Part I of this article, published yesterday, explained how long-term exposure to weightlessness causes some really significant negative effects on astronauts' health, and how creating artificial gravity in space to counteract these problems is a lot more complicated than anyone had counted on. But scientists at MIT have come up with something that just might do the trick. As was discussed in Part I, doing exercise even in micro-gravity has a demonstrated though limited effect of counteracting the negative effects of long-term exposure to weightlessness. And so astronauts work out vigorously for a minimum of two hours a day while they're in space. There is another school of thought that says that the only effective way to deal with the ill effects of long-term exposure to weightlessness is to expose astronauts to artificial gravity as much as possible. But, also, as discussed in part I of this article, that would be heavy, complicated, and expensive.
The MIT scientists are testing out the idea of taking a little from column A and combining it with a little from column B. What if, they asked, you combined a small centrifuge, not much taller than a bed, which they had already been working on, with a piece of exercise equipment, and made it compact enough to fit inside an existing space station module? Could such a combination device split the difference, and end up being the most efficient possible design?
That's exactly what the MIT team has been finding out. They have created and are currently testing a compact human centrifuge with a cycle ergometer (basically an exercise bike fitted with sensors that measure how much and in what ways energy is being expended by the rider) inside it. Test subjects are fitted with a host of sensors that measure blood pressure, heart rate, respiration rate, muscle activity, and the amount of force created by each pedal. The final version will look a bit like a human sized hamster wheel.
So far, the exercise centrifuge has only been tested here on Earth, but the results have certainly been encouraging. If you'e wondering, wait, don't we already have gravity here on Earth? they put the whole device on its side and rigged the test subjects with shock cords to simulate weightlessness. Then the twelve subjects pedaled for 15 minutes at a time, at three different intensities, or levels of resistance, under one of three different levels of artificial gravity: zero G, during which the centrifuge did not rotate; 1 G, measured at, in this system the "lowest" part of the subjects, the feet, during which the centrifuge spun at 28 revolutions per minute (rpm); and 1.4 G, also measured at the feet, during which the centrifuge spun at 32 rpm. They also spent about five minutes of each session speeding up and about five minutes slowing down. "When it spins around," Ana Diaz, a member of the MIT team explains, "we create centrifugal force, which depends on the angular velocity, or how fast we are rotating-the higher the angular velocity, the greater the artificial gravity."
A major concern going into the testing was that such a small centrifuge could cause potentially debilitating dizziness, nausea, and disorientation. But participants filled out surveys after each session to measure their symptoms, and all of them agreed that, aside from mild light-headedness while speeding up and slowing down, subjects experienced very little motion sickness, even when they were spinning at relatively high speeds.
The results of this Earth-based are looking good. Ultimately this device will have to be tested on the ISS, but if it works there, and is able to counteract the ill effects of long term exposure to weightlessness, this will be a very big deal. It will mean that we have cracked the problem, and can get on to solving other obstacles standing in the way of long term human space flight.
Andrew J. Dunlop lives and writes in a little town near Boston. He's interested in space, the Earth, and the way that humans and other species live on it.
