Naro Space Center Research Articles

A Pattern Search Method to Optimize Mars Exploration Trajectories

The Korean National Space Council recently released “Mars Exploration 2045” as part of its future strategic plan. The operations for a Mars explorer can be defined based on domestically available capabilities, such as ground operations, launch, in-space transport and deep space link. Accordingly, all of our exploration scenarios start from the Naro space center, and the pathway to Mars is optimized using an objective function that minimizes the required ∆V. In addition, the entire phase of Mars orbit insertion should remain in contact with our deep space antennas, a measure that is imposed as an operational constraint. In this study, a pattern search method is adopted, as it can handle a nonlinear problem without relying on the derivatives of the objective function, and optimal trajectories are generated on a daily basis for a 15-day launch period. The robustness of this direct search method is confirmed by consistently converged solutions showing, in particular, that the ascending departure requires slightly less ∆V than the descending departure on the order of 10 m/s. Subsequently, mass estimates are made for a Mars orbiter and a kick stage to determine if the desired ∆V is achievable with our eco-friendly in-space propulsion system when launched from our indigenous launch vehicle, KSLV-II.

A Study on the Characteristics of Lightning Detection over the Naro Space Center

A Study on the Characteristics of Lightning Detection over the Naro Space Center

Geostationary Orbit Transfer with Lunar Gravity Assist from Non-equatorial Launch Site

We show that it is possible to launch a satellite to Geostationary Equatorial orbit (GEO) from the non-equatorial launch site (Naro Space Center in South Korea) even though that is located in the mid-latitudes of the northern hemisphere. When launched from this site, the equatorial inclination after separation will be 80°. We use a lunar gravity assist (LGA) transfer to avoid the excessive ∆V costs of plane change maneuvers. There are eight possible paths for the LGA; there are four paths consisting of Earth departures and free-return types, and there are two nodes of the Moon’s orbit (ascending and descending). We analyze trajectories over five launch periods for each path using a high-fidelity orbit propagation model. We show that the LGA changes the orbital energy of the “cislunar” free-returns more than for the “circumlunar” free-returns, resulting in less geostationary insertion ∆V for the cislunar free-returns. We also show that the geometrical ∆V variation over the different paths is greater than the seasonal ∆V variation. Our results indicate that an ascending departure and cislunar free-return at the descending node have lower ∆V requirements than the other paths, and lower than described in several previous studies.

Preliminary Analysis on Launch Opportunities for Sun-Earth Lagrange Points Mission from NARO Space Center

In this work, preliminary launch opportunities from NARO Space Center to the Sun-Earth Lagrange point are analyzed. Among five different Sun-Earth Lagrange points, L1 and L2 points are selected as suitable candidates for, respectively, solar and astrophysics missions. With high fidelity dynamics models, the L1 and L2 point targeting problem is formulated regarding the location of NARO Space Center and relevant Target Interface Point (TIP) for each different launch date is derived including launch injection energy per unit mass (C3), Right ascension of the injection orbit Apoapsis Vector (RAV) and Declination of the injection orbit Apoapsis Vector (DAV). Potential launch periods to achieve L1 and L2 transfer trajectory are also investigated regarding coasting characteristics from NARO Space Center. The magnitude of the Lagrange Orbit Insertion (LOI) burn, as well as the Orbit Maintenance (OM) maneuver to maintain more than one year of mission orbit around the Lagrange points, is also derived as an example. Even the current work has been made under many assumptions as there are no specific mission goals currently defined yet, so results from the current work could be a good starting point to extend diversities of future Korean deep-space missions.

Method for Estimating Optimal Position of S-Band Relay Station through Path Loss Analysis in an Outdoor Environment

This article investigates a novel estimation method to optimize the position of a relay station of the S-band telemetry system in outdoor environments. To determine an optimal relay station position, complex terrain surface and buildings near the Naro Space Center are included in the EM (Electromagnetic) simulation. The optimal relay station position is then determined using the estimation method by comparing the path losses from the rocket to the main station and some candidate positions of the relay station. To better understand the path loss, the ray analysis is also conducted, and the result demonstrates that once the rocket altitude to be covered by the relay station is determined, it is possible to find the optimum position of the relay station.

