In this paper, backward transition controller study was conducted focusing on the principle that general fixed wing aircraft control altitude through pitch control. During backward transition process, pitch control was performed based on the altitude rate in the high/middle speed section where the fixed wing control force was strong to stabilize the rotary-wing throttle, and in the low speed section where the fixed wing control force was weak, the pitch control was performed based on the acceleration to perform fast deceleration. In addition, if the rotary-wing actuator control command is excessively applied in the high-speed section, vibration may occur, so the rotary-wing actuator control command was generated according to airspeed. In order to verify the performance of backward transition controller based on altitude rate and acceleration, the PX4 open platform and Matlab/Simulink integrated simulation environment were established and the simulation was performed to verify the performance. In addition, it was mounted on an actual Lift & Cruise UAV and performed flight tests to verify the performance of backward transition controller based on altitude rate and acceleration.
With the growing global interest in manned-unmanned teaming(MUM-T), this study refines the operational concept of MUM-T and conducts verification research to support its implementation. Based on operational concept in which LAH(Light Armed Helicopter) and multiple Unmanned Aerial Vehicles(UAVs) cooperate, the operational requirements for UAVs have been derived and applied to the design of UAV flight control system. The simulink-based simulation environment has been then established to verify its system through operational procedures such as takeoff and route flights. This paper presents the process of deriving the operational requirements and the UAV flight control system design in detail, as well as the simulation results for each operational procedure. In future work, the proposed system will be further validated in an integrated verification environment to comprehensively assess the feasibility of MUM-T operations.
The model following technique is a significant part of modern helicopter flight control law design, and provides an attitude command/attitude hold(ACAH) response which is particularly representative of its implementation. Modernized flight control laws were originally designed for fly-by-wire(FBW) systems, but the profound research has extended their range of application. The research has demonstrated the successful application of these control laws to the control systems with limited authority, thereby enhancing the handling qualities of legacy helicopters. In this study, the attitude command system has been designed as an inner loop using a model following technique, based on a flight dynamics model and a mechanical control system model of LCH (Light Civil Helicopter). Additionally, various upper modes of autopilot functions have been designed as a outer loop controls. The validity of the control laws proposed in this study has been demonstrated through the real-time hardware-in-the-loop simulation(HILS) environment. The results of this study can be applied to the conventional type of Automatic Flight Control System(AFCS) for manned helicopters currently in operation, thereby improving their handling qualities. Furthermore, the research experience gained can contribute to risk mitigation when developing future FBW systems.
In this study, a comparison and analysis were conducted on noise evaluation aspects targeting Korea's KAS Part 36 (Aircraft Technical Standard Part 36: Aircraft Noise Standards), the United States' 14 CFR Part 36 (14 CFR Part 36 Noise Standard: Aircraft Type and Airworthiness Certification), and Europe's EASA EPTS (Environmental Protection Technical Specifications applicable to VTOL-capable aircraft powered by tilting & non-tilting rotors). Commonalities and differences in noise evaluation metrics, noise measurement methods, flight procedure-specific reference and test procedures, and maximum allowable noise levels were derived. In particular, it was identified that EASA EPTS is differentiated from the existing standards in that it additionally stipulates noise evaluation procedures during hover flight, considering the urban operational characteristics of aircraft. Based on this, a practical foundation was established to overcome the limitations of applying existing noise certification standards and to build a customized noise certification system suitable for Korea's Urban Air Mobility (UAM) operational environment.
Although helicopters have the advantage of being able to hover and take off and land vertically, they also have the disadvantage that their maximum horizontal speed is difficult to exceed a certain limit due to the drag on the advancing rotor blade and the stall on the retreating rotor blade. To overcome the speed limitations of conventional helicopters, research is being actively conducted on high-speed compound helicopters that use auxiliary thrust devices in addition to rotors. An example of a compound helicopter is a configuration that applies coaxial counterrotating rotors and a pusher propeller. In this study, the inner loop of the flight control laws for a compound helicopter with a coaxial counter-rotating rotor and a pusher propeller was designed and evaluated against the ADS-33E-PRF, the international standard for helicopter handling qualities, using CONDUIT(Control Designer's Unified Interface). In addition, various simulations were performed in a nonlinear simulation environment built by linking with FLIGHTLAB to evaluate the target performance of attitude hold accuracy.
