SITUATION: As an internal research and development project the problem of how to prolong the life of a spacecraft or space-based asset was addressed. Typical control moment gyros (CMGs) maintain the attitude requirements of the spacecraft as they orbit around Earth. Periodically these CMGs need to have their momentum dumped requiring the use of stored onboard propellant. Once the fuel has been used, the CMGs are no longer able to dump their momentum and hence effectively control the attitude of the spacecraft, ending its life.
TASK: How to use CMGs in such a way that their momentum could be recycled between other CMGs connected together in for example an array so that the build of momentum was not required and an externally applied momentum such as that from the use of rocket thrusters would not be required.
ACTIONS: Physics based mathematical models of a freely falling rotatable platform with various configurations of CMGs attached to it were developed and rapidly prototyped into into a Matlab/Simulink simulation. CMGs model variables were parameterized such that they could be varied to determine how they needed to operate in order to meet the goal zero momentum build-up over time.
RESULT: Experimentation found that the use of variable speed scissored CMGs placed in a particular arrangement was able to prevent the build up of momentum during the rotation about a single axis of the platform. Further research and development was required in order to determine the feasibility of the approach about all three rotation axes of the platform.