An Attitude Control Strategy Using Four Cold Gas Thrusters for the SCRAMSPACE 1 Experiment

摘要

The design and simulation of an attitude control strategy using four cold gas thrusters is detailed. The system is designed to re-orient the hypersonic experimental vehicle SCRAMSPACE 1 outside the atmosphere so that on re-entry at 80 km altitude, it is within a 10.0 degree total angle of attack. This constraint is equates to 2.5 degrees total angle of attack at 32 km altitude where a scramjet is to be tested at Mach 8. Monte-Carlo simulations show that the final attitude accuracy at 80 km is constrained to a 1 degree error in pitch and yaw about the velocity vector. The reaction control strategy is to step through a number of control modes: nutational damping, de-spin and coarse roll angle acquisition, fine attitude tracking after de-spin, coarse pitch-over, midcourse fine tracking, terminal fine tracking and re-entry rate damping. Higher level logic allows for measurement of thruster force and re-starts of the algorithm. Planar Containment Guidance is developed and used during the pitch-over to constrain the vehicle to a plane whilst maintaining a constant pitch-rate. Re-entry rate damping is shown to widen the allowable angle of attack range at 80 km altitude to 19 degrees. The reaction control system presented is robust to trigonometric singularities and mathematical ambiguities.