Giri Prasad - Academia.edu (original) (raw)
Papers by Giri Prasad
Aircraft Engineering and Aerospace Technology, 2009
ABSTRACT Purpose – The purpose of this paper is to propose a new guidance algorithm for launching... more ABSTRACT Purpose – The purpose of this paper is to propose a new guidance algorithm for launching a satellite using an expendable rocket from an equatorial site to an equatorial low-Earth orbit. Design/methodology/approach – Guidance during endoatmospheric portion is based on a nominal trajectory computed prior to take-off. A set of updating computations begins anew at the time instant tg of transition from endoatmosphere to exoatmosphere. The updating computations determine a guidance trajectory and an associated control law for the remainder of path by taking into account the rocket state at time tg. Thus, the overall guidance involves both initial and midcourse operations, and it has both open- and closed-loop aspects. Findings – Viability and performance in terms of speed, precision, and effectiveness of the proposed scheme is demonstrated through three-dimensional simulations and comparisons to other methods. Originality/value – The updating computations and the fashion in which they are incorporated into the entire guidance process constitute the novel features of the proposed algorithm.
Azimuth resolution of Missile-borne synthetic aperture radar(SAR) is affected by the trajectory a... more Azimuth resolution of Missile-borne synthetic aperture radar(SAR) is affected by the trajectory and look angle. In order to acquire the fixed azimuth resolution within a minimum time for SAR imaging seeker, a new approach of solving optimal control problem, that is, Gauss Pseudospectral Method(GPM), is proposed to optimize imaging phase trajectory of Missile-borne SAR. First of all, optimization model of imaging phase is built, the missile command acceleration is used as control variables, the minimum dwell time is used as objective function and expression of objective function, imaging constraint as well as over loading constraint is proposed. And then, the state and control variables is discretized by GPM. Through this transformation, the continuous-time optimal control problem is transcribed to a nonlinear programming (NLP). At last, GPOPS software package based on matlab is used to solve this problem. Simulation results show that a smooth trajectory can be got by GPM, and GPM isn't sensitive to initial value of state and control variables. Compared with genetic algorithm, GPM have a faster solution speed and a better robustness.
A method is described for analyzing dispersion records from long-range missiles in terms of equiv... more A method is described for analyzing dispersion records from long-range missiles in terms of equivalent electron-density and electron-content profiles above a fixed location. This method takes account of varying horizontal gradients in electron density and the varying local zenith angle of the ray path as a function of range time and height in the ionosphere. Refraction has been considered for
Acta Simulata Systematica Sinica, 2002
… Report, Virginia Tech, Blacksburg, Va, USA, 2004
Optimal estimation techniques are applied to certain fundamental problems associated with ballist... more Optimal estimation techniques are applied to certain fundamental problems associated with ballistic missile testing. These problems include multiple vehicle trajectory reconstruction and performance analysis of metric, telemetry and vehicle subsystems. The mathematical background and guidelines for program implementation are provided for a recursive filtering and smoothing realization of the optimum linear estimator. Considerable emphasis is placed on efficient computation with minimal introduction of processing error. System considerations are applied to the aggregate tracking and estimation functions, and the optimum interface between tracking (data collection) and estimation (data processing) is identified.
Operating instructions for a computer program designed to provide a best estimate of the accuracy... more Operating instructions for a computer program designed to provide a best estimate of the accuracy with which the motion of a vehicle can be determined on the basis of either inertial guidance measurements or external tracking, or both are presented. The performance of the moving vehicle is described by the estimated deviation from its nominal performance. The program, developed by and used at Rand, should prove useful in the fields of ballistic missile accuracy, range instrumentation, and navigational satellites.
Journal of spacecraft and rockets, 1998
System Simulation and Scientific …, 2008
A calculation method that gives the temperature distribution within a body placed in a flow and f... more A calculation method that gives the temperature distribution within a body placed in a flow and following a trajectory, corresponding to the flight conditions of a missile, is defined. The method is to be incorporated in a minicomputer program. Heat transmission across the flow boundary layer, and then by conduction through a body composed of a succession of mediums whose thermic characteristics differ, was studied, supposing that the heat flow is monodimensional. Results are used to elaborate calculation schemes, and a program is established. An application of the program is recounted.
