Development of a scramaccelerator based hypervelocity launcher

The Scramaccelerator, a novel type of supersonic-combustion, tube-based launcher has been developed that can accelerate projectiles to velocities of 3 to over 7 km/sec. Extremely flexible in application, the Scramaccelerator could launch impact specimens, wind tunnel specimens, projectiles, satellites, or spacecraft. This paper describes the technology demonstration of the concept by firing 120 gram projectiles into a 38 mm barrel at 2.8 to 3.2 km/sec at the Titan/CRT Impact Research Laboratory in Albuquerque. This technology promises an upward scalability beyond that of any conventional ballistic guns and electromagnetic launchers for high mass hypervelocity applications. It is the objective of this program to demonstrate the practical application of detonation physics to hypervelocity launchers. Critical test issues discussed include sabot seperation, venting requirements, Scramaccelerator tube requirements, and test performance. The current data indicate projectile accelerations were achieved in excess of 5,000 g's. Hence, these tests finally demonstrate that oblique detonation/supersonic combustion can be harnessed as a useful mechanism for hypervelocity propulsion. In addition, these tests demonstrate hypersonic propulsion at Mach numbers above 9, acceleration at greater than 3 kilometers per second, and system integration technology sufficient to accomplish this success. Scalability of the device allows for the hypervelocity launch of large masses.     

Acceleration fields induced by hypervelocity impacts on spacecraft structures

This paper presents an overview of the hypervelocity impact test campaign ongoing in the frame of the ESA contract “spacecraft disturbances from hypervelocity impact”. The project aims at analyzing the propagation of shocks due to hypervelocity impacts from the external shell of a spacecraft to its internal components. The object of the study is the GOCE satellite, which has been recognized to be very sensitive to small disturbances because of its payload that has been designed to measure even very low acceleration levels. In the first step presented hereafter, the test campaign has been focused on the qualification of the background environment inside the impact chamber and on the determination of the vibration levels induced by perforating and non-perforating hypervelocity projectiles on simple aluminum plates. The results currently obtained and a preliminary data analysis will be presented in the following.     

Simulations of hypervelocity impact damage and fracture of aluminum targets using a constitutive-microdamage material model

The material damage and fracture of Aluminum 1100 target plates that experience hypervelocity impact by glass projectiles traveling at 6 km/s are simulated using a proposed constitutive-microdamage material model. The model is best suited for polycrystalline metals that are subject to hypervelocity impact at the lower range of velocities. Simulations are performed for three projectile diameter-target thickness ratios that produce a wide range of damage features. The predicted damage is compared with that of the corresponding test laboratory specimens, illustrating the capability of the constitutive-microdamage model.     

Hypervelocity penetration of plate targets by rod and rod-like projectiles

This paper has summarized the results of experimental tests and analytical studies of the hypervelocity impact of rod and rod-like projectiles which were conducted at the Naval Research Laboratory. The results presented here provide relatively simple analytic expressions from which one can calculate the results of a hypervelocity impact of a rod or rod-like projectile even into complex targets under most impact configurations of interest. The methodology does require a knowledge of certain empirical constants which depend on the projectile and target materials. For those cases where the values of these constants have not been provided, they can easily be determined by performing a relatively few experimental impacts.     

A review of explosive accelerators for hypervelocity impact

A technical overview of experimental methods using high explosive techniques for conducting hypervelocity impact studies is presented. The explosive techniques use the explosive detonation fronts as means of accelerating the projectile, or as means of compressing a light gas which is then used to launch the projectile.

The explosive launchers are in six subdivisions: high explosive pellet accelerators, flyer plate accelerators, shaped charges, explosive-formed projectiles, fragment and microparticle accelerators, and explosive gas guns. Each one of the subdivisions presents the various techniques, their advantages and disadvantages, the range of mass and velocity capable of being accelerated, and whether the technique can be scaled for larger or smaller masses.     

Crater distribution on the rear wall of AL-Whipple shield by hypervelocity impacts of AL-spheres

All spacecraft in low orbit are subject to hypervelocity impact by meteoroids and space debris, which can in turn lead to significant damage and catastrophic failure. In order to simulate and study the hypervelocity impact of space debris on spacecraft through hypervelocity impact on AL-Whipple shield, a two-stage light gas gun was used to launch 2017-T4 aluminum alloy sphere projectiles. The projectile diameters ranged from 2.51 mm to 5.97 mm and impact velocities ranged from 0.69 km/s to 6.98 km/s. The modes of crater distribution on the rear wall of AL-Whipple shield by hypervelocity impact of AL-spheres in different impact velocity ranges were obtained. The characteristics of the crater distribution on the rear wall were analyzed. The forecast equations for crater distribution on the rear wall of AL-Whipple shield by normal hypervelocity impact were derived. The results show that the crater distribution on the rear wall is a circular area. As projectile diameter, impact velocity and shielding spacing increased, the area of crater distribution increased. The critical fragmentation velocity of impact projectile is an important factor affecting the characteristics of the crater distributions on the rear wall.     

