Trajectory Simulations for Laser-Launched Microsatellites Using a 7-DOF Flight Dynamics Model

Abstract

Laser launch trajectories are being developed for boosting nano- and micro-satellite sized payloads (i.e., 1 to 100 kg) using a 7-Degree Of Freedom (DOF) flight dynamics model that has been extensively calibrated against 16 actual trajectories of small scale model lightcraft flown at White Sands Missile Range, NM on a 10 kW pulsed CO2 laser called PLVTS. The full system 7-DOF model is comprised of individual aerodynamics, engine, laser beam propagation, variable vehicle inertia, reaction controls system, and dynamics models, integrated to represent all major phenomena in a consistent framework. The suborbital trajectory results presented herein are for a 240 cm diameter lightcraft (100 kg payload; 100 MW beam power) flown under three different laser-boost scenarios: 1) liftoff and vertical climb-out on a vertically oriented laser beam; 2) liftoff and climb-out along a constant laser beam pointing angle (fixed azimuth and zenith) defined relative to the launch pad; 3) liftoff and climb-out on a beam with a time-varying pointing schedule (azimuth and zenith) to “slingshot” the lightcraft laterally, making maximum use of the engine’s autonomous beam-riding feature. For simplicity, simulations assume a solid ablative rocket propellant (e.g., Teflon®-like performance) with a vacuum specific impulse of 644 seconds, momentum coupling coefficient of 190 N/MW, and overall efficiency of 60%. This flight dynamics model and associated 7-DOF code provide a physics-based predictive tool for basic research investigations into laser launched lightcraft for suborbital and orbital missions. An investigative protocol was developed to identify and quantify phenomena that dominate each phase of the launch trajectory. These protocols are specified herein, along with physics-based explanations for such phenomena, both predicted and observed.

Basic Research Investigations into Multimode Laser and EM Launchers for Affordable Rapid Access to Space (Volumes 1 and 2)

“…The first attempt at modeling the flight dynamics with a 6-DOF code was performed by Libeau [7]; this was followed by Ballard et. al [8], and several subsequent iterations [1,9] before arriving at the most current model [10]. The ultimate goal is a research tool that can facilitate invention of new lightcraft engine/vehicle geometries, assist creation of active flight control systems, and enhance understanding of experimental flight trajectories.…”

Theoretical and Numerical Studies of Dynamic Scaling of a Six-Degree-of-Freedom Laser Propulsion Vehicle

“…Deviation from the laser beam line must be avoided to obtain continuous thrust in a beam-driven flight. The degree of success achieved in capturing the laser beam line, which is referred to as the beam-riding performance, is crucial 2 International Journal of Aerospace Engineering to maintaining stable flight without deviation from the laser beam [16][17][18][19][20][21][22][23][24]. The beam-riding performance is totally assessed from the feedback performance with respect to the translational and angular misalignments of the incident laser.…”

“…In previous studies of the lightcraft, experiments for the beam-riding physics were conducted to examine the recentering and angular impulses for lateral offset only with a single pulse [18,19]. In addition, a flight orbit was simulated for multiple pulses using experimental impulse data for lateral offset only [16,[19][20][21]. However, it is difficult to predict the flight trajectory from the lateral offset alone because the laser incident condition is complicated by the angular offset and the combined lateral-angular offset during the actual flight.…”