• International Journal of Control, Automation, and Systems
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• v.4 no.5
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• pp.529-538
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• 2006

Separating a reentry vehicle into warhead and body is a conventional and efficient means of producing a huge decoy and increasing the kinetic energy of the warhead. This procedure causes the radar to track the body, whose radar cross section is larger, and ignore the warhead, which is the most important part of the reentry vehicle. However, the procedure is difficult to perform using standard tracking criteria. This study presents a novel tracking algorithm by integrating input estimation and modified probabilistic data association filter to solve this difficulty in a clear environment. The proposed algorithm with a new defined association probability in this filter provides a good tracking capability for the warhead ignoring the radar cross section. The simulation results indicate that the errors between the estimated and the warhead trajectories are reduced to a small interval in a short time. Therefore, the radar can produce a beam to illuminate to the right area and keep tracking the warhead all the way. In conclusion, this algorithm is worthy of further study and application.

• Advances in aircraft and spacecraft science
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• v.4 no.4
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• pp.487-501
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• 2017

The main purpose of the paper is to analyze effect of geometrical parameters of the reentry capsules such as radius of the spherical cap, shoulder radius, back shell inclination angle and overall length on the flow field characteristics. The numerical simulation with viscous flow past ARD (Atmospheric Reentry Demonstrator), Soyuz (Russian) and OREX (Orbital Reentry EXperimental) reentry capsules for freestream Mach numbers range of 2.0-5.0 is carried out by solving time-dependent, axisymmetric, compressible laminar Navier-Stokes equations. These reentry capsules appear as bell, head light and saucer in shape. The flow field features around the reentry capsules such as bow shock wave, sonic line, expansion fan and recirculating flow region are well captured by the present numerical simulations. A low pressure is observed immediately downstream of the base region of the capsule which can be attributed to fill-up in the growing space between the shock wave and the reentry module. The back shell angle and the radius of the shoulder over the capsule are having a significant effect on the wall pressure distribution. The effects of geometrical parameters of the reentry capsules will useful input for the calculation of ballistic coefficient of the reentry module.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.2
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• pp.156-165
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• 2015

A survivability-analysis program has been developed to analyze the ground collision risk of atmospheric reentry objects, such the upper stages of a launch vehicle or satellites, which move at or near the orbital velocity. The aero-thermodynamic load during the free fall, the temperature variation due to thermal load, and the phase shift after reaching the melting point are integrated into the 3 degree-of-freedom trajectory simulation of the reentry objects to analyze the size and weight of its debris impacting the ground. The analysis results of the present method for simple-shaped objects are compared with the data predicted by similar codes developed by NASA and ESA. Also, the analysis for actual reentry orbital objects has been performed, of which results are compared with the measurement data.

• Advances in aircraft and spacecraft science
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• v.11 no.2
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• pp.177-194
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• 2024

The objective of this paper is to compute entire flow field over Apollo-II, Aerospace Reentry Demonstrator (ARD), Orbital Experiment (OREX) with sharp shoulder and rounded shape shoulder and Space Recovery Experiment (SRE) at different flare-cone half-angle of 20° and 35°. This paper addresses numerical solutions of the compressible three-dimensional Euler equations on hexahedral meshes for a freestream Mach 6 and at an angle of incidence 5°. Furthermore, spatial discretization is accomplished by a cell centred finite volume formulation solution and advanced in time by an explicit multi-stage Runge-Kutta method. The flow field characteristics, distribution of surface pressure coefficient and Mach number on fore-body and aft-body are presented as a function of the geometrical parameters of many reentry capsules. The surface pressure variation is numerically integrated to obtain the aerodynamic drag and compared well with impact theory. The present numerical study has observed the significant dependence of the blunt body and the aft-body geometry of the vehicle and can be used to study atmospheric conditions during re-entry trajectory. The numerical analysis reveals the significant influence of capsule geometry on the flow characteristics of the mechanism of upstream and structure of the flow near the wake region and aerodynamic drag coefficient.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.1
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• pp.23-34
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• 2012

