Korea Space Launch Vehicle Research Articles

Introduction of Level Sensor Assembly in Korea Space Launch Vehicles II

Level sensors are widely used in the aerospace field to measure the quantity of propellant. Especially, measuring the quantity of the propellant is very important in launch vehicles because the performance of launch vehicles strongly depends on the weight of the propellant. Many launch vehicles use cryogenic propellants, such as oxygen, hydrogen, and methane, and level sensors for cryogenic propellants are needed in these applications. In this study, the development process for the newly designed level sensor assembly based on a magnetostrictive level transmitter is introduced. Based on the thermal analysis, a level sensor assembly using a magnetostrictive level transmitter for cryogenic propellants was proposed. Several experimental studies have been conducted for the assembly level and the complete integrated system level to confirm the performance of the level sensor assembly. Finally, this newly designed level sensor assembly is successfully validated by flight tests of Test Launch Vehicle and Korea Space Launch Vehicle II.

Numerical and Experimental Study of Nose for LOx Floating Ring Seal in Turbopump

Floating ring seals are widely used as a leakage control solution for turbomachines because they effectively operate with small clearances between the shaft and seal. The oxidizer pump of the 7 tonf liquid engine in the Korea Space Launch Vehicle II (KSLV-II) operates at high rotational speeds and under cryogenic conditions and has floating ring seals in the bearing cooling path to reduce leakages. In this study, we evaluated the frictional force acting on the nose of the floating ring in the oxidizer pump of the 7 tonf turbopump using numerical analysis, and we investigated the radial force on the floating ring induced by the vibration of the rotor and the flow characteristics around the floating ring seal. Through a comparison of the frictional and floating forces according to the change in the diameter of the floating ring noses, we also estimated the dynamic positioning of the floating ring. In addition, we examined the leakage of the floating ring seals with the rotational speed and gap size of the floating ring, and we used the results as data for designing a floating ring seal. Finally, we performed turbopump real-propellant tests with the floating ring seal of the high and the middle noses, finding that the test result was in good agreement with the results of numerical analysis.

Development of Engineering Qualification Model of a Small ETG for a Launch Environmental Test

According to the development plan for the Korea Space Launch Vehicle, a performance verification satellite will be installed in the launch vehicle in 2021. In addition, three payloads, including a small electrically heated thermoelectric generator (ETG), will be developed and installed in the satellite. In particular, a small ETG has been developed by the Korea Atomic Energy Research Institute for the purpose of evaluating the characteristics of the ETG in the space environment prior to the development of a radioisotope thermoelectric generator for lunar missions. In this study, shock and vibration tests were carried out to check whether the ETG can endure the launch environment of the spacecraft. In addition, a thermal cycle test and a thermal vacuum test were conducted to check whether the ETG maintains its performance, even at drastic temperature changes, which can be applied to the ETG in space. Finally, a periodic performance test was carried out to measure the degradation level of the small ETG.

A Numerical Study on the Effect of the Umbilical Plate on Longitudinal Controllability of a Low Aspect Ratio Launch Vehicle

The Korea Aerospace Research Institute (KARI) is developing the Korea space launch vehicle (KSLV)-II for a flight test in 2021, and it has already produced the test launch vehicle (TLV) for a performance test of the 75 tonf liquid engine that will be used in the KSLV-II for the first time. The TLV utilizes, with slight changes, the same parts of the KSLV-II to avoid development delays and reduce development costs. In this study, the aerodynamic coefficients are predicted through a CFD analysis of the TLV with the umbilical plate used at the beginning of its development, and the flow characteristics around the umbilical plate are analyzed. In addition, we calculate the control ratio, which is the design requirement of the control system, using the predicted aerodynamic coefficients and investigated the effect of the umbilical plate mounted on the aft body of the TLV on its longitudinal stability. This study presents the aspects to be considered in the design of the umbilical plate and control system of a low aspect ratio launch vehicle.

