Learning to Take the Weight off your Feet
In dreams we sometimes fly above imaginary landscapes, floating as if weightless in a sleepy sea. Is this what it's like to be in space?
Nearly 500 or so people have been into space, not including the 150 or so who have been buried in orbit, their ashes released from a rocket. So, unless you count the Vomit Comet or bad turbulence at 35,000 feet during a long-haul flight, there’s not many people alive who can truly tell you what its like to be weightless. And that’s a problem if you are training astronauts for mission critical spacewalks and you need to have them experience weightlessness for extended periods of time.
The solution, quite literally, is water. The nearest approximation to being weightless in space is to float with what's called neutral buoyancy, a state of perfect balance where you add weights to your diving or space suit so that you neither sink nor float. With a little practice you can tune your buoyancy so perfectly that you can go up or down just by breathing in and out. The change in the volume of your lungs is enough to disturb the equilibrium of floatation and the minute effort of breathing is all you need to control your underwater flight.
Once I was lucky enough to scuba dive in the Gulf of Mexico, with two miles of water below. Usually, unless someone spills a lot of oil, the Gulf has the crystal waters of the open ocean. Such clarity completes the illusion of being in space and there's a uniform quality of light. Often I had to check my depth gauge and the direction my bubbles to determine which way was up. These are just the conditions created in a giant training pool for astronauts such as the one in the Neutral Buoyancy Laboratory (NBL) in the Johnson Space Center, Houston, Texas.
The NBL pool contains over six million gallons of water. That's a mini lake and it took a month to fill (presumably from a normal sized tap!) when it was made. It's big enough to fit simulations of the cargo bay of space shuttles or the Hubbel telescope so that the aquanauts can try out the same maintenance and repair work they will do as astronauts in space. The giant pool is also filtered so well that it cycles its entire volume through the filters in just 19 hours, hence it has the clarity to trick the mind that you really are floating in the abyss. It's not exactly like space because there's some drag from the water and Earth's relentless gravity will still accentuate downward movement compared to zero-G. But the astronauts say that its about as good as it gets to the real thing.
By the way, if you want to give it a try you can pay for a trip to a similar facility in Star City, Russia. Or if that's not practical, James Cameron's film, The Abyss, gives a feel for the giant pool environment too. It was made in the seven million gallon containment tank of an unfinished nuclear power station.