대메뉴 바로가기 본문 바로가기

Nuri, the Korean launch vehicle

Space Launch Vehicle: the Only Means of Space Transportation

Space Launch Vehicle

Transportation to space

The United States and Russia have secured space launch vehicle technology since the 1950s. Europe, Japan, China, and India are also pursuing space development, such as launching satellites, space probes, and transporting space cargo, by securing space launch vehicle technology. All of the satellites developed in Korea have been launched using foreign space launch vehicles. As a latecomer in the research and development of space launch vehicle, Korea does not own a space launch vehicle yet. Since countries restrict cross-border technology transfer for space launch vehicles, it takes much time and development cost and many trials and errors due to technical difficulties. With the recent introduction of innovative recycled launch vehicles by US private space enterprise Space X, Europe and Japan are also developing low-cost and high-efficiency launch vehicles. Moreover, many startups around the world are developing ultra-small launch vehicles capable of launching nanosatellites. The global commercial space launch vehicle market is expected to expand as the number of space development countries increases and more small satellites are developed.

Development of space launch vehicle with domestic technology

KARI has cultivated its rocket design and manufacturing capabilities by developing single-stage solid propulsion science rocket (KSR-I, 1993), double-stage solid propulsion mid-sized science rocket (KSR-II, 1998), and Korea’s first liquid propulsion science rocket (KSR-UUU, 2002). It acquired space launch vehicle know-how and experience by developing Naro (successfully launched in 2013), the double-stage space launch vehicle consisting of a first-stage liquid engine and a second-stage solid engine, through international cooperation with Russia. It is currently developing a 3-stage Korean launch vehicle (Nuri) with domestic technology to launch a 1.5t-class application satellite into a solar-synchronous orbit at an altitude of about 600~800km. The Nuri is a space transportation vehicle necessary for Korea to become a space powerhouse and a key vehicle for stable space development. KARI plans to launch a domestically developed satellite using the Nuri between 2022 and 2027. With the Nuri development, Korea has finally secured the three elements of space development: the satellite, the launch vehicle, and the launch site. They will enable Korea to launch its satellite at any desired time.

Status of Rocket Development in Korea

Status of Rocket Development in Korea
Subject KSR-I KSR-II KSR-III Naro (KSLV-I) Korean Launch Vehicle (KSLV-II)
Purpose Localization of single-stage non-guided scientific observation rockets and exploration of the ozone layer over the Korean Peninsula Localization of double-stage solid propulsion scientific observation rockets with initial altitude control function Securing base technology for independent development of liquid propulsion rockets and small satellite launch vehicles Securing technology and experience for independently developing launch vehicles that can carry a 100kg- class satellite into low-earth orbit Securing development know-how of a launch vehicle that can carry a 1.5-ton application satellite into low-orbit
Development period 1990.7 ~ 1993.10 1993.11 ~ 1998.6 1997.12 ~ 2003.2 2002.8 ~ 2013.4 2010.3 ~ 2022.3
Development cost (KRW 100 million) 28.5 52 780 5,025 19,572
Length (m) 6.7 11.1 14.0 33.0 47.2
Diameter (m) 0.42 0.42 1.0 2.9 3.5
Weight (kg) 1,268 2,048 6,000 140,000 200,000
Launch date Unit1 1993.6.4 1997.7.9 2002.11.28 2009.8.25 2021
Unit 2 1993.9.1 1998.6.11 2010.6.10
Unit 3 - - 2013.1.30
Features
  • - Single-stage solid propulsion science rocket
  • - Double-stage solid propulsion science rocket
  • - Successful separation of two stages during flight
  • - First liquid propulsion rocket independently developed in Korea
  • - Secure base technology for small satellite launch vehicle
  • - Development of Korea’s first satellite launch vehicle
  • - Joint development by Korea and Russi
  • - Securing system technology through technical cooperation with Russia
  • - Development of Korea’s first application satellite launch vehicle
  • - Independent domestic development
  • - Developed 75 ton-class liquid engine

