A special design condition to increase the performance of two-stage light-gas guns

This paper reports a theoretical and numerical study aimed at increasing the operating efficiency of two-stage light-gas guns by appropriately changing their working conditions. In particular, a method is presented for increasing the projectile speed without any rise of the maximum breech pressure. The classic design theory of two-stage guns starts from the assumption that the highest velocity is reached in a gun which constantly maintains the maximum acceptable pressure at the base of the projectile during the full launching time. The main drawback of this working condition is that it may require an unfeasible rise of the gun maximum pressure, especially when very high muzzle speed is requested. To overcome this limitation, a new reference case different from the constant-base-pressure one is presented, based on a novel gas-dynamics solution that can be expressed in exact form if losses are not accounted for. According to such an approach, it is theoretically shown that the projectile base-pressure can be appropriately shaped (i) to improve the final speed without increasing the breech pressure or, in other terms, (ii) to achieve a given muzzle velocity with reduced maximum gas pressure. The analytical application of the new gas-dynamics condition showed the capability of obtaining a 1 km/s velocity improvement with no increase of the breech pressure or, alternatively, a pressure reduction up to 30% with no penalty on the model final speed. A numerical verification of the calculations was performed through the CISAS light-gas gun full numerical model, which includes real effects such as friction losses and heat transfer. Finally, an experimental verification of the numerical test case was attempted and a speed augmentation of 0.8 km/s with no increase in the breech pressure was confirmed in laboratory, highlighting the agreement with numerical predictions.     

Hugoniot measurement by hyper-velocity impact at velocities up to 9 km/s using a two-stage light-gas gun under optimized shot conditions

The optimization for acceleration of a projectile was performed by varying piston mass in consideration with the correlation with projectile mass and the engineering limits of the two-stage light-gas gun, and the projectile velocity has been achieved 9.2 km/s using the optimum acceleration conditions. Moreover, the Hugoniot measurements of oxygen-free copper were performed using the line reflection method at pressures up to 380 GPa by symmetric impact. The tilt and curvature of shock front were investigated according to the impact velocity, and it is proved to be important that the continuous spatial profile of shock front would be recorded.     

Active piston technique to optimize the chamber pressure in two-stage light-gas guns

We report a study in the field of gun design and optimization, paying particular attention to the issue of energy matching between the pump tube and the barrel. The objective was to set up a technique in order to obtain a nearly constant pressure at the projectile base, without using a high-pressure tapered section in which the piston extrusion occurs. In a first step, it was analyzed the opportunity of using two separate pistons inside the pump tube, in which the back piston sustains the stroke of the first one for a longer time. Then, to cope with technological problems, the same idea was implemented by developing a single piston characterized by an active core. In the following, after having presented a general overview on the proposed technique, we describe the numerical model used for performance evaluation and a numerical comparison of the performance achievable with a single piston and with the proposed method. Finally, we report some experimental results that were used for the model validation and also for demonstrating the technological feasibility of an active-core free-piston for two-stage light-gas guns.     

Development of a three-stage, light-gas gun at the University of Dayton Research Institute

An elusive goal of the hypervelocity impact community has been the evaluation of the ballistic response of space hardware to impact velocities ranging from 8 to 11 km/s using projectiles with known properties. The design, development, and use, during the 1960s, of a three-stage, light-gas gun at McGill University is reviewed. The developers of this gun claim that they were able to launch cylindrical, 12.7-mm-diameter Lexan disks with masses of 1.5 and 1.1 g to velocities of 9.6 and 10.5 km/s, respectively. This paper presents the results of an internally funded program at the University of Dayton Research Institute (UDRI) to duplicate the published performance of the McGill University launcher. A support structure and various components of a third stage which used an 8.1-mm-diameter launch tube were added to the UDRI 75/30-mm, two-stage, light-gas gun, making the arrangement of the components similar to the one used by McGill University. Work on the development of the UDRI three-stage, light-gas gun is a continuing effort, with the goal of successfully launching small diameter (3 mm or less) aluminum spheres to velocities in excess of 9 km/s. To date, the highest projectile velocity achieved with the UDRI three-stage, light-gas gun has been 8.65 km/s.     