Venting Analysis of the Payload Fairing of Korea Space Launch Vehicle II

Our study involved an investigation of the venting analysis of payload fairing of Korea Space Launch Vehicle II with vent valves. Two types of vent valves with a spring-loaded door were developed for a payload adapter and compartments of Korea Space Launch Vehicle II. First, the performance of the vent valves was evaluated through three-axis random vibration tests and flow tests. Structural robustness of the vent valves was validated through random vibration tests. Flow characteristics were investigated through flow tests. The cracking pressure of the vent valves for the payload adapter was in the range of 74–86 Pa, whereas the cracking pressure of the vent valves for compartment was in the range of 384–447 Pa. The results of flow tests were used to determine valve models of the vent valves for the venting analysis. Subsequently, venting analysis was conducted to predict the maximum pressure difference and pressure drop rate of payload fairing, and the results were compared with those of other space launch vehicles. The maximum values of the pressure difference were and 1.27 kPa. The maximum pressure drop rate was 4.68 kPa/s. The values were lower than the maximum values of other space launch vehicles. Consequently, the vent valves were suitable for Korea Space Launch Vehicle II.

Vent Valve for Test Launch Vehicle of Korea Space Launch Vehicle II

The performance of a vent valve with a spring-loaded door is evaluated for the test launch vehicle of Korea Space Launch Vehicle II. Twelve vent valves are manufactured for the three compartments of the test launch vehicle. The structural robustness of the vent valves is evaluated via random vibration tests of . All the vent valves properly operate even after the vibration tests. The flow characteristics of the vent valves are investigated via flow tests. The cracking pressure of the vent valves is 431–514 Pa. The flow area of the vent valves is calculated from the test results, and two models for the valves for the venting analysis are determined on the basis of the flow area. The pressure difference between inside and outside the compartments and the pressure drop rate in the compartments during flight are predicted via a venting analysis. The maximum values of the pressure difference are and 7.30 kPa. The maximum pressure drop rate is . The maximum pressure difference in the test launch vehicle is much lower than that in Korea Space Launch Vehicle I measured in the first flight test, and the maximum pressure drop rate of the test launch vehicle is similar to that of Korea Space Launch Vehicle I. Consequently, the vent valve with a spring-loaded door is suitable for the test launch vehicle.

한국형발사체 추진제공급시스템 충전모드 해석

한국형발사체 추진제공급시스템 충전모드 해석

추진제 및 연소 사이클을 고려한 액체로켓 엔진의 신뢰도 예측

액체로켓 엔진의 신뢰도는 설계 추력, 추진제, 연소 사이클, 및 연소시험 시간의 영향을 받는다. 기존 연구에 따르면 신규 개발하는 엔진과 같은 추진제 및 연소 사이클을 가지는 참조 엔진들의 연소시험 자료가 알려져 있다면 참조 엔진들의 설계 추력과 연소시험 시간을 보정하여 신규 엔진의 신뢰도를 예측할 수 있다. 본 연구에서는 신규 개발하는 엔진과 같은 추진제 및 연소 사이클을 가지는 참조 엔진의 자료가 존재하지 않은 경우를 고려하여 두 엔진 사이의 유사성 분석을 통하여 고장률을 보정한 후 신뢰도를 예측하는 방법을 제시하였다. 또한 액체산소/케로신 추진제와 가스 발생기 사이클을 사용하는 한국형 발사체의 1단 엔진을 이용하여 제안된 방법을 예시하였다. It is known that reliability of liquid rocket engines depends on the design thrust, propellant, engine cycle, and hot firing test time. Previously, a method was developed for estimating reliability of a new engine by adjusting the design thrust and hot firing test time of reference engines where reference engines have the same propellant and engine cycle with the new engine. In this paper, we provide a procedure to predict the engine reliability when the new engine and the reference engine have different propellant and engine cycles. The proposed method is illustrated to estimate the engine reliability of the first stage of Korea Space Launch Vehicle II.

케로신/공기 와류 화염의 화학발광 세기 특성에 관한 실험적 연구

The present study presents experimental results on the characteristics of emission spectra of kerosene/air swirl flames. The aviation fuel Jet A-1, which is used for the liquid rocket engines of the Korea Space Launch Vehicle, is used with three different swirlers to investigate the swirl strength effects. The emission spectra from the flames are measured with a spectrometer as the swirl strength and combustion air temperature are varied. Chemiluminescence intensities of , and are identified from the spectra. The chemiluminescence intensities from the kerosene flames show sensitivity to the swirl strength and are affected by changes in the combustion air temperature. Among the three radicals of interest, show the most significant changes in chemiluminescence intensity with the swirl strength and equivalence ratio. The intensity ratios and are adequate for indicating changes in the equivalence ratio with the air and fuel mass flow rates, respectively.