Nuri, the Korean launch vehicle

Updates : 2021.06.25

Development of space launch vehicle with independent technology

As a Korean three-stage launch vehicle, the Nuri can directly put a 1.5-ton application satellite into a 600-800 km solar synchronous orbit. The engine is a 75-ton liquid engine and 7 ton-class liquid engine. The first stage consists of four clustered 75-ton engines, the second stage has one 75-ton engine, and the third stage features a one 7-ton engine. The Nuri was developed with independent domestic technology throughout all processes of design, manufacturing, and test. Phase 1 of the Nuri development project constructed a propulsion engine test facility and performed the 7-ton liquid engine combustion test. Phase 2 developed the 75-ton liquid engine and succeeded in launching the test launch vehicle (2018). The single-stage test launch vehicle consists of one 75-ton liquid engine to check the 75-ton liquid engine's flight performance. With the successful launch of the test launch vehicle, Korea became the world’s seventh country to have a mid- to large-sized liquid rocket engine of 75 tons or more. The Nuri is currently undergoing the final Phase 3 of the development project. KARI completed the verification of the second and third stages by launching the test launch vehicle and the three-stage comprehensive combustion test, and it is currently assembling the flight model. KARI began the integrated combustion test to verify the clustering technology that bundled four 75-ton engines and the performance of the 1st stage. The first launch of the Nuri, scheduled for 2021, will be without a satellite since it will focus on the verification of the launch vehicle performance. The second test launch for the performance verification will have the satellite loaded. Afterward, the Nuri will carry out the mission of launching domestically developed satellites from 2022 to 2027.

Korean Launch Vehicle's Development Plan

Korean Launch Vehicle's Development Plan
Phase 1 (2010.3 - 2015.7) Phase 2 (2015.8 - 2019.3) Phase 3 (2018.4 - 2022.3)
Development of 7 ton- class liquid engine Test facility construction Test launch using one 75-ton liquid engine (2018.11) Assembly of four 75 ton- class (1st stage) + one 75 ton-class (2nd stage) + one 7 ton-class (3rd stage) and launch (scheduled in 2021)

Securing the core technology for space launch vehicles

The Nuri is the first project to carry out the entire process from design to production, testing, and launch operation independently in Korea. One of the keys to the development of the Nuri is to develop a 75-ton thrust liquid engine and a propellant tank containing fuel and oxidizing agents and accounting for 70 to 80% of the total volume of the Nuri. Over 150 domestic companies are participating in developing the Nuri. The 75 ton-class mid- and large-sized liquid engine development is based on the know-how of developing 30 ton-class liquid engine in previous research. KARI was able to develop the world’s 7th mid- and large-sized liquid engine by overcoming the technical limitations of combustion instability and completing ground combustion tests and flight performance tests with test launch vehicles. KARI also independently developed a large propellant tank despite the many technical difficulties in design and manufacturing because of the thickness of only 2-3mm while the diameter was 3.5m. To overcome the problem of having to depend on overseas test facilities to check the performance of core engine components at the time since there was no such facility in Korea, a propulsion engine test facility was constructed at the Naro Space Center in order to verify the performance and reliability of core engine components, engine system, and propulsion engine system.

Major Participating Companies in Nuri Development

Major Participating Companies in Nuri Development
Area Company
System assembly Korea Aerospace Industry
Engine Engine assembly Hanwha Aerospace
Turbopump Hanwha Aerospace, S&H, and others
Combustor/Gas generator Vitzrotech
Propulsion engine/supply system Hy-Lok Korea, Neopec, Teba Corporation, and others
Pyro igniter (starter) Hanwha, Neopec, Samyang Chemical, and others
Measurement system E&E
Mission Mission control system Hanwha Defense and others
System integration Ground control system, piping assembly, etc. Hanwha, Yukon System, and UREATac
Guidance control Drive system, thruster system, and others Hanwha, Space Solutions, and others
GPS receiver NAVcours and others
Electronics Electronic payload DANAM Systems, GigaRF, Syscore, and others
Structure Tank, fuselage, and others S&K Aerospace, Innocom, Doowon Heavy Industries, Hankuk Fiber, DACC Aerospace, Poongsan, and others
Heat/Aerodynamic Heat control/Fire safety Hanyang ENG and others
Ground systems Launch pad Hyundai Heavy Industries and others
Hyundai Heavy Industries and others Equipment installation Hanwha, Hanwha Aerospace Hyundai Rotem, Hanyang ENG, Vitzrotech, and others
Construction/Architecture Hanjin Heavy Industries, Gyeryong E&C, Dongil E&C, DW Development, Sunjin, and others
  • Total lengthAbout 47.2 m
  • Total weight200 tons
  • Diameter3.5m
  • Thrust1st stage 300 tons (four 75-ton engines) /one 2nd-stage 75-ton engine /one 3rd-stage 7-ton class engine
  • Launch date2021
Nuri the Korean launch vehicle
Nuri the Korean launch vehicle

