A flexible reflector antenna is designed, fabricated, and experimentally validated for application to small satellites. A doubly curved reflector surface is constructed using a triaxially woven fabric-reinforced silicone (TWFS) composite. The mechanical properties of the TWFS are analyzed through finite element analysis based on a representative unit cell model. In addition, both the mechanical and electromagnetic properties are experimentally characterized and utilized as fundamental parameters for the structural and electromagnetic design of the reflector antenna. To demonstrate the feasibility of the proposed concept, a prototype reflector with a diameter of 0.6 m is manufactured, and a series of performance tests are conducted. Based on the experimental results, the potential applicability of TWFS based flexible reflectors to small satellite communication antennas is presented.
This study proposes an optimal flight path planning method to minimize the radar detectability of unmanned aerial vehicles. To this end, a virtual mission environment was constructed by applying the Lambert conformal conic projection to digital terrain elevation data. Radars were placed at arbitrary locations within the mission area, and terrain-induced visibility was analyzed and reflected in the detectability assessment. The detectability metric was defined as the signal-to-interference ratio, which incorporates the effects of ground clutter into the conventional signal-to-noise ratio. The ground clutter was modeled using the Constant Gamma Model. For optimal path generation, a particle swarm optimization algorithm was employed. The proposed method was evaluated on both simplified and real-world terrain datasets, and the resulting waypoint sequences successfully guided the UAV along routes characterized by low detectability, short flight distance, and frequent traversal through radar shadow regions.
The fixed-wing UAV, which is launched from a canister for rapid mission deployment, has a tandem-wing configuration that ensures a large wing area even under constrained design conditions, considering storage requirements. Therefore, it is essential to develop a nonlinear simulation model that accurately reflects dynamic characteristics. In this study, the aerodynamic characteristics are analyzed using Computational Fluid Dynamics (CFD) and Vortex Lattice Method (VLM) methods, and the propulsion system was modeled by converting the thrust and torque coefficients for commercial propellers into advance ratio based equations. The proposed guidance and control approach for the nonlinear dynamic model was demonstrated using a hardware-in-the-loop simulation (HILS) environment.
This study presents the development of a computational landing guidance and control algorithm for a reusable launch vehicle technology demonstrator (RLV-TD), designed to validate key technologies for reusable launch systems. To generate fuel-optimal trajectories that satisfy vehicle performance and stability constraints, an onboard trajectory optimization method is implemented using a customized SOCP (Second-Order Cone Programming) solver tailored for embedded system environment. A trajectory tracking guidance algorithm is developed to ensure accurate execution of the optimal trajectory under model uncertainties and disturbances. Furthermore, a precision attitude control algorithm is designed to maintain stability in the presence of flexible body dynamics, including structural bending and sloshing. The proposed algorithms are validated through high-fidelity 6-degree-of-freedom simulations and verified via flight experiments using the RLV-TD platform. The results confirm the feasibility and effectiveness of the proposed approach in real-world scenarios.
A store is any device intended for internal or external carriage, mounted on air vehicle suspension and release equipment, which may or may not be intended to be for in-flight separation from the air vehicle. Stores include missiles, rockets, bombs, nuclear weapons, mines, fuel and spray tanks, torpedoes, sonobuoys, dispensers, pods, targets, decoys, chaff and flares, and suspension equipment. In this study, the effect on the backflow of the aircraft is examined through flow analysis according to the installation of the 2.75-inch rocket launcher fairing mounted on the Rotary-Wing Aircraft (500MD). The structural safety of pairing following high-temperature/high-pressure firing was compared and examined by analysis. The componet hammer test was conducted on the ground to confirm the vibration impact of the additional installation of external mounts. When the main excitation frequency was avoided, the effectiveness of the installation of rocket launcher fairing was confirmed through a flight shooting test. In addition, it is possible to determine the airworthiness of the tail of the aircraft due to the launch of a 2.75-inch rocket mounted on a Rotary-Wing Aircraft.
