Skillful satellites: "perpetual motion" engines will help to develop asteroid resources

Russian engineers have developed plasma engines with an almost unlimited service life. In them, the particles accelerated to create thrust almost do not come into contact with the parts, the wear of which usually limits the service life of the unit. The increased durability will increase the maneuverability of satellites in orbit and use them in missions to remote objects, including planets and asteroids. The development is ready for serial production, and its adaptation to a specific spacecraft may take about six months. As experts noted in an interview with Izvestia, ion engines with a very long service life already exist today, but plasma engines are compact and efficient. At the same time, the factors limiting the service life of such installations have not yet been completely eliminated.

Why doesn't the plasma destroy the engine

The development of the staff of the MAI Scientific Research Institute of Applied Mechanics and Electrodynamics belongs to the class of plasma engines in which thrust is created by a stream of accelerated ions and electrons. The main advantage of the installation is that during its operation, the key parts on which the engine characteristics depend practically do not wear out.

— The innovation is based on an approach to the formation of work processes in the engine. In particular, with the help of magnetic fields, the plasma acceleration zone is organized in a special way — the place where a jet of charged particles arises, creating jet thrust," explained Egor Shilov, chief designer of the engine, a leading engineer at the MAI Institute of Physics and Technology.

According to him, in traditional plasma engines, during operation, charged particles hit the walls of the ceramic discharge channel at high speed, which leads to their gradual destruction. As a result, the original shape of the channel is distorted. This leads to a decrease in thrust and plasma flow rate.

In the new engine, the design was changed so that the acceleration zone of charged particles was completely removed from the discharge channel. Due to this, as they accelerate, they do not hit the surface of the insulator and do not destroy it.

According to the developer, the engine power is 900 watts, and the estimated number of turns on and off is more than 10,000 cycles. Such parameters make it possible to operate the unit as part of spacecraft weighing from several hundred kilograms to a ton or more.

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— Depending on the type, electric rocket engines may exhibit high performance at the beginning of operation, which gradually decrease over time. As a result, it takes more and more time to complete the same orbital tasks. Therefore, the flight task has to be adjusted regularly," explained Alexander Bogatyi, Project Manager, Deputy Director for Development at the MAI SPME Research Institute.

According to the expert, with the new engines, there will be no need for such adjustments. During the development work, it was experimentally confirmed that the propulsion systems will work stably and predictably throughout the entire life of the satellite in orbit — until its planned replacement, that is, at least five to seven years after commissioning. This will simplify spacecraft management, save time and money, and increase the efficiency of the orbital constellation.

— In particular, the new engines will expand the maneuvering capabilities of the satellites. The devices will be able to quickly change the flight path, avoid collisions with space objects and hold positions in the orbital groupings. This is important for the development of complex multi-element satellite systems. In addition, at the end of its service life, the engine can be used to bring the spacecraft down from orbit so that it does not remain space debris," explained Alexander Bogatyi.

The almost unlimited resource of the propulsion system also opens up opportunities for more ambitious missions, including expeditions of small spacecraft to the Moon, as well as to Mars, Venus and other planets, the developers said.

Another promising area is the study of near—Earth asteroids. The satellites will be able to assess their resource potential and develop mining technologies, including rare earths and precious metals.

According to Alexander Bogatyi, the engine is currently undergoing life tests. Tests have shown that thrust and specific impulse remain stable for almost 2,000 hours of continuous operation. The next stage is further testing, which will make it possible to more accurately determine the maximum service life of the installation.

From a technical point of view, the product is ready for mass production. If orders are available, it will take about six months to adapt the engine to a specific spacecraft. In the future, the development may become the basis for the creation of a whole family of domestic plasma engines.

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Why plasma engines are more profitable than ion engines

— A plasma engine accelerates ions to a speed of about 20 km/s and consumes five to seven times less fuel than a chemical engine. However, its thrust is low, so maneuvers can take weeks. In long-range missions, fuel economy will allow small vehicles to visit several asteroids in one flight. In particular, the Psyche probe is now heading for a metallic asteroid using engines of a similar type," Artyom Bogatyrev, market expert at NTI Aeronet, told Izvestia.

Such installations go back to the developments of the domestic OKB Fakel. At the same time, the strength of the MAI engine is its stability. However, the cathode, the power supply system and other elements of the propulsion system wear out, and their resource also affects the overall service life of the unit, the specialist noted.

— Plasma engines allow vehicles to perform long maneuvers with limited fuel supply. "Mega—constellations of hundreds and thousands of vehicles without such installations would be economically unjustified," said Igor Egorov, head of the Laboratory of Plasma Jet Engines at the National Research Nuclear University MEPhI, Chief Design Engineer at STAR.

Another prospect that has not yet been realized is small interplanetary stations weighing only a few tens of kilograms. Plasma thrusters will allow them to travel from high Earth orbit to other bodies of the Solar system. Such devices can be launched into space not as a separate launch, but as an associated payload along with other satellites. This will significantly reduce the cost of research.

"The life of modern plasma engines is about one year," Igor Egorov added. — Such a reserve can be enough for a decade and a half of flight and more. The exceptions are interplanetary stations, including asteroid exploration vehicles: their engines can operate for a significant part of the mission. NASA has developed an ion rocket engine for such tasks. Its ground tests lasted 48,000 hours (5.5 years), after which the installation remained operational. Such an engine can be considered almost eternal.

However, ion and plasma engines differ in the principle of operation. In ion installations, only heavy positively charged ions are accelerated, whereas in plasma installations, the entire working fluid consisting of ions and electrons forming a plasma is accelerated. Therefore, ion engines are bulkier and heavier, consume more electricity and generate less thrust. At the same time, it is impossible to guarantee an "unlimited" resource, since this would require endless trials. In practice, they rely on the resource confirmed during the tests, the expert noted.