The Institute of Plasma Physics and Laser Microfusion's (IPPLM) Hall effect thruster (Krypton Large IMpulse Thruster, KLIMT) is a 500 W class plasma engine with a mean diameter of discharge channel of 42 mm. KLIMT was developed within ESA/PECS project aiming to provide relatively small thruster for satellites that would be able to effectively operate with krypton propellant. Being several times less expensive than xenon, which is regarded as a propellant of choice for electric propulsion of electrostatic type, krypton since years has been suggested as an attractive alternative. In this paper, a design as well as performance tests of the laboratory model of KLIMT are discussed. It is shown that precise adjustment of magnetic field topography results in the stable operation of the thruster in wide range of operating conditions providing similar thrust and specific impulse production for both propellants. Maximum thrust produced with the use of xenon and krypton reached about 16–17 mN for mass flow rate of 1.15–1.2 mg/s resulting in specific impulse in the range of 1300–1500 s (13–15 km/s). However, for krypton the anode efficiency drops by ~10% in comparison with xenon. For krypton plasma beam divergence as measured by an average half-angle with respect to the beam axis was found to remain within the range of 19–23° for the whole set of the examined operating conditions. The reported characteristics are reasonable for Hall thruster of the discussed size and power.

The Krypton Large IMpulse Thruster (KLIMT) ESA/PECS project, which has been implemented in the Institute of Plasma Physics and Laser Microfusion (IPPLM) and now is approaching its final phase, was aimed at incremental development of a ~500 W class Hall effect thruster (HET). Xenon, predominantly used as a propellant in the state-of-the-art HETs, is extremely expensive. Krypton has been considered as a cheaper alternative since more than fifteen years; however, to the best knowledge of the authors, there has not been a HET model especially designed for this noble gas. To address this issue, KLIMT has been geared towards operation primarily with krypton. During the project, three subsequent prototype versions of the thruster were designed, manufactured and tested, aimed at gradual improvement of each next exemplar. In the current paper, the heat loads in new engine have been discussed. It has been shown that thermal equilibrium of the thruster is gained within the safety limits of the materials used. Extensive testing with both gases was performed to compare KLIMT’s thermal behaviour when supplied with krypton and xenon propellants.

Abstract.A new type of pulsed plasma thruster (PPT) for small satellite propulsion is investigated, of which the most innovative aspect is the use of a non-volatile liquid propellant. The thruster is based on an open capillary design. The thruster achieved a thrust-to-power ratio above 45 N/W, which constitutes a 5-fold improvement over the water-propelled pulsed plasma thruster, and which is also slightly above the performance of a similarly sized PPT with a solid propellant.

Krypton Large Impulse Thruster (KLIMT) project was aimed at incremental development and optimization of a 0.5 kW-class plasma Hall Effect Thruster in which, as a propellant, krypton could be used. The final thermally stable version of the thruster (the third one) was tested in the Plasma Propulsion Satellites (PlaNS) laboratory in the Institute of Plasma Physics and Laser Microfusion (IPPLM) in Warsaw as well as in the European Space Agency (ESA) propulsion laboratory in the European Space Research and Technology Centre (ESTEC).During final measurement campaign, a wide spectrum of parameters was tested. The plasma potential, electron temperature, electron concentration, and electron energy probability function in the far-field plume of the thruster were measured with a single cylindrical Langmuir probe. Faraday probes were used for recording local values of ion current. Using several collectors in different locations and moving them on the surface of a sphere, the angular distribution of the expelled particles was reconstructed which was a local measure of beam divergence. Angular distribution of ion flux as measured with a central Faraday probe was parameterized with krypton mass flow rate, voltage, coil current ratio, and the cathode mass flow rate. Beam divergence measurements with Faraday probes as well as plasma parameters derived from Langmuir probe seem to be consistent with our understanding of the operating envelope. Obtained results will serve as a baseline in the design of plasma beam structure diagnostics system for the PlaNS laboratory.

We have studied the relationship between three different versions of the sunspot number (Group, International and American sunspot number) and the number of active days (i.e., the number of days with spots on the solar disk). We have detected an approximately linear relationship for low solar activity conditions. However, this relationship for the International sunspot number is very different to the ones obtained with the other versions of the sunspot number. The discordant values correspond to older observations.