The work considers passive dynamic stability of sail craft, propelled by microwave beams. Such systems are under consideration as low-cost means of interstellar travel. Sail-craft shapes offering passive dynamic (neutral) stability are identified. Passive stability is a key mission-enabling attribute. Very large, umbrellalike structures made of strong, lightweight materials, such as carbon-fibers, attached aft of the payload can provide sufficient propulsive power by reflecting incident microwave energy. Not all reflector shapes are stable, however. The key contribution of this work is the identification of reflector shapes which possess passive dynamic stability in translation and attitude. Reflector substructure must be concave to incident radiation and must be located aft of the vehicle center of gravity, c.g. (i.e., the incident radiation encounters c.g. first). Critical parameters for passive dynamic stability are identified. A simulation/analysis tool is also developed which can be used to adequately address the stability issue of other potential sail-craft configurations.

This work was performed by Gurkirpal Singh of Caltech for NASA's Jet Propulsion Laboratory. To obtain a copy of the report, "Stable Microwave Beam-Riders," access the Technical Support Package (TSP) free on-line at  under the Mechanics category


This Brief includes a Technical Support Package (TSP).
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Stable Microwave-Beam-Riding Spacecraft

(reference NPO-21035) is currently available for download from the TSP library.

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