Olivier Duchemin

Ariane 5-ME and Electric Propulsion: GEO Insertion Options

Electric propulsion is now widely used on commercial satellites, and the prospects of allelectric satellites may be considered for future comsats where all propulsive duties are fulfilled by the electric propulsion subsystem, including orbit raising. In such a configuration, the full benefits of using higher specific impulse devices for the satellite onboard propulsion would be realized. These benefits may be expressed in terms of increased payload capability in geostationary orbit, but also in terms of increased satellite operational life or decreased launch costs, depending on market demands. This study examines the best match options between electric propulsion and a launch vehicle with frozen specification, with Ariane 5-ME taken as a reference example. Departure orbit options before the electric orbit raising to GEO are traded in order to realize the full potential of both the launch vehicle performance and electric propulsion. The selection of the best options is discussed, depending on the priority given to fast electric orbit raising and low radiation fluence versus improved dry mass capability to geostationary orbit.

Cryostorage of Propellants for Electric Propulsion

*† ‡ All noble gases can be stored in liquid form at cryogenic temperatures. This possibility, however, has not yet been used in the field of Electric Propulsion. This paper discusses the trade off between state of the art, supercritical (high pressure) storage, and cryostorage of (liquid) propellants for Electric Propulsion. The performance of propulsion subsystems using either liquid xenon or liquid krypton is assessed for three types of missions : orbit topping of a geostationary comsat; a solar electric interplanetary probe; and a 100-kW nuclear electric service module or heavy probe. In each case, the use of liquid storage enables significant dry mass and volume savings, and simplified ground operations. The other great benefit of liquid storage is the possibility of replacing xenon by krypton with no major modifications of the propulsion subsystem.

Thrust Vector Control Using Multi-Channel Hall-Effect Thrusters

*† A Hall thruster design is presented, in which multiple discharge chambers share a common magnetic circuit, cathode, and power supply. This arrangement provides not only most of the advantages commonly attributed to multi-thruster assemblies, or clusters, but also facilitates control of the direction of thrust without the need for a complex gimbal mechanism. In addition, it reduces the mass penalty associated with clustering multiple, independent thrusters. Several conceptual designs are presented, and the thrust steering performance is discussed. Finally, the main electrical propulsion sub-system trade-offs associated with such an architecture are presented.

High Power Electric Propulsion System for NEP: Propulsion and Trajectory Options

Recent US initiatives in Nuclear Propulsion lend themselves naturally to raising the question of the assessment of various options and particularly to propose the High Power Electric Propulsion Subsystem (HPEPS) for the Nuclear Electric Propulsion (NEP). The purpose of this paper is to present the guidelines for the HPEPS with respect to the mission to Mars, for automatic probes as well as for manned missions. Among the various options, the technological options and the trajectory options are pointed out. The consequences of the increase of the electrical power of a thruster are first an increase of the thrust itself, but also, as a general rule, an increase of the thruster performance due to its higher efficiency, particularly its specific impulse increase. The drawback is as a first parameter, the increase of the thruster’s size, hence the so‐called “thrust density” shall be high enough or shall be drastically increased for ions thrusters. Due to the large mass of gas needed to perform the foreseen miss...