The satellite flight software is a core component responsible for managing various mission operations, including communication between the satellite and the ground station, and thus demands high reliability and security. In particular, the communication link between the satellite and the ground station is vulnerable to external threats, making network security essential. In this study, an encryption module based on the Korean block cipher algorithm SEED was implemented on the core Flight System (cFS), a modular flight software framework developed by NASA. The implemented module was shown to ensure the confidentiality and integrity of satellite communication data, thereby enhancing the network security of cFS-based satellite flight software.
In this paper, we propose the design of a distributed control law for a helicopter reconfigured from a single tail-rotor to four tail-rotors. The proposed control law ensures that the reconfigured tail-rotors effectively generate the thrust previously produced by the single tail-rotor. In particular, considering potential variations in the dynamic characteristics of the tail-rotors due to environmental factors, the proposed control law takes the variations into account and so makes the helicopter system robust against such uncertainties. A simple control gain adjustment is utilized in the control design, making the implementation practical and efficient. Furthermore, the proposed design enables rapid uncertainty estimation and real-time control gain adjustment, preventing the helicopter system from destabilization due to the uncertainties at an early stage.
In this paper, we propose a feature-density based path planning algorithm for a quadcopter to execute a Return to Home (RTH) task in GPS-denied environments. The algorithm enhances the accuracy of VINS(Visual-Inertial Navigation System) by employing feature-rich trajectory when satellite signals are jammed or interrupted. In challenging scenarios like dense forests, urban canyons, or underground areas where visual landmarks may be sparse, our method dynamically adjusts the drone's trajectory to maximize the traversal of visually rich areas. By utilizing DBSCAN (Density-Based Spatial Clustering of Applications with Noise), we identify feature-rich regions with high feature density and abundant visual information, so that include them into the planned route. The outlier removal techniques are used to avoid inefficient detours that do not contribute to visual-based navigation, further optimizing the path. A weighted vector summation strategy is applied to balance between the shortest RTH route and maximizing the use of these high-density feature regions to enhance localization accuracy. Through simulation in environments with varying feature densities, our results demonstrate that the proposed algorithm avoids visually sparse areas while maintaining efficient path planning. The drone's ability to adapt its route to the environment improves overall navigation stability and ensures accurate localization even in feature-sparse conditions.
In this paper, we perform observation scheduling for a single Low Earth Orbit (LEO) satellite with a task of observing multiple targets on Earth, aiming for a schedule with minimal speed change. For optimal scheduling, Genetic and Greedy Algorithms (GA and GrA, for short) are introduced and their solutions are compared and analyzed. GA spends a relatively large amount of computational cost but has a merit of returning a near-optimal solution. In contrast, GrA spends a little amount of computational cost but yields a solution with a large distance to the optimal. Therefore, GrA is applied with a variable maximum-observation-time-interval to yield a solution whose quality is comparable to that of GA. In fact, it is found that the GrA solution's quality approaches the GA one for the observation time interval of 1.9 day, in case of visiting 10 targets. This result and its aspect of computational complexity are thoroughly verified and confirmed on random sets of target positional data with various numbers of targets. Also, the effect of satellite's roll maneuver is investigated and a new data visualization scheme (so-called Snail Plot) is introduced to effectively explain the concept of GrA.
With the advent of the privately-led "New Space" era, the space industry is diversifying beyond the development of technologies and components that support state-led space missions, expanding into areas such as pharmaceuticals, tourism, and agriculture. Accordingly, the success factors of space startups are likely to differ from those of startups in general industries and may also vary depending on the national context. However, there is little empirical research on this topic. Therefore, the purpose of this study is to propose a theoretical framework that explains the success factors of startups entering the space industry and to empirically validate it using real-world data. To achieve this, we employ the internationalization process theory, which explains the internationalization process of firms, as the theoretical background and use Crunchbase data to examine space startups that emerged after the New Space era. Additionally, we conduct a Feature Importance analysis on Chinese and U.S. space startups to explore cross-national differences in space business success and derive relevant implications.
