| || Effect of flyer plate velocity and rate of crater expansion
Author : Yadav, H. S.
Source : Defence Science Journal ; Vol:52(4) ; 2002 ; pp 429-438
Subject : 623.4 Armaments and Ballistics;623 Military Science and Engineering
Keywords : Explosive reactive armour ;Shaped charge jet ;Warheads ;Precision shaped charge warhead ;Target penetration ;Flyer plate velocity ;Crater
Abstract : "The reduction in the penetration power of the jet due to its interaction with an obliquely moving plate of explosive reactive armour (ERA) sandwich has been studied. It has been assumed that the length of the jet, which gets disturbed due to its interaction with the edge of the hole made by the impact of the tip of the jet when the plate was stationary, does not contribute to penetration in the target. The jet length, which comes out of the hole undisturbed, penetrates the target. This length of the jet has been calculated considering the variation in plate velocity and rate of expansion of the crater in the plate with time. The time taken by the jet to shift its position from the centre to the wall of the hole has been determined for different velocities of the sandwich plate and varying expansion rates of the hole produced by the jet in the plate, corresponding to a constant velocity of the jet. This analysis has been used to obtain the length of undisturbed jet coming out of the hole and its penetration in the target. The present study establishes the effect of the plate velocity and rate of crater expansion on the performance of the ERA. It has been found that both these parameters affect the performance of the ERA, and the metal plates of lower density and higher strength make the ERA more effective. "
| || Ballistic Missile Warhead Recognition based on Micro Doppler Frequency
Author : Hui-xia, Sun;Zheng, Liu;Ning, Xue
Source : Defence Science Journal ; Vol:58(6) ; 2008 ; pp 705-709
Subject : 629.7 Aeronautics;629.762 Missiles
Keywords : Spinning precession target recognition;Micro-doppler;Feature extraction;High-resolution time-frequency transform;Warheads;Ballistic missile warhead
Abstract : To elucidate the spinning-precession signatures of ballistic warhead, the model of spinning precession for ballistic missile warhead is established and the mathematics of micro-Doppler signatures caused by spinning precession is derived. Then the micro-Doppler features are analysed using high-resolution time-frequency transform, and the model predictions match the experimental data well. Based on different mass of warheads and decoys, the feature, which can reflect the mass of the targets, is extracted from the time-frequency plane, proving a new method for recognising warheads and discriminating these from decoys. Finally the validity of the feature extracted in this study is verified by computer simulations even with low signal-to-noise ratio.
| || Motion state of fuel within shell in projection acceleration process
Author : Zhang, Qi ;Lin, Dachao;Bai, Chunhua
Source : Defence Science Journal ; Vol:53(3) ; 2003 ; pp 259-265
Subject : 623.4 Armaments and Ballistics;531.55 Projectiles
Keywords : Projection acceleration process;Fuel air explosive;Warheads;Liquid solid mixture fuel;FAE;FAE warheads;Projectile motion;Projection process;FAE weapons
Abstract : The fuel-air explosive (FAE) warheads are charged with the liquid-solid mixture fuel. The fuel is different from conventional solid explosives in physical and mechanical properties. The mass centre of the charged fuel changes during projecting the projectile. In this study, a method to calculate the mass centre change of the charged fuel is suggested and the influence of this change on the projectile motion state in the projection process is discussed. The results show that in projection, the fuel mass centre varies with the projection acceleration and the deformation characteristics of the mixture fuel. The higher is the acceleration, the larger is the displacement of the mass centre. This displacement also increases with the compressibility of the fuel. It constitutes an influence on the state of motion for the whole projectile in the projection process, whose calculation approach is also proposed. The result provides a theoretical basis for the design of the FAE weapons.