A Study on the Characteristics of Convective Activities related to Atmospheric Stability Index and Thunderstorms over the Naro Space Center

A Study on the Characteristics of Convective Activities related to Atmospheric Stability Index and Thunderstorms over the Naro Space Center

Numerical study for flame deflector design of a space launch vehicle

A flame deflector is a structure that prevents damage to a launch vehicle and a launch pad due to exhaust plumes of a lifting-off launch vehicle. The shape of a flame deflector should be designed to restrain the discharged gas from backdraft inside the deflector and to reflect the impact to the surrounding environment and the engine characteristics of the vehicle. This study presents the five preliminary flame deflector configurations which are designed for the first-stage rocket engine of the Korea Space Launch Vehicle-II and surroundings of the Naro space center. The gas discharge patterns of the designed flame deflectors are investigated using the 3D flow field analysis by assuming that the air, in place of the exhaust gas, forms the plume. In addition, a multi-species unreacted flow model is investigated through 2D analysis of the first-stage engine of the KSLV-II. The results indicate that the closest Mach number and temperature distributions to the reacted flow model can be achieved from the 4-species unreacted flow model which employs H2O, CO2, and CO and specific heat-corrected plume.

한국형발사체 7톤 파워팩 시스템 고주파 신호 분석

7톤 엔진 시험 전에 엔진 시동/정격구동/종료 특성을 확인하고자 나로우주센터 터보펌프 실매질 시험설비에서 파워팩 시험을 수행하였다. 가스발생기 연소실의 동압은 0.2 bar이하로 측정되어 연소 불안정을 발생하지 않았고, 터보펌프에 장착된 RPM 및 가속도 센서 신호 분석 결과, 예측 RPM 범위 안에서 파워팩 시험이 안정하게 수행되었다는 것을 확인하였다. The 7tonf-class power pack test at turbopump test facility in Naro space center was performed for confirmations of starting/running/ending operation characteristics before 7tonf rocket engine hot-firing test. The dynamic pressure mounted on a combustion chamber of gas generator is measured under 0.2 bar which does not conditioned to the unstable combustion. The analysis results of RPM and acceleration sensors mounted on the turbopump, the power pack test was performed to the estimated RPM with the stable combustion.

원격자료수신장비의 발사체궤적 추정정확도 향상을 위한 궤적데이터마이닝의 적용

본 논문은 궤적데이터마이닝의 2차 회귀분석 기법을 이용하여 나로우주센터 내 원격자료수신장비에서 우주발사체의 실시간 비행궤적을 보다 정확하게 추정하기 위한 방법을 제시하고 있다. 원격자료수신장비는 추적손실 없이 실시간으로 우주발사체의 비행위치와 상태정보를 수신하기 위한 정확한 위치추정 알고리즘이 필요하다. 따라서 나로호 1차 발사 시, 기존 보간법에 의한 원격자료수신장비 안테나의 거친 구동특성을 보완하고 안정적인 발사체의 위치추정을 위한 2차 회귀기법을 고려하였다. 성능분석을 위해 나로호 1차 비행시험데이터를 사용하였고, 수학적 모델링을 통해 실시간 발사체의 비행위치정보를 추정한 결과가 분석되었다. 분석결과, 궤적데이터마이닝의 2차 회귀기법을 적용한 위치추정알고리즘이 기존의 보간법에 의한 위치추정알고리즘보다 향상된 안테나 구동특성 및 추정정확도를 보였다. This paper is focused on how the trajectory of launch vehicle could be optimally estimated by the quadratic regression of trajectory data mining for the operation of telemetry ground system in NARO space center during real-time. To receive the telemetry data, the telemetry ground system has to track the space launch vehicle without tracking loss, and it is possible by the well-designed algorithm to estimate a flight position in real-time. For this reason, the quadratic regression model instead of interpolation was considered to estimate the exact position data of launch vehicle and the improvement of antenna performance. For analysis, the real trajectory data which had been logged during NARO 1st launch mission were used, the estimation result of launcher current position was analyzed by the mathematical modeling. In conclusion, the algorithm using quadratic regression based on trajectory data mining showed the better performance than previous interpolation algorithm to estimate the next flight position and the antenna driving performance.