01Test launch vehicle

More Close

Comprehensive verification of safety and performance of 75-ton engines

The test launch vehicle is a single-stage launch vehicle to check the performance of the 65-ton liquid engine, which is the main engine and is applied to the first and second stages of the Nuri, through actual flights. The test launch vehicle launched in the afternoon of November 28, 2018 from the Naro Space Center in Goheung-gun, Jeonnam exceeded the target time of 140 seconds and burned for 151 seconds, reaching a maximum altitude of 209 km and then falling to the point of about 429 km on the southern open sea. The test confirmed the soundness of the performance of ground systems such as structures, electronics, controls, heat/aerodynamics, launch pad, and tracking system, which are subsystems that make up a launch vehicle, including liquid engines developed with domestic technology. With the successful launch of the test launch vehicle, Korea became the world’s 7th country to have the technology to develop medium and large liquid rocket engines of 75 tons or more. The test launch vehicle's development and launch were named one of the Top Ten Outstanding Research Outcomes in 2018 by the National Research Council of Science and Technology.
  • SpecificationsTotal length of 25.8m
  • Total weight52.1 tons
  • Diameter2.6m.
  • Thrust75 tons
  • Launch dateNovember 28, 2018
Test launch vehicle
Test launch vehicle

02Nuri engine

More Close

Engine development with domestic technology

KARI developed an engine, considered the heart of the Korean launch vehicle (Nuri), with domestic technology. Except for some such as the bearings used in the engine turbopump, all parts were successfully localized. The complex liquid engines of space launch vehicles were engineered and manufactured with Korean technology. Even developed countries possessing long-time accumulated engine development know-how, professionals, and infrastructure require a considerable amount of physical time to develop a new engine. The average development period for major liquid rocket engines using non-toxic propellants is 9.17 years. An engine using a liquid oxygen-kerosene (fuel oil) combination requires an average of 8.50 years. An engine with liquid oxygen-liquid hydrogen combination requires an average of 9.83 years.

Liquid engine configuration

- Combustor: A device that produces propulsion by ejecting high-temperature, high-pressure gas generated by the combustion reaction of fuel and oxidizer through nozzles - Turbopump: A device that supplies high-pressure fuel and oxidant to the combustion chamber - Gas generator: A drive that drives the turbopump turbine through the combustion reaction of high-pressure gas - Supply system parts such as valves
Engine System = Combustor + Turbopump + Gas Generator + Supply System Parts

Engine performance test like quenching

Liquid rocket engines have many risk factors because they must be built to provide the best performance while violent chemical reactions occur inside the liquid engine at the same time. Therefore, securing reliability is most important, and repeated tests are essential to apply the newly developed engine to rockets. The Nuri's 75-ton liquid engine, developed with domestic technology, overcame technical difficulties such as combustion instability in the early stages of development and confirmed the flight process's combustion performance through a test launch in 2018. KARI has continuously conducted engine combustion tests to ensure the performance and reliability of the 75-ton engines. The 75-ton engine used in the Nuri’s first stage should burn for 123 seconds, and the second-stage 75-ton engine for high altitude needs to continue combustion for 142.2 seconds. A total of 25 75-ton engines were assembled and tested in April 2016 until November 2020. Units 1 and 2 were manufactured to determine each component's operability and performance and the various sequences of the important engines. As a result, unit 3 and later one have had a shape similar to that of the flight model. Afterward, KARI delivered the test launch vehicle certified model and flight model after successful acceptance tests and continuously conducted the engine verification test. As of November 2020, 25 75-ton engines had been produced, and they have gone through a cumulative combustion time of 16,690 seconds in 168 tests. The single longest combustion time was 260 seconds. Moreover, the initial layout of the 7-ton engine was designed by identifying and correcting problems through the power pack tests from April 2015 before the engine test. After that, the engine assembly process was established through manufacturing and assembly, and the first combustion test was successfully conducted in July of the same year. The 7-ton engine's flight model assembly began after the manufacturing and test following the three-stage certified model. Since the three-stage liquid engine does not operate during the first and second stages of flight but is exposed to a vibrating environment, a vibration environment test was conducted to verify structural stability and operability during combustion. Eleven 7-ton engines were developed, achieving cumulative combustion time of 16,385.7 seconds in 89 tests.

