They added to the gas: engines on krypton will accelerate the creation of multi-satellite groups

Russian engineers have developed a new propulsion system for small spacecraft, a plasma engine adapted to run on krypton. This "fuel" is an alternative to the scarce xenon, which is traditionally used in space exploration. Krypton is 5-10 times cheaper and much more affordable, which will potentially reduce the cost of creating multi-satellite groupings. The new engine is designed to operate for seven years and is capable of providing thrust for at least 7.5 thousand hours. However, experts note that krypton is more difficult to ionize and turn into plasma than xenon. Therefore, its application will depend on the objectives of a particular mission.

What gases can "accelerate" satellites

MAI specialists, together with scientists from MIPT, have created a low-power plasma engine that runs on krypton. The unit is designed for high-precision control of satellites in low-Earth orbits.

According to the developers, the power plant will make it possible to perform maneuvers to maintain orbital altitude, avoid collisions with space debris and bring the device out of orbit in a controlled manner at the end of its service life. After starting operation in space, the engine will be able to operate for up to seven years. Its resource is designed to repeatedly turn on, off and create thrust for at least 7.5 thousand hours.

— The development will be Russia's first low-power propulsion system specifically designed to use krypton as fuel. The structure is designed for mass production, which should ensure a relatively low cost," said Alexander Bogatyi, project manager, Deputy Director for Development at the MAI Research Institute of Applied Mechanics and Electrodynamics.

According to him, the development is based on a Hall effect plasma engine. In it, an electric field accelerates the ions of the gas, creating a reactive thrust. The main advantage of such systems is the ability to develop high speeds with a relatively low consumption of working matter. Traditionally, xenon, a noble gas that is easily ionized and provides high thrust efficiency, is used as the working fluid for such engines. However, its use is limited by high cost and scarcity: the global production of xenon is only a few tens of tons per year.

How Krypton can replace xenon in space engines

Krypton is an affordable alternative, it is obtained in large quantities, while it is 5-10 times cheaper, the scientist explained. Savings on the cost of the working substance make the project attractive for commercial and government low-orbit groups. Currently, in Russia, such engines run only on xenon.

At the same time, switching to krypton in low—power engines is technically not an easy task, noted Alexander Bogatyi. This gas has a higher ionization energy, so it is more difficult to convert it into plasma. In addition, when reducing the size of the installation, it is more difficult to ensure acceptable traction efficiency.

— Previously, work on the creation of low-energy engines based on krypton in our country was not carried out due to the availability of more expensive, but also more efficient xenon. Nevertheless, the need to create cheap multi—satellite groupings has forced developers to look for new solutions," the scientist added.

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According to him, similar engines are already used in the global space industry. In particular, they are produced by Busek and Astra companies, and they are used in motion control systems for Starlink satellites. Russia has also accumulated significant scientific and technical groundwork in this area, which has made it possible to move from basic research to the development of prototypes.

— This is another step in space exploration. It makes it possible to make propulsion systems for multi—satellite groups of small spacecraft affordable," emphasized Alexander Bogatyi.

Currently, MAI is manufacturing a prototype of the installation and simultaneously testing individual components and structures. Work began in 2025. In parallel, engineers are creating control systems, power supply, storage and supply of krypton. The project is being implemented within the framework of the Decade of Science and Technology announced by the President of the Russian Federation.

Alternative fuels for spacecraft

— The development of plasma engines using the krypton working fluid is extremely relevant. In 2023, the Fakel Design Bureau tested this type of high-power engine. The MAI project makes it possible to apply similar technologies for small devices," Ivan Zubrilin, director of the Engineering Center at Samara University named after S.P. Korolev, commented to Izvestia.

The choice of xenon or krypton is determined depending on the mission objectives — a cheap working fluid, but a more energy-intensive, heavy ionization system, or vice versa. In general, electric rocket engines are suitable if there is a time reserve. For example, it will take six months to put a satellite into orbit. Low-thrust chemical-fueled rocket engines are suitable for dynamic solutions. A similar installation, which runs on a mixture of nitrous oxide and propane, an environmentally friendly and cheap fuel, is being created by students and graduate students of Samara University.

— With the development of mega-constellations of satellites, finding a replacement for xenon is an important task. Krypton is an obvious alternative. It is closer in properties to xenon than other gases. It is the fastest way to adapt existing engines to work on it," said Igor Egorov, Head of the Laboratory of Plasma Jet Engines at the National Research Nuclear University MEPhI, Chief Design Engineer at STAR.

According to him, mega-constellations consist of hundreds and thousands of satellites that need fuel to maintain their orbit. There is simply no capacity to produce such a quantity of xenon. Krypton is produced from the air at the same time as xenon, but in a volume that is an order of magnitude larger.

As the expert noted, there are other alternatives. For example, the latest generation of Starlink satellites use argon engines, but their efficiency is lower, plus this gas requires heavier storage tanks. Nevertheless, this is a relatively endless resource — about one percent of argon is in the air. The engines are also adapted to run on iodine, but this is even more difficult due to its chemical activity.

— Promising Russian groups, such as Rassvet, assume the launch of no more than a few hundred satellites. Krypton engines are enough for them. Further development of this area will depend on the plans of Roscosmos and private domestic companies," Igor Egorov emphasized.

In his opinion, microsatellites weighing up to 100 kg may be more in demand, for which propulsion systems operating on different physical principles and with other working bodies are preferable. It is also possible that Russia will rely on the development of nuclear space tugboats, the expert suggested.