Marine acoustic environment characteristics around Naro Space Center

This study was aimed to identify the marine acoustic environment characteristics around Naro Space Center.BR Regarding marine environment, water temperature, salinity, sound speed, sediment and water depth were measured and noises were measured as air noises and underwater noises.BR Water temperatures in study area was about 22℃, salinity is about 32 psu, and sound speed was about 1524 m/s. Surface layer and lower layer didn

발사체 추적자료 후처리를 통한 비행궤적 생성

나로우주센터의 발사통제시스템은 우주발사체의 비행궤적과 상태정보를 감시하기 위하여 지상추적시스템(추적레이더 2대, 원격자료수신장비 4대, 광학추적장비 1대)으로부터 정보를 받아 처리한다. 각 추적장치는 주로 다중경로나 클러터, 전파굴절에 의해 자체 오차를 나타내고 있어 전송된 정보들 중 하나만을 이용해서는 우주발사체의 실제 궤적을 판별할 수 없다. 본 논문에서는 취득된 추적자료의 후처리를 통해 우주발사체 비행궤적을 생성해내는 방법을 제시한다. 본 후처리 알고리즘은 크게 대기의 전파굴절에 따른 오차를 보정하는 부분과 다중센서 정보를 융합하는 부분으로 나뉘며, 효과적인 센서 융합을 위해 등가속 운동모델에 기반한 분산식 칼만필터를 구성하였다. 실측 자료의 후처리 적용 결과, 어떤 단일 센서에 의한 것 보다 오차가 최소화된 발사궤적을 얻을 수 있었다. For monitoring the flight trajectory and the status of a launch vehicle, the mission control system in NARO space center process data acquired from the ground tracking system, which consists of two tracking radars, four telemetry stations, and one electro-optical tracking system. Each tracking unit exhibits its own tracking error mainly due to multi-path, clutter and radio refraction, and by utilizing only one among transmitted informations, it is not possible to determine the actual vehicle trajectory. This paper presents a way of generating flight trajectory via post-processing the data received from the ground tracking system. The post-processing algorithm is divided into two parts: compensation for atmosphere radio refraction and multi-sensor fusion, for which a decentralized Kalman filter was adopted and implemented based on constant acceleration model. Applications of the present scheme to real data resulted in the flight trajectory where the tracking errors were minimized than done by any one sensor.

가스발생기의 연료과잉가스 후연소용 O2/CH4가스 공급시스템 설계

나로우주센터에 구축되는 연소기 연소시험설비(CCTF)에는 한국형발사체(KSLV-II)에 적용된 터보펌프식 엔진의 가스발생기 시험시 생성되는 연료과잉가스를 연소시키기 위한 후연소시스템이 포함되어 있다. 후연소시스템은 <TEX>$O_2$</TEX>와 <TEX>$CH_4$</TEX> 가스를 공급받아 연료과잉가스를 소모시킨다. 본 연구는 연소기 연소시험설비의 상세설계 자료를 바탕으로 후연소시스템의 가스공급시스템에 대해 AMESim 상용프로그램을 이용하여 해석하였다. 그 결과 상세설계에 적용된 레귤레이터, 공급배관, 오리피스크기 등으로 가스사용량을 예측하고, 상세설계의 타당성을 검증하였다. Combustion Chamber Test Facility (CCTF) to be constructed in Naro Space Center for re-burning the fuel-rich gas of gas generator have afterburner system. The afterburner system is supplied the Oxygon (<TEX>$O_2$</TEX>) gas and Methane (<TEX>$CH_4$</TEX>) gas to reduced the harmful exhaust gas. The detailed design for the planned CCTF afterburner system is simulated and analysed by AMESim program through the all of gas supply system components. Afterburner system is performed to verify the pipe size, orifice diameter, and gas supply conditions according to the total gas consumption from analysis of gas supply system.

연소기 연소시험설비 고압가스 공급시스템 설계

To develop liquid propulsion engine, the development of combustion chamber must be preceded. For performance validation of the combustion chamber, the designed and manufactured combustion chamber should be tested in combustion chamber test facility (CCTF). The CCTF is the test facility to develop the combustor of rocket engine, which uses liquid oxygen as a oxidizer and kerosene as a fuel. Present paper introduces the detailed design results of compressed gas supply system of CCTF, which is planned to be installed at Naro Space Center.

