Experiments were performed to study penetration through multiple aluminum plates followed by impact into an inert steel anvil using a High-velocity Impact-ignition Testing System (HITS). The projectiles are intermetallic pellets launched from a propellant driven gun into a catch chamber equipped with view ports and imaging diagnostics. Penetration, impact and reaction are monitored using high-speed cameras that provide local and macroscopic perspectives of projectile and target interaction as well as overall reactivity. Results demonstrate the range of visual data that can be captured by a non-gas generating intermetallic projectile that fragments and reacts upon penetration and impact. Results show that higher velocity projectiles (~ 1300 and 800 m/s) produce smaller fragments upon target penetration that result in flame spreading through the chamber upon impact while lower velocity projectiles (~ 500 m/s) negligibly fragment upon target penetration and produce no flames even upon anvil impact.

The Hopkins Extreme Materials Institute (HEMI) recently installed a hypervelocity impact facility (HyFIRE) including a two-stage light gas gun at Johns Hopkins University in Baltimore, MD. The HyFIRE launcher has a launch tube bore diameter of 7.62 mm and is designed to attain launch velocities up to 7 km/s. The enclosed ballistic range and terminal test chamber provide multiple axes with which to view both projectile free flight and terminal impact, maximizing diagnostic access to events of interest. Initial test diagnostics include ultra-high-speed optical video and orthogonal 300 kV flash x-ray imaging. Photon doppler velocimetry for surface velocity measurement—currently used in HEMI’s laser shock facility—as well as emission spectroscopy/pyrometry are planned, providing researchers across multiple disciplines with the ability to investigate the coupling of mechanics, physics and chemistry present in high energy density impact events. Initial experiments at the facility investigate the fragmentation of inert impactors on anvil targets, with an aim towards identifying the dominant mechanisms controlling the fragmentation characteristics, temperature distributions and trajectories of generated debris fields.

Space debris travels at a velocity of 7-8 km/s in low Earth orbit (LEO) and at 3 km/s in geostationary Earth orbit (GEO). An impact between space debris and spacecraft will result in tremendous damage. In particular, particles less than 1mm in diameter pose a risk of causing permanent sustained discharge (PSD). PSD may affect a satellite’s power system. The effect on solar arrays has been well-studied given their large area, but the effect on the bundle of a satellite’s wire harness (called the power harness) has yet to be clarified, even though the power harness is usually exposed to the space environment without protection. We conducted hypervelocity impact experiments using a two-stage light gas gun, and investigated the risk resulting in PSD from hypervelocity impacts of particles less than 1mm in size. In addition, we compared two kinds of circuit configurations: a more realistic circuit configuration with internal resistance and a circuit configuration without it, so as to investigate whether internal resistance affects the occurrence of PSD. Stainless steel and aluminum oxide projectiles measuring from 0.3 to 1 mm in diameter were gun-accelerated up to 7.16 km/s. Targets entailed a three-layered power harness under a simulated power condition of typical satellites operating in LEO or GEO. As a result, 11 of 28 shots resulted in PSD. With the more realistic circuit configuration we could not confirm any results regarding PSD. We thus found that PSD is less likely to occur in a more realistic circuit configuration.

Eulerian hydrocode simulations using the Mechanical Threshold Stress (MTS), Zerilli-Armstrong (Z-A), and Johnson Cook (J-C) flow stress models were performed to provide insights into dynamic tensile extrusion (DTE) experiments with copper (Cu) and tantalum (Ta). The extrusion of Cu and Ta projectiles was simulated with an explicit, two-dimensional Eulerian continuum mechanics hydrocode and compared with data to determine if this extrusion concept is a useful indirect hydrocode material strength model evaluation experiment. The data consisted of high-speed images of the extrusion process, photon Doppler velocimetry (PDV) to measure the projectile velocity history and die transit time, dynamic temperature measurements of the extruded material, recovered extruded samples, and post-test metallography. The hydrocode was developed to predict large-strain and high-strain-rate loading problems. The code features a high-order advection algorithm, material interface tracking scheme, and van Leer monotonic advection-limiting algorithm. The strength models were utilized to evolve the flow stress (σ) as a function of strain, strain rate, and temperature. Average strain rates on the order of 10 4 s −1 and plastic strains exceeding 300% were predicted in the extrusion of copper at impact velocities between 400–450 m/s, while plastic strains exceeding 800% were predicted for Ta. The predicted and measured deformation topologies, projectile velocity profiles and die transits times, plastic strains, and temperatures were qualitatively compared. The flow stress distributions predicted by the three strength models were also compared for one experiment. Finally, the feasibility of using DTE to evaluate hydrocode strength models will be discussed.

