Reentry control of a low-lift maneuverable spacecraft

Commercial operation of space laboratories will rely on small, unmanned reentry capsules to retrieve experimental products independent from Shuttle services. An example for such a concept is the Space Mail system studied by the European Space Agency. This paper presents a trajectory control system based on linear state feedback to guide and control the reentry glide of low-lifting capsules. A technique to design a time-varying controller is derived and applied. Simulation results of spatial flights over a rotating earth show that the designed controller effectively responds to entry condition offsets on several reference trajectories. Also, the controller is capable of tolerating modified vehicle parameters as well as atmospheric disturbances, and the same controller gain functions are successfully applied to different reference trajectories. Nomenclature Distance from planet's center of gravity Radius of the Earth Reference area on vehicle Flight time Vehicle's relative speed Flight path angle Lift-to-drag ratio, CL/CD Geodetic longitude Atmospheric density Atmospheric density a t sea level Bank angle Geodetic latitude