Launch vehicles are a combination of complex and diverse mechanic systems. There are two types of rocket engines—solid and liquid. Usually, rocket engines using solid fuels have simple structures and high reliability, but scaling-up and guided control are difficult. On the other hand, liquid rocket engines have complex structures and are hard to develop but are easy when scaling up and controlling. Launch vehicles that we often see in the media use liquid rocket engines. Liquid rockets create propulsion by combusting fuel and oxidizer, which are propellants, at high pressure through turbopumps. Therefore, turbopumps are necessary parts required for building launch vehicles.

Professor Ryu researches these liquid rocket engines. His research team has accomplished outstanding achievements by being consecutively selected since 2017 for the Ministry of Science and ICT’s “New Research Support Program,” “Core Space Technology Development Program,” and “Mid-career Researcher Support Program.” Recently, they received the Best Presentation Paper Award in the 55th Korean Society of Propulsion Engineers Conference. The title was “Static Load Characteristics of Hybrid Fluid Film Thrust Bearings for Liquid Rocket Engine Turbopumps in Reusable Launch Vehicles: Comparisons between Experiments and Predictions.” This research is expected to largely contribute to securing fundamental technology on liquid rocket engine turbopumps.

“It is necessary to secure the reliability of the bearing system and the safety of rotor dynamics to reuse liquid rocket engines. Ball bearings used in liquid rocket engine turbopumps had limits in durability and reliability, thus making them difficult to reuse. On the other hand, fluid film bearings can be used sustainably.”

For designing and testing the fluid film bearings, Professor Ryu developed the designing technology of fluid film bearings and the rotating system applicable to turbopumps using cryogenic fluids. He researches to evaluate the performance with an experimental device made by the developed technology. This year, he explores the bearing and rotating body systems for launch vehicle turbopumps that use methane as fuels. As research on fluid film bearings lubricated with methane is rarely done globally, securing fundamental technologies is drawing great attention.

There is a distinct difference in how citizens of Korea and the United States think about space tours. For instance, there is not a single company in Korea hiring rocket development engineers in job search websites, but there are numerous in the U.S., as many private companies are jumping into the space industry.

At present, leading countries in space development, such as the United States, Japan, Russia, and China, are conducting development based on their own fundamental technologies for parts and focusing on economic feasibility and reliability. They are widening the technology gap from the countries that recently joined the space development field through next-generation launch vehicle development. They are also rapidly commercializing the technologies in cooperation with private enterprises.

Lately, Korea independently developed a 75-ton liquid rocket engine and a launch vehicle, Nuri, with a seven-ton liquid rocket engine, securing the technology to launch satellites to outer space. Diverse liquid rocket engines are being developed, led by the Korea Aerospace Research Institute. Korea plans to acquire a largescale launch vehicle platform technology that can carry out various space missions by 2040. As the engine technology for launch vehicles is a strategic technology closely related to military technology and national security, it is essential to secure fundamental technologies. Unfortunately, Korea currently lacks research infrastructures and technologies, especially in mechanical element parts.

“To complete the mid-and long-term plans for space development in Korea, it is imperative to develop launch vehicles domestically and secure fundamental technologies for technological independence in the space industry and future exports of related technologies and technology transfer. In addition, in the long term, there is a need for change from the current government-led research and development to a private company-led or -cooperating structure for commercialization.”

The key to securing technology is training talents. National and social attention and support are necessary to allow excellent young talents to continue working while maintaining interest in space technology. It is also required to expand the workforce in government-supported research institutes and create an environment where private companies can participate eagerly. Space launch vehicles are the essential transport method for satellite launch and space exploration. However, we should remember that independent development is crucial as there is little technology transfer between countries.