NASA - National Aeronautics and Space Administration

What is Neutral Buoyancy?
Neutral Buoyancy
Neutral buoyancy is the term used to describe something that has an equal tendency to float as it does sink. Articles that are configured to be neutrally buoyant (which is accomplished with a combination of weights and flotation devices) seem to "hover" under water and large, neutrally buoyant items can be easily manipulated much like in orbit. However, there are two important differences. First, a suited astronaut in the NBL is not truly weightless; while it is true the suit/astronaut combination is neutrally buoyant, the astronauts feel their weight while in the suit (they are lying or standing in the suit depending on its orientation; that is one reason why suit fit is so critical). Second, water drag acts to hinder motion; this makes some things easier to do in the NBL than on orbit and some things more difficult. Both effects are unlike the conditions of space and must be recognized during EVA training. However, even with these limitations, neutral buoyancy is currently the best available method for EVA training.

Sonny Carter Training Facility - Neutral Buoyancy Laboratory
Johnson Space Center
Houston, Texas

Public tours of the NBL are available through Space Center Houston

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Last Updated: May 30, 2012