Development of railgun accelerator combined with two-stage light gas gun

The status of railgun development at T.I.T. is summarized. A Zm railgun combined with two-stage light gas gun has been developed for high pressure research. Further multi-acceleration experiments using two railguns connected in series are in preparation. The purpose of this experiment is to establish the techniques for multi-stage railgun. Computer simulations show that the segmented multi-stage railgun has enough potential for use in the field of Impact Fusion.     

Preliminary study of counter impact with two-stage light gas gun using electrothermal–chemical gun technology

Recently, hypervelocity impacts between space structures and space debris have been brought to attention with the advance of space development. The impact velocity at low earth orbit (LEO) is up to 15 km/s. Such impact velocity cannot be attained by the current two-stage light gas gun (TSLGG). Therefore we have a plan of counter impacts that used two sets of TSLGGs in order to raise impact velocity. There are three problems in order to realize the counter impacts. They are launch timing, recovery of target and alignment of gun axis. In this research, we considered launch timing of TSLGG among them. It is important to control variation of delay time from propellant ignition to projectile launch in the counter impacts. In a conventional TSLGG, combustion rate changes every time and impact position will vary widely. In order to stabilize combustion rate, we developed a new TSLGG that used the technology of electrothermal–chemical (ETC) gun for its 1st stage. In a conventional TSLGG, the variation of delay time is 20–30 ms. On the other hand, in a new TSLGG, we have succeeded in suppressing the delay time variation less than 200 μs. It is concluded that the TSLGG based on the technology of ETC gun is effective to control the delay time in this paper.     

Hydrodynamic characteristics of a flat-flame injector torch with a vortex injector

The optimum twist of an injected flow is established through studies of a function describing the hydrodynamic characteristics of a flat-flame burner.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 41, No. 4, pp. 708–711, October, 1981.     

轨道炮固体电枢的设计

目的　设计固体电枢的传导性和电枢 -轨道的接触区几何形状 .方法　对理论模型与实验结果进行对比分析 ,寻求最佳结果 .结果　在趋肤深度远小于轨道电阻层厚度以及使用φ=2 0°,d0 =(5～ 1 0 ) mm的梯形固体电枢时 ,VSE影响最小 .结论　采用具有一定传导性电枢和梯形电枢可以减小速度趋肤效应 (VSE)的破坏作用     

Plasma opening switch with a ferroelectric plasma injector

A generator with a plasma opening switch employing a ferroelectric plasma injector has been designed, constructed, and studied in operation. The generator was tested in two regimes, being loaded on an electron-beam diode or vircator for the generation of bremsstrahlung (X-ray) or microwave radiation, respectively.     

Analysis of the second stage of the STAR 28 mm two-stage light gas gun

An engineering model of the second stage operation of the 28 mm two-stage light gas gun at the Shock Technology and Applied Research (STAR) facility of Sandia National Laboratories has been developed. It describes the piston motion and loading of the accelerated reservoir (AR) and the coupled projectile motion. The model was developed to better assess the safety of the AR and to determine the significance of various parameters to the gun performance. Validity of the model is supported by calculated results that compare closely with projectile velocity data over a range of piston masses, piston velocities, and projectile masses and correlate satisfactorily with AR diameter growth data in a typical high-performance test. For this test, bounds on the factor of safety (FS) for the piston velocity are determined to be 1.3 < FS < 1.5. Results indicate that the projectile velocity can be increased and the AR loading reduced by changes in the piston density and break diaphragm opening pressure.     

The performance of fighting vehicle hydraulic gun buffers

This paper describes research into the performance of high-energy gun recoil absorbers, usually referred to as gun buffers, for use on military fighting vehicles. A test facility, built at the University of Birmingham, to simulate the gun reaction loads imposed on the recoil absorbers is described. Tests to examine the sensitivity of the buffer performance to change in recoil mass, velocity, fluid and density are presented. A theoretical model to predict the buffer behaviour is derived which enables parameters such as fluid compressibility, aeration and elasticity of the system to be investigated. The theoretical predictions are shown to agree with data obtained from tests.     

