Energy-momentum-wheel for satellite power and attitude control systems

In an earlier paper by the author on a 2500 W low Earth orbit satellite, such as NASA Goddard Space Flight Center's EOS-AM, the mass and volume reductions by replacing the battery with a flywheel were estimated to be 35% and 55% respectively. Further savings are possible by using a dual function flywheel that stores energy for the electrical power system and momentum for the attitude control system of the satellite. This paper analyzes the operation of such a dual function flywheel, termed the energy-momentum-wheel. As the spacecraft cannot discharge energy without discharging momentum, the maximum depth of energy discharge is limited by the minimum momentum storage requirement on a given axis. Such mission level operating constraints are analyzed and presented in the form of circle diagrams.