Angelo Genovese, Electric propulsion Engineer/Thales Deutschland
Angelo Genovese, Mr., Electric propulsion Engineer/Thales Deutschland
The business unit Electron Devices of Thales Deutschland started the development of a new electric propulsion technology, the High Efficiency Multistage Plasma Thruster (HEMPT) at the end of the 90’s. After having carried out several basic studies supported by DRL and ESA, Thales was able to achieve impressive results with its innovative technology. In 2008, the 1.4kW HEMPT-3050 model was selected for the OHB´s SmallGeo Program. The aim of this project was to qualify a complete electric propulsion system, the HEMPT thruster assembly (HTA), composed by two HEMPT-3050 thrusters, their power/processing unit, the xenon gas flow controllers, and other minor components. The HTA project was fully commissioned by the DLR’s Space Administration.
The HTA propulsion system has been integrated on the German geostationary satellite H2Sat, launched in July 2023; the HEMPT propulsion system is performing the NSSK maneuvers with nominal performance since early 2024. This represents the first in-orbit demonstration of the HEMPT propulsion technology.
The number of satellites utilizing electric propulsion units is dramatically increasing, in particular thanks to the mega-constellations that require an extensive amount of propellant. This results in a strain on the availability of Xenon propellant in the context of a volatile noble gas market. due to its scarcity, associated with high production costs, and recent political influence, the price of Xenon has significantly risen. Utilizing alternative propellants has been recognized as a strategy to reduce the total propellant cost; Krypton is currently the most widely used alternative to Xenon as it is approximately 5 times less expensive. An even larger saving in propellant costs could be realized using Argon as propellant, as it is more than 50 times cheaper than Xenon. This is why SpaceX has decided to use high-power Argon ion thrusters on the Starlink satellites. However, low-power ion thrusters showed very low performance with Argon as of today.
Thales is currently qualifying a new HEMPT model, the 700W-class EV0 thruster for LEO/MEO constellations and small GEO satellites. The HEMPT technology provides great benefits to the SmallSat and LEO constellation market due to its unique ability of using different propellants (Xenon, Krypton, Argon) without any design modification, its long lifetime thanks to a very limited thruster erosion, and its cost-effective design.
Furthermore, the HEMPT-EV0 thruster allows operation up to 700W with anode voltages ranging from 300V to 800V, enabling different operational modes suitable for orbit rising, for NSSK in the final orbit and for the EOL debris disposal.
The thruster can generate up to 33mN with Xenon and 27mN with Krypton in high-thrust mode (300V-700W). It can also be operated at higher voltages in high-Isp mode; it reaches an Isp of more than 2000s with 800V-700W. A recent test with Argon has shown very promising results with anode efficiencies similar to Krypton and significantly higher specific impulses.
Thales Ulm has also started the development of an enlarged version of the EV0 adapted for a higher power range, the HEMPT-EV0+. The thruster uses the same module design as the EV0 and the same neutralizer, allowing a reuse of the processes already qualified for the EV0. The target maximal power of the EV0+ is 1.5 kW, with an expected total impulse of 1.5 MNs. This thruster can generate more than 75 mN with Xenon and 65 mN with Krypton in high-thrust mode (300V-1.5 kW). In high-Isp mode, it can reach an Isp of more than 2500 s with 800V-1.5 kW.
This paper will give an update on the HEMPT-EV0 qualification status and its first commercial applications. Furthermore, the first results with Argon will be reported and compared to the operation with Krypton and Xenon. The paper will include the development status of the high-power HEMPT-EV0+ thruster.