The Planetary Impact Lab (PIL) at the Johns Hopkins University Applied Physics Laboratory (JHUAPL) includes a single-stage, compressed inert gas gun that can be used for impact experiments. The impact angle can be varied from 15° to 90° with respect to horizontal, a capability which enables oblique impacts into unconsolidated or granular materials (e.g., regolith analogs). The gun currently achieves impact velocities up to 400 m/s, although future enhancements could increase the maximum projectile velocity. Experiments can be done with atmospheric pressures ranging from ambient pressure down to ~75 Pa. The gun uses sabots produced with state-of-the-art additive manufacturing techniques (AM). Several engineering challenges had to be overcome to create a reliable AM sabot; however, AM sabots are ~45% lighter than and provide substantial cost savings over machined sabots. The PIL gun is currently being used to investigate impact processes on sloped coarse-grained surfaces, with application to planetary science and, specifically, rubble-pile asteroids. In contrast to previous studies of impacts onto slopes, we kept the projectile trajectory perpendicular to the target surface, thereby disentangling the effects of oblique impacts from the effects caused by a sloped surface. Initial results show enhanced crater collapse in the sloped target, with most of the collapse occurring in the direction parallel to the surface gradient. Consequently, final craters on sloped targets have smaller volumes and reduced depth-to-diameter ratios.

The high-velocity launch of a projectile is subjected to a number of disturbances which exert an influence on the flight trajectory. In the case of sub-caliber projectiles, sabot separation is one of the critical aspects. In this work, we focus on the projectiles and the launch package of an electric railgun launch, i.e. on the behavior of the launch-package, when transitioning from the gun barrel to free-flight. This work further addresses the use of a hydrocode for creating numerical models which are capable of predicting the motion and deflection of the sabot parts during their separation from the projectile after exiting the muzzle. An earlier study showed that the air flow around the projectile and the sabot can be modeled with sufficiently high accuracy by means of a simulation code that uses an Eulerian description of the gas flow. Within a time interval of several milliseconds, just the duration that a projectile needs to enter quasi-stationary flight, viscous effects of the air or gas flow have relatively little influence on the sabot discard process. If the Eulerian gas flow is coupled with the Lagrangian structural parts, the mechanical response of the latter to the gas pressure can be complex in terms of deformation and damage, and in that way, can affect the gas flow. In this study, the hydrocode model is applied to a medium caliber launch package concept for accelerating long rod projectiles. The computed results agree well with the corresponding experimental values obtained from a launch package model test in the shock tunnel at Mach 4.5. This demonstrates that the presented hydrocode model can be used for launch package design optimizations with high confidence.

When high-velocity projectiles penetrate an enclosed fluid-filled structure, the projectiles transfer the kinetic energy to the surrounding structure through the fluid and cause excessive structural damage. This process is referred to as a hydrodynamic ram (HRAM) [1]. The HRAM can be divided into five phases[1]: penetration, shock, drag, exit, and cavity oscillation. The HRAM phenomenon has been studied analytically [2,3], experimentally [4–7] and numerically [8–10]. However, few studies have been performed on the hydrodynamic ram caused by multiple penetrators. In the present work, a previously validated numerical model was used to analyze the differences of hydrodynamic rams caused by one and two projectiles impacting water-filled containers.

The DebriSat hypervelocity impact experiment, performed at the Arnold Engineering Development Center, is intended to update the catastrophic break-up models for modern satellites. To this end, the DebrisSat was built with many modern materials including structural panels of carbon-fiber, reinforced-polymer (CFRP). Subsequent to the experiment, fragments of the DebrisSat have been extracted from porous, catcher panels used to gather the debris from the impact event. Thus far, one of the key observations from the collected fragments is that CFRP represents a large fraction of the fragments and that these fragments tend to be thin, flake-like structures or long, needle-like structures; whereas, debris with nearly equal dimensions is less prevalent. As current ballistic limit models are all developed based upon spherical impacting particles, the experiment has pointed to a missing component in the current approach that must be considered. To begin to understand the implications of this observation, simulations have been performed using cylindrical structures at a representative orbital speed into an externally-insulated, double-wall shield that is representative of shielding on the current International Space Station crew transport vehicle, the Soyuz. These simulations have been performed for normal impacts to the surface with three different impact angles-of-attack to capture the effect on the shield performance. This paper documents the simulated shield and the models developed to study the effect of fragments and derives the critical characteristics of CFRP impacting particles for the selected shield. This work gives a deployable form of a critical, non-spherical projectile ballistic limit equation for evaluating non-spherical space debris for orbital debris environment modeling.