An optimal design framework is developed for composite rotor blades that accounts for structural strength requirements under ultimate load condition. The ultimate load condition is defined as a case with a large bending moment at the blade root. The design framework integrates the commercial finite element (FE) modeler MSC.Patran, the sectional analysis program KSAC2D and a surrogate model of rotor comprehensive analysis within the global optimization algorithm PSGA (Particle Swarm assisted Genetic Algorithm). The baseline HART (Higher harmonic control Aeroacoustic Rotor Test) II blade is redesigned with the goal of improving strength and rotor resonance characteristics. Optimization results indicate that strength requirements under the ultimate load condition is satisfied and that resonance is avoided by keeping the rotating natural frequencies away from integer multiples of the rotor speed. In addition, the blade mass is reduced by about 5% compared to the baseline blade while decreasing the overall hub vibration level slightly.
This study aims to enhance the accuracy of Gauss Initial Orbit Determination (Gauss IOD) by applying the YOLOv4 deep learning model to detect orbital streaks in actual observation images obtained from Korea's first Electro-Optical Satellite Surveillance System (EOSS). Conventional algorithms often fail to extract orbital streaks under adverse weather conditions, leading to mismatches with measurement epochs and subsequent degradation in orbit determination accuracy. To address these limitations, we performed image preprocessing on EOSS data, orbital streak detection using YOLOv4, and coordinate registration through plate solving and World Coordinate System (WCS) analysis. Based on real optical observation data of ARIANE rocket debris and STARLINK satellites, Two-Line Elements (TLE) and the SGP4 propagator were used to compute satellite observer distances. The initial orbits were then determined using both the Gauss method and the deep learning approach. Experimental results demonstrated that the proposed method reduced initial orbit determination error by up to 72%. This study highlights the significance of incorporating deep learning models into initial orbit determination, achieving markedly improved accuracy compared to the conventional Gauss method.
Hit-to-kill interceptor missiles, neutralize incoming warheads through direct impact, require well-balanced performance across multiple subsystems-including aerodynamics, propulsion, structures, and guidance. This study addresses the problem of interceptor missile configuration design and proposes an iterative LHS-based design-space exploration method capable of efficiently searching the design space and identifying approximate Pareto-optimal solutions without performing full optimization. Starting from an initial LHS sample set, the method iteratively re-samples around the vicinity of the Pareto front to progressively refine performance. A comparison with GA-based optimization demonstrates that the proposed approach can substantially increase computational efficiency while achieving comparable or even broader Pareto fronts.
This paper presents a midcourse guidance approach for ducted rocket missiles. To effectively intercept long-range targets, the missile needs to be guided optimally using a performance index that reflects interception capability. To this end, the midcourse guidance problem is formulated and solved as a trajectory optimization problem, and the missile is guided to follow the resulting optimal trajectory using augmented pursuit guidance. Furthermore, the velocity control loop is designed to ensure that the missile reaches the target point at the prescribed time. Numerical simulations are conducted to demonstrate the effectiveness of the proposed method.
A numerical Vibration Correlation Technique (VCT) is applied to determine the buckling design criterion, or the Knockdown Factor (KDF), for a semi-monocoque launch-vehicle propellant tank with skin-stringer-frame construction. Finite-element modeling and analysis are performed using ABAQUS, and geometric initial imperfections are introduced using the Single Perturbation Load Approach (SPLA). The buckling load is predicted by correlating the compressive load with the first-mode natural frequency obtained from normal-mode analysis. The KDFs derived from VCT differs by at most 4.48% from the results of nonlinear post-buckling analysis and are 59.6 to 63.7% higher than the KDF given in NASA SP-8007. In addition, the VCT analysis reduces computational time by up to 85% compared with nonlinear post-buckling analysis. These results indicate that the KDFs derived from numerical VCT are applicable to the lightweight design of semi-monocoque propellant tanks, and that VCT substantially improves computational efficiency.
In this study, first-, second-, and fourth-order benchmark control systems were implemented to determine the optimal proportional-integral-derivative (PID) gains Kp, Ki, and Kd by minimizing a physics-informed loss function using a physics-informed neural network (PINN), enabling stable convergence to the target value (Setpoint). The derived PID gains were validated in MATLAB/Simulink under various cases. Simulation results using PID gains obtained from conventional PID, PID-neural network (PID-NN), and PINN-PID methods demonstrated that the proposed PINN-PID approach significantly improved convergence stability and consistently stabilized the system at the target value, exhibiting superior control performance compared to the other techniques.
