Beam-Riding Simulation and Diagnostics for Beamed-Energy Vehicles

Kurzfassung

The separation of energy source and aerospace vehicle allows for a variety of sophisticated beamed-energy propulsion concepts. Beyond the question of the technological realization of suitable high power lasers, beam-riding of the vehicle plays a crucial role for the maturity of any remotely driven laser propulsion device. Whereas usually flight stability is experimentally analyzed with respect to lateral and angular motion separately, this paper presents an analytical approach to consider as well the independency of both movements. A quasi-continuous approximation of impulse coupling yields a system of coupled differential equations describing the laser-driven motion in a two-dimensional case. A specific matrix of flight dynamics is derived yielding necessary and sufficient criteria for beam-riding stability. This approach can be applied on experimental data of any beamed-energy vehicle and shows its inherent capabilities of beam-riding and possible needs of technological assistance measures, e.g. spin-stabilization. As an example, the specific matrix of flight dynamics of a parabolic laser-thermal thruster is derived from impulse field data of recent hovering experiments. The theoretical analysis of stability criteria and simulated flight trajectories is in good accordance with the experimentally found results which had shown poor flight stability due to the specific coupling between lateral and angular motion. Furthermore, it is shown that in the mentioned case an optimization of alignment accuracy at the launch position by one order of magnitude would lead to an increase of flight time by only 1 second. The theoretical criteria for beam-riding stability are analyzed for alternative options of lightcraft configurations with respect to mass, momentum of inertia and center-of-mass position. While theoretical configurations for 2D beam-riding stability are found, alternative concepts using spin-stabilization are discussed. Model limitations with respect to full 3D dimensionality and pulsed motion are briefly illustrated.