A Versatile Switching Logic for Discontinuous Attitude and Maneuvering Control Systems For Spacecraft

Attitude control systems for space vehicles using reaction jets for the generation of control moments become particularly simple and potentially reliable if the reaction jets are operated with constant thrust in an on-off fashion. This paper is concerned with the design of the switching logic of these so called ¿bang-bang¿ systems. Four different logic systems are compared by means of analysis as well as analogue computer tests. One of the systems investigated, called ¿time switched integration¿ has been developed by Lockheed and is shown to be advantageous in certain applications. The advantages include a remarkable insensitivity of the optimum time response behavior to slow variations of the level of system acceleration such as are produced e.g. by fuel consumption and/or staging. In this sense the time switched integration system in some mechanizations may be termed selfadaptive, but achieves this feature with very simple means.