The European Space Agency has reported the first test of a ramjet ion engine using air from the surrounding atmosphere as fuel. A press release published on the agency's official website states that in the future, such engines can be used in small satellites, which will allow them to operate for an almost unlimited amount of time in an orbit with an altitude of 200 kilometers or less.
Ion engines are based on the principle of ionization of gas particles and their acceleration using an electrostatic field. Due to the design features, gas particles in such engines are accelerated to much higher speeds than in chemical engines. Ion engines are capable of creating a much higher specific impulse and show lower fuel consumption, but they have one significant drawback - they create extremely low thrust compared to conventional chemical engines. That is why now ion engines are rarely used in practice. Recent examples of their use include perhaps the Dawn spacecraft, currently orbiting the dwarf planet Ceres, and the BepiColombo mission to explore Mercury, which will begin at the end of 2018.
Diagram of a ramjet air ion engine.
The standard configuration of ion thrusters in use today assumes a supply of fuel, which is usually xenon gas. But there is also the concept of ramjet ion engines, which has never been used in real space missions. It differs from conventional ion engines in that the source of fuel is not a finite supply of gas that must be loaded into the tank before starting, but directly air from the Earth's atmosphere or another body with an atmosphere.
In theory, a small spacecraft equipped with such an engine can be in low orbit almost forever with an altitude of 150 kilometers. In this case, atmospheric braking will be compensated for by the thrust of the engine, which draws air from this atmosphere.
Back in 2009, the European Space Agency launched the GOCE satellite, which, thanks to an always-on ion engine with a supply of xenon, has been in 255-kilometer orbit for almost five years. As a result of the experiment, ESA decided to start developing a concept of a ramjet ion engine for similar low-orbit satellites.
Gas sampling installation.
Promotional video:
Ion engine test with xenon as fuel.
The prototype was tested inside a vacuum chamber. Initially, accelerated xenon was fed into the installation. As part of the second part of the experiment, a mixture of oxygen and nitrogen was fed into the gas intake system, which simulated the atmospheric composition at an altitude of 200 kilometers. In the last part of the test, engineers used a clean air mixture to test the system's functionality in the main mode.
Ion engine test with air as fuel.
Nikolay Khizhnyak