Dominique Valentian

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.

Preliminary Comparison Between Nuclear‐Electric and Solar‐Electric Propulsion Systems for Future Mars Missions

Recent US and European initiatives in Nuclear Propulsion lend themselves naturally to raising the question of comparing various options and particularly Nuclear Electric Propulsion (NEP) with Solar Electric Propulsion (SEP). SEP is in fact mentioned in one of the latest versions of the NASA Mars Manned Mission as a possible candidate. The purpose of this paper is to compare NEP, for instance, using high power MPD, Ion or Plasma thrusters, with SEP systems. The same payload is assumed in both cases. The task remains to find the final mass ratios and cost estimates and to determine the particular features of each technology. Each technology has its own virtues and vices: NEP implies orbiting a sizeable nuclear reactor and a power generation system capable of converting thermal into electric power, with minimum mass and volumes compatible with Ariane 5 or the Space Shuttle bay. Issues of safety and launch risks are especially important to public opinion, which is a factor to be reckoned with. Power conversio...

Development status of the PPS 1350 plasma thruster

A new SPT thruster is jointly developed and qualified by FAKEL and SEP. It is intended to be flown on STENTOR experimental spacecraft in year 2000. The technical design has been frozen two years ago. It has been validated by a 3500 h test on a Development Model. Now the program is entering in two qualification phase. A first model -MIwill undergo a 7000 h test and a second one -QMthe environmental qualification. The qualification program includes also the cycling test of several cathode. The test facilities LI-A and LI-B have been updated to perform the endurance test and the thermal vacuum test. INTRODUCTION The PPS 1350 specifications reflect the need to increase the total impulse delivered by the thruster, itself linked to the mass increase of geostationary spacecrafts and to the increase of AV requirements (NSSK plus orbit injection). The vibrations resistance is also improved in order to accommodate higher vibrations levels induced by new spacecraft design. The formal qualification needs new or updated facilities especially to perform thermal vacuum test on an operating thruster. THRUSTER CHARACTERISTICS The thruster specifications have been established by an integrated team (CNES, AEROSPATIALE, MMS and SEP). The thruster specifications are summarized in table 1 below. Table 1 PPS 1350 functional specifications Reference thrust Discharge voltage Propellant flowrate Discharge power Specific impulse Specific power Total efficiency Total impulse Operating cycles Divergence angle 88 mN 350V 5,2 mg/s 1500W 1720s 17 W/mN 51% 1.44MN.S 5200 42° PPS 1350 environmental specifications Temperature: Operating Qualification Random vibrations: Acceptance Qualification Sinus vibrations : Acceptance 5-21 Hz 21-100 Hz Qualification 5-21 Hz 21 -100 Hz Shock: Acoustic noise: -43, +205°C -48,+210°C

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...