Time-Optimal Attitude Control of an Axially Symmetric Spinning Spacecraft

Abstract

This report considers the problem of controlling both the attitudc and angular velocities of an axially symmetric spacecraft while minimizing the maneuver duration. In particular, various combinations of thrust limited reaction jets are employed to properly orient a spinning space body with respect to specified reference directions starting from known initial conditions of the vehicleva attitude and angular rates. Five control jet configurations are considered: two gimballed systems where torques can be applied about, In cases where the total angular momentum vector and the spin axis are aligned at the initiation and termination of control three modes of operation which characterize optimal steering are defined.These include the two limiting cases where, for example, the control magnitude is very large (small) compared to the angular momentum due to spin. The third mode is characterized by the transition region iii between the "short" and ".long" time solutions. In the latter case, the maneuver duration may be from one to ten revolutions of the spacecraft about its axis of symmetry. Finally, for certain values of the dimensionless physical parameters the response of the non-linear system is typified by that of the linear plant. Hence the results of this report are useful in determining the minimum time required for arbitrarily large reorientations of a vehicle's spin axis.iv r ACKNOWLEDGMENTS