Feasibility of All-Electric Three Axis Momentum Management for Deep Space Small Body Rendezvous

Abstract

An all-electric approach to deep space missions offers significant benefits to spacecraft designers. The absence of a chemical propulsion system and the associated hazardous operations from the spacecraft offers a dramatically easier spacecraft integration process and simpler launch base operations. This paper provides a survey of different methods that can be used to accomplish three axis momentum management during the interplanetary transit ("cruise") portions of deep space Solar Electric Propulsion (SEP) missions without the use of chemical propulsion. The strategies described are based on the use of xenon ion or Hall effect thrusters, which are used alone or in combination with a xenon cold gas system. The methods described use currently existing flight-qualified hardware and apply only to the cruise phase of the mission. It is shown that the use of existing flight hardware combined with the existence of previously flown momentum management flight software for Earth orbit, existing experience with all-chemical momentum management in deep space, and the option to implement "primary" and "backup" momentum management methods using common hardware, all lead to the conclusion that all-electric momentum management can be effectively implemented on deep space small body rendezvous missions with relatively low development, implementation, and operational risk. Nomenclature e = elementary charge ν z = axial ion velocity B r = radial magnetic field E z = axial electric field Fθ = azimuthal force acting on an ion F z = axial force acting on an ion I sp = specific impulse L = acceleration scale length M = ion mass R = mean discharge chamber radius T = total thrust U z = potential drop over the acceleration scale length