Micrometeorite impact simulation at EMI — a review

Activities at EMI in the field of hypervelocity impact techniques are reported. Optimization experiments have been carried out with a light gas gun in order to achieve projectile velocities up to 10 km/s. Different methods for measuring the projectile velocities have been developed and adapted according to respective velocity and mass ranges of projectiles. Experimental efforts have been undertaken to accelerate also microgram particles in light gas guns. Masses as small as 37 μg can be accelerated as individual particles. As examples, several contributions to recent space projects are described.     

椭球弹丸超高速撞击防护屏碎片云数值模拟

低地球轨道的各类航天器易受到微流星体及空间碎片的超高速撞击.本文采用AUTODYN软件进行了椭球弹丸超高速正撞击及斜撞击防护屏碎片云的数值模拟.给出了三维模拟的结果.研究了在相同质量的条件下,不同长径比椭球弹丸以不同速度和入射角撞击防护屏所产生碎片云的特性,并与球形弹丸撞击所应产生的碎片云特性进行了比较.结果表明:在相同的速度下,不同长径比椭球弹丸撞击的碎片云形状、质量分布和破碎程度是不同的,随撞击入射角的增加弹丸的破碎程度增大,滑弹碎片云的数量增加;随撞击速度的增加,弹丸的破碎程度也增加.     

Nomex Kevlar平纹织物超高速撞击本构模型开发

为了研究Nomex-Kevlar平纹织物对空间碎片的超高速撞击力学特性, 运用LS-DYNA本构模型二次开发技术开发了Nomex-Kevlar平纹织物在超高速撞击条件下的带最大应力失效标准的线弹性正交各向异性本构模型, 并定义了Nomex-Kevlar平纹织物在超高速撞击条件下的Gruneison状态方程参数。运用光滑粒子流体动力学方法和有限元方法建立了与NASA试验工况相同的Al-2017-T4球形弹丸以6.84km/s速度斜向30°撞击Nomex-Kevlar平纹织物的数值分析模型。仿真结果与试验结果的比较表明, 本文中开发的本构模型以及建立的数值分析模型可以准确描述Nomex-Kevlar平纹织物的超高速撞击力学特性。      

Response of space structures to orbital debris particle impact

All long-duration space and aerospace and transportation systems, such as the Space Station Freedom and the Space Shuttle, are susceptible to impacts by pieces of orbital debris. These impacts occur at high speeds and can damage the flight-critical systems of such spacecraft. Therefore, the design of a structure that will be exposed to a hazardous orbital debris environment must address the possibility of such hypervelocity impacts and their effect on the integrity of the entire structural system. A technique is developed for analyzing the response of dual-wall structures to oblique Hypervelocity projectile impact. Ballistic limit curves that predict the potential of an impacting projectiles to perform the main wall of a dual-wall strucutral system are obtained using the techniques and are compated against experimentally derived curves. Comparisons are performed for a variety of impact velocities, trajectory obliquities and projectile masses. It is shown that the results obtained using the technique developmed herein compare very well with experimetanl results.     

Cavity and crater depth in hypervelocity impact

We discuss the depth of cavities and craters caused by hypervelocity impacts as a function of impact parameters such as impact velocity, projectile and target densities, and projectile diameter, in two extreme cases: the penetration of intact projectiles at low impact pressure and the hemispherical excavation at very high impact pressure. The relations between the depth and the impact parameters are obtained. Then, previous experimental results are compiled; crater depth normalized by projectile diameter and the ratio of projectile and target densities is plotted for glass, plastic, and metal projectiles and metal, rock, ice, foam, sheet-stack, and aerogel targets. The trends of the data are consistent with the relations in the extreme cases.     

高速粒子撞击作用下LF6合金多层靶结构防护能力研究

针对总厚度为４ｍｍ的ＬＦ６合金双层靶和总厚度为２ｍｍ的三层靶进行了直径为２ｍｍ,速度分别为５．８和７．２ｋｍ／ｓ的ＧＣｒ１５粒子 撞击试验,并对双层靶进行了不同前靶厚度和靶间距的撞击试验,试验结果表明：与同样碰撞条件下半无限体靶上产生的破坏情况相比,多层靶被击穿的总厚度远淖于半无限体靶上形成的弹坑深度,采用多层靶结构可显著提高材料的抗高速粒子撞击能力,并大大降低航天器抗高速粒子撞击的防护结构的重量     

Oblique hypervelocity impacts into graphite

Investigations have been conducted into the morphology of craters formed by impacts of aluminium and HDPE projectiles at oblique angles to graphite target plates. The experiments were conducted with a two-stage gas gun capable of launching projectiles of differing density and strength to speeds of about 6 kms⁻¹ at right angles into target plates. It was found that, as the impact angle is decreased from the normal, the crater dimensions scaled as the normal component of the impact velocity as predicted by the ‘2/3 power law’ until a critical normal velocity was reached below which the conditions for a hypervelocity impact no longer apply. In this regime, new scaling laws were derived for the crater dimensions. It was also possible to identify a fragmentation angle below which the projectile remains intact as it ricochets across the target surface.     

