A theoretical study for the design of a new ballistic range
01 Jul 2006-Journal of Mechanical Science and Technology (Korean Society of Mechanical Engineers)-Vol. 20, Iss: 7, pp 1019-1029
TL;DR: In this article, a theoretical work has been made to develop a new type of ballistic range which can easily simulate a flying projectile, which consists of high pressure tube, piston, pump tube, shock tube and launch tube.
Abstract: The ballistic range has long been employed in a variety of engineering fields such as high-velocity impact engineering, projectile aerodynamics, creation of new materials, etc, since it can create an extremely high-pressure state in very short time. Of many different types of ballistic ranges developed to date, two-stage light gas gun is being employed most extensively. In the present study, a theoretical work has been made to develop a new type of ballistic range which can easily simulate a flying projectile. The present ballistic range consists of high-pressure tube, piston, pump tube, shock tube and launch tube. The effect of adding a shock tube in between the pump tube and launch tube is investigated. This improvement is identified as the reduction in pressures in the high pressure tube and pump tube while maintaining the projectile velocity. Equations of motions of piston and projectile are solved using Runge-Kutta methods. Dependence of projectile velocity on various design factors such as high pressure tube pressure, piston mass, projectile mass, area ratio of pump tube to launch tube and type of driver gas in the pump tube are also analyzed. Effect of various gas combinations is also investigated. Calculations show that projectile velocities of the order 8 km/sec could be achieved with the present ballistic range.
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01 May 2007
TL;DR: In this paper, a theoretical analysis has been carried out to investigate various unsteady processes involved in the operation of the ballistic range and to assess the performance of the two-stage light-gas gun.
Abstract: The ballistic range has long been employed in a variety of engineering fields such as high-velocity impact engineering, projectile aerodynamics, and aeroballistics, since it can create an extremely high-pressure state in a very short time. Of many different types of ballistic ranges developed to date, a two-stage light-gas gun is being employed most extensively. Since the operation of the ballistic range involves many complicated gas dynamic processes, optimization of various design parameters of the ballistic range is important for the durability of its components. In the present study, a theoretical analysis has been carried out to investigate various unsteady processes involved in the operation of the ballistic range and to assess the performance of the ballistic range. The results obtained are validated with the available experimental data. A shock tube is added in between the pump tube and launch tube and its effect on the performance of the ballistic range is quantified using the present the...
9 citations
01 May 2007
TL;DR: In this paper, a computational fluid dynamics (CFD) method has been applied to simulate unsteady near-field aerodynamics of the projectile which is launched from a ballistic range.
Abstract: A computational fluid dynamics (CFD) method has been applied to simulate unsteady near-field aerodynamics of the projectile which is launched from a ballistic range. A moving coordinate scheme for a multi-domain technique was employed to investigate the unsteady flow with moving boundary. The coordinate system fixed to each moving domain was applied to the multi-domains, and the effect of virtual mass was added in the governing equations for each domain. The unsteady, axi-symmetric Euler equation systems were numerically solved using the third-order Chakravarthy-Osher total variation diminishing scheme, with Monotone Upstream-centered Scheme for Conservation Laws (MUSCL) approach. The present computations were validated with results of some other CFD works and experimental data available. The computed results reasonably capture the major flow features, such as shock waves, blast waves, shear layers, vortical flows, etc which are generated in launching a projectile up to a supersonic speed. The pro...
9 citations
TL;DR: In this paper, a computational analysis has been made to investigate the fluid dynamic aspects of the compression process in the pump tube of a ballistic range and to assess how it affects the performance of the ballistic range.
Abstract: The ballistic range has long been employed in a variety of engineering fields such as high-velocity impact engineering, projectile aerodynamics and aeroballistics, since it can create an extremely high-pressure state in very short time. Since the operation of the ballistic range includes many complicated phenomena, each process should be understood in detail for the performance enhancement of the device. One of the main processes which have significant influence on the device performance is the compression process of the driver gas. Most of the studies available in this field hardly discuss this phenomenon in detail and thus lack a proper understanding of its effect on the whole system performance. In the present study, a computational analysis has been made to investigate the fluid dynamic aspects of the compression process in the pump tube of a ballistic range and to assess how it affects the performance of the ballistic range. The results obtained are validated with the available experimental data. In order to evaluate the system performance, several performance parameters are defined. Effect of a shock tube added in between the pump tube and launch tube on the performance of the ballistic range is also studied analytically. Performance of the ballistic range could be significantly improved by the proper selection of the pump tube and high-pressure tube parameters and the addition of the shock tube.
2 citations
Journal Article•
TL;DR: In this article, the performance of a two-stage gas gun is studied using the theory of the two stage gas gun proposed by Rajesh, numerical simulation using combined Eulerian/ Lagrangian elements in Autodyna commercial code and experiment using a gas gun developed by the authors of this study.
