• Journal of IKEEE
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• v.25 no.4
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• pp.766-769
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• 2021

In order to perform tasks such as design, control, optimization, and prediction of flight vehicle trajectories based on machine learning techniques including deep learning, a certain amount of flight vehicle trajectory data is required. However, there are cases in which it is difficult to secure more than a certain amount of flight vehicle trajectory data for various reasons. In such cases, synthetic data generation could be one way to make machine learning possible. In this paper, to explore this possibility, we generated and evaluated synthetic flight vehicle trajectory data using time-series generative adversarial neural network. In addition, various ablation studies (comparative experiments) were performed to explore the possibility of using synthetic data in the aircraft trajectory prediction task. The experimental results presented in this paper are expected to be of practical help to researchers who want to conduct research on the possibility of using synthetic data in the generation of synthetic flight vehicle trajectory data and the work related to flight vehicle trajectories.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.5
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• pp.46-55
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• 2006

In general, 3-dimensional point-mass equation has been widely used for the trajectory optimization of the fixed-wing aircraft and reentry vehicle. But it should be modified and represent target vehicle's own characteristics. For a lighter-than-air vehicle such as an airship, there exists different and peculiar flight characteristics compared with the aircraft. The first part of this paper is to derive the dynamic equation of motion for the mid-altitude unmanned airship and the second part is to obtain the optimal trajectories under the minimal time flight given constraints. The trajectory optimization problem is converted into the nonlinear programming problem using Sequential Quadratic Programming approach. Finally numerical solutions are presented in the last part of the paper.

• Journal of the military operations research society of Korea
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• v.32 no.1
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• pp.176-187
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• 2006

It is difficult to estimate missile flight trajectory since a ballistic missile velocity is highly fast and has inherent behavior such as corkscrew due to unstable descending. This paper describes a comprehensive analysis of the flight trajectory characteristics of ballistic missiles. Various missile flight ranges based the comprehensive flight trajectory characteristics are derived by an analytical approach. It is shown analytically that threat due to the flight characteristics is significantly increased with reducing maximum missile ranges. This work is basic research of the establishment of operational concept for the lower tier missile defense system implementation.

• Journal of the Korea Society for Simulation
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• v.27 no.4
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• pp.1-8
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• 2018

The most common way to control a target point using artificial intelligence is through reinforcement learning. However, it had to process complicated calculations that were difficult to implement in order to process reinforcement learning. In this paper, the enhanced Proximal Policy Optimization (PPO) algorithm was used to simulate finding the planned flight trajectory to reach the target point in the virtual environment. In this paper, we simulated how this problem was used to find the planned flight trajectory to reach the target point in the virtual environment using the enhanced Proximal Policy Optimization(PPO) algorithm. In addition, variables such as changes in trajectory, effects of rewards, and external winds are added to determine the zero conditions of external environmental factors on flight trajectory learning, and the effects on trajectory learning performance and learning speed are compared. From this result, the simulation results have shown that the agent can find the optimal trajectory in spite of changes in the various external environments, which will be applicable to the actual vehicle.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.6
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• pp.72-80
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• 2004

In this paper, the design procedure of a guidance algorithm in the boosting phase of missiles with free-flight after thrust cut-off is introduced. The purpose of the guidance is to achieve a required velocity vector at the thrust cut-off. Trajectory optimizations for four cost functions are performed to investigate implementable trajectories in the pitch plane. It is observed from the optimization results that high angle of attack maneuver in the beginning of the flight are required to satisfy the constraints. The proposed guidance algorithm consists of the pitch program to produce open-loop pitch attitude command and the yaw attitude command generator to nullify the velocity to go. The pitch program utilizes the pitch attitude histories obtained from the trajectory optimization.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.05a
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• pp.411-413
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• 2009

This paper deals with supersonic vehicle. A supersonic vehicle has very complicated and high nonlinear thrust characteristics with respect to outer and inner environment during operation. For this reason, supersonic vehicle has many maneuver constraints and allows to operate within more narrow flight envelope. In this paper, trajectory optimization of supersonic vehicle is accomplished. The trajectory optimization problem is formulated by a discrete parameter optimization problem and the operation constraints are considered during trajectory optimization. It is shown that results of trajectory optimization give senses to fuel supply and nozzle throttle area control into effectiveness. Furthermore, general operation direction and its application for supersonic vehicles are discussed.

• Journal of Space Technology and Applications
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• v.2 no.2
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• pp.67-80
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• 2022

The missile early-warning satellite systems have been developed and upgraded by some space-developed nations, under the inevitable trend that the space is more strongly considered as another battle field than before. As the key function of such a satellite-based early warning system, the prediction algorithm of the missile flight trajectory is studied in the paper. In particular, the evolution computation, receiving broad attention in the artificial intelligence area, is applied to the proposed prediction method so that the global optimum-like solution is found avoiding disadvantage of the previous non-linear optimization search tools. Moreover, using the prediction simulator of the launch vehicle flight trajectory which is newly developed in C# and Python, the paper verifies the performance and the feature of the proposed algorithm.

• Journal of IKEEE
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• v.25 no.3
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• pp.540-543
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• 2021

In this paper, we present an experimental comparative study of recurrent neural network based techniques for trajectory prediction of flight vehicles. We defined and investigated various relationships between input and output under the same experimental setup. In particular, we proposed a relationship based on the relative positions of flight vehicles. Furthermore, we conducted an ablation study on the network architectures and hyperparameters. We believe that this comprehensive comparative study serves as a reference point and guide for developers in choosing an appropriate recurrent neural network based techniques for building (flight) vehicle trajectory prediction systems.

• Journal of Aerospace System Engineering
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• v.13 no.3
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• pp.70-77
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• 2019

This study presents the numerical investigation of the trajectory of rocket launched from a helicopter. The nonlinear mathematical model of armed configuration of UH-60 helicopter was developed while Hydra 70 unguided rocket was modeled to simulate the rocket behavior. The effects of various inflow models on the launched rocket trajectory are obtained. Similarly, rocket launch simulation was performed to determine the unsafe flight maneuver condition where the rocket trajectory is critically close to the helicopter main rotor tip path plane.

• Journal of the Korean Society of Propulsion Engineers
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• v.25 no.1
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• pp.29-41
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• 2021

The PID controller with fin angle and thrust as control input was designed based on the aerodynamic data of scramjet system. Flight simulation following a given trajectory which strike the target point after climb and cruise with constant dynamic pressure was conducted. After that, the required thrust for the climb and cruise was calculated and the required fuel flow rate for the hydrogen fuel dual mode scramjet combustor was analyzed. The combustor analysis of this study which conducted on integrated model of independently developed inlet, combustor, nozzles and external aerodynamic models, laying the foundation for the integrated design of the air breathing hypersonic system.