AAS 97-635
SATELLITE DRAG COEFFICIENTS
G.R. Karr and J.C. Gregory - University of Alabama
Abstract
As a near earth satellite moves in its orbit, gas molecules of the earth's atmosphere impinge on the exposed satellite surface at a mean velocity of order 1-10 km/s. The interaction of gas molecules with the surface causes a net force to be exerted on the exposed surface of the satellite. The net effect of the interaction force, when summed over all exposed surfaces of the satellite, is a single force vector on the satellite which can be divided into a drag and lift component in general. In this paper we will discuss the lift and drag characteristics of satellites of various shapes. The size of the satellite will be assumed to be small enough such that free-molecular conditions exist (Knudsen number>> 1).
The determination of drag and lift coefficients for a satellite in free-molecular flow is made through knowledge of the nature of the interaction of the atmospheric gas molecules and the solid surfaces of the satellite. The "gas-surface interaction" is fundamental to the determination of the drag and lift properties of a near earth satellite. In this paper we will review the current state of knowledge of the gas-surface interaction as determined from experiments in space and in ground based beams. We then use this information to develop the corresponding current knowledge of satellite lift and drag coefficients.