Domestic researchers successfully conducted performance tests on the 'Radiative Cooling Nozzle' that cools rocket engines. The radiative cooling nozzle helps the engine withstand internal heat through a radiation method that naturally dissipates heat, which can reduce launch expenses. If successful, it is expected to contribute to domestic rockets.
According to the Korea Aerospace Research Institute (KARI) on the 24th, researchers from the small launch vehicle research division recently applied the radiative cooling nozzle to a methane-oxygen combustor and successfully verified the technology to effectively dissipate the engine's heat during a maximum combustion time of 60 seconds.
The rocket engine burns fuel inside the combustion chamber. The high-temperature and high-pressure combustion gases are expelled through a conical nozzle to gain propulsion. The temperature of the combustion gases can exceed 3,500 degrees Celsius. If the heat from the combustion gases is not dissipated in time, it can lead to fires or cause parts to melt and fail. Thus, technology managing the engine's heat is a critical factor that determines launch success.
The KARI researchers created the nozzle using high-temperature resistant materials, allowing the engine to naturally dissipate heat without additional cooling. This method, known as the radiative cooling nozzle, has the advantage of a simpler structure compared to existing cooling methods, thereby reducing engine manufacturing and maintenance expenses and lightening weight.
The researchers used a 3D (three-dimensional) printer to make the nozzle with niobium (Nb) alloy powder as ink. The nozzle surface was coated with an oxidation-resistant layer. Recent verification experiments confirmed that the radiative cooling nozzle effectively dissipated internal heat while maintaining engine performance. The engine operated for 60 seconds and produced high-temperature combustion gases; however, no damage occurred to other components due to the use of the radiative cooling nozzle.
Kim Hyun-jun, the lead researcher who developed the radiative cooling nozzle, noted, "Due to the characteristics of metal materials, the nozzle expansion section oxidizes at high temperatures, making coating technology important," and added, "This technology is classified as a strategic technology, making it challenging to apply foreign technology domestically. The fact that we developed the technology in collaboration with domestic companies InssTek and Bedell Surface Treatment Research Center is significant."
The ultimate research goal is to secure radiative cooling nozzle technology that continues throughout the nozzle expansion section where combustion gases are expelled. The researchers stated that applying the radiative cooling method to the nozzle expansion section could reduce the engine's weight and manufacturing expenses without compromising rocket performance.
Previously, the regenerative cooling method used in the Naro and Nuri rockets has the disadvantage of increasing thickness within the engine, which simultaneously increases the overall weight. Applying radiative cooling technology allows cooling of the engine without additional structures, significantly reducing engine weight. This is effective in reducing launch expenses. It is already utilized in the upper engine of SpaceX's Falcon 9.
Kim Hyun-jun, the lead researcher, remarked, "It's more significant that we confirmed the potential for the successful development of radiative cooling nozzle manufacturing technology rather than saying we've fully developed it in Korea," adding, "Once complete, we will continue research to secure the essential technology needed for the advancement of rocket engine technology."