Satellites: the future is electric!
Snecma is a European pioneer in this field, with full development, production and testing facilities for plasma thrusters at its plant in Vernon, about an hour west of Paris. Here is a short course in electric propulsion for satellites.
What is plasma propulsion?
Plasma thrusters, powered by electricity instead of conventional rocket fuels, are used on telecommunications satellites for orbital transfer (into geostationary orbit) and, once there, to keep these satellites in place (stationkeeping). They can also be used for various propulsion duties on observation, navigation and scientific satellites. Snecma makes thrusters with power ratings from 500 to 20,000 watts.
How does it work?
A typical geostationary telecom satellite is released into an elliptical geostationary transfer orbit (GTO). But to carry out its mission, it needs to reach a circular orbit at a geostationary altitude of about 36,000 kilometers (i.e., stationary in relation to the Earth's rotation). Plasma thrusters can be used to circularize this orbit in three to six months, with just a few grams of thrust. In the vacuum of space, this weak thrust is enough to displace an object. Xenon gas is injected into a ceramic chamber, where is it bombarded by electrons, becoming ionized and forming a plasma. The ions are ejected at very high speed by an electric field – 15 to 25 km/sec. – generating the thrust.
What is the market for these thrusters?
Electric propulsion systems such as these considerably reduce the weight of the propulsion system by eliminating the large quantity of chemical propellants in a conventional rocket system. Using electric propulsion, satellite operators can either save weight, allowing them to reduce launch costs, or increase the payload. Worldwide, about 20 to 25 communications satellites are built per year, and one-fifth to one-fourth of them are equipped with electric thrusters. This proportion has been growing steadily since 2014, and should reach 50% in five to ten years, and even more according to the Space Propulsion conference forecasts. To support this growth, we will produce 12 thrusters in 2016 and we're aiming for an annual rate of 40 thrusters by 2020.
We recently signed two major contracts: to supply the PPS®5000 thruster, now under development, to Airbus Defence and Space; and a breakthrough in the export market, with SSL, the world's leading producer of communications satellites, ordering the PPS®1350.