Trajectory Analysis Program for Determining Range Safety Considerations for a Reusable Launch Vehicle Using Multiple-Phase Pseudospectral Optimization

Due to the high visibility of flight testing hypersonic vehicles, range safety is paramount. This makes flight planning, trajectory analysis, and risk mitigation extremely important activities. Due to the high energy of hypersonic flight, the consequences of a failed mission may be disastrous. As population near formerly isolated testing ranges increases, so does the risk of casualty associated with the loss of a vehicle. The test planner is responsible to ensure safety both on and off the range. It is therefore desirable to identify and avoid conditions that may unnecessarily increase risk. To this end, when designing trajectories for hypersonic missions, the test engineer may establish ”keep-out” zones. These may include areas of high population, environmental sensitivity, air or ground traffic routes, or political boundaries. The trajectory may be constrained so that no overflight of a zone occurs, or so that a failed vehicle has a very low probability of impacting in the area, or both. A trajectory optimization tool has been developed by the Hypersonic Combined Test Force (HCTF) at Edwards Air Force Base, a historic location for hypersonic flight testing. The tool is multidisciplinary and flexible, capable but easily modifiable to represent the various types of experimental vehicles and complicated trajectories tested on the range. It’s primary function is to design trajectories that minimize the above described risks, while still achieving required mission performance. Examples of mission performance parameters include payload mass, heat rate, Mach number achieved, or overall flight time. Typically, changing the trajectory to avoid a keep-out zone will result in decreased mission performance. Using a multidisciplinary optimization tool enables the test planner to find solutions which minimize the detriment to mission performance while satisfying range safety concerns. This paper will present representative examples of how the tool may be used by range planners to accomplish the test mission while minimizing risk.