What
is "Neutral Buoyancy"?
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| | Small
flotation devices strapped to an astronaut's ankles help
to simulate microgravity as he practices a spacewalk in
the pool. |
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"Neutral
buoyancy" is a term used to describe something that has an
equal tendency to float as it does to sink. This effect is accomplished
with a combination of weights and flotation devices.
Articles that
are configured to be neutrally buoyant 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 Neutral Buoyancy Lab, or 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, which 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 in space and some things more difficult. Both effects
are unlike the conditions of space and must be recognized during
spacewalk training. However, even with these limitations, neutral
buoyancy is currently the best available method for long-duration
spacewalk training.
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