1503. Spacecraft Dynamic Balance With Boundary Layer Control
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Paper
Abstract
Aerodynamic loads can cause problems in the dynamic balance of large diameter spacecraft.
The problems include.
* Asymmetric loads cause systematic errors.
* The steady aerodynamic load limits the spin rate.
* Fluctuating aerodynamic loads increase the noise.
A method of controlling the air velocity in the boundary layer of a cylindrical enclosure
with an external fan has been developed. It was expected that this boundary layer control
would cause the air to rotate as a forced vortex, and would greatly reduce the aerodynamic
loads on a spacecraft spinning inside the enclosure.
The enclosure has a diameter of 20 feet, and is 20 feet all. A reversible fan in a double
ended plenum chamber is used to control the air velocity. A maximum vortex spin rate of more
than 10 rpm in either direction was achieved.
A dynamic balance test program was performed on several test models in the enclosure. The
test results indicates that the boundary layer control was generally working as expected. Both
the asymmetric and the steady aerodynamic loads were greatly reduced.
The boundary layer control did not provide the desired reduction in fluctuating aerodynamic
loads in some test configurations. It is expected that an improved enclosure design would
provide the desired reduction.
This method has particular application to the dynamic balance of large asymmetric spacecraft
that are spinning at low angular rates. It is a low cost alternative to performing the balance
in a vacuum chamber.
