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Since the late 1990s, a new type of propulsion has started to appear in orbit: rather than carrying tanks of heavy and dangerous chemical propellants, plasma thrusters only require a small amount of inert gas—typically xenon—accelerated by the Hall effect using electrical energy from a satellite’s solar panels. Hall effect thrusters are more efficient and offer the potential to shave several tonnes off the mass of a communications satellite or significantly increase the size of its payload, while dispensing with the operational constraints associated with chemical propellants (handling and corrosion). On the other hand, they generate less thrust.
CNES first became involved with developing electric satellites in 1994 through the French STENTOR project and then the European ALPHABUS/ALPHASAT project. Building on this experience, the agency subsequently worked with Safran from the early 2000s to develop a range of thrusters, the PPS 1350 and PPS 5000. Hall effect thrusters were initially used only to position satellites on their final orbit, but today, thanks to research and development of more powerful thrusters and carefully designed spacecraft buses, it has become possible to conceive ‘all-electric’ satellites that use the technology to reach geostationary orbit and then stay on station for more than a decade of operational service.
Through two budget lines of the government’s PIA future investment plan and the European NEOSAT programme, CNES is leading the effort to establish these new applications and foster technology spin-off from research to industry. France has gained a leadership position through Safran (propulsion), Airbus Defence & Space and Thales Alenia Space in adapting existing satellite buses (Eurostar 3000EOR) and creating the new-generation Space-busNEO and EurostarNEO.
The first demonstration of an all-electric satellite stemming directly from these programmes is underway with the EUTELSAT 172B satellite sent aloft from Kourou on 1 June 2017. Equipped with new and powerful Hall effect thrusters on a Eurostar E3000 bus (Airbus DS), the satellite weighed no more than 3.5 tonnes on launch, a gain of more than 30% over satellites with an equivalent payload, enabling it to be carried in the ‘low’ position on ARIANE 5 and thus generating significant launch cost savings. Eutelsat 172B was positioned in record time, taking only 4 months to reach orbit, against 6 to 7 months for competing U.S. satellites. It has been operational since mid-November 2017.