Due to its significant impact, the aerodynamic interference in multi-propeller aircraft must be evaluated quantitatively and reflected appropriately in the construction of aerodynamic database. This study conducted a computational fluid dynamics analysis using the actuator disk method(ADM) to investigate the interference effects in a lift-cruise type urban air mobility aircraft, as a preliminary step to constructing a database of aerodynamic interference to apply the component build-up method framework. The aerodynamic characteristics of each component of the aircraft and the changes in performance of propellers under various operating configurations were quantitatively evaluated, by considering each propeller as an individual element. The validity and applicability of the ADM for obtaining aerodynamic interference data were also evaluated through comparisons with sliding mesh method(SMM) results. The wake generated by the front lift propellers creates a significant downwash on the main wing, which subsequently results in a decrease in lift, and is identified as a dominant factor influencing the overall aerodynamic performance. For the front lift propellers, certain conditions were identified that revealed discrepancies in thrust and torque between the ADM and SMM, whereas the propulsion propeller exhibited a consistency in overall trend, maintaining performance differences within 5% even under wake interference.
This study proposes a detailed methodology for constructing an aerodynamic database of a quad tilt-propeller vehicle, intended for integration into flight simulation environments. The database was developed using a component synthesis method, which linearly combines the baseline aerodynamic forces with the variations with by influencing factors. Separate aerodynamic databases were generated for the airframe and propellers. Each was further divided into rotorcraft and fixed-wing modes, considering distinct baseline configurations and associated factors. To balance computational efficiency and accuracy, multiple solvers with varying fidelity levels were used. The constructed databases were evaluated against full-geometry computational fluid dynamics results. Comparative analysis was conducted on the individual databases for the airframe and propellers, as well as on the overall aerodynamic forces derived from their integration. Observed discrepancies in aerodynamic forces were primarily attributed to the exclusion of interactions between starboard and port propellers, and the absence of forward and rear wing components. The database constructed in this study is considered an effective approach for reducing computational cost while also being suitable for application in flight simulators and for capturing vehicle-specific aerodynamic characteristics.
Recent advancements in lunar landing missions have demonstrated a growing interest in transitioning from conventional storable propellants to cryogenic alternatives., particularly liquid methane and liquid oxygen. For example, in 2024, Intuitive Machines' methane-based lunar lander IM-1 and IM-2 attempted a landing on the moon in 2024 and 2025, respectively. Both missions employed pressure-fed methane propulsion systems, but their incomplete or ambiguous results suggest that methane-based lunar lander technology-while promising-has yet to be fully validated in operational conditions. Around May 2026, Blue Origin's Blue Moon lunar lander based on a liquid hydrogen engine is scheduled to launch and after that, the methane-engine based SpaceX Starship is scheduled to launch for a lunar landing. In this study, we investigate an alternative architecture based on an electric pump-fed methane propulsion system. This approach enables higher combustion chamber pressure and regenerative cooling, resulting in increased specific impulse and reduced structural mass. The performance implications are analyzed in terms of payload capacity and system robustness, highlighting the potential advantages of electric pump-fed designs for future lunar landing missions.
With the increasing utilization of multi-rotor drones across various fields, the emergence of new applications demanding high performance has elevated technological requirements. Coaxial rotor drones possess the potential to meet these demands with their superior thrust efficiency and control torque; however, achieving stability and precise attitude control remains a challenge. In particular, the fluctuating maximum control torque due to varying flight conditions leads to model uncertainties, complicating real-time state constraint control. This study proposes a novel approach by applying High-Order Control Barrier Functions (HOCBF) to the attitude control of coaxial rotor drones. HOCBF enables robust and computationally efficient control against model uncertainties, ensuring the system state remains within safe boundaries. Simulation results demonstrate that the proposed HOCBF-based controller achieves safe and superior attitude control performance with significantly lower computational load compared to Model Predictive Control (MPC). Furthermore, it is confirmed that the coaxial rotor drone system provides enhanced thrust efficiency and control stability compared to multirotor drone systems. This research contributes to the advancement of high-performance drone applications by resolving the real-time safe control issue of coaxial rotor drones through HOCBF.
