Neutral Buoyancy Lab
Published on Jan 12, 2009 at 6:56 am.
1 Comment.
Filed under NASA.
The pressure chamber that I wrote about in my last posting is at the Sonny Carter Training Center, home to NASA’s Neutral Buoyancy Lab. The NBL is the latest of NASA’s attempts to simulate the weightlessness of space using water immersion. In the early days of spaceflight, nobody knew what to expect during weightlessness. Astronauts soon found that they could rather quickly adapt to the weightless environment while seated in their capsule. However, the Mercury astronauts were strapped into their seats inside a tiny capsule. During the Gemini program, astronauts began to do spacewalks outside their spacecraft. That is where the problems began. They soon found that even the simplest tasks on Earth became very complex in the weightlessness of space. So, they obviously needed to train for doing those tasks in space. The only problem is that what made those tasks so much tougher to do in space was that the astronauts didn’t have the weight that they do on Earth. They obviously have the same mass, of course, but not the weight. Gravity did not pull them down, so there is no friction between them and the ground, so they did not have the leverage in space that they do while standing on the ground. When they try to turn a wrench, they tend to turn in the opposite direction to what they are trying to turn the wrench. Clearly, the astronauts had to be trained to perform tasks in space. But, the only problem is that when on Earth, gravity does pull down on the astronauts, so they don’t have the same experience as in weightlessness.
So, NASA came up with two solutions to the problem. The best one was the reduced gravity aircraft, in which the aircraft executes a maneuver that provides a short period of time of weightlessness. Unfortunately, this period of weightlessness lasts only a few seconds. The aircraft could keep up weightlessness for only a minute or so, but seldom more than 30 seconds, for safety purposes. That gives a true feeling of weightlessness, but it is very short. But, there is another environment that is analogous to weightlessness, and that is being underwater.
So, NASA built a large swimming pool in which astronauts wearing weighted spacesuits could float as if they were in space. This gave invaluable insight into how to maneuver in space, and this sort of training has been going on ever since. Reportedly, astronauts train for over 10 hours in the tank for every hour of spacewalk.
The term neutral buoyancy comes from the fact that the astronauts in their suits are precisely weighted so that the water buoyancy exactly equals their weight. That means that they float wherever they are in the water. That is sort of like in space. Now, it is not exactly like in space. After all, there really is gravity pulling on them in the water. If one end of the suit is heavier than the other, then gravity will exert a torque turning the heavy end down. Also, while the suit with the astronaut in it may float in the water like it is weightless, the astronaut inside the suit is not in a weightless environment. They will tend to be pulled towards the downward side of the suit. If they are floating upside down, they feel like they are upside down, with the blood running to their heads. Also, if they drop a tool, the tool will sink to the bottom of the pool if it is denser than water or float to the top of the pool if it is less dense than water. Still, it gives a good analog to weightlessness that lasts much longer than the few seconds aboard the aircraft. But, the Space Shuttle and plans for an orbiting space station required a much larger water tank than existed at the Johnson Space Center. So
MJ on January 13, 2009 at 7:11 pm: 1
Way to go Ray! So glad you made a successful trip on the Vomit Comet!