Russian engineers have developed a new propulsion system for small spacecraft—a plasma thruster adapted to operate on krypton. This propellant serves as a viable alternative to the scarce xenon traditionally used in spaceflight. Krypton is 5 to 10 times cheaper and significantly more accessible, which could potentially lower the cost of creating multi-satellite constellations. The new engine is designed for a seven-year operational lifespan and is capable of providing thrust for at least 7,500 hours. However, experts note that krypton is more difficult to ionize and turn into plasma than xenon, meaning its application will depend on the specific requirements of a given mission.
Which Gases Can "Accelerate" Satellites?
Specialists from the Moscow Aviation Institute (MAI), in collaboration with scientists from the Moscow Institute of Physics and Technology (MIPT), have created a low-power plasma thruster that runs on krypton. The unit is designed for high-precision maneuvering of satellites in low Earth orbits (LEO).
According to the developers, this propulsion system will enable satellites to perform station-keeping maneuvers, execute collision avoidance maneuvers with space debris, and perform controlled deorbiting at the end of their service life. Once operational in space, the engine will be able to function for up to seven years. Its resource is calculated for multiple on/off cycles and thrust generation for no less than 7,500 hours.
"This development will be the first low-power propulsion system in Russia specifically designed to use krypton as a propellant. The design is engineered for mass production, which should ensure a relatively low cost," stated Alexander Bogaty, Project Lead and Deputy Director for Development at the Research Institute of Applied Mechanics and Electrodynamics at MAI.
He explained that the development is based on a Hall-effect plasma thruster, where an electric field accelerates gas ions to create reactive thrust. The main advantage of such systems is the ability to achieve high velocities with a relatively low consumption of propellant. Traditionally, xenon—a noble gas that is easily ionized and provides high thrust efficiency—has been used. However, its application is limited by high cost and scarcity: global xenon production amounts to only a few dozen tons per year.
How Krypton Can Replace Xenon in Space Engines
Krypton is an accessible alternative; it is produced in large volumes and is 5 to 10 times cheaper, the scientist explained. The savings on propellant costs make the project highly attractive for commercial and state-owned LEO constellations. Currently, in Russia, similar engines operate exclusively on xenon.
However, transitioning to krypton in low-power engines is a technically challenging task, Alexander Bogaty noted. This gas has a higher ionization energy, making it more difficult to turn into plasma. Furthermore, as the size of the unit decreases, it becomes harder to maintain acceptable thrust efficiency.
"Previously, work on creating low-power krypton engines in our country was not pursued due to the availability of the more expensive but more efficient xenon. Nevertheless, the growing need to create affordable multi-satellite constellations has forced developers to seek new solutions," the scientist added.
According to him, similar engines are already being used in the global space industry. In particular, companies like Busek and Astra manufacture them, and they are utilized in the propulsion systems of Starlink satellite constellations. Russia has also accumulated a significant scientific and technical foundation in this area, allowing the transition from fundamental research to the development of prototype models.
"This is another step in space exploration. It makes propulsion systems for multi-satellite constellations of small spacecraft more accessible," emphasized Alexander Bogaty.
Currently, MAI is manufacturing a prototype of the unit while simultaneously testing individual components and structures. The work began in 2025. In parallel, engineers are developing control, power supply, storage, and krypton feed systems. The project is being implemented within the framework of the Decade of Science and Technology, declared by the President of the Russian Federation.
Alternative Propellants for Spacecraft
"The development of plasma thrusters using krypton as a propellant is highly relevant. In 2023, Fakel Design Bureau tested a high-power engine of this type. The MAI project allows for the application of similar technologies to small spacecraft," commented Ivan Zubrilin, Director of the Engineering Center at Samara University, in an interview with Izvestia.
The choice between xenon and krypton depends on the mission's objectives: a cheaper propellant requires a more energy-intensive, heavier ionization system, or vice versa. Generally, electric rocket engines are suitable when there is a time reserve—for example, six months to bring a satellite into its final orbit. For dynamic solutions, low-thrust chemical rocket engines are more appropriate.
Notably, students and postgraduates at Samara University are currently developing just such an engine, which operates on a mixture of nitrous oxide and propane—an environmentally friendly and inexpensive propellant.
"With the development of mega-constellations of satellites, finding a replacement for xenon is a crucial task. Krypton is an obvious alternative. Its properties are closer to xenon than those of other gases, making it the fastest to adapt existing engines to," noted Igor Egorov, Head of the Plasma Jet Engines Laboratory at NRNU MEPhI and Chief Design Engineer at STAR Company.
According to him, mega-constellations consist of hundreds and thousands of satellites that require fuel for station-keeping. There are simply no production capacities to manufacture that much xenon. Krypton, on the other hand, is extracted from the air simultaneously with xenon, but in volumes an order of magnitude larger.
The expert noted that other alternatives exist. For instance, the latest generation of Starlink satellites uses argon-based engines, but their efficiency is lower, and this gas requires heavier storage tanks. Nevertheless, it is a virtually infinite resource, as argon makes up about 1% of the Earth's atmosphere. Engines are also being adapted to work with iodine, but this is even more complex due to its high chemical reactivity.
"Promising Russian constellations, such as 'Rassvet' (Dawn), involve the launch of no more than a few hundred satellites. Krypton engines are sufficient for them. The further development of this sphere will depend on the plans of Roscosmos and private domestic companies," emphasized Igor Egorov.
In his opinion, microsatellites weighing up to 100 kg may become more in demand, for which propulsion systems operating on different physical principles and with other propellants would be preferable. The expert also suggested that Russia might place a strategic bet on the development of nuclear space tugs.
Source: Izvestia (iz.ru)
