A domestic research team has developed a satellite propulsion technology that can ignite on demand in space and be stored safely for long periods without using highly toxic fuel.
A team led by Professor Lee Anna in the Department of Mechanical Engineering at Pohang University of Science and Technology POSTECH, together with Senior Researcher Kang Hong-jae at the Korea Institute of Machinery & Materials (KIMM), said on the 5th that it proposed a way to overcome the limits of nitrous oxide–based propulsion using plasma technology and experimentally demonstrated the potential of a next-generation eco-friendly "storable propulsion system." The research was published in the international journal Aerospace Science and Technology in Nov.
As overseas launch vehicles such as SpaceX have recently improved operational efficiency and Korea has seen continued success with Nuri rocket launches, observers say the road to space to put satellites into orbit is closer than before. What becomes important here is a "storable propellant." Simply put, it is a propellant that can be kept in a tank for a long time with low risk of degradation or danger and can power the engine immediately when needed. However, hydrazine-based fuels, which are widely used today, are highly toxic, making handling procedures cumbersome and imposing significant safety and environmental burdens related to leaks and contamination. The industry has therefore been steadily seeking safer propulsion technologies that can replace hydrazine.
One alternative that has drawn attention is nitrous oxide. Because it is relatively easier to handle—used as a sedative and anesthetic adjunct in dentistry, for example—it has been cited as an option to reduce toxicity concerns. But burning it with a fuel can be inefficient, especially in small thrusters, and using a catalyst to aid the reaction can make the device heavier and more complex. A premixed approach, which mixes fuel and oxidizer in advance, makes ignition easier but can raise explosion risks, posing significant safety concerns.
The team addressed the safety-versus-efficiency dilemma with plasma. Plasma, like lightning or auroras, is matter in a very high-energy state; put simply, it strongly activates air (or gas) to help initiate reactions even under conditions where ignition is difficult. The technology applied in this study is a Rotating Gliding Arc (RGA) plasma, which creates plasma in three-dimensional space in a short time to lower the threshold for initiating combustion.
The researchers applied this technology to a bipropellant system using nitrous oxide and methane and conducted experiments. Bipropellants store fuel and oxidizer separately and supply them for combustion as needed. While this offers storability and operational flexibility, reliable ignition is regarded as the core technical challenge.
The team confirmed that immediate ignition was possible with low power of just 30–100 W and that stable combustion could be maintained even under ultra-lean conditions that were difficult with conventional methods. Ultra-lean conditions mean the fuel is very scarce, an environment where flames usually extinguish easily. Even so, the plasma assisted the reaction and sustained combustion.
In particular, it operated stably without a catalyst even under extreme conditions with an oxidizer-to-fuel mass ratio of 1,000, and the combustion efficiency reached 87.8%. The team likened this to "plasma lowering the threshold for ignition, like fanning embers to light wet firewood." In the ideal fuel-ratio range, they also observed efficiency near the theoretical limit at 99.9%.
The achievement is drawing attention for its safety and practicality. Reducing reliance on complex, heavy catalytic or preheating devices can lower the mass of the entire propulsion system, and securing ignition without premixing can reduce explosion risks while simplifying operating procedures.
Professor Lee Anna said, "We confirmed the potential of next-generation eco-friendly propulsion technology through plasma," and Senior Researcher Kang Hong-jae noted, "Because high reliability can be achieved even at low power, the technology could be used widely, from small satellites to long-duration mission propulsion systems."
References
Aerospace Science and Technology (2025), DOI: https://doi.org/10.1016/j.ast.2025.111256