Experimental Investigations of a Krypton Stationary Plasma Thruster

Stationary plasma thrusters are attractive electric propulsion systems for spacecrafts. The usual propellant is xenon. Among the other suggested propellants, krypton could be one of the best candidates. Most studies have been carried out with a Hall effect thruster previously designed for xenon. The ATON A-3 developed by MSTU MIREA (Moscow) initially defined for xenon has been optimized for krypton. The stable high-performance ATON A-3 operation in Kr has been achieved after optimization of its magnetic field configuration and its optimization in different parameters: length and width of the channel, buffer volume dimensions, mode of the cathode operation, and input parameters. For a voltage of 400？V and the anode mass flow rate of 2.5？mg/s the anode efficiency reaches 60% and the specific impulse reaches 2900？s under A-3 operating with Kr. The achieved performances under operation A-3 with Kr are presented and compared with performances obtained with Xe. 1. Introduction Hall effect thruster (HET, also named electron drift thrusters or Stationary Plasma Thrusters—SPT or PPS) is currently considered as the most efficient propulsion device for station-keeping of geostationary satellite for telecommunication. In this electrostatic plasma thruster, positive ions are created in an annular channel by inelastic collisions between neutral atoms and electrons emitted by an external hollow cathode. This process requires electron trapping in the channel by a radial magnetic field which is generated by a set of external magnetic coils or by permanent magnets. The ions are accelerated from the thruster by an axial electric field which is generated by a decrease of the electron mobility controlled by the magnetic field. But in the range of values of electron and ion parameters, only the electrons are magnetized (electron Larmor radius channel size ion Larmor radius). The first electric thruster in space was a FEEP (Field Emission Electric Propulsion) on board the ZOND2 soviet satellite in 1964 and the first SPT was tested in space in 1972 on the Soviet Meteor meteorological satellite. Now, more than 300 SPTs have been used on-board geostationary satellites for telecommunications. Moreover, a PPS1350 Hall effect thruster from Snecma-Group SAFRAN (France) has been used with success for primary propulsion on the SMART-1 interplanetary mission. This European mission arrived on a Lunar orbit (2003-2004) with only 80？kg of xenon propellant. This very low consumption is due to the high velocity of the ejected ions in HET thruster (15–20？km s？1) giving a high specific