Research on ISS has found that prolonged spaceflight causes vision problems and might even damage the human eye.


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Research on ISS has found that prolonged spaceflight causes vision problems and might even damage the human eye.

There had been hints of this discovery in an earlier report, but today’s paper is the first published science on the subject.

The results are not only important for finding out the medical challenges of weightlessness. They illustrate once again the need to do long extended flights on ISS. Without that research we are never going to be able to fly humans to other planets.

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7 comments

  • Paul

    Why don’t we just spin the craft? I know that would take some engineering, might be expensive, but I haven’t heard one person suggest it since a space odyssey… seems like the obvious solution to a lot of space medical issues.

  • Paul,

    The engineering involved is beyond our capabilities at this moment. The Soviets tried spinning during an eighteen day Soyuz mission in the early 1970s, and found that if the spacecraft is small, like a Soyuz, the spin causes more problems than it solves. The cosmonaut in question had serious balance problems once he returned to Earth. Thus, the rotation has to have large circumference, requiring a larger space vessel that at this time is too heavy and therefore too expensive or difficult to get into orbit.

    Eventually I think we’ll do it, but not for a good number of decades. The first humans to go to Mars will likely go in weightlessness.

  • Patrick Ritchie

    Unfortunately the ISS isn’t designed to spin. But I do believe you are on the right track, we know migrogravity is harmful to the human body, what we don’t know is how much gravity we need to solve the issues.

    LEO is a great place to do partial gravity research, the ISS is reasonably well equipped to perform this research. There was even a planned centrifuge module:

    http://en.wikipedia.org/wiki/Centrifuge_Accommodations_Module

    It was unfortunately cancelled and the only near term partial gravity research I am aware of is an experiment to be performed in a nanorack.

    Bob: do you have any details on the Soyuz flight? I’m also curious of your assertion that the engineering is beyond our capabilities, what are you basing this on?

  • The Soyuz mission was launched June 1, 1970 and set a new record for the longest spaceflight, for that time. To quote from page 89 of my Chronological Encyclopedia of Discoveries in Space,

    Soyuz 9 was devoted to medical science to see how the human body was affected by the environment of space. The most significant discovery on this flight was the apparent negative consequences on the human body caused by spin stabilization. … This spin created centrifugal force inside the spacecraft, a kind of artificial gravity. The force, however existed in differing amounts, depending on position and location. This caused the cosmonauts some motion sickness, and when they returned to earth they were surprisingly debilitated. … Nikolayev and Sevastyanov could not stand after landing, despite the much larger size of the Soyuz spacecraft and scheduled daily exercise periods during the entire flight. Both commented that the earth’s gravity felt instead like they were under several g’s of force, and it took both men ten days before their bodies returned to normal.

  • Patrick Ritchie

    Having a very hard time finding more information about Soyuz 9. But are you referring to the flat spin that all soyuz craft use when in free flight?

    If the spin rate is the same as the one used now that would be 2 rpm. Given a 3-4m radius that gives a centripetal force of ~0.01g.

    2 rpm is about the limit before the Coriolis effect starts making things uncomfortable. If they spun Soyuz 9 faster than that then I would expect dizziness, nausea & disorientation to start kicking in. Given the size of the Soyuz you’re probably not going to get enough centripetal force to be worthwhile before the Coriolis effect makes things unbearable. And as you mentioned the small space means different parts of your body are experiencing different centripetal forces, adding to the disorientation.

    But what if we use a larger structure? If we use the ISS as an upper bound of what current engineering could accomplish we get a radius of 54m. That gives us about 1/4. Is that enough to counter the negative effects of micro-gravity? Maybe, maybe not — but it’s most certainly within our current engineering capability.

    References:

    http://www.artificial-gravity.com/sw/SpinCalc/SpinCalc.htm

  • Patrick Ritchie

    Whoops, got the rpm wrong on the current Soyuz. The current flat spin is 0.5 rpm for 0.001g… the same argument still applies to faster spin rates than 2 rpm though.

  • The spin they used on Soyuz 9 was called spin stabilization, which from my notes suggests it was similar to the “barbeque” mode used on the Apollo capsules, with the capsule rotating along its axis. I don’t have any data on the actual spin rate unfortunately.

    We could certainly spin ISS, but the structure was not designed for that spin, which will cause innumerable problems. For example, the solar panels need to be oriented to the sun, which limits how you can spin the structure. Then there is the interior, which was designed for weightlessness. If you add gravity some parts of the interior will become difficult to use. There is also the fuel question: ISS doesn’t have the fuel or the right kinds of engines for this.

    This is the crux of the problem. If you spin a space vessel to obtain artificial gravity you really need to design and build it with that in mind. And that is much easier said then done, at this stage of our space engineering knowledge. At the moment we are still learning how to build a vessel simply capable of keeping people alive for years. Adding the engineering of a spinning spacecraft makes that research task much harder.

    Don’t get me wrong. I am all for doing this. I just think it ain’t practical at this time.

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