A Study on Mechanical Properties of Friction Stir Welded and Electron Beam Welded AA2195 Sheets

Aluminum-Copper-Lithium alloys are used as substitute for conventional aerospace Al alloys in cryogenic tank of liquid rocket engines, aircraft wing box and satellite systems due to their high specific modulus and specific strength. For this reason they are currently under consideration for one of the potential choices for a large structure of Korea Space Launch Vehicle. In this study, friction stir welding and electron beam welding were conducted on AA2195 sheets, in butt joint configuration in order to compare the two processes and to evaluate mechanical properties. The results provide valuable information for the optimal condition of joining AA2195 sheets for a large tankage structure of the space launcher.

A Study on Precipitation Kinetics of an Al-Cu-Li Alloy

Aluminum-Copper-Lithium alloys are of strategic important [1] in lightweight aerospace structures due to their high specific modulus and specific strength and are under consideration for one of the potential choices for Korea Space Launch Vehicle structure. However, this is one of the most complicated alloys due to the precipitation of a large number of second phase particles. In this study, the precipitation kinetics of an Al-4.3%Cu-1.2%Li alloy was studied by differential scanning calorimetry (DSC) technique since precipitation plays an important role for hardening of this alloy. Several models including Kissinger’s, Starink’s and Chaturvedi’s were used to obtain the activation energy and precipitation kinetics.

나로호의 EMC 통제를 위한 규격설정 및 검증

소형 위성 발사체 나로호의 전자파 적합성 성능은 탑재 위성과 우주센터에 설치되는 지상 장비, 그리고 다른 무선통신망 사이에서 정상적인 동작을 보장하도록 확보되고 검증되어야 한다. 전자파 적합성 성능을 검증하기 위해서는 서브 시스템과 시스템에 대한 적절한 시험 규격과 방법, 그리고 절차가 발사체의 운용 특성과 전자기 환경을 고려하여 수립되어야 한다. 그리고 프로그램 종료단계까지 결정된 규격에 따라 지속적으로 전자파 적합성 특성을 유지 관리하는 것이 요구된다. 본 논문에서는 나로호의 발사체 개발 전 주기 동안 수행된 순차적인 관리 업무를 기술하고, 나로호와 각 서브 시스템의 각 모델에 대한 단계별 시험계획뿐만 아니라, 시험 방법, 규격, 검증시험 결과 등이 제시된다. 또한, 멀티팩션 분석에 대한 결과를 기술한다. Electromagnetic compatibility(EMC) performance of the first Korea space launch vehicle(KSLV-I) should be ensured and verified in order to guarantee the normal operation among the spacecraft, ground facilities which are installed in the space center, and other wireless communication networks. For the purpose of the EMC performance verification, pertinent EMC test specifications, methods, and procedures for both the subsystems and the system should be established in consideration of operational properties and electromagnetic environmental effects. And it is required to maintain and control the EMC properties consistently in accordance with the determined specifications up to the program closing phase. In this paper, sequential management work conducted during the overall development process of the KSLV-I is explained, and not only the phased EMC test plan for each model of the KSLV-I and its subsystem but also test method, specification, and results of the verification tests are presented. And also, multipaction analysis results are presented.

발사체 연소기용 산화제 개폐밸브의 핵심요소 기술 개발

A main oxidizer shut-off valve (MOV) controls the supply of cryogenic liquid oxygen to the combustion chamber of liquid rocket engines by on/off operation s. The main subjects to be introduced are not only the valve transient response during valve on/off procedures but also the characteristics of pneumatic and seat/poppet parts as core technologies in the dev elopment of the MOV, which is expected to be adopted for the Korea Space Launch Vehicle II. It is shown that the analytical prediction of the transient valve travel is in good agreement with experimental results. Friction and elastic forces on the valve moving part are quantitatively evaluated by structural analysis.