An equation was previously-presented to predict the ballistic-limit velocity for the perforation of aluminum armor plates by fragment-simulating projectiles (FSP). The ballistic-limit equation was presented in terms of dimensionless parameters so that the geometric and material problem scales are identified. Previously published predictions and data for two different FSP projectile calibers (12.7 mm and 20 mm) and two different strength aluminum alloys show the scaling law to be accurate. In this paper we extend the same concept to several other alloys and show that this scaling law is predictive.

The study of high-velocity microparticles is important to a wide range of both space and terrestrial applications. In space, high- and hyper-velocity micro-debris and micrometeorites, while also a subject of study, pose a threat to equipment and personnel integrity [1–4]. On earth, high-velocity microparticle impact can be, for instance, utilized for therapeutic purposes in the field of biolistics [5] or to build metallic coatings via the cold spray method [6]. While macroscale projectile impacts have been studied using well established experimental tools, such as light-gas guns, optical methods are gaining interest in the field of micro-particle impacts.

The purpose of this study is to analyse how the thickness of Rolled Homogeneous Armor (RHA) and impact velocity of an Explosively Formed Projectile (EFP) influence the middle mass behind-armor debris (BAD) when a variable cross-section EFP penetrates RHA normally. Numerical simulation is adopted, the thickness of RHA varies from 10mm to 70mm, and the impact velocity of the EFP varies from 1650m/s to 1860m/s. The results indicate that: (1) when the impact velocity of the EFP is 1650m/s and the thickness of RHA varies from 10mm to 70mm, p 1g of the RHA and EFP decreases with increasing H 0 . The thin target could be used to produce a large proportion of the middle mass BAD from RHA (including BAD from the EFP and BAD from the RHA and EFP). (2) When the impact velocity of the EFP varies from 1650m/s to 1860m/s and the thickness of the RHA is 40mm, p 1g of the RHA is less than 50%, p 1g of the EFP is more than 70%, and p 1g of the RHA and EFP is more than 50%.

During more than one decade of studying initiation phenomenology numerous papers at the previous HVIS and other symposia ([1] - [12]) were published. Most of them dealt with the hypervelocity impact initiation of plastic bonded high explosive charges by shaped charge jets (SCJ) and a few ones reported results in the ordnance velocity impact regime with STANAG projectiles and explosively formed projectiles (EFP) ([2] & [11]). A recent finding of our investigations of shaped charge jet (SCJ) attacks suggests that the critical stimulus S = v 2 ∙d (v = SCJ / projectile velocity; d = SCJ / projectile diameter) for the initiation of a munition can no longer be seen as a constant (S ≠ const.) ([11] & [10]). Also, known equations, e.g. Jacobs-Roslund [13], are not capable to describe low velocity and hypervelocity impacts with the same parameter set.

For the numerical description of high velocity impact, Smooth-Particle-Hydrodynamics (SPH) has gained more and more interest. The standard Lagrangian Finite-Element (FE) approach has difficulties in describing large deformations and fracture. However, a simulation based on SPH only is very expensive due to the small size of the particles. A well adopted solution to this is to couple both methods, using SPH only where it is necessary, and capturing the outer boundary conditions with a bias FE-mesh correctly - without considerable extra computational cost. We apply such a hybrid approach in LS-DYNA® for the characterization of threats in terminal ballistics. Different meshing approaches for the projectile and target were implemented to guarantee an optimal initial condition. The particle size and the required size of the SPH-region were studied to exclude discretization effects. Exemplarily, a projectile surrogate with simplified geometry is investigated for a fixed impact velocity and two different angles of obliquity. A qualitative comparison between experiments, observed with X-ray cinematography, reveals a good potential of this approach towards predicting fracture and ricochet during high velocity impact events.

Dynamic fragmentation through high-rate impact generates large numbers of fragments with various shapes and sizes. The fragmentation failure mode is an important part of the protection capacity of advanced ceramics which typically feature high strength and low density but fail in brittle modes. The penetration resistance of these brittle materials has been linked to the fragment size and shape created through impact in the literature [1]. Such studies have shown that particular fragment size and shape combinations can more effectively erode incoming projectiles, presenting a possible route to improve penetration resistance. These results stand in contrast to other studies that examine links between penetration resistance and material properties (e.g. fracture toughness or stiffness) which have sometimes resulted in contradictory correlations. Boron carbide has received a strong focus in the literature in recent years as an advanced ceramic with one of the highest specific strengths and lowest densities [2]. Yet boron carbide exhibits poor penetration resistance at higher loads, a phenomenon that some researchers attribute to a phase transformation termed “amorphization” [2]. To better understand the protection capacity of boron carbide under high rate loading, we use a laser-driven micro-flyer apparatus to impact boron carbide specimens.

