An analysis has been performed to investigate the ballistic performance of the 155mm K307 extended range projectile provided with base bleed unit. Different tools were used to perform this analysis; including analytical modeling and available computational resources. Drag reduction modeling has been used to study the effect of different parameters on base bleed performance such as burning rate, number of base bleed grain parts and the grain dimensions. The study has showed that a better ballistic performance could be obtained when the exit mass flow rate of the burnt gases is relatively large at the first few seconds of the projectile flight. To change this mass flow rate along the trajectory, a newly developed technique has been introduced. The technique depends on filling the base bleed unit with a grain subjected to burning by two rates resulting in extending the projectile range.

Base bleed unit is one of the active methods to increase the range of artillery projectiles. Ballistic performance of base bleed unit has been experimentally assessed using firing tests and wind tunnel experiments. Meanwhile, analytical and numerical studies have been carried out. In some of these studies, solid propellant is used as the source of the burnt gases ejected into the wake behind the projectile base. But, in other studies, different types of gases such as air, argon, hydrogen, and helium are ejected at different temperatures. In this paper, the effects of the main dimensions of 2-parts tubular base bleed grain unit on its ballistic performance are studied analytically. These dimensions are base bleed grain maximum radius, length, inner diameter of the grain, and exit diameter of base bleed unit. The study is applied to the base bleed unit which is installed to K307 155mm projectile. The study leads to a new method to control the ejected mass flow rate. This method is based on changing the exit diameter of base bleed unit in order to get higher injection parameter in the first few seconds of projectile flight and lower values in the remaining time of base bleed grain burning. Therefore, the base bleed projectile range is increased by 1.7 % when comparing with its counterpart which is supplied with base bleed unit having constant exit diameter and the same base bleed grain.

Solid propellant Base bleed unit is one of the effective methods to increase the range of artillery projectiles. As far as we search, no published study focuses on the optimal dimensions of the base bleed grain. However, few studies focus on the effect of base bleed grain parameters on its ballistic performance in which each parameter was studied separately. The present optimization study is performed on base bleed grain which performed as longitudinally slotted tubular cylinder. Different case studies have been introduced according to the number of design variables which are: grain outer, inner radius, length, burn rate, base bleed grain unit orifice diameter. Moreover, the study is extended to demonstrate the effect of these parameters on the innovative multi-burn rate base bleed grain. In this new idea, the grain is splitted into two horizontal parts one with higher burn rate than the other part. The idea is to have a grain that provides high mass flow rate in the first seconds of projectile flight, while keeping long bleeding time. The optimization constrains are the upper and lower limits of each design variable. An analytical model has been developed in C++ environment to accurately evaluate the range of the projectile. This model is then utilized in combination with design of experiment (DOE) and the response surface method (RSM) to develop a smooth response function which can be effectively used in the design optimization formulation as the objective function. The objective of the optimization is to find the design variables which contribute the maximum range. Paper: ASAT-16-171-AE The results show the importance of applying optimization and provided the optimized values of the studied parameters at each case. Also it shows that the application of the new idea of multi-burn rate base bleed increases the range in all cases with percentage up to 12 % with respect to the range increase for the original base bleed grain.

In this paper, Autodyn-2D hydrocode is used to simulate the penetration process of a small caliber projectile into a ceramic tile with finite thickness backed by a semi-infinite 4340 steel armor. Input data to the code are those used by Reaugh, et al. [1]. These data include six types of ceramic material, projectile material and 4340 semi-infinte steel armor, respectively. The ceramic material types are: Alumina with purity 85 and 96%, respectively, Boron Carbide, Aluminium Nitride, Silicon Carbide and Titanium Diboride. Each tile thickness of a ceramic material type is backed by a 4340 steel semi-infinite armor to form a bi-element target; each target is impacted by a tungesten alloy projectile having a certain velocity in the range from 1300 to 1750 m/s. The main procedures used to simulate the penetration process are introduced. The obtained numerial results of Autodyn-2D are compared with the corresponding experimental measurments of Ref. [1]; good agreement is generally obtained. In addition, samples of the time histories predicted by the hydrocode are presented, together with pertinent analyses and discussions. Finally, It is concluded that the Autodyn-2D hydrocode is a useful tool in designing and evaluating the ballistic efficiency of a bielement target when encountering a certain threat.

In this paper, an analytical model is proposed to describe the penetration of a high-speed projectile into a metallic bi-element target, consisting of a finite thickness metallic layer facing a semi-infinite RHA armor. The proposed model identifies two main phases for target penetration; these are: (i) penetration of the front metallic layer and (ii) penetration of backing semi-finite metallic armor. During the target penetration phases, three modes of the projectile front may occur; these are erosion, mushrooming and rigid modes [1, 6]. Main assumptions and governing equations of each target penetration phase for each mode of projectile front are presented. These equations are arranged and compiled into a computer program. The input data to the program are easily determined. The measured penetration depths of depleted uranium (DU) projectiles into semiinfinite RHA armor at different impact velocities of Ref. [4, 5] are compared with the corresponding model predictions to determine the RHA flow stress. In addition, the model predictions are compared with the ballistic measurements of Ref. [4] to determine the flow stress of front metallic layer materials of the bi-element targets. The present model is also used to predict the ballistic efficiencies of the front titanium plates with different thicknesses when each of them is backed by a semi-infinite RHA armor. Moreover, predicted samples for the influence of the projectile impact velocity on the ballistic efficiency are presented and discussed.