Modeling and Optimization of Hybrid Transfers to Near-Earth Objects

Hybrid propulsion combines chemical propulsion and electric propulsion on the same platform. The brand-new hybrid transfers are thus achieved by sequential combination of high thrust (impulsive maneuvers) and low thrust (continuous arcs). In this chapter, hybrid propulsion transfers are applied to the trajectory optimization for missions to the Near Earth Objects (NEOs). These have been obtained with an optimization based on a direct transcription procedure. The problem is formulated as a nonlinear programming problem and solved for a finite set of variables, which maximize the final spacecraft mass. Effort has been put in modeling the propulsion subsystem. Realistic limitations on both the impulsive maneuvers and low-thrust magnitude have been considered, as well as gravity losses and variation of available electrical power with the distance from the Sun. The transfer to asteroid 162173/1999 JU3 is considered as case study. The designed hybrid propulsion transfers have been compared with purely chemical transfers proposed for the ESA’s Marco Polo mission.