Dynamics of an electromagnetically flown formation of spacecraft within the Earth's magnetic field

Abstract

The ultimate limiter of mission lifetime for current space systems is onboard propellant supply. In the past, propellant usage once on-orbit was primarily for station keeping, requiring only a modest amount of mass. However, the increased interest in flying spacecraft in formations that evolve in some prescribed way over time has greatly increased the potential amount of propellant needed over a mission lifetime. For cluster missions that are insensitive to their center of mass location this constraint can be lifted by using internally generated electromagnetic forces between vehicles as an alternative method of formation control. Such missions include rendezvous and docking applications and sparsely distributed apertures for interferometry. The dipole nature of the electromagnetic force allows for full control of the relative degrees of freedom, position and orientation, provided reaction wheels are used for angular momentum storage and control. This paper briefly presents the current research in this area at the MIT Space Systems Laboratory (SSL), and develops the theory behind electromagnetic formation flight under the far field approximation, specifically addressing the operation of clusters within the Earth's magnetic field. Discussion of the hardware technology associated with Electromagnetic Formation Flight (EMFF) and the testbed currently under development at the SSL is also provided.