Requirements Analysis of Propulsion Systems for Lunar-Exploration Mission

Requirements of a propulsion system for lunar-exploration missions using a launch vehicle, the development of which has recently started in Korea, were conceptualized. A new three-stage-to-orbit launch system, the Korea Space Launch Vehicle 2 will be a middle-class launch vehicle in that its expected payload capacity to low Earth orbit will be about 2.6 tons. The Korea Space Launch Vehicle 2 is under development and may possibly launch a lunar orbiter and a lander within 10–15 years. Considering some of the limitations and requirements a new space-propulsion system must be developed, and it has been found that a rocket is the optimum propulsion system among several types of chemical rockets. The optimum thrust and burn-time requirements for orbital transfers and landing using rockets were also derived by mass budget design and three-degree-of-freedom orbit-trajectory calculations. It has been found that, using the Korea Space Launch Vehicle 2, 1800 N-class propulsion system with a continuous burn time of more than 340 s and an accumulated burn time of more than 710 s needs to be developed for the lunar-exploration missions.

신뢰성 보정된 발사체 개발비용 추정방안 연구

본 연구에서는 발사체의 개념설계 단계 동안 성능 변수뿐만 아니라 신뢰성에 따른 개발비용 추정방안을 분석하고자 하였다. 과거에는 발사체의 개발비용을 예측하기 위해서 주로 발사체의 성능과 건조 질량 등을 독립변수로 하는 추정 방법이 많이 이용되었다. 이러한 접근 방법은 비교적 근사하였지만 신뢰성 수준에 따른 비용 변화를 반영할 수 없기 때문에 원하는 신뢰성을 가진 발사체의 개발비용을 근접하게 예측하기는 쉽지 않았다. 본 논문에서는 이러한 비용추정 방법의 한계를 개선하기 위해 성능과 질량을 기반으로 한 비용 모델인 TRANSCOST에 신뢰성 개념을 도입하여 발사체 비용을 추정할 수 있는 방법론을 제시하였다. 이를 기반으로 신뢰성에 따른 한국형발사체(KSLV- II)의 개발비용을 추정했다. The purpose of this study is to perform the reliability-corrected development cost estimation of the launch vehicle at the conceptual design phase. In order to estimate the launch vehicle development cost, the estimation method based on the independent variable such as the rocket performance and dry mass has been mainly implemented up to now. This approach has made the approximate cost estimation possible, however, the cost variation according to the reliability requirement could not be reflected. In this paper, the cost estimation methodology that introduces the reliability factor in addition to the performance and mass in the TRANSCOST model is presented in order to improve the limitation of current cost estimation method. The development cost of KSLV(Korea Space Launch Vehicle)-II is estimated on the basis of this newly implemented concept with reliability as an added parameter.

나로우주센터 발사장에서 나로호 GPS 수신기 시스템의 운용

본 논문은 고흥에 위치한 나로우주센터 발사장에 나로호가 발사대기하고 있을 때에 나로호에 탑재된 GPS 수신기 시스템의 운용결과에 대하여 다룬다. 나로호가 발사대에서 수직으로 기립하고 있는 동안에 GPS 수신기 시스템을 포함한 나로호의 모든 탑재장비들은 나로호의 이륙 직전까지 동작상태와 성능이 점검되어야 한다. 나로호에 탑재된 GPS 수신기는 기체 표면에 설치된 3개의 패치형 GPS 안테나와 연결된다. 각각의 GPS 안테나에서 수신된 GPS 위성신호를 바탕으로 나로호가 발사대에 발사대기중일 때에 발사장 환경에 의해 GPS 수신기에서 관찰된 신호간섭과 다중경로로 인해 발생한 현상 등을 분석한다. This paper describes the operation results of the GPS receiver system for KSLV (Korea Space Launch Vehicle)-I on the launch site at Naro Space Center that is the first spaceport of South Korea located at Goheung. All equipments of KSLV-I including the GPS receiver system should be monitored and controlled through hard-wired interface during KSLV-I is on standby at the launch pad. The GPS receiver for KSLV-I is connected to triple almost omni-directional patch antennas mounted on the cylindrical surface of KSLV-I that should be erected vertically on the launch pad until lift-off. Signal interference and multipath effects observed in the GPS receiver on the launch site are analyzed in this paper based on the GPS signals received from each GPS antenna.