Journal of Spacecraft and Rockets, 1976
A methodology was developed to predict in real time the probabilistic boundaries of the dispersio... more A methodology was developed to predict in real time the probabilistic boundaries of the dispersion of debris from a missile destroyed at that instant of time in flight. The method uses prelaunch tabulated data based on statistical characterization of wind, missile trajectory, and missile breakup characteristics, which are input into a real-time program and transformed from the predicted to actual conditions to compute the debris pattern. The method was evaluated for accuracy and efficiency for a variety of flight conditions, missile types, and display presentation. In addition, a comparison with the actual debris impacts from an aborted launch showed that the debris landed within the predicted debris pattern.
Science Technology and Engineering, 2007
A trajectory prediction program was developed to predict the full trajectory (partially tracked b... more A trajectory prediction program was developed to predict the full trajectory (partially tracked by a satellite or a radar) of a tactical ballistic missile. In order to improve the accuracy of the ballistic coefficient an adaptive C/sub D/ model is developed. Dynamic model, filtering of measurements, geocentric Earth model and atmosphere model were applied and the details of the models and test results are presented. Input to the program is coordinates of the tracked trajectory portion and output is the full trajectory. In this way the launch and target point can be obtained within seconds of execution time.
Science & Global Security, 2007
Journal of guidance, control, and dynamics, 2008
Washington, DC: American Institute of Aeronautics and …, 1994
The present volume discusses numerical techniques relevant to missile guidance, the fundamental c... more The present volume discusses numerical techniques relevant to missile guidance, the fundamental considerations of tactical missile guidance, the 'method of adjoints' and the homing loop, and guidance system noise analysis, covariance analysis and the homing ...
This paper addresses tracking tactical ballistic missiles (TBMs) from space and ships. Modeling e... more This paper addresses tracking tactical ballistic missiles (TBMs) from space and ships. Modeling errors in the tracking system produce an uncertainty covariance matrix. Determining the critical error sources and identifying the needed elements of the covariance matrix is one analysis objective. Given the shooter ship has received the TBM's state via a cue link, then a trajectory propagation model is needed to predict impact parameters and uncertainty error ellipses. Determining trajectory fidelity and quantifying the resulting errors is the second object of this paper
IEEE Transactions on Aerospace and Electronic Systems, 1993
The author explores the influence of a priori uncertainties in launch time and trajectory fly-out... more The author explores the influence of a priori uncertainties in launch time and trajectory fly-out profiles, along with sensor angle measurement errors, on the estimation of missile launch location and heading angle. An error model is developed to compute the statistics of the estimation errors using a single pair of angle measurements, one from each of two satellites, or both
Aircraft Engineering and Aerospace Technology, 2009
ABSTRACT Purpose – The purpose of this paper is to propose a new guidance algorithm for launching... more ABSTRACT Purpose – The purpose of this paper is to propose a new guidance algorithm for launching a satellite using an expendable rocket from an equatorial site to an equatorial low-Earth orbit. Design/methodology/approach – Guidance during endoatmospheric portion is based on a nominal trajectory computed prior to take-off. A set of updating computations begins anew at the time instant tg of transition from endoatmosphere to exoatmosphere. The updating computations determine a guidance trajectory and an associated control law for the remainder of path by taking into account the rocket state at time tg. Thus, the overall guidance involves both initial and midcourse operations, and it has both open- and closed-loop aspects. Findings – Viability and performance in terms of speed, precision, and effectiveness of the proposed scheme is demonstrated through three-dimensional simulations and comparisons to other methods. Originality/value – The updating computations and the fashion in which they are incorporated into the entire guidance process constitute the novel features of the proposed algorithm.
Azimuth resolution of Missile-borne synthetic aperture radar(SAR) is affected by the trajectory a... more Azimuth resolution of Missile-borne synthetic aperture radar(SAR) is affected by the trajectory and look angle. In order to acquire the fixed azimuth resolution within a minimum time for SAR imaging seeker, a new approach of solving optimal control problem, that is, Gauss Pseudospectral Method(GPM), is proposed to optimize imaging phase trajectory of Missile-borne SAR. First of all, optimization model of imaging phase is built, the missile command acceleration is used as control variables, the minimum dwell time is used as objective function and expression of objective function, imaging constraint as well as over loading constraint is proposed. And then, the state and control variables is discretized by GPM. Through this transformation, the continuous-time optimal control problem is transcribed to a nonlinear programming (NLP). At last, GPOPS software package based on matlab is used to solve this problem. Simulation results show that a smooth trajectory can be got by GPM, and GPM isn't sensitive to initial value of state and control variables. Compared with genetic algorithm, GPM have a faster solution speed and a better robustness.
