Mars Entry Bank Profile Design for Terminal State Optimization

Abstract

One challenge examined in NASA’s DRM 5.0 study is that of entry, descent, and landing (EDL) on Mars for high-ballistic-coefficient, human-class payloads. To define best-case entry scenarios for the evaluation of potential EDL system designs, a study is conducted to optimize the entry-to-terminal-state portion of EDL for a variety of entry velocities, vehicle ballistic coefficients ( �), and lift-to-drag ratios ( L/D ). The terminal state is envisioned as one appropriate for the initiation of terminal descent via parachute or other means. A particle swarm optimizer varies entry flight path angle and ten bank profile points to find maximum-final-altitude trajectories. A baseline set of optimizations is performed, as are fulllift-up and relaxed-deceleration-constraint sets fo r comparison. In total, an estimated 9 million trajectories are analyzed to yield 1800 opt imal trajectories. Parametric plots of maximum achievable altitude are shown, as are examples of optimized trajectories. Characteristic vehicle contours are overlaid on the parametric plots, and conclusions are drawn on the feasibility of vehicles in the L/D vs. � design space. It is shown that entry bank angle control is highly deserving of consideration early in design, particularly for vehicles with mid- or high-L/D values, high entry velocities, and deceleration-li mited trajectories. Key conclusions are also drawn regarding trends in optimal bank profiles and in the constraints which impose particularly severe limits on the design of these trajectories.