Space launch vehicles are designed to fly according to the elaborate pre-determined path. However, if a vehicle went out of the planned trajectory or its thrust terminated abnormally, or if a free-fall atmospheric reentry vehicle tracked by a tracking sensor became impossible to be measured, it is required to attempt to track by a another track equipment or estimate its impact point rapidly. In this paper a new algorithm is proposed, named the ITS-EKF combined with the Integrated Track Splitting (ITS) algorithm and the Extended Kalman Filter (EKF) to obtain the location information of a ballistic projectile without thrust, create its track and maintain it in an environment with clutter. For the reentry vehicle, the track performance is to be verified and the impact point is estimated by applying the simulation through ITS-EKF algorithm. To ensure the proposed algorithm's adequacy, by comparing the track performance and impact point distribution by the ITS-EKF with those of ITS-PF combined with ITS and Particle Filter (PF), it is confirmed that the ITS-EKF algorithm can be used an effective real-time On-line impact point prediction.

• 제어로봇시스템학회:학술대회논문집
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• 1998.10a
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• pp.47-52
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• 1998

This study deals with guidance and control laws for an optimal reentry trajectory of a vertical landing reusable launch vehicle (RLV) in the future. First, a guidance law is designed to create the reference trajectory which minimizes propellant consumption. Then, a nonlinear feedback controller based on a linear quadratic regulator is designed to make the vehicle follow the predetermined reference trajectory, The proposed method is simulated for the first stage of the H-II scale rocket.

• International Journal of Aeronautical and Space Sciences
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• v.14 no.3
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• pp.247-255
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• 2013

The flight control of re-entry vehicles poses a challenge to conventional gain-scheduled flight controllers due to the widely spread aerodynamic coefficients. In addition, a wide range of uncertainties in disturbances must be accommodated by the control system. This paper presents the design of a roll channel controller for a non-axisymmetric reentry vehicle model using the trajectory linearization control (TLC) method. The dynamic equations of a moving mass system and roll control model are established using the Lagrange method. Nonlinear tracking and decoupling control by trajectory linearization can be viewed as the ideal gain-scheduling controller designed at every point along the flight trajectory. It provides robust stability and performance at all stages of the flight without adjusting controller gains. It is this "plug-and-play" feature that is highly preferred for developing, testing and routine operating of the re-entry vehicles. Although the controller is designed only for nominal aerodynamic coefficients, excellent performance is verified by simulation for wind disturbances and variations from -30% to +30% of the aerodynamic coefficients.

• Advances in aircraft and spacecraft science
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• v.4 no.4
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• pp.437-448
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• 2017

The problem of flow through the vent is formulated as an unsteady, nonlinear, ordinary differential equation and solved using Runge-Kutta method to obtain pressure inside payload faring. An inverse problem for prediction of the discharge coefficient is presented employing measured internal pressure of the payload fairing during the ascent phase of a satellite launch vehicle. A controlled random search method is used to estimate the discharge coefficient from the measured transient pressure history during the ascent period of the launch vehicle. The algorithm predicts the discharge coefficient stepwise with function of Mach number. The estimated values of the discharge coefficients are in good agreement with differential pressure measured during the flight of typical satellite launch vehicle.

• International Journal of Aeronautical and Space Sciences
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• v.6 no.2
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• pp.46-55
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• 2005

A rocket-powered vehicle is designed conceptually which uses an engine running on methane and oxygen and delivering 10 tons of thrust. The aerodynamic coefficients of the vehicle are taken to be those of the Japan's HOPE-X, and the weight of this vehicle is estimated using a method developed by NASA. The resulting vehicle will be about 9 meters long, 5.8 meters in wing span, weigh about 2 tons empty, carry a maximum of 5.6 tons of propellant, and endure a g-load of 4.5. The craft will be able to carry five passengers, in addition to a pilot, and fly for space tourism between a northern and a southern airport with a maximum g-load varying from 3g to 4g depending on the route flown.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.12
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• pp.997-1010
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• 2021

This study collected and analyzed flight data of SpaceX's Falcon 9 launch vehicle. All missions were classified by orbital types, such as Polar, SSO, ISS, LEO and GTO missions. In characteristic maneuvers of main engine cutoff, boostback, reentry and landing burn at each stage of 1st stage launch vehicle, changes of the physical parameters like speed, altitude, dynamic pressure and acceleration were investigated. The guidelines derived from detailed maneuver analysis were suggested, which can be used as design and evaluation references for developing reusable launch vehicle.