A method is described for analyzing dispersion records from long-range missiles in terms of equiv... more A method is described for analyzing dispersion records from long-range missiles in terms of equivalent electron-density and electron-content profiles above a fixed location. This method takes account of varying horizontal gradients in electron density and the varying local zenith angle of the ray path as a function of range time and height in the ionosphere. Refraction has been considered for
Acta Simulata Systematica Sinica, 2002
… Report, Virginia Tech, Blacksburg, Va, USA, 2004
Optimal estimation techniques are applied to certain fundamental problems associated with ballist... more Optimal estimation techniques are applied to certain fundamental problems associated with ballistic missile testing. These problems include multiple vehicle trajectory reconstruction and performance analysis of metric, telemetry and vehicle subsystems. The mathematical background and guidelines for program implementation are provided for a recursive filtering and smoothing realization of the optimum linear estimator. Considerable emphasis is placed on efficient computation with minimal introduction of processing error. System considerations are applied to the aggregate tracking and estimation functions, and the optimum interface between tracking (data collection) and estimation (data processing) is identified.
Operating instructions for a computer program designed to provide a best estimate of the accuracy... more Operating instructions for a computer program designed to provide a best estimate of the accuracy with which the motion of a vehicle can be determined on the basis of either inertial guidance measurements or external tracking, or both are presented. The performance of the moving vehicle is described by the estimated deviation from its nominal performance. The program, developed by and used at Rand, should prove useful in the fields of ballistic missile accuracy, range instrumentation, and navigational satellites.
Journal of spacecraft and rockets, 1998
System Simulation and Scientific …, 2008
A calculation method that gives the temperature distribution within a body placed in a flow and f... more A calculation method that gives the temperature distribution within a body placed in a flow and following a trajectory, corresponding to the flight conditions of a missile, is defined. The method is to be incorporated in a minicomputer program. Heat transmission across the flow boundary layer, and then by conduction through a body composed of a succession of mediums whose thermic characteristics differ, was studied, supposing that the heat flow is monodimensional. Results are used to elaborate calculation schemes, and a program is established. An application of the program is recounted.
Journal of Spacecraft and Rockets, 1976
A methodology was developed to predict in real time the probabilistic boundaries of the dispersio... more A methodology was developed to predict in real time the probabilistic boundaries of the dispersion of debris from a missile destroyed at that instant of time in flight. The method uses prelaunch tabulated data based on statistical characterization of wind, missile trajectory, and missile breakup characteristics, which are input into a real-time program and transformed from the predicted to actual conditions to compute the debris pattern. The method was evaluated for accuracy and efficiency for a variety of flight conditions, missile types, and display presentation. In addition, a comparison with the actual debris impacts from an aborted launch showed that the debris landed within the predicted debris pattern.
Science Technology and Engineering, 2007
A trajectory prediction program was developed to predict the full trajectory (partially tracked b... more A trajectory prediction program was developed to predict the full trajectory (partially tracked by a satellite or a radar) of a tactical ballistic missile. In order to improve the accuracy of the ballistic coefficient an adaptive C/sub D/ model is developed. Dynamic model, filtering of measurements, geocentric Earth model and atmosphere model were applied and the details of the models and test results are presented. Input to the program is coordinates of the tracked trajectory portion and output is the full trajectory. In this way the launch and target point can be obtained within seconds of execution time.
Science & Global Security, 2007
Journal of guidance, control, and dynamics, 2008
Washington, DC: American Institute of Aeronautics and …, 1994
The present volume discusses numerical techniques relevant to missile guidance, the fundamental c... more The present volume discusses numerical techniques relevant to missile guidance, the fundamental considerations of tactical missile guidance, the 'method of adjoints' and the homing loop, and guidance system noise analysis, covariance analysis and the homing ...
This paper addresses tracking tactical ballistic missiles (TBMs) from space and ships. Modeling e... more This paper addresses tracking tactical ballistic missiles (TBMs) from space and ships. Modeling errors in the tracking system produce an uncertainty covariance matrix. Determining the critical error sources and identifying the needed elements of the covariance matrix is one analysis objective. Given the shooter ship has received the TBM's state via a cue link, then a trajectory propagation model is needed to predict impact parameters and uncertainty error ellipses. Determining trajectory fidelity and quantifying the resulting errors is the second object of this paper
IEEE Transactions on Aerospace and Electronic Systems, 1993
The author explores the influence of a priori uncertainties in launch time and trajectory fly-out... more The author explores the influence of a priori uncertainties in launch time and trajectory fly-out profiles, along with sensor angle measurement errors, on the estimation of missile launch location and heading angle. An error model is developed to compute the statistics of the estimation errors using a single pair of angle measurements, one from each of two satellites, or both