Formation Flying for a Dense Cluster of Autonomous Spacecraft

Formations of small cooperative spacecraft can be used to accomplish mission objectives that are either too expensive or impractical for a single monolithic spacecraft. Large groups of micro or nano satellites can be put into orbit for a fraction of the cost of a single large satellite. By working cooperatively, dense formations of these small satellites can address many challenging applications such as high-resolution imaging, storm or forest-fire tracking, space weather (e.g., solar storm) measurement, and cooperative repair of a large spacecraft. However, formation flying with tens or hundreds of autonomous satellites requires coordinated control that allows spacecraft to form dense clusters and avoid collisions, while relying on limited spacecraft control authority (i.e., limited thruster capability) and little-to-no communication between the members of the formation. In this project, we will develop a formation flying method for a cluster of autonomous spacecraft. This method will allow a group of autonomous spacecraft to form a dense cooperative cluster while avoiding collisions. The primary challenge for spacecraft formation flying is the nonlinear gravity-based dynamics. Existing formation flying methods assume double-integrator dynamics, which provide reasonable models for air vehicles but are not acceptable for space vehicles. Moreover, feedback control cannot be used to cancel the effects of gravity because this approach requires large control forces and thus expends too much fuel. We will leverage our previous work on multi-vehicle coordinating flocking to develop a formation flying method that explicitly accounts for nonlinear spacecraft dynamics. Specifically, we will develop formation flying methods for two scenarios: (1) a cluster of small spacecraft orbiting a large celestial body (e.g., the Earth), and (2) a cluster of small spacecraft orbiting a larger spacecraft (e.g., a space station), which in turn orbits a large celestial body.