Abstract: Two stages gas guns are used for various purposes, particularly for mechanical characterization of materials at high rate of deformations. The performance of a two stages gas gun is studied in this work using the theory of the two-stage gas gun proposed by Rajesh, numerical simulation using combined Eulerian/ Lagrangian elements in Autodyna commercial code and experiment using a two stage gas gun developed by the authors of this study. Equations governing the motion of the piston and projectile are solved using Runge-Kutta method. The effects of parameters such as chamber pressure, pump tube pressure and piston mass on the performance of gun are explored. The results of numerical simulation and analytical methods are validated by experiment. Finally, a comparison between the analytical, numerical and experimental results shows that the theory proposed by Rajesh, yields reasonable predictions for the two stage gas gun performance in the first place, and Autodyn software, using combined Eulerian/ Lagrangian elements, gives accurate estimations for gas gun parameters, in the second place. A 3-D working diagram is provided for prediction of projectile velocity for any state of pump and chamber pressures which are the most important variables for a gas gun with a fixed geometry. Two stages gas guns are used for various purposes, particularly for mechanical characterization of materials at high rate of deformations. The performance of a two stages gas gun is studied in this work using the theory of the two-stage gas gun proposed by Rajesh, numerical simulation using combined Eulerian/ Lagrangian elements in Autodyna commercial code and experiment using a two stage gas gun developed by the authors of this study. Equations governing the motion of the piston and projectile are solved using Runge-Kutta method. The effects of parameters such as chamber pressure, pump tube pressure and piston mass on the performance of gun are explored. The results of numerical simulation and analytical methods are validated by experiment. Finally, a comparison between the analytical, numerical and experimental results shows that the theory proposed by Rajesh, yields reasonable predictions for the two stage gas gun performance in the first place, and Autodyn software, using combined Eulerian/ Lagrangian elements, gives accurate estimations for gas gun parameters, in the second place. A 3-D working diagram is provided for prediction of projectile velocity for any state of pump and chamber pressures which are the most important variables for a gas gun with a fixed geometry.
1 citations
Cites background or methods from "A theoretical study for the design ..."
...Rajesh et al. [20] investigated the fluid dynamic features of the compression process in the pump tube of a ballistic range and to assess how it affects the performance of the ballistic range....
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...Rajesh et al. [18-20] studied analytically the effects of important parameters such as pump tube pressure, piston mass, type of light gas, and the diameters of pump and launch tubes on the performance of two stages gas gun....
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...The performance of a two stages gas gun is studied in this work using the theory of the two-stage gas gun proposed by Rajesh, numerical simulation using combined Eulerian/ Lagrangian elements in Autodyna commercial code and experiment using a two stage gas gun developed by the authors of this study....
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...Rajesh, G., Lee, J., Back, S. and Kim, H.D., "A theoretical study for the design of a new ballistic range", Journal of mechanical Science and Technology, Vol. 20, No. 7, (2006), 1019-1029....
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...Rajesh, G., Kim, H., Setoguchi, T. and Raghunathan, S., "Performance analysis and enhancement of the ballistic range", Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Vol. 221, No. 5, (2007), 649-659....
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TL;DR: In this article , a numerical analysis in Computational Fluid Dynamics uses the Finite Volume Method to visualize the external flow characteristics over a supersonic bullet speeding at Mach 2.0.
Abstract: In this research paper, a numerical analysis in Computational Fluid Dynamics uses the Finite Volume Method to visualize the external flow characteristics over a bullet speeding at Mach 2.0. The simulation results evaluate the experimental drag coefficient of the supersonic bullet airflow in a wind tunnel. The numerical simulation assumes that the inviscid model remains non-rotating. The generation of the mesh geometry varies between Coarse, Medium, and Fine types, and proper selection of the grid density improves the accuracy of the numerical result. The Fine Quadrilaterals mesh of 150,000 elements achieved considerable punctuality along with the numerical method of the second-order linear differential equations. The drag coefficient value of 0.222 gives a 0.9 percent error relative to the attained experiment value. The Mach number, pressure ratio, and flow simulation velocity contours obtained with ANSYS FLUENT software represent the validation of the experimental data with numerical analysis method in a typical fluid mechanics problem.
References
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202 citations
TL;DR: In this article, the Sandia hypervelocity launcher achieved velocities up to 15.8 km/s by using a graded-density assembly to impact a stationary flier-plate.
Abstract: A systematic study is described which has led to the successful launch of thin flier plates to velocities of 16 km/s. The energy required to launch a flier plate to 16 km/s is approximately 10 to 15 times the energy required to melt and vaporize the plate. The energy must, therefore, be deposited in a well-controlled manner to prevent melt or vaporization. This is achieved by using a graded-density assembly to impact a stationary flier-plate. Upon impact, time-dependent, structured, high pressure pulses are generated and used to propel the plates to hypervelocities without melt or fracture. In previous studies, a graded-density impact of 7.3 km/s was used to launch a 0.5 mm thick plate to a velocity of over 12 km/s. If impact techniques alone were to be used to achieve flier-plate velocities approaching 16 km/s, this would require that the graded-density impact occur at - 10 km/s. In this paper, we describe a new technique that has been implemented to enhance the performance of the Sandia hypervelocity launcher. This technique of creating an impact-generated acceleration reservoir, has allowed the launch of 0.5 mm to 1.0 mm thick plates to record velocities up to 15.8 km/s. In these experiments, both titanium (Ti-6A1-4V) and aluminum (6061-T6) alloy were used for the flier-plate material. These are the highest metallic projectile plate velocities ever achieved for masses in the range of 0.1 g to 1 g.
