Schematic of the air-breathing electric propulsion system. Source: ESA

The Gravity Field and Steady-State Ocean Circulation Explorer Satellite launched by the European Space Agency (ESA) in 2009 flew as low as 250 km for more than five years with the aid of an electric thruster that continuously compensated for air drag. However, the craft’s service life was limited by the 40 kg of xenon it carried as propellant, and the mission was over once it was consumed.

An alternative termed an "air-breathing" electric thruster is under development to replace onboard propellant with atmospheric molecules and will foster a new class of satellites able to operate in very low orbits for long periods.

A complete thruster developed by Sitael in Italy was tested in a vacuum chamber to simulate the environment at 200 km altitude. A ‘particle flow generator’ provided the oncoming high-speed molecules for collection by the Ram-Electric Propulsion novel intake and thruster.

No valves or complex parts are used: the only requirement is to power the coils and electrodes, creating an extremely robust drag-compensation system.

Molecules collected with a new intake design from QuinteScience of Poland are given electric charges so that they can be accelerated and ejected to provide thrust. A dual-stage thruster was engineered by Sitael to ensure better charging and acceleration of incoming air, which is harder to achieve than in traditional electric propulsion designs.

The system has been repeatedly ignited solely with atmospheric propellant to prove the concept’s feasibility.