Enduring extreme conditions: the engine combustion test

According to the engine’s operating environment, combustion tests can be divided into ground combustion tests and high-altitude combustion tests. The ground combustion test checks whether the engine operates normally at an altitude of about 50 km, which is the operating section of the first stage of the Nuri. The key to the high-altitude combustion test is to verify that the engine operates normally at an altitude of 50 km or higher, which is the operating section of the second and third stages of the Nuri. The propulsion engines operating in high-altitude environments, such as double-stage 75-ton engines for the 2nd stage and the 7-ton engines for the 3rd stage, have a very high nozzle expansion ratio since the atmospheric pressure of the operating altitude is much lower than that of the ground. As a result, it is difficult to measure the thrust accurately through a combustion test on the ground because of the flow separation phenomenon wherein the nozzle fluid does not flow well but appears irregularly away from the wall. Therefore, it is necessary to simulate the actual flight environment on the ground and check the exact thrust characteristics such as ignition and combustion to prove the propulsion engine's performance on the ground.

Clustering of four engines for a powerful thrust

The Nuri’s first stage has adopted a clustering method that generates 300 tons of thrust by bundling four 75-ton liquid engines. Clustering is a method of bundling multiple engines together to generate the necessary thrust. Although it can exhibit strong power while maintaining structural stability, the clustering method is difficult to control compared to a one-engine operation. Control becomes more difficult as there are more engines bundled. In engine clustering, multiple engines must produce the same thrust as if they were one engine. Fuel and oxidant must be supplied to all engines with the same requirements to ensure such. It is necessary to maintain constant temperature, pressure, and flow rate for the four engines to perform the same as if they were one engine. Moreover, the engine components such as the turbopump, piping, and combustor must have high reliability. It is also important to secure a technology that can determine whether the four engines' thrust is normal and how much the engine thrust error is. Maintaining the engines' level and balance is an important factor in preventing the four engines from interfering with each other when they are ignited simultaneously and in developing a highly reliable engine.

The fruit of complex and precise space technology

The space launch vehicle's liquid engine is the output of extreme technology, and many technical difficulties arose during the development process. First of all, the highly explosive fluid must be stably controlled at extreme temperatures and high pressures. The Nuri’s liquid rocket engine reacts with kerosene and liquid oxygen at -183°C to generate propulsion through combustion. When combustion starts, the engine combustion chamber’s internal temperature soars to 3,000°C. The fluid with extreme temperature difference between -183° and 3,000°C must be operated within the confined engine space. Above all, developing a liquid rocket engine is difficult because of its complex structure. It is also hard to ignite a space launch vehicle’s liquid engine. Ignition requires valves and components supplying fuel and oxidant in an extremely short time of less than a second to operate correctly in a precisely defined sequence. Nuri's 75-ton engine burns 255 kg of fuel and oxidant per second, and even a slight startup sequence error can lead to an explosion. The same principle of the gas stove used at home is at work; when it is turned on, an explosive ignition occurs instantly when the spark rises even with a slight delay.

Advanced research and development of multistage combustion cycle engines

KARI is also conducting preliminary research on future space launch vehicles while developing the Nuri. It is developing a 9-ton multistage combustion-cycle liquid engine with high combustion efficiency in parallel, although it is more difficult to develop than the existing open-cycle liquid engine. KARI has completed more than 60 tests, including a single combustion test for a maximum of 600 seconds since 2016 to develop a multistage combustion-cycle engine for which only some advanced countries such as the United States, Russia, and China have the technology. It confirmed the ability to lower the engine thrust by up to 40%. The multistage combustion cycle engine will be used to improve the performance of the Korean launch vehicle (Nuri) in the future. Applying the 9-ton multistage combustion cycle engine to the space launch vehicle to be developed after the Nuri is expected to increase the payload weight from 1.5 tons to 2.7 tons. Moreover, it can put two or more satellites into various orbits and even launch a lunar probe. KARI is also developing a combustor that can withstand higher combustion pressure than the existing 75-ton class combustor to improve the 75-ton class engine's performance.