This paper proposes a quantitative strike assessment method for Network-Enabled Anti-ship Cruise Missiles (NE-ASCM). Based on an analysis of operational concepts and relevant technologies, it introduces a novel metric, the Bomb Hit Indicator (BHI), computed using limited information received via datalink and reflecting the constraints derived from these concepts and technologies. Using this metric, a practical evaluation framework is developed for real-world implementation. The proposed system supports re-engagement decision-making in networked combat environments, thereby enhancing operational effectiveness and improving combat sustainability.
This study examines the feasibility of operating seekerless anti-ship cruise missiles whose terminal guidance relies on target information received via a weapon datalink from cooperating seeker-equipped missiles. Monte Carlo simulations are conducted to evaluate the effects of missile position errors, seeker-derived measurement errors, datalink limitations, and target-motion uncertainties under simultaneous time-on-target(STOT) scenarios involving heterogeneous missile salvos. The results indicate that seekerless missiles can achieve high hit probabilities, particularly when approaching a target's broadside and when updated target information is received within 5 km from a cooperating seeker-equipped missile at a favorable relative approach angle. Based on these findings, cooperative engagement of multiple heterogeneous missiles through datalinked information sharing is expected to reduce missile unit costs, shorten target response times, and provide additional operational benefits, thereby enhancing strike efficiency. Overall, under the specified conditions, datalink-based operation of seekerless missiles supported by cooperative engagement is shown to be feasible, and cooperative engagement emerges as an effective means of improving anti-ship strike performance.
In this study, an optimal aerodynamic shape design method considering the uncertainty of Kriging models was applied to a strake-equipped missile. To reduce the high computational cost of high-fidelity CFD analysis at the early design stage, Kriging models based on CFD results were constructed and utilized. The objective function was set to minimize wing weight, and static stability under flow conditions of Mach 2.86 and a bank angle of 45 degrees was considered as a constraint. A genetic algorithm was used for the optimization, and the prediction uncertainty of the Kriging model was reflected at a 95% confidence level to ensure more reliable constraint evaluation. As a result of the optimization, an optimal shape was derived in which the strakes were reduced and moved rearward, while the tail fins were enlarged. The optimal shape showed a slight increase in wing weight but satisfied the required static stability. The effectiveness of the proposed design method was verified through an uncertainty impact analysis.
The global space industry is rapidly evolving toward service-driven and data-driven value chains, with the private sector playing an increasingly central role and positioning the industry as a strategic core of national economies. In Korea, the "Future Space Economy Roadmap" announced in late 2022, marked a policy shift toward a private-led space economy. However, empirical assessments of its impact on private space firms remain scarce. This study integrates ValueSearch financial data from 2018-2024 with the Space Industry Survey conducted by the Korea Association for Space Technology Promotion to compare 96 space firms with more than 40,000 general firms of similar size and industry. Employing fixed-effects panel regression and propensity score matching (PSM), we estimated performance changes before and after the policy. The results indicated that space firms achieved, on average, 8.86 percentage points higher revenue growth and 6.25 percentage points higher employment growth than non-space firms, with larger differences observed among the top 25% and 50% growth groups. These findings suggest that the Roadmap contributed to early performance gains and highlighted the need for targeted support for high-potential, multi-domain space enterprises.
This study investigates the performance of a high altitude test facility with respect to the geometry of the test engine nozzles. Three types of nozzles, conical, bell and pintle, were evaluated under identical throat and outlet diameter conditions. Both numerical simulations and cold-flow tests were conducted to assess the supersonic diffuser's performance depending on nozzle shape and the presence of internal inserts. Numerical results indicated that all nozzle types were capable of achieving the target altitude, with performance ranked in the order of bell, pintle, and conical. The differences were attributed to variations in the ratio of axial to radial velocity components at the nozzle exit. The bell nozzle achieved the lowest chamber pressure and consequently the highest simulated altitude because its greater ratio of axial to radial velocity vomponents significantly amplifgied the entrainment effect. The cold-flow test results showed consistent trends with the numerical simulations.