In this study, an impact-resistant structure was designed to reduce shock of a secondary battery pack used as a next-generation powertrain, and its effectiveness was validated through numerical analysis and experimental evaluation. The force transmitted to the spacer structure under external impact was measured through drop tests, and this data was used as an input data for finite element analysis (LS-DYNA) to evaluate the shock absorption performance of the proposed impact-resistant structure in terms of energy absorption and deformation. Experimental results from drop tests demonstrated that the application of the impact-resistant structure reduced both the maximum acceleration in time-domain and the peak acceleration in the Shock Response Spectrum (SRS). These findings confirm that the proposed impact-resistant structure can effectively improve the shock mitigation performance of the secondary battery pack.
This study investigates the aerodynamic performance and internal drag correction accuracy of an air-breathing vehicle with a coaxial ramjet inlet through wind tunnel tests. Two tests were conducted to evaluate the inlet's performance and validate the internal drag correction methodology. In the first test, the vehicle's aerodynamic forces and moments were measured, and the drag coefficient was obtained by applying the internal drag correction based on the pressures measured at the end of the internal duct. In the second test, an inlet test was conducted to obtain the performance characteristics of the vehicle's inlet. The larger-scale model was used by omitting the section behind the AIP, allowing for more precise pressure measurements at the AIP. Additionally, a flow meter was used to measure the mass flow ratio more accurately than the first test. The mass flow ratio obtained in the second test was compared with the results from the first test to verify the reliability of the internal drag correction.
Coaxial rotorcraft and tiltrotor aircraft are attracting attention as the next-generation VTOL aircraft. In this study, the radar cross section (RCS) of the UH-60A, SB>1 Defiant, and V-280 Valor models were compared to analyze the survivability related to radar signals of VTOL aircraft. The RCS analysis was conducted using the PO(Physical Optics) method in the X-band region of 10 GHz. In order to identify the main RCS sources of the next-generation VTOL aircraft, the RCS of the SB>1 Defiant and V-280 Valor was analyzed by component. The results showed that the next-generation VTOL aircraft had an overall higher RCS than the existing VTOL aircraft. In particular, a small number of components were found to have a dominant effect on the overall RCS.
Six Ground Telemetry Stations in Naro Space Center acquire the telemetry signal from KSLV-II in real-time, process major data such as trajectory, events and transmit them to Mission Control System. After the launch mission, using the minor frame stored in each station, it generates Best minor frame including the entire launch process for detailed analysis. In this paper, we verified the post-processing function of telemetry data processing system by analyzing the result of the KSLV-II 3rd launch mission.
The urban air mobility (UAM) market has grown rapidly in recent years. While UAM is expected to be deployed within a few years, ensuring safety is essential for successful implementation. One of the factors related to UAM safety is the urban wind environment. Characterized by strong and unpredictable turbulence and building-induced winds due to complex urban topography, the urban wind environment poses significant risks to UAMs, which are lightweight and slow. This study analyzes the flight hazards of UAMs caused by urban wind environments. A realistic urban wind environment was simulated by combining the Weather Research & Forecasting model with large-eddy simulation. By integrating the simulated urban wind environment with two types of UAM simulators, a UAM flight database was constructed. Qualitative and quantitative analyses of the flight database identified hazardous wind speeds caused by crosswinds and vertical winds for the two UAM types. For the Gangnam area, hazardous regions were predicted based on wind speeds. The results revealed that the hazard from crosswind was influenced by shear layers, corner effects, and atmospheric boundary layer, while hazard from vertical wind was primarily occurred at wake regions.
Rendezvous and orbit control are essential for on-orbit servicing. However, when continuous thrust is applied, thrust vector misalignment or biases caused by thruster failures can lead to persistent attitude disturbances. To mitigate this and improve attitude stability, this study proposes a method of shifting the center of mass of the satellite system toward the thrust vector direction. In this paper, we describe a technique to estimate the satellite's inertial parameters using a robotic arm mounted on the servicing satellite, based on the conservation of linear and angular momentum. We implement center of mass relocation of the robotic arm using inverse kinematics, which incorporates a quasi-Newton method and null-space based techniques. This approach was presented along with simulation results, and is expected to serve as a foundation for future research that improves energy efficiency and reduces reaction wheel saturation and fuel consumption.
