OPTIMAL COOPERATIVE POWER-LIMITED RENDEZVOUS WITH PROPELLANT CONSTRAINTS

Minimum-fuel cooperative rendezvous of two power-limited spacecraft is investigated. Both vehicles are active and provide thrust to complete the rendezvous. Total propellant consumption is minimized subject to propellant constraints. Two gravitational models are investigated: the Hill-Clohessy-Wiltshire linearized field and the two-body, inverse-sq uare field. Analytical solutions are obtained for the linearized gravi tational field. A numerical method using direct collocation with nonli near programming is used for the nonlinear gravitational field. Numeri cal results are presented and compared for various efficiencies, as me asured by spacecraft power-to-mass ratios. For vehicles having differe nt efficiencies, an interesting paradox can occur. Due to a propellant constraint on the more efficient vehicle, the optimal solution can re quire the initially less efficient vehicle to provide the majority of the thrusting, leaving the initially more efficient vehicle with a sur plus of propellant. An explanation of this paradox is provided.