The European Space Agency conducted tests of a direct-flow ion engine, which uses air from the surrounding atmosphere as a working fluid. It is assumed that small satellites with such an engine will be able to practically unlimitedly stay in orbit with a height of 200 km or less, according to a press release from the agency.
The principle of operation of ion engines is based on the ionization of gas particles and their acceleration with the help of an electrostatic field. The gas particles in such engines are accelerated to much higher speeds than in chemical engines, which is why ionic motors have a much larger specific impulse and use less fuel. But the ion engine has an important drawback – an extremely low thrust compared to chemical engines. Because of this, they are rarely used in practice, mainly on small devices. For example, such engines are used on the probe of Dawn, located today in the orbit of the dwarf planet Ceres, and will be used in the mission BepiColombo , which is to go to Mercury at the end of 2018.
As in chemical engines, the currently used ion engines use a fuel reserve, usually xenon. But there is also the concept of straight-flow ion engines, which, however, has not yet been applied to spacecraft flying in space. Its difference lies in the fact that it is proposed to use as the working fluid not the final gas reserve loaded into the tank before launching, but air from the atmosphere of the Earth or other atmospheric body.
It is assumed that a relatively small device with such an engine will be able to practically unlimitedly stay in low orbits with a height of about 150 kilometers, compensating for the atmospheric braking by the thrust of the engine operating on incoming air from the atmosphere. In 2009, ESA launched the GOCE satellite , which was able to stay on a 255-kilometer orbit for almost five years due to a constantly switched-on ionic engine with a xenon supply. After that, the agency engaged in developing a ramjet ion engine for similar low-earth orbiting satellites, and now conducted the first tests of such an engine.
The tests were carried out in a vacuum chamber in which the engine was located. Initially, he was served accelerated xenon. After that, a mixture of oxygen and nitrogen was added to the gas-intake device, imitating the atmosphere at an altitude of 200 kilometers. At the end of the tests, the engineers conducted tests with an exclusively air mixture to test the performance in the main mode.
It should be noted that a similar engine is being developed by specialists from the MAI and TsAGI, and its tests began in 2017. As reported by N + 1 Professor MAI Sergey Khartov, during the successful tests of this engine, another electric motor was used. He supplied a gas flow to the gas intake device at a pressure of 10 -5 atmospheric and a speed of about 8 kilometers per second. This simulated real conditions for a satellite flying in a low orbit. It is assumed that a direct-flow electric motor will be used to support small vehicles in circular orbits with a height of about 150-250 kilometers or high-elliptical orbits with low altitude at perigee