This paper is a study on ricochet characteristics of metal plates hit by 25 mm APDS-T projectile. A series of ballistic tests has been carried out on three different armor steel types chosen to present a range of hardness. Each armor steel target was impacted at varying angles of incidence until ricochet was observed. This investigation is not only expected to help in understanding the phenomenon of projectile ricochet but also to provide some useful data that can be used for calibration and validation of the finite element (FE) models. In general, the ricochet angle was found to decrease with an increase in target hardness due to different failure mechanism.

Existing DOD and NASA satellite breakup models are based on a key laboratory test, the 1992 Satellite Orbital debris Characterization Impact Test (SOCIT), which has supported many applications and matched on-orbit events involving older satellite designs reasonably well over the years. To update and improve these models, the NASA Orbital Debris Program Office, in collaboration with the Air Force Space and Missile Systems Center, The Aerospace Corporation, and the University of Florida, conducted a hypervelocity impact test using a high-fidelity mock-up satellite, DebriSat, in controlled and instrumented laboratory conditions. DebriSat is representative of present-day LEO satellites, having been constructed with modern spacecraft materials and techniques. The DebriSat fragment ensemble provided a variety of shapes, bulk densities, and dimensions. Fragments down to 2 mm in size are being characterized by their physical and derived properties. A subset of fragments will be analyzed further in laboratory radar and optical facilities to update the existing radar-based NASA Size Estimation Model (SEM) and develop a comparable optical-based SEM. Thoroughly understanding size estimates from ground-based optical and radar sensors is one of the key parameters used in assessing the environment and the risks that debris present to operational spacecraft. The data will inform updates to the current NASA Standard Satellite Breakup Model (SSBM);, which was formulated using laboratory and ground-based measurements of on-orbit fragmentation events to describe an average breakup for spacecraft and upper stage collisions and explosions. DebriSat will extend the laboratory data ensemble. The DebriSat shape and density categories provide a baseline for non-spherical projectile hypervelocity impact testing for damage assessment. The data from these tests, simulations, and analyses will be used to update the NASA Orbital Debris Engineering Model (ORDEM) with more realistic simulations of catastrophic fragmentation events for modern satellites and to assess the risk posed by the orbital debris environment. This paper provides an overview of the project, updates on the characterization process, and the NASA analysis status.

Hypervelocity impacts (HVI) often cause significant fragmentation to occur in both target and projectile materials, and is often encountered in space debris and planetary impact applications [1]–[5]. In this paper, we focus on determining the individual velocities and sizes of fragments tracked in high-speed images. Inspired by velocimetry methods such as Particle Image Velocimetry (PIV) [6] and Particle Tracking Velocimetry (PTV) [7] and building on past work [8], we describe the setup and algorithm used for measuring fragmentation data.

A series of experiments and simulations were performed as proof of concept that an electrically powered research gun could propel small cylindrical projectiles to hypervelocities. Although small-caliber electrothermal accelerators and other electromagnetic launch systems have been utilized for some years for laboratory hypervelocity impact and other studies [1-5], we developed a simple, reproducible device that allows impact studies and direct comparison to magnetohydrodynamic (MHD) simulations for design considerations, efficiency improvements, and validation studies. This work focusses on 4.8 mm cylindrical 7075-T6 aluminum projectiles with a length to diameter ratio of one (nominally a mass of 0.24 grams) and a 150-mm long, 25-mm outer-diameter 4043 steel barrel with a 4.8-mm diameter bore and 9.5-mm chamber that acts as the electrical cathode. The anode consists of a 6.3-mm diameter copper rod that is reduced to 2.9 mm then tapered to a point with the tip length over diameter ratio (L/D) varying from 2 to 5. The tip is placed at the chamber/bore junction. The copper anode is insulated by a polyethylene sleeve and epoxy surrounding the electrode such that the arc initiates only at the very tip. A 191 μF capacitor was used as the power source for all experiments. The applied voltage was varied from 10 kV to 20 kV, and the resulting inductance of the system varied from approximately 320 nH to 450 nH (due to varying separation in the copper transmission lines). Fits to the current pulse using an LRC circuit resulted in resistance on the order of 10 mΩ to 15 mΩ. Typically the portion of the electrical pulse responsible for the bulk of the acceleration of the projectile occurs within the first 15 μs; however, the projectile is accelerated during the entirety of the time it remains in the barrel, which is on the order of 40 μs to 50 μs.