Sustainability performance analysis of environment innovation systems using a two-stage network DEA model with shared resources

The term environmental innovation system refers to an innovation network composed of enterprises, universities, and research institutions involved in the development and diffusion of environmental technology, with the participation of a government. An environmental innovation system not only exerts important impact on the achievement of carbon neutrality but also affects social and economic activities. Investigations on environmental innovation system performance constantly assume a single-stage independent system while ignoring its internal structure. However, such systems are composed of environmental innovation research and development (R&D) and environmental innovation conversion subsystems. A two-stage data envelopment analysis (DEA) model is developed in this study to analyze the efficiency of Chinese regional environmental innovation system by opening the “black box” and considering shared resources. Empirical results indicated that China presents high overall environmental innovation efficiency although some regions need to improve. Regions with low efficiencies in both environmental innovation R&D (EIR) and environmental innovation conversion (EIC) subsystems should expand their investment in and strengthen the management of environmental innovation resources. Regions with low EIR efficiency should improve the absorption and transformation of environmental innovation achievements. Regions with low EIC efficiency should increase investment in the commercialization of environmental innovation achievements and encourage green economy industries, such as new energy, art, tourism, and environmental protection.     

Numerical investigation of real gas effects on a two-stage pulse tube cryocooler performance

In this paper, a one-dimensional CFD code was developed to simulate a two-stage pulse tube cryocooler. The aim is to investigate the effects of real gas on cryocooler performance. Conservation equations were derived based on real gas equations of state in general form and then were discretized with control volume approach. Results based on four distinct equations of state including ideal gas, Van der Waals, Virial and Helium gas were compared. Results showed that at the first and second stage mean pressures of 25 and 12.5 bar, and the minimum no load attainable temperatures of almost 60 and 18 K, employing Helium equation of state, the deviation of almost 6.5 and 2.5% relative to ideal gas equation of state was observed respectively. Meanwhile the ideal gas equation of state was fairly accurate and could be proposed to reduce the calculation cost.     

The Open University planetary impact facility: A compact two-stage light gas gun for all impact angles

For liquid and planetary regolith target studies, requiring a horizontal target plain, a two-stage light gas gun (LGG) was designed by UniSpaceKent and constructed at the Open University. Based on a 4.7 mm bore launch facility, supplied by Physics Applications International (PIA), the design provides high mechanical rigidity under varying angles of launch, using an integral small target chamber (200 mm diameter) or an intermediate planetary target chamber; the entire gun and target chambers can be rotated from horizontal to vertical. It can also move horizontally and rotated to mate with fixed larger target facilities beneath its mezzanine location; for this configuration pre-set angles through vacuum ports are used. The position of the axis of rotation, assisted by trim weights, provides for balancing out of residual force moments.     

Vacuum evaporation experiences with a ring-type electron beam gun

The ring-type electron beam gun is a relatively simple device, working on the principle of a hot cathode, high vacuum diode. In vacuum evaporation applications, the presence within the gun of the material to be evaporated and its vapour can lead to anomalous performance in several ways. An understanding of these anomalies and their consequences is helpful in achieving more effective operation of the ring gun as a vacuum evaporation source.     

Hydrogen-pellet injector using a screw extruder

The first injector design capable of injecting an unlimited supply of fuel pellets into a fusion reactor plasma in prolonged, continuous operation is reported. More than a thousand pellets 2 mm in diameter are formed without interruption from the screw extruder at frequencies of 1 Hz and 2 Hz and are accelerated to 0.8 km/s. Pis’ma Zh. Tekh. Fiz. 23, 43–46 (October 26, 1997)     

Sequencing a hybrid two-stage flowshop with dedicated machines

We treat the n -job, two-stage hybrid flowshop problem with one machine in the first stage and two different machines in parallel in the second stage. The objective is to minimize the makespan. We demonstrate that the problem is NP-complete. We formulate a dynamic program, which is beyond our grasp for problems of more than 15 jobs. Our search for heuristic approaches led to the adoption of the Johnson sequence, which motivated two of the three approaches: dynamic programming and sequence-and-merge. The third approach, the greedy heuristic, was included as example of an elementary heuristic.