위성발사체용 GPS 수신기 시스템의 개발

A GPS receiver system utilized on satellite launch vehicles should operate normally under harsh environments as well as high-dynamic conditions. The GPS receiver system to use for range safety of KSLV(Korea Space Launch Vehicle)-I that is the first satellite launch vehicle developed by KARI(Korea Aerospace Research Institute) has been confirmed to survive under the environment of the launcher through extensive terrestrial tests including humidity, high and low temperatures, vacuum, sinusoidal and random vibrations, shocks, acceleration, EMI/EMC(Electromagnetic Interference/ Electromagnetic Compatibility), etc. Several performance tests have been also carried out in order to evaluate tracking capability and accuracy of the GPS receiver under high-dynamic conditions using a GPS signal simulator. Some lessons-learned during development of the GPS receiver system and its special characteristics compared with COTS(Commercial-Off-The-Shelf) GPS receiver systems are described in this paper.

The Korean Sounding Rocket Program

As a part of the Korea National Space Program, the Korean government has led the Sounding Rocket Program by Korea Aerospace Research Institute (KARI) providing enhanced capabilities across a spectrum of earth sciences and/or astrophysics-related disciplines. In this paper, the Korean Sounding Rocket Program during 1993–2002 is introduced. This program includes Korea Sounding Rocket (KSR)-I, KSR-II, and KSR-III, and a total of five soundings were carried out. Two had flown in KSR-I series, two in KSR-II, and one in KSR-III. The main mission objective is to provide the opportunity to scientists for researching earth sciences and/or astrophysics and to improve Korean rocket development technologies including payload instruments, flight systems, ground systems, operational techniques, and interfaces between subsystems. As demand increased for launching of low-orbit earth satellites internally and externally, the Korean government was ambitiously firing the Korea Space Launch Vehicle (KSLV) Program in 2002, based on experience throughout the Sounding Rocket Program and preparing the world market for space launch vehicles.

우주발사체 탑재용 리튬이온 배터리 개발

높은 중량에너지밀도로 배터리 무게를 줄일 수 있는 장점을 갖는 리튬이온 배터리는 중량이 중요한 관심사인 많은 항공우주 응용분야에서 빠른 속도로 Ni-Cd, Ni-H2 등의 기존 배터리를 대체하고 있다. 또한 리튬이온 배터리는 낮은 열 손실 특성과 높은 에너지 효율 그리고 저렴한 셀 단가를 갖는다. 80개의 소니 US18650 리튬이온 셀을 사용한 KSLV-I 탑재배터리 모듈은 셀을 8개씩 직렬로 구성한 후 각 열을 병렬로 10개 연결하여 요구되는 전압과 용량을 공급한다. 본 논문에서는 우주발사체용 리튬이온 배터리의 설계 및 그 특성에 대해 소개하며, 예상되는 우주환경에서 배터리가 신뢰성 있게 동작하는지를 검증하는 환경시험 프로그램 절차를 보였다. 배터리 성능은 전자부하기를 이용한 시뮬레이션 시험을 통해 확인하였고 발사체 2단에 장착하여 각 전장품들과의 연계시험을 통해 검증하였다. Lithium-ion batteries providing high gravimetric energy density are rapidly replacing Ni-Cd and Ni-H2 in aerospace applications. The main advantage is the weight reduction of the battery system. Weight is a major concern in aerospace applications. Also, lithium-ion offer low thermal dissipation, high energy efficiency, and low cell cost. The Onboard battery module for KSLV-I(Korea Space Launch Vehicle) contains 80 Sony US18650 cells configured as 10 strings in parallel, with each string containing 8 series connected cells. This allows to meet voltage and capacity requirements specified for the mission. In this paper design description and specifications of lithium-ion battery developed are presented. Qualification test flow is also shown to make sure the performance in the predicted space environment. Electrical performance was simulated by dedicated program, and verified with electronic load. Lastly, the capacity was proven on real equipment load assembly.