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To clarify the combustion process of a modular charge system with a primer gap, the rules governing the cartridge movement and pressure change in the chamber are analyzed. Based on the characteristics of the modular charge system, an axisymmetric two-phase flow model of the interior ballistics is established, with the monotonic upward-centered scheme for conservation laws adopted to calculate the combustion process. Compared with the experimental results, the difference in the peak pressure is less than 5%, which indicates that the mathematical model and scheme are reliable and accurate. The results show that, during the initial stage of ignition, the combustible container remains unbroken, and the gas and solid particles are prevented from spreading to the chamber by the end cap of the cartridge. Thus, only the gas inside the igniter tube influences the flow field in the chamber. After the combustible container has broken, the gas and solid particles move rapidly toward the cavity from the combustible container. The axial movement of solid particles is more intense than that of the gas particles, but the radial movement of solid particles is relatively weak. Furthermore, the existence of the primer gap leads to a delay in the ignition time of the solid particles, which delays the rupture time of the igniter tube and the module cartridge. [ABSTRACT FROM AUTHOR]

Two-phase flow numerical methods are applied in internal ballistics widely, which has made higher fidelity analysis with minimal cost become an urgent demand. Current methods are based on independent dimension, and there is no definite conversion criterion and data transmission method, which have limited the application of efficient hybrid models applied to calculation. In this paper, we propose a hybrid method by linking a two dimensional (2D) model to a one dimensional (1D) model for two-phase flow. First, 1D and 2D two-phase flow models are established according to the flow field states in different phases. Next, the criterion of conversion between the two models is established, which is a quantitative index to judge the degree of radial effect and axial effect. Finally, dimension transformation in the radial direction and grid mergence in the axial direction are conducted to complete the whole computing model. The simulation results show that the hybrid method is more efficient in the interior ballistic process and maintains the level of trust in classical codes. Compared with the 2D method, the hybrid method significantly improves the computational efficiency by 86.5%. By analyzing the state in the chamber, the accuracy of the conversion criterion is confirmed. This criterion can be used as the transformation criterion of the hybrid model to form the standard multi-dimensional calculation transformation criterion of interior ballistics and may be promising for the rapid simulation of two-phase flow in interior ballistics. [ABSTRACT FROM AUTHOR]

This paper describes an experimental and a numerical study of a recently developed high-efficiency, low-resistance launching method for an underwater launcher. The so-called gas-curtain launch method overcomes the problems of poor safety and low muzzle velocity in traditional fully submerged launchers. By introducing part of the gas inside the chamber to the front of the projectile, the water inside the barrel will be driven out. A low-resistance gas passage is then provided for projectile motion in the bore, thus delivering better interior ballistics performance than that in fully submerged launchers. Experiments are carried out using a 12.7-mm underwater launcher. A pressure sensor is used to record the chamber pressure, and high-speed video recordings allow the projectile motion around the muzzle to be determined. The experimental results show that the muzzle velocity is 172.8 m/s and the maximum chamber pressure reaches 116.0 MPa in a fully submerged launch, compared with a maximum chamber pressure of only 41.8 MPa and a muzzle velocity of 177.5 m/s when the gas-curtain launch method is adopted. The significant drag reduction effect of the gas-curtain launch greatly improves the interior ballistics performance, reducing the maximum chamber pressure by about 64.1% while retaining a similar muzzle velocity. Following the experiments, a numerical model is established and simulations are performed under various ventilation mass rates. The results clarify the drag reduction mechanism and the partial characteristics of the flow field in the gas-curtain launch. [ABSTRACT FROM AUTHOR]

We report on initial observations of high velocity outflows from the ends of a rod compressed using pulsed power. 1 mm and 2 mm diameter copper rods were placed in a water bath and driven by ∼0.6 MA currents with rise times of ∼700 ns. Laser backlit framing images and streak photography showed an outflow of the material from the ends of each rod, of the initial velocity of up to 7 km/s, which began ∼500 ns after the start of the current pulse and continued throughout the experiment. Ballistics gel was used to help separate low density gas/plasma from any solid/liquid component in the outflow, successfully capturing the material from larger diameter rods (enabling an estimate of its energy) and tracing the path of the material that passed straight through the gel with smaller rods. Experimental results were compared to 1D and 2D MHD simulations performed with the Gorgon code. These suggested that the outflow had two different components, resulting from two different physical processes. Differences in the resistivity between the copper rod and stainless steel anode result in the opening of a small gap between them and ablated stainless steel being projected above the rod, which is captured in framing and streak images. Later in time, a dense copper material, pinched by the magnetic pressure, is launched—explaining the ballistics gel results. The simulations also suggest that the tamped explosion of the rod surface plays a small role in any outflow. [ABSTRACT FROM AUTHOR]

A ballistic model-based method, which builds upon previous work by Lo and Ferguson [J. Acoust. Soc. Am. 132, 2997-3017 (2012)], is described for ranging small arms fire using a single acoustic sensor node collocated with the target, without a priori knowledge of the muzzle speed and ballistic constant of the bullet except that they belong to a known two-dimensional parameter space. The method requires measurements of the differential time of arrival and differential angle of arrival of the muzzle blast and ballistic shock wave at the sensor node. Its performance is evaluated using both simulated and real data. [ABSTRACT FROM AUTHOR]

Analytical forms for the envelopes of trajectories for particles radially ejected from a moving source in uniform gravity are derived. These results generalize Torricelli's (safety) parabola for ballistic problems. As a motivating scenario we consider the spherical case shot, later named the shrapnel shell. Several cases that illustrate interesting features of the problem are presented along with an example inspired by the spherical case shot. [ABSTRACT FROM AUTHOR]

We study the ballistic pendulum in a situation that is not usually considered where the bullet shot into a hanging block requires a finite time (the collision time) to come to rest relative to the block. During this time the block undergoes a non-negligible displacement. A slow collision is one for which the block's displacement during the collision time is an appreciable fraction of its maximum displacement. For slow collisions, the quantitative results of our model differ significantly from the standard ballistic pendulum treatment. Suitably generalized momentum and energy relations are evaluated and provide a check on the numerical solutions. This work extends the treatment of a familiar problem and demonstrates the utility of computational tools accessible to undergraduates. [ABSTRACT FROM AUTHOR]

Presents a case study relating to field-induced quantum tunneling in a three-dimensional environment which exhibits ballistic motion. Discussion of the classical motion of particles subject to a constant force; Identification of the problem of electron tunneling out of a three-dimensional, zero-range potential well in a constant electric field.

A dual parameter representation of the barrier height and transmission extracted from ballistic electron emission spectroscopy spectra is presented and evaluated with respect to the noise present in the spectra and the conditions used for data fitting. Simulated dual parameter distributions incorporating only Gaussian (white) noise are compared to experimental dual parameter distributions for two interfaces, namely, Au/n-Si and Au/pentacene/n-Si. The authors find that for both measurements, noise and data fitting conditions can have significant influence on the distributions. Once these contributions are accounted for, such dual parameter representations provide statistical information related to the interfacial homogeneity of devices. [ABSTRACT FROM AUTHOR]