Eutelsat’s new 172B satellite marks a new step in the operator’s push toward widespread use of electric propulsion. Company executives believe all conditions are gradually being met to make such power both a reliable and economical option. There is more than one launcher available for this size spacecraft, a trade-off has been found between efficiency and transfer time to orbit, and an Ariane 6 feature will further reduce time to market.Assuming that VASIMR technology can reach a commercially acceptable state, it could provide relatively high thrust at lower efficiencies for orbital transfer, and lower thrust, and higher efficiency for station keeping, which would allow for both the advantages of Ion and Hall effect thrusters.
Mainly thanks to electric propulsion, the weight of 172B has been limited to 3.5 metric tons (7,700 lb.) instead of 6 tons for a more conventional satellite. For that weight class, the lower position under Ariane 5’s fairing had long been the only option for launch, Eutelsat’s chief technology officer Yohann Leroy, notes. Other options that were technically feasible were not economical. Satellite operators are leery about relying on a single launcher, Leroy emphasizes, and that reluctance had stalled the advent of electric propulsion. “SpaceX’s Falcon 9 changed the game,” he says.
As a second launcher became available for the new weight class in commercial communications geostationary satellites, Eutelsat forged ahead, and in 2015 a Falcon 9 launched Eutelsat 115 West B, the operator’s first satellite using electric power for both station-keeping and orbit-raising.
The Eutelsat 115 West B was built by Boeing. But the France-based operator no longer has to depend on the U.S. industry. Thales Alenia Space and Airbus now also offer all-electric platforms, thus increasing the number of supplier options.
In 2014, Eutelsat ordered 172B from Airbus. The satellite uses Airbus’s upgraded Eurostar 3000 EOR (electric-orbit-raising) platform. “It is the first fully electric satellite not developed in the U.S.; it is a first for us and the European industry,” says Nicolas Chamussy, head of space systems at Airbus Defense and Space. Airbus was hoping to source the thrusters from Safran, in an attempt to have an entirely European spacecraft. Autonomy in space technology is a goal shared by the European Commission and the Continent’s industry.
Energy use onboard 172B is optimized thanks to two robot arms—two thrusters can be found at the end of each arm. Thrust can thus be precisely vectored. The axis of the thrust always goes through the satellite’s center of gravity, Arnaud de Rosnay, Airbus Defense and Space’s director for communications satellites, explains. Moreover, the arms help remove heat from the electronics hardware inside the spacecraft.
In either case, this promises to reduce the cost of satellites, because, much like ground round, you pay for launches by the pound.