Reduced-Weight Reaction Sphere Makes Way for Extra Satellite Payload

Leopoldo Rossini, Emmanuel Onillon, & Olivier Chetelat

CSEM SA, Neuchatel, Switzerland

CSEM is a private applied research and development center specializing in micro-technology, system engineering, micro-electronics, and communications technologies. One of their latest projects is working on minimizing the weight of satellite attitude control systems as every gram of payload matters when launching a satellite into orbit (€15,000 per kilogram).

CSEM hopes to accomplish this task by replacing the four conventional single-axis reaction wheels with a multi-axis reaction sphere. The sphere would be an iron ball covered with permanent magnets and held in position with magnetic levitation through magnetic fields generated by a number of electric coils. The sphere would act as a rotor, accelerating about any axis and increasing torque.

Using COMSOL Multiphysics and its LiveLink™ for MATLAB® module, the initial guess of an analytical model can be finely tuned for optimization. The models are also making possible testing of designs which could not previously have been tested using the analytical approach. A preliminary design has been created, and CSEM hopes to replace the lead with a lighter material.

Radial magnetic flux density at the rotor surface (surface plot)and current density in the coils (arrow plots).