基于A-T模型的长杆弹超高速侵彻陶瓷靶体强度分析

Alekseevskii-Tate(A-T)模型广泛应用于长杆弹超高速冲击的终点效应分析中。A-T模型对于金属弹靶强度有明确的表达式,而对于陶瓷靶体强度尤其是弹体初始冲击速度大于1 500 m/s时还没有统一的结论。基于长杆钨弹超高速(1 500~5 000 m/s)侵彻三种陶瓷(Al N,B4C,Si C)/铝复合靶体的缩比逆弹道实验数据;基于A-T模型,给出了上述陶瓷材料在不同侵彻速度范围内的靶体强度表达式。进一步通过与47发长杆钨弹超高速(1 250~2 500 m/s)侵彻陶瓷(Al N,B4C,Si C,AD85)/RHA钢复合靶体DOP实验数据对比,验证了提出的陶瓷靶体强度表达式的适用性。     

Hypervelocity impact on laminate composite panels

Phenomenological results on the damage of flat glass-, aramid- and carbon-fiber reinforced epoxy laminated composites under the impact of steel and glass projectiles at velocity up to 8–11 km/s are presented. The damage of composite panels under hypervelocity impact is shown to differ significally from that observed for elastoplastic materials. However, it is shown that a number of qualititative results may be adequately described by the empirical dependences established earlier for metals.     

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.     

A new hypervelocity shotgun

This paper presents a technique for launching multiple, hypervelocity projectiles in a predictable pattern. The technique has been successfully applied to collections of 4–42 projectiles launched at velocities of 2 to 5 km/s. The projectile dispersion is obtained by impairing a pre-determined radial impulse to the collection of projectiles as the sabot exits the gun muzzle.     

Simulation of orbital debris impact on the Space Shuttle wing leading edge

A series of three dimensional hypervelocity impact simulations has been performed to study the effects of orbital debris impact on the Space Shuttle wing leading edge. The simulations employed an improved hybrid particle-finite element method and an orthotropic elastic-plastic material model recently developed for reinforced carbon–carbon. The simulation results are consistent with the available experimental data, and suggest the use of momentum scaling to estimate damage effects for impact conditions outside the range of current light gas gun technology. Projectile shape and orientation effects appear to be modest for flat plate projectiles at impact velocities above the ballistic limit.     

Application of a 100-kV electric gun for hypervelocity impact studies

The Lawrence Livermore National Laboratory 100-kV electric gun has been used to launch flat-plate projectiles for use in studies of spall and hypervelocity impact penetration of thin plates. Impactors were 0.3-mm thick Kapton with dimensions and velocities ranging from 100 mm² at 4 km/s to 10 mm² at 18 km/s. A Fabry-Perot laser velocimeter, an electronic streak camera, and a flash x ray were used as diagnostics of the flyer-plate impact on the selected specimen. Experiments generally included the recovery of the remnant specimen and fragments for detailed examination, permitting a study of incipient spall, onset of melting, and fraction fragmented. Experiments to be described include spall measurements on simple and composite target walls at normal and oblique incidence and “reverse ballistics” impacts of the thin-plate impactor on a stationary penetrator (e.g., Kapton impactors at 15 km/s incident on rods of steel, aluminum, and lead) for calibration of hypervelocity impact codes.     

Debris fragment characterization in oblique hypervelocity impacts

A case history in debris characterization is presented for oblique impacts of chunky tungsten projectiles against thin plates. The integrated approach of scaled experiments and hydrocode simulations led to a semi-analytic model of behind the plate debris fragment distributions. This debris distribution model agreed quite well with the experimental fragment distributions derived from witness plate measurements. The 1/4 scale test program included three projectile masses, two target geometries (single and dual plates), a velocity range of 4–7 km/s and a strike angle range of 15–55 degrees. Close correlation of measured and predicted fragment distributions encouraged the extension of the model to higher velocities not currently obtainable in the laboratory.

The paper also includes discussions of critical features of debris in oblique hypervelocity impact, the scalability of fragment data, and the utilization of the derived fragment models in semi-analytic damage assessment codes.