77 citations
TL;DR: Weldon and Wenzel as mentioned in this paper analyzed the performance of the Reference Gun and showed that the velocity limit can be increased to 7 km/s if the gun is loaded with hydrogen and the length is doubled.
Abstract: The subjects of this paper are the historical overview and development of the high-velocity gas-dynamics gun. These are guns that derive their energy from a reservoir of compressed gas. Other 3uns derive their energy from electricity or from high explosive. Their historical overviews and developments are covered in papers by Mr. William Weldon and Mr. Alex Wenzel. The gas dynamics gun is viewed first from the standpoint of modern technology. An idealized configuration, the “Reference Gun”, is analysed in order to quantify the effects of gun diameter and length, projectile mass, and propellant gas pressure and composition. The analysis assumes that the propellant is an ideal gas, and formulae are derived for the base pressure and velocity of the projectile as functions of the size and loading parameters of the gun. The analysis demonstrates that the prime requirements for high velocity are a high gas pressure, a low molecular weight gas, a light projectile, and a long gun. The history of guns is reviewed briefly from 14th century black-powder muzzle-loaders to 20th century, nitrocellulose -propellant, breech-loaded guns. The velocity limit of the modern gun is shown to be around 3 km/s, if the gun is loaded with nitrocellulose propellant and is very long (200 calibers). However, if the gun is loaded with hydrogen and the length doubled, it is shown that the velocity limit can be increased to 7 km/s, thus approaching current needs. The problem of using hydrogen has been solved by the invention of the piston-compression light-gas gun (PCLGG). However, the limited strength of the fragile, sabot-model projectiles of experimental research has capped the maximum acceleration and has placed a demand on the gun's operating cycle to generate a constant pressure at the base of the projectile for the launching run. This second problem has been partially solved by the invention of a modification to the PCLGG known as the piston-compression, accelerated-reservoir, light-gas gun (PCARLGG). Both the PCLGG and the PCARLGG are described. The performance of the PCARLGG has been analyzed by a hydrocode developed for this purpose, and the results of the calculations are presented and compared with experiment. The concept of a frictionless, adiabatic “Ideal Gun” is introduced in order to simplify the analysis of performance. It is shown that the performance of any ideal gun is given by a simple equation involving two dimensionless parameters that relate the projectile's velocity to its mass, its average base pressure, and the diameter and length of the gun. Based on the ideal gun equation, the maximum operating velocity of the gas-dynamics gun is estimated to be about 12 km/s.
56 citations
TL;DR: The results show that a two-stage free-piston driver is capable of driving hypervelocity expansion tubes and therefore new facilities of increased size but reduced cost are now possible.
Abstract: The overall cost of free-piston driven facilities can be substantially reduced if the contraction between the compression and shock tubes is replaced with a constant area section. However, with such an implementation, a new driver concept is required in order to achieve a realistic facility length. This paper describes a new free-piston driver type for expansion tubes which satisfies the above criteria. The technique is known as the two-stage free-piston driver where the driver gas is compressed in two distinct stages with a unique compound piston design. A new facility has been constructed (X-2) which is described in some detail. A quasi-one-dimensional numerical model of the compression process is also developed which agrees well with driver tube experimental results. This new driver is coupled to an expansion tube arrangement where super-orbital test flows are generated. The results show that a two-stage free-piston driver is capable of driving hypervelocity expansion tubes and therefore new facilities of increased size but reduced cost are now possible.
33 citations
TL;DR: In this study, numerical method was developed by using the KRC shock capturing scheme and by modeling the flow losses in suitable forms for a quasi-1D numerical computation and the applicability of the present numerical method as a design tool is discussed briefly.
Abstract: A free-piston shock tunnel (FPST) is one of the most useful ground testing facilities for hypervelocity flow research of re-entry vehicles and scramjet engines. For an efficient operation with tuned piston motion, the design of facility and the comprehension of the physical phenomena in a FPST, a numerical simulation which can properly predicts the flow with actual losses is required. But there are few successful numerical methods which can simulate its overall performance. In the present study, numerical method was developed by using the KRC shock capturing scheme and by modeling the flow losses in suitable forms for a quasi-1D numerical computation. The present numerical results were compared with the data obtained in two different facilities, T4 and T5. The applicability of the present numerical method as a design tool is discussed briefly.
29 citations