- Conference date: 3-6 Feb 2002
- Location: Albuquerque, New Mexico (USA)
Stability is a neglected issue in concepts for propelling ultralight sails by beamed power. Whether the beam comes from a laser or a microwave antenna, power falls with angle from the beam center. This drives a sail sideways under any lateral perturbation—“tumbling down the hill.” The basic mechanics of pressures and sail averaging of them across its area remain unexplored in experiment, and have only recently been treated in theory. Here we report the first experiments on beam-riding dynamics in the laboratory, using a slightly over-weighted pendulum. In the experiments, a sail attached to the pendulum bottom is made unstable by adding weight to the top end. Sail stability and oscillation are possible if this is countered by electrodynamic beam pressure on the sail, directed from below, torquing the pendulum into a stable state. We present both data and analysis that shows that the beam-riding effect does in fact occur: microwave powers of a few hundred W can hold an otherwise unstable sail steady. This is made possible because of the gradient in beam power with sidewise angle. Our experiments verify the University of New Mexico simulations, which show similar stability conditions. Beam powers comparable to the strength of perturbing forces can plausibly achieve these stability effects in free sail flight.
- Microwave power transmission
- Data analysis
- Laboratory procedures
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