Spacecraft missions at very low altitudes represent both a great opportunity and an extreme challenge.

On the plus side, the closest you fly to ground the better the resolution of Earth observation missions is. Moreover, very low Earth Orbits –VLEO– enable scientific mission as higher atmosphere studies and Earth’s gravitational field measurement. Finally, such orbits would open a brand new market niche for ultra-high speed telecommunication applications, IoT connections and more.

On the minus side, the drag associated with the residual atmosphere imposes severe limitations to the spacecraft, either in terms of on board propellant mass or in terms of mission duration.

As a matter of fact, under 250 km, drag needs to be continuously compensated with thrust, otherwise the spacecraft orbit rapidly decays.

Atmospheric drag effect as a function of the orbit
Spacecraft lifetime at a particular orbit (source: ISO TC 20/SC 14)
Artist’s view of a platform with an air-breathing electric propulsion system, GOCE-like configuration of the solar panels; intake on the left side, electric thruster operated with oxygen and nitrogen on the right side

Air-breathing Electric Propulsion is the solution to the VLEO problem.

An Air-breathing or ram-EP system is basically composed of an intake and of an electric thruster.

The intake is used to collect the atmospheric gas molecules, and to direct them to the thruster, possibly increasing the pressure in a compression stage. The collected residual atmosphere is then ionized by the thruster, accelerated and expelled at high velocity to generate thrust. A power system, likely a combination of solar arrays and batteries, provides the required electric power.

By using as propellant the same atmospheric particles that are responsible for the generation of drag, air-breathing electric propulsion allows long-lasting thrust generation in low orbits without any need for on-board propellant.

The mass reduction associated with the lack of stored propellant and fluidic system has a direct impact on the launch costs. At the same time, the extension of satellite lifetime improves the profit margin for commercial satellites and the data outcome of scientific platforms.

Air-breathing EP opens a new range of mission scenarios, from VLEO orbits of high scientific interest, to governmental and commercial applications, to exploration missions on other planets with atmosphere (primarily, Mars).

Artist’s view of a platform with an air-breathing electric propulsion system, shuttlecock-like configuration of the solar panels; intake in frontal part, electric thruster operated with oxygen and nitrogen not visible

The main objective of the AETHER project

is to demonstrate, in a relevant environment, the critical functions of an air-breathing electric propulsion mock-up, and its effectiveness in compensating atmospheric drag.

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