Computer Science – Performance
Scientific paper
Oct 2004
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004esasp.555e..39k&link_type=abstract
Proceedings of the 4th International Spacecraft Propulsion Conference (ESA SP-555). 2-9 June, 2004, Chia Laguna (Cagliari), Sard
Computer Science
Performance
Scientific paper
Electric Propulsion (EP), attracts in the last years an increasing interest for all types of space applications as for instance the north/south station-keeping and orbit transfer of commercial GEO-stationary satellites, the drag compensation for LEO- and MEO- satellites and constellations and navigation for scientific interplanetary missions. Reasons for that, as summarised in [1], are: - The propellant mass savings compared with chemical thrusters in the order of more than 90%. - The increasing availability of sufficient electric power on board of satellites (today >10 kW). - The demonstrated in orbit performance and life over more than 10 years of various thruster types (Hall effect thrusters, ion thrusters, arc jets). A new concept of a High Efficiency Multi-stage Plasma (HEMP) thruster to be used for satellite and space probe orbit control and navigation has recently been developed by THALES Electron Devices GmbH in Ulm. In the framework of a 3 year feasibility study sponsored by the German Space Agency DLR the HEMP thruster concept has been successfully realised. Not only its feasibility but very promising unique features have been verified by direct thrust measurements performed at ONERA, Palaiseau, in March 2003 and at University of Gießen in July 2003. Aside the clear advantage of a plasma confinement, which eliminates discharge chamber wall erosion, the HEMP thruster has shown performance characteristics already comparable to those of state-of-the-art grid and Hall-effect thrusters which are being developed for more than 40 years. At the test in the large vacuum chamber at the University of Gießen, the HEMP thruster model DM6 demonstrated for instance a maximum thrust of 139 mN, corresponding to an electric propulsion world record thrust density of 36mN/cm2 at a specific impulse of 3230 s and a total efficiency of 40% at the same operating point. Furthermore, the thermal efficiency (conversion from electric power into kinetic beam power) reached a unique level of 85%. A DLR follow-on-contract to consolidate the HEMP thruster concept started in Sept. 03. Further performance improvements could be obtained meanwhile. Measured again in the large vacuum chamber at the University of Gießen in May 2004, the HEMP 3050 breadboard DM7 reached a total efficiency of up to 46% and a thrust level up to 152 mN at 3420 s specific impulse. Present activities are concentrated on the further optimisation of a low thrust design HEMP 3050 (flexible within 10 to 50 mN @ Isp>3000 s) and a medium level thruster HEMP 30250 (flexible within 50 to 250 mN @ Isp>3000 s), with a goal to improve the total efficiency of the thruster to more than 60% by further reduction of the ion beam angle. THALES Electron Devices GmbH is also developing an efficient hollow cathode neutraliser to be used with all types of ion thrusters, including the HEMP thruster. A demonstrator model N3000 #1, based on the previous experience with RIT10 neutralisers and the meanwhile improved W/Os mixed metal matrix cathode technology, has been set up. It is shown in the fig.1 below in operation with the HEMP 3050 DM7 at the Gießen test facility
Harmann H.
Koch N.
Kornfeld G.
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