ESA team demonstrates “world-first” air-breathing thruster

Replacing onboard propellant with atmospheric molecules would create a new class of satellites able to operate in very low orbits for long periods

Propelled at around 7.8 km/s, a satellite would ingest air molecules from the top of the atmosphere (left) to fire its ion thruster (right), providing thrust to overcome atmospheric drag, allowing it to stay in low orbit indefinitely (ESA–A. Di Giacomo)

5 March 2018

A European Space Agency research team has announced a world-first electric thruster that uses scarce air molecules from the top of the atmosphere for propellant, potentially allowing satellites to fly in very low Earth obits indefinitely, with no fuel. These so-called air-breathing electric thrusters could also be used at the outer fringes of atmospheres of other planets, drawing on the carbon dioxide of Mars, for example.

Supported by ESA’s Technology Research Programme for developing promising new ideas for space, the challenge was to design a new type of intake to collect the air molecules so that instead of simply bouncing away they are collected and compressed. The project “began with a novel design to scoop up air molecules as propellant from the top of Earth’s atmosphere at around 200km altitude with a typical speed of 7.8 km/s,” explains ESA’s Louis Walpot.

QuinteScience in Poland designed the intake. Molecules collected are then given electric charges so they can be accelerated and ejected to provide thrust. Italy’s Sitael designed a dual-stage thruster to ensure better charging and acceleration of the incoming air and tested it in a vacuum chamber at the company’s test facilities, simulating the environment at 200 km altitude. The thruster has no valves or complex parts – everything works on a simple, passive basis. All that is needed is power to the coils and electrodes.

The test was successful and Walpot says this means “air-breathing electric propulsion is no longer simply a theory but a tangible, working concept, ready to be developed, to serve one day as the basis of a new class of missions.”

The air-breathing electric propulsion test set-up inside its vacuum chamber at Sitael in Italy. The thruster sits in front of a particle flow generator used to generate a simulated flow of orbital-velocity air (ESA)
The special intake (right) collects air molecules instead of them simply bouncing them away (ESA)