Projectile

About: Projectile is a research topic. Over the lifetime, 13047 publications have been published within this topic receiving 115563 citations.

Real gas effects on the prediction of ram accelerator performance

Abstract: The analysis of ram accelerator performance is based on one-dimensional modelling of the flow process that propels the projectile. The conservation equations are applied to a control volume travelling with the projectile, and quasi-steady flow is assumed. To date the solution obtained, namely the generalized thrust equation, has been based on the ideal gas assumption. At the high level of pressure that is encountered during the ram accelerator process, this assumption cannot be regarded as adequate. Thus, a more appropriate equation of state (EOS) should be used instead. Depending upon the level of pressure, several equations of state are available for dense gaseous energetic materials. The virial type of EOS can be more or less sophisticated, depending upon the extent of complexity of the intermolecular modelling, and turns out to be totally appropriate for most gaseous explosive mixtures that have been investigated at moderate initial pressures, i.e., less than 10MPa. In the present case the Boltzmann EOS was applied. It is based on very simplified molecular interactions, which makes it relatively easy to use in calculations. Moreover, the energetic EOS needs to be taken into account. This concerns all the calorimetric coefficients, as well as the thermodynamic parameters, which can no longer be expressed as only a function of temperature. The higher the pressure level, the more sophisticated these corrections become, but the main relationships that account for real gas effects are basically the same. These include the use of a general form of analytical operators applied to correct the thermodynamic functions and coefficients. The equations governing the one-dimensional model were taken as a basis for the real gas corrections and were solved analytically. The parameters which play the most crucial roles in this correction can thus be highlighted. A complete set of equations involving the real gas effects are presented in this paper. The QUARTET code was used in this investigation, especially for determining chemical equilibrium compositions. This more accurate model can better predict the projectile acceleration of the thermally choked propulsive mode. Although the present analysis is applied to the fuel-rich methane-oxygen-nitrogen mixture currently used in the ram accelerator experiments, its general formulation makes it readily applicable to any other mixture. The projectile velocity and acceleration histories determined by the Hugoniot analysis for the thermally choked ram accelerator mode, assuming the Boltzmann EOS, turn out to be in much better agreement with experimental observations up to the CJ detonation velocity than that when based on the ideal gas assumption.

Comparative numerical and experimental study of projectile impact on reinforced concrete

Abstract: Concrete structures in military areas are subject to projectile impact both as a result of direct fire and in the form of splinters from explosives. These structures may be damaged, resulting in partial loss of integrity, but must leave the objects or individuals within them unharmed to the largest extent possible. The degree of damage depends on a variety of factors relating to the projectile, including its mass, geometry, impact velocity, trajectory and material properties. A number of controllable factors also relate to the characteristics of the concrete structure itself and the reinforcing material used to produce barriers. In order to analyse the structural response and optimize design parameters, various dynamics simulations have been performed in this work relating to projectile impact on concrete structures. To correctly model the impact, both non-linear material response and progressive finite element erosion have been taken into account. The numerical results have been discussed and compared with experimental results for three different impact scenarios, with good alignment achieved in terms of both penetration depth and crater size. This correspondence also demonstrated the pertinence of a specific material model, the Riedel-Hiermaier-Thoma (RHT) model within the LS Dyna FEM software package, in guiding and interpreting physical experiments in the case of impulsive projectile loading and penetration of concrete. The alignment between experiments and simulations also confirmed the robustness of the material model, specifically selected for this particular application.

Rupture disc gas launcher

Abstract: This invention relates to pneumatic guns that use a source of compressed gas to launch a projectile toward a target. A variety of trigger mechanisms have been used to apply the compressed gas to the base of the projectile in such a gun. In the present invention, replaceable discs of known rupture pressure threshold are mounted in the gas launcher between a compressed gas chamber and the launch tube. The gas launcher launches its projectile by the operator causing the pressure in the launcher to build up to the rupture threshold of the replaceable disc, at which point the disc ruptures and the compressed gas escapes from the compressed gas chamber past the rupture disc to push the projectile out of the launch tube. The rupture disc is a metal disc of known burst pressure. When the disc ruptures, the resulting disc segments are pressed by the outflow of compressed gas against an electrical contact to switch on an arming circuit for a delayed detonator in the explosive payload of the projectile that is launched from the gas launcher.

Projectile operating with rocket propulsion

Abstract: The present invention relates mainly to rocket projectiles, by which is meant projectiles whose velocity is increased after they leave the gun muzzle, by means of the thrust produced by the reaction on the air of gases discharged rearwardly from the projectile, said gases being developed by...