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The Korea Space Launch Vehicle (KSLV-II) development project is a national space development project with a budget of KRW 1.957 trillion over ten years. Its goal is to develop an independent Korea Space Launch Vehicle capable of putting a 1.5 ton multipurpose satellite into low orbit at 600~800km altitude.
In addition to the technology and know-how accumulated through the development of ‘Naroho’, Korea will acquire key technologies such as a high thrust liquid engine and propulsion engine testing equipment, as well as comprehensive launch vehicle operational know-how needed for the development of a launch vehicle.
The Korea Space Launch Vehicle is a 3-stage launch vehicle consisting of 300 ton 1st stage with 4 75 ton liquid engines, 2nd stage with a 75 ton liquid engine and 3rd stage with a 7 ton liquid engine.
The Korea Space Launch Vehicle development project is being executed in 3 phases. Phase 1 (Mar. 2010~Jul. 2015), which involved a review of the launch vehicle system and preliminary, the construction of a propulsion engine testing facility, and the successful ground testing of a 7-ton-class liquid engine, was successfully completed. Phase 2 is currently ongoing. Phase 2 (Aug. 2015-Dec. 2018) will complete the detailed design of the launch vehicle and engine and the development of a 75-ton ground engine and test launch vehicle. Finally, Phase 3 (Apr. 2018-Mar. 2021) will complete the development of the 3-stage launch vehicle system technology, which will be followed by two trial launches to confirm the successful completion of the project.
The development of a 75-ton-class liquid engine and a 7-ton-class liquid engine is also the key agenda of the Korea Space Launch Vehicle development project.
The research and development of Naroho paved the way for the development of the Korea Space Launch Vehicle, and included the development of a 30-ton-class liquid engine parts and the design of a 75-ton-class liquid engine.
The 75-ton-class and 7-ton-class liquid engines to be mounted on Korea Space Launch Vehicles are both being developed for gas generator and turbo pump operation in order to reduce the time, cost and technical difficulties of development. They use kerosene as the fuel and liquid oxygen as the oxidizer.
As part of the development of an engine for the Korea Space Launch Vehicle, ten propulsion engine test facilities - including a burner combustion test facility, a turbo pump real-propellant test facility, an engine ground/air combustion test facility, and a propulsion engine system test facility - were built at the Naro Space Center and in various other locations. Previously, it had been difficult to develop engines in Korea due to a lack of sufficiently large facilities at which to test high-thrust engines. These test facilities enable step-by-step testing of the performance of components of the burner, turbo pump and gas generator, which are key components of the 7-ton and 7-ton engines, and performance assembled engine system on ground and air environments.
The plan is to conduct tests (each of which requires around one week of preparation) on each component and engine anywhere between several dozens and 200 times, and analyze the results.
There are many technical difficulties associated with the development of the Korea Space Launch Vehicle, the greatest of which is unstable combustion. Unstable combustion occurs when vibration generated during combustion, or disturbance of the propellant supply system or acoustic field affects the pressure, temperature and/or flow rate inside the combustion chamber. It is extremely dangerous as it can cause major accidents including engine explosion. Although combustion instability was identified as a technical difficulty in the 1930s when the development of liquid-powered rockets was in its initial stage, it remains to be definitively resolved.
Since combustion instability cannot be completely eliminated with the current technology, its occurrence can interfere with the development of a new structure such as a combustion stabilization system, which means that it may have to be mounted or the design may have to be changed, and the equipment refabricated, in the worst case scenario. That is why development experience and know-how in addition to technology are important for the successful development of a launch vehicle.
The development of a rocket engine also involves the development of a system that can withstand high pressure and both extremely high and low temperatures at the same time within a short combustion period. Therefore, the development or application of difficult technologies such as overheating prevention technology, heat resistant alloy technology and material handling at extremely low temperatures is needed in addition to resolving the combustion instability issue.