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Reduced Gravity Demonstrator
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SAMPLE EXPERIMENTS
 
The sample experiments shown here illustrate the behavior of fluids, flames, and mechanical systems in microgravity. After each description, a picture of the experiment, followed by its appearance in normal gravity (1g) and then micro-gravity (ug) are given.

Weightlessness

The weight (W) of a body of mass (m) in a gravitational field of strength (g) is given by W=mg. In microgravity, g is virtually eliminated and therefore the weight of the body is also eliminated. To demonstrate this principle, a mass on a scale is dropped. The two counterbalancing forces in this experiment are (1) the gravitational force acting on the mass and (2) the force of the spring in the scale. During the drop, g tends towards zero and the restoring spring force pushes the indicator from the original weight of the body toward zero. Shown in figure 3.

     
postage scale - normal gravity  

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Fig. 3. - Weightlessness (normal gravity shown in the image on the left and microgravity is shown in the video on the right).


Fluid Interface

The fluid interface experiment highlights the role of surface tension in the absence of gravity. In 1g, the effect of surface tension is evident only near the container walls and most of the surface looks flat. In reduced gravity, surface tension leads the liquid to assume a very different shape. Specifically, the liquid creeps up the walls of the container by capillary forces; this is most evident in the corners. Given enough ug time, the liquid would wet the walls of the vessel, leaving a bubble of air in the center. Shown in figure 4.

 
red cappilary normal gravity  

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Fig. 4. - Fluid Interface (normal gravity shown in the image on the left and microgravity shown in the video on the right).


Candle Flame

The candle flame experiment demonstrates the effect of buoyant convection and its absence on combustion phenomena. In normal gravity (1g), the combustion gases are much hotter, and thus lighter than the surrounding air. Buoyancy causes the hotter, less dense combustion gases to rise, giving the candle flame its vertically-elongated, conical shape. However, during the drop experiment, the hot gas expands in all directions. As a result, the flame becomes shorter and wider. In longer periods of reduced gravity, the flame becomes spherical and entirely blue. This was observed in a candle flame experiment performed on the Space Shuttle (USML-1/STS-50, June-July, 1992). Shown in figure 5.

 
candle flame - normal gravity  

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Fig. 5. - Candle Flame (normal gravity is shown in the image on the left and microgravity is shown in the video on the right).


Magnetic Repulsion

Two magnets are oriented with like polarities opposing one another (i.e., N-N or S-S). The lower magnet is fixed to the experiment platform while the upper magnet is freely supported on a lever arm. In 1g, the upper magnet is levitated by the magnetic repulsive force which is balanced by the gravitational force pulling the upper magnet downward. During the drop, the magnetic repulsion becomes dominant and the upper magnet moves rapidly away from the lower magnets. Shown in figure 6.

 
hinged magnet - normal gravity  

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Fig. 6. - Magnetic Repulsion (normal gravity is shown in the image on the left and microgravity is shown in the video on the right).
   
   
Demonstrator Description
Sample Experiments
What is Microgravity?
NASA's Microgravity Facilities
Microgravity References
 
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