Direct Momentum Accommodation Coefficient Measurements for Satellite Applications

Momentum Accommodation Coefficient (MAC) measurements are required to predict the lift and drag of satellites. Typically the MACs have been inferred from tedious and costly measurements of the velocity distribution of the incident and reflected moleculesin a molecular beam facility. The reflected molecules velocity and flux must be measured in all directions. A significant burden would be removed if one could measure MACs directly, without measuring the reflected molecules properties.In Phase I, Busek Co. Inc. will demonstrate the feasibility of measuring the momentum accommodation coefficients directly by utilization of a torsion balance to measure the force applied to a surface by a well-characterized beam. In order to simulateorbital conditions, this beam must be composed of atomic oxygen with velocity of 5-8 km/s. We propose to develop a plate-neutralized-ion-beam source of atomic oxygen produced by an RF inductive discharge. This type of source can produce nearly unlimitedgas composition and a wide range of velocities, important for complete orbital simulation. Our recently developed sub-micro-Newton torsion balance will form the synergism required of this program.A complete, efficient, and widely manipulated direct force momentum accommodation coefficient measurement facility will be constructed and characterized in Phase II. Accurate MAC measurements will lead to optimization of satellite design, including one orall of the following: increased orbital life, reduced propulsion requirements and/or increased payload. The proposed effort would revolutionize the way satellite designers/builders estimate the drag of, or energy transfer to, exterior satellite surfaces.This approach does not require past flight data of satellites and their materials nor complete measuring of reflected particles, both expensive and time consuming. Any potential satellite material can be characterized for Momentum AccommodationCoefficients (MAC) in just a few days at greatly reduced costs. Busek approaches the MAC measurement facility commercialization in one, or combinations, of the following three methods including: fabricating and selling of complete facility, licensing ofthe technology and in-house testing of sample materials.