직접 전이궤적을 이용한 한국형 달 궤도선 임무설계 및 분석

달 궤도선은 한국형발사체(KSLV-II)에 실려 지구 저궤도에 투입된 후, 지상 안테나를 이용한 달 궤도선의 추적데이터 획득 및 궤도결정 과정을 거쳐 적절한 시점에서 TLI(Trans Lunar Injection) 엔진을 점화시켜야 한다. 본 논문은 달 궤도선을 나로우주센터에서 발사하여 달 궤도에 진입하기까지 여러 단계로 나누고 발사 방위각 및 발사창 분석부터 TLI 및 LOI(Lunar Orbit Insertion) 분사 위치에 따른 속도증분(<TEX>${\Delta}V$</TEX>) 그리고 가시성 및 식 기간 분석까지 수행하여 직접 전이궤적의 전반적인 특성을 분석하였다. 본 논문은 향후 달 임무 설계 시 관성비행 기간 및 전이기간에 따라 속도증분이 어떻게 변하는지에 대한 전반적인 내용을 파악하는데 도움이 되고, 발사 시각 선정과 연료소모를 줄일 수 있는 파라미터 선정에 도움을 줄 것으로 판단된다. The Lunar orbiter is expected to be inserted into a ~300km low Earth orbit using Korea Space Launch Vehicle-II(KSLV-II). After the states are successfully determined with obtained tracking data, the Trans Lunar Injection(TLI) burn has to be done at appropriate epoch to send the lunar orbiter to the Moon. In this study, we describe in detail the mission scenario of the Korean lunar orbiter from the launch at NARO Space Center to lunar orbit insertion(LOI) stage following direct transfer trajectory. We investigate the launch window including launch azimuth, delta-V profile according to TLI and LOI burn positions. We also depict the visibility conditions of ground stations and solar eclipse duration to understand the characteristics of the direct transfer trajectory. This paper can be also helpful not only for overall understanding of <TEX>${\Delta}V$</TEX> trend by changing TOF and coasting time but for selecting launch epoch and control parameters to decrease fuel consumption.

연소기 연소시험설비 산화제 공급시스템 해석

발사체의 추진기관은 일반적으로 산화제와 연료를 연소실로 공급하여 추진력을 얻게 된다. 개발 중에 있는 한국형 발사체(KSLV-II) 2단 엔진의 경우 산화제로는 액체산소(Liquid Oxygen)를 사용하고 연료로는 JET-A1이 사용될 예정이다. 터보펌프 공급방식인 2단 엔진의 주요 구성은 연소기와 터보펌프, 엔진공급시스템 등으로 구성되어 있다. 액체 추진 엔진 개발을 위해서는 서브시스템인 연소기 개발이 선행되어야 하고 설계 및 제작된 연소기의 성능 검증은 연소기 연소시험설비(CCTF)에서 수행된다. 우주센터에 구축 예정인 연소기 연소시험설비에 대한 상세설계가 수행되었으며, 본 설계 결과를 기준으로 AMESim을 사용하여 산화제공급시스템에 대한 모델링을 수행하여 산화제 공급특성을 해석하였다. The propulsion system of space launch vehicle generates thrust by supplying oxidizer and fuel to combustion chamber. KSLV-II 2nd stage engine, currently under development by KARI, is to use liquid oxygen as a oxidizer and JET-A1 as a fuel. The 2nd stage pump-fed engine is mainly composed of combustion chamber, turbo-pump and engine supply system. To develop liquid propulsion engine, the development of combustion chamber must be preceded. For performance validation of the combustion chamber, the designed and manufactured combustion chamber should be tested in combustion chamber test facility (CCTF). The detailed design for the planned CCTF in Naro Space Center was conducted. The oxidizer supply system modeling using AMESim was performed based on the results of the detailed design, and the oxidizer supply characteristics was analyzed in this paper.

A Fuzzy Logic Method for Lightning Prediction Using Thermodynamic and Kinematic Parameters from Radio Sounding Observations in South Korea

Abstract Lightning is one of the most troubling weather phenomena for weather forecasters at space centers. In this study, proximity sounding and lightning data were used to evaluate the utility of thermodynamic and kinematic parameters for forecasting lightning prior to launch operations. Various parameters from 4138 radio sounding observations at five sites and cloud-to-ground (CG) stroke data from the Korea Meteorological Administration’s Lightning Detection Network (KLDN) over South Korea during 2004–09 were used. To support launch operations, forecasts of the total membership function for lightning (TMF) were derived from the combination of membership functions of selected thermodynamic and kinematic parameters with each objective weight using a fuzzy logic algorithm. The forecast skill of TMF was evaluated by computing several skill statistics, which include probability of detection (POD), false alarm rate (FAR), percent correct (PC), critical success index (CSI), and the true skill statistic (TSS). The lightning forecasting method for Gwangju, South Korea (site nearest to the Naro Space Center), was found to have a POD of 0.68, an FAR of 0.45, a PC of 0.76, a CSI of 0.44, and a TSS of 0.47.

