were sent off on special parabolic trajectories, snatching a few seconds of free-fall at a time, during which hapless test subjects gulped down ‘space food’ in an effort to find out whether anything could be swallowed in free-fall (and usually threw them straight back up because these flights were a fast way to make people airsick – there are reasons why they were called ‘vomit comets’).
The good news? It turned out that swallowing is a muscular process, and this was already known – it’s called peristalsis, and yes, humans can swallow even if upside down (but don’t try this at home, folks).
There were still dire bio-medical predictions that, well, maybe you could survive a few minutes or hours. But what about two or three days? Or three or four? Or fourteen – the time required for a lunar flight. All this had to be proven step-wise, on both sides of the Iron Curtain, by sending men up on flights which – from this perspective – were as much bio-medical research as anything else. One of the more heroic was Gemini VII – in which Jim Lovell and Frank Borman spent fourteen days orbiting Earth with about as much space between them as the front seats of a Volkswagen Beetle. That was their living room, bedroom, dining room, kitchen and, inevitably toilet. Waste liquids were ejected into space in a spray of liquid that froze and caught the sun (‘urion’, quipped Wally Schirra, on another mission), while solids were bagged and stored. As you can imagine, this meant that by about Day 4 or 5 they were living inside what amounted to a commode.
That research continues today. One of the main functions of the International Space Station is as a test lab for studying prolonged free-fall exposure – something that has had huge direct outcomes in, as I say, understanding how osteoporosis works and how to alleviate it.
The thing is that, while we know that humans won’t die even after months or a year in free fall, there’s one major gotcha that nobody thought of in the early days and which exercise can’t fix.
Free-fall makes you functionally short-sighted, often to an absurd degree.
Here’s how it works. Our systems evolved in gravity, meaning that they’re optimised to expect body fluids to be pulled downwards. Everything (such as one-way flapper valves in the main leg arteries) is optimised on the basis of a one-way pull – down. But that doesn’t happen in free fall, and the result is that astronauts end up with fluids accumulating in the upper body – hence the slightly puffy look many astronauts gain after even a short time in space.
The problem is that this fluid accumulation also occurs internally, behind the eye, and over time it flattens the eyeball – destroying clarity of vision by affecting focal length. Eyesight on some astronauts has dropped from 20/20 down to levels approaching the US definition of legal blindness (20/100 on the eye chart) in one case. Furthermore, although this alleviates on return to Earth, it doesn’t entirely reverse and some astronauts have been left with permanent visual impairment.
What this implies is that astronauts might arrive around Mars after an eight-month Hohmann-orbit transfer (the practical one with today’s tech) with eyesight so degraded they can’t even read their instruments. And that’s a worry. The only real answer is to provide artificial gravity – for example, by spinning the spacecraft – which is another hurdle because it requires specific equipment that adds mass and complexity.
My take is that we need better propulsion systems. Something that can lob a spacecraft to Mars in a month or less, for instance. That’s going to mean some fairly esoteric tech – I’m thinking not just VASIMIR-type enhanced electric drives but maybe even something more capable, like a nuclear-fluorescent system. Whatever we use, it’ll have to be reliable, because at the velocities that implies, you’d be on a one-way trip out of the solar system if you couldn’t fire the motor for a braking burn. The problem, as always, would be the cost – literally astronomical – and then maintaining funding for such a project over the generation or more it might take to bring it to reality.
Copyright © Matthew Wright 2018