
Electrostatic
Levitator
Project
Abstract
The electrostatic levitator senior design
project objective is to develop an apparatus for continuing research of
fluid viscosity in microgravity. The measurement of transport properties,
specifically viscosity, near the critical point of a fluid is required
to test our understanding of the unified theory of second order phase transitions.
Viscosity can be calculated by spinning the levitated sphere in a fluid
of interest and measuring the rate of decay of the angular velocity as
it spins down. Levitation isolates the sphere from external forces
which would interfere with the precise measurement of viscosity.
Team ZeroG is developing a levitator which
utilizes high voltages applied to two electrodes to generate an electrostatic
field that imparts a force on a charged sphere in the electric field.
The sphere is capacitively charged at launching; a negative charge is induced
on the sphere’s surface by the attraction of electrons to the positively
charged top electrode. The current electrode configuration is designed
to operate in one earth gravity, with a passive centering force in the
radial direction. As described by Earnshaw’s Theorem, an electrostatic
field cannot create a three dimensional potential well, therefore, this
apparatus requires an active control system that varies the potential difference
between the electrodes to attain stable levitation.