Performance of Multistage Combustion Cycle Engine

Performance of Multistage Combustion Cycle Engine
category Design specification
Vacuum thrust (tonf) 8 - 10 tonf
Vacuum non-thrust, lsp (sec) Last 350 seconds or more
Mixing ratio (O/F) 2.5 - 2.6
Turbo pump inlet pressure(bar) 4/1.5
Combustion pressure of the smoke absorber 210 bar More
Main Combustor Combustion Pressure 90 bar More
Propulsion agent LOX/Kerosene
Engine cycle Staged Combustion
Weight(kg) 300 kg Less than
Operating hours 600 second Less than
  • Composed of turbopump, combustor, gas generator, and various valves
  • Four 75-ton thrust engines (1st stage), one 75-ton class engine (2nd stage), and one 7-ton class engine (3rd stage)
  • 912 Kg per 75-ton engine for the 1st stage, 1,115kg per 75-ton engine for the 2nd stage, and 187 kg for the 7-ton engine
Nuri engine
Nuri engine

03Nuri propellant tank

More Close

Development of propellant tank with advanced technology

The Nuri is a space launch vehicle that uses cryogenic oxidizing agents and room temperature fuel as propellants. Most parts of the launch vehicle consist of a propellant tank containing fuel and oxidant, and the propellant tank accounts for 70-80% of the projectile volume. Reducing the propellant tank weight leads directly to the launch vehicle’s performance improvement. Therefore, the propellant tank is made of lightweight yet durable aluminum alloy and configured with a cylinder corresponding to the body and a dome corresponding to the head. Nuri's propellant tank has maximum height of 10m and diameter of 3.5 m but is only 2.5-3 mm thick. Nevertheless, the propellant tank must be able to withstand 4 to 6 times the atmospheric pressure applied to the inside of the propellant tank and the load from inertia and aerodynamic forces during the flight. In particular, since the propellant tank is a cylindrical structure whose column is longer than the cross-section, the buckling phenomenon occurs when the load reaches a certain level.
Therefore, the inner walls of the propellant tank, considered to be the launch vehicle body, are made in a form called isogrid structure to withstand such pressure and load. It is a method of efficiently increasing the cylindrical structure’s rigidity compared to the weight with a pattern of repeated triangular grid reinforcement structure. The isotropic lattice structures are derived from extremely difficult techniques that require repetitive calculations and analysis. Unlike advanced countries such as the United States and Russia, which have a long history of space development, Korea had to find the optimal isotropic grid structure through repetitive calculations and numerical analysis since it was the country's first time to develop a propellant tank for a launch vehicle.

Design and manufacturing optimized for liquid flow

Kerosene and liquid oxygen acting as oxidant are the liquid fuel of the launch vehicle, and their constant flows inside the tank exert an impact. Even in automobiles and large ships using oil as fuel, this flow makes it difficult to control the altitude, and devices for reducing this phenomenon are installed. It is the same for the Nuri’s propellant tank. Because it is much larger, and it contains large amounts of fuel and oxidants, strong flow inside the tank can have a devastating effect. For this reason, it is necessary to find and apply a design and manufacturing method optimized for the tank size and flow of fuel and oxidizing agent. In addition, the Nuri uses liquid oxygen as an oxidizing agent. Since the liquid oxygen temperature is -183℃ in cryogenic state, and the vaporization rate is very high, the tank plays an important role in injecting and storing it.

04Research on future launch vehicle technology Development of large and small launch vehicles using the Nuri as a platform

More Close
Korea plans to develop large space launch vehicles using the Nuri as a platform to strengthen space transport capability. In 2025-2030, in preparation for the increase in demand for small satellites weighing less than 500 kg, KARI plans to link and expand the Nuri technology into a platform for small satellite launch vehicles. The small launch vehicle is used for launching small satellites with loading weight of 500 kg or less into space. The 1st stage applies a 75-ton engine, and the 2nd one, a 3-ton methane engine. From 2030 through 2040, it plans to secure large launch vehicle platforms if necessary to meet domestic demand and perform various space missions of large low-orbit satellites and geostationary orbit satellites. KARI plans to advance space launch vehicle technologies by developing low-cost, high-efficiency launch vehicles, nano launch vehicle technology, and solid propellant rocket technology. Following the Nuri development, KARI plans to improve the Nuri’s performance by optimizing the shape and operating conditions, enhancing the main engine performance, developing the upper section re-ignition technology, and reducing the weight and developing multiple payload/separation technologies. It will improve mission performance, such as launching satellites and lunar probes. Moreover, it plans to enhance domestic industries' capacity through the reinforcement of Nuri-based space transport capabilities and technology transfer to the private sector.
Additionally, KARI is developing advanced technologies that can increase the double-stage engine’s performance to enable engine re-ignition. The application of engine re-ignition will allow missions to put multiple satellites into the desired orbit and enable deep space exploration.
Research on future launch vehicle technology Development of large and small launch vehicles using the Nuri as a platform
TOP