나로호에 탑재된 GPS 수신기의 항법해와 신호대잡음비의 일반복 특성

본 논문은 다중경로신호를 포함한 위성항법신호의 특성에 관한 정량적 분석을 수행하고, 나로우주센터의 발사대에 나로호가 발사대기중일 때에 저장된 데이터를 바탕으로 발사장 주변환경으로부터 발생한 다중경로신호로 인하여 GPS 수신기에서 계산된 항법해 및 신호대잡음비에서 나타난 일반복 특성에 대하여 다룬다. 발사대에 설치된 나로호에서는 GPS 안테나와 주위환경 및 GPS 위성궤도가 거의 변하지 않으므로 계산된 항법해와 신호대잡음비의 변화율과 크기가 그대로 일반복 되고 있음을 확인하였다. 다중경로의 영향에 관한 분석과 발사대에서 관찰된 항법해와 신호대잡음비의 일반복 특성은 위성발사체가 발사대기하고 있을 때에 GPS 수신기의 성능을 안정화시키기 위한 방법을 찾는데 크게 도움이 될 것이다. This paper deals with quantitative analysis about the characteristics of GNSS(Global Navigation Satellite System) signals contaminated with multipath signals and day-to-day repeatability of the navigation solution and SNR(Signal to Noise Ratio) caused by multipath signals using the collected data from GPS receiver installed on KSLV-I which was on standby on the launch pad at Naro Space Center. Since the GPS antennas, surrounding environments and GPS satellite orbits were very slightly changed with respect to the day, the repeating pattern of the solution and SNR caused by the multipath signals was verified from the collected data. Analytic result of the multipath effects and day-to-day repeatability of the navigation solution and SNR observed at the launch pad would be used for obtaining more stable performance of the GPS receiver when the satellite launch vehicles are on standby.

The organizations for space education and outreach programs in the Republic of Korea

Korea has a short history in space development compared to neighboring countries like Japan, China, India and Russia. During the past 20 years, Korea has focused on developing satellite and rocket space technology under the national space development plan. KOMPSAT-1 and 2, and KSLV-1 are the results of the selection and concentration policy of the Korean government. Due to the arduous mission of developing hardware oriented space technology, the topic of space education and outreach for the general public has not received much in the national space program. But recently, the Korean government has begun planning a space science outreach program in the detailed action plan of the mid-long term national space development plan. This paper introduces and analyzes the organizations performing space education and outreach programs for primary and secondary schools in the Republic of Korea. “Young Astronaut Korea (YAK)” is one such program. This is a non-profit organization established to provide space education for students in 1989 when Korea just started its space development program. “YAK” is a unique group in Korea for space education and outreach activities because it is organized by branches at each school in the nation and it is much like the Boy Scout and Girl Scout programs. Space Science Museum and National Youth Space Center (NYSC), which are located near NARO space center in the southernmost part of the Korean peninsula are other examples of space education and outreach programs. NARO space center, which is the only launch site in Korea became the center of public interest by showing the KSLV-1 launch in 2009 and will be expected to play a key role for the space education of students in the Republic of Korea. The NYSC will perform many mission oriented space education programs for students as Space Camp in the USA does. This paper introduces the status of the space education and outreach programs of each organization and presents the future direction of space education and outreach for the Korean public and students. If these three organizations cooperate with each other and develop systematic programs of space education and outreach for the people, they will prepare a base for growth and progress in future space science and technology in Korea.

Development and Flight Testing of an Onboard Video System for the KSLV-I

Korea Space Launch Vehicle-I (KSLV-I) carrying the STSAT-2A satellite, made its maiden flight on August 25, 2009. Liftoff was from the Korea Aerospace Research Institute (KARI) launch site at the Naro Space Center in a southern coastal province of the Korean peninsula. A video telemetry system provided visual monitoring of flight critical events, as well as dynamic moving images, through two cameras equipped on the upper stage. This paper describes the development of the onboard video system consisting of two video cameras, a video compression unit and an RF transmitter meeting the requirements of the KSLV-I launch vehicle. During the flight, the ETTARS, an especially reconstructed small telemetry ground station for the KSLV-I, received the video telemetry data and simultaneously measured automatic gain control (AGC) signal levels from the receiver. The onboard video system achieved a 15fps video rate, flew with a 2Mbps data rate and transmitted data using NRZ-L PCM/FM in the S-band. Errors on real telemetry channels occurred as predicted by link budget equations based on thermal noise and multipath interference. According to error analysis, the BER versus SNR performance degradation from the laboratory reference was about 1dB, which is close to expected limit.

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.