Two-stage Light Gas Gun Research Articles

Thermophysical properties of multi-shock compressed dense argon

In contrast to the single shock compression state that can be obtained directly via experimental measurements, the multi-shock compression states, however, have to be calculated with the aid of theoretical models. In order to determine experimentally the multiple shock states, a diagnostic approach with the Doppler pins system (DPS) and the pyrometer was used to probe multiple shocks in dense argon plasmas. Plasma was generated by a shock reverberation technique. The shock was produced using the flyer plate impact accelerated up to ∼6.1 km/s by a two-stage light gas gun and introduced into the plenum argon gas sample, which was pre-compressed from the environmental pressure to about 20 MPa. The time-resolved optical radiation histories were determined using a multi-wavelength channel optical transience radiance pyrometer. Simultaneously, the particle velocity profiles of the LiF window was measured with multi-DPS. The states of multi-shock compression argon plasma were determined from the measured shock velocities combining the particle velocity profiles. We performed the experiments on dense argon plasmas to determine the principal Hugonoit up to 21 GPa, the re-shock pressure up to 73 GPa, and the maximum measure pressure of the fourth shock up to 158 GPa. The results are used to validate the existing self-consistent variational theory model in the partial ionization region and create new theoretical models.

Fluorescence imaging of microbe-containing particles shot from a two-stage Light-gas gun into an aerogel.

We have proposed an experiment (the Tanpopo mission) to capture microbes on the Japan Experimental Module of the International Space Station. An ultra low-density silica aerogel will be exposed to space for more than 1year. After retrieving the aerogel, particle tracks and particles found in it will be visualized by fluorescence microscopy after staining it with a DNA-specific fluorescence dye. In preparation for this study, we simulated particle trapping in an aerogel so that methods could be developed to visualize the particles and their tracks. During the Tanpopo mission, particles that have an orbital velocity of ~8km/s are expected to collide with the aerogel. To simulate these collisions, we shot Deinococcus radiodurans-containing Lucentite particles into the aerogel from a two-stage light-gas gun (acceleration 4.2km/s). The shapes of the captured particles, and their tracks and entrance holes were recorded with a microscope/camera system for further analysis. The size distribution of the captured particles was smaller than the original distribution, suggesting that the particles had fragmented. We were able to distinguish between microbial DNA and inorganic compounds after staining the aerogel with the DNA-specific fluorescence dye SYBR green I as the fluorescence of the stained DNA and the autofluorescence of the inorganic particles decay at different rates. The developed methods are suitable to determine if microbes exist at the International Space Station altitude.

Experimental Study on the Behavior of a New Multilayer Shield against Hypervelocity Debris Impact

To protect the spacecraft from hypervelocity impact of the space debris, a new kind of multilayer shield laminated of aluminum layers and CFRP layers was designed and investigated. Three different shields with the same area density were manufactured, including single aluminum alloy layer, single CFRP layer, and multilayer of aluminum/CFRP. The hypervelocity impact experiment was carried, in which the hypervelocity projectile was launched by a two-stage light gas gun. To compare the hypervelocity impact behavior and evaluate the protection ability of the different shields, the area and depth of the projectile pits were analyzed. The experiments results show that the protection effect of the multilayer shield laminated of aluminum/CFRP layers is better than the single aluminum layer or the single CFRP layer, though they are in the same area density.

The signal characteristics of light flash generated by hypervelocity impact natural dolomite plate

To investigate light flash produced during hypervelocity impact in the laboratory, we have conducted a series of experiments on a two-stage light gas gun at different impact velocities and the same impact angle. Light flash were acquired through optical fiber pyrometer measurement system during the whole physical process in hypervelocity impact, Experimental results showed that the maximum light flash intensity decreases with impact velocity increasing, and maximum light flash intensity should exist a critical impact velocity for polycarbonate projectile impacting natural dolomite plate, which may be between 2.52 km/s and 4.21 km/s at the wavelength of 550 nm–700 nm. In addition, the light flash intensity peak value was 0.4∼0.5 mW.cm−2.nm−1 in the experimental conditions in the paper.

Experimental study on hypervelocity impact characteristics of density-grade thin-plate

Hypervelocity impact (HVI) characteristics of Ti6Al4V/Ly12 Al/polyamide fibre density-grade thin-plate are investigated experimentally in a velocity range of 4.0–6.5 km/s by using two-stage light gas gun. The perforation in target, damage to witness wall, and ballistic limit curve are obtained and compared with those in the case of aluminum thin-plate. The results show that the diameter of the perforation hole is larger than that of aluminum thin-plate, the crater size in witness plate is smaller, and the ballistic limit curve is 50% larger than the latter. The analysis of shock wave propagation and the calculation of energy dissipation property in the density-grade thin-plate show that higher peak shock pressure is produced in it, and it has longer pressure duration time. Thus, more dissipation energy is consumed than in the case of aluminum thin-plate. So the density-grade thin-plate has a very good performance in withstanding HVI, and is promising in engineering application, e.g. protecting spacecraft from HVI of micro-meteoroid and orbital debris.

High Velocity Impact Response of Composite Lattice Core Sandwich Structures

In this research, carbon fiber reinforced polymer (CFRP) composite sandwich structures with pyramidal lattice core subjected to high velocity impact ranging from 180 to 2,000 m/s have been investigated by experimental and numerical methods. Experiments using a two-stage light gas gun are conducted to investigate the impact process and to validate the finite element (FE) model. The energy absorption efficiency (EAE) in carbon fiber composite sandwich panels is compared with that of 304 stainless-steel and aluminum alloy lattice core sandwich structures. In a specific impact energy range, energy absorption efficiency in carbon fiber composite sandwich panels is higher than that of 304 stainless-steel sandwich panels and aluminum alloy sandwich panels owing to the big density of metal materials. Therefore, in addition to the multi-functional applications, carbon fiber composite sandwich panels have a potential advantage to substitute the metal sandwich panels as high velocity impact resistance structures under a specific impact energy range.

A Hypervelocity Impact Facilities Based on Double-Barreled Two-Stage Light Gas Gun

For almost all materials the hypervelocity regime has been reached when the impact speed above 2 km/s. A double-barreled two-stage light gas gun (TSLGG) system used for the hypervelocity impact tests is described. The proposed TSLGG can accelerate 50 g projectile masses up to velocities of 2.2 km/s. The craters produced with this equipment reach a diameter of up to 20 cm, a size unique in laboratory cratering research. The experiment results show our TSLGG system work effectively, velocity of the projectile mass is measured highly accurate by means of the proposed optical method.

Research of Performance about Ceramic Coating on Aluminum Bumper to Resist Hypervelocity Impact

Shield structure based on ceramic coating on aluminum bumper was designed, and a series of hypervelocity impact tests were practiced with a two-stage light gas gun facility. Impact velocities were varied between1.5km/s and 5.0km/s. The diameter of projectiles were 3.97mm and 6.35mm respectively. The impact angle was 0°. The damage of the ceramic coating on aluminum bumper under hypervelocity impact was studied. It was found that the ceramic coating on aluminum bumper could help enhancing the protection performance of shield to resist hypervelocity impact. The results indicated when the ceramic coating is on the front side of aluminum bumper, it was good for comminuting projectile and weakening the kinetic energy of projectile. For a certain aluminum bumper, existing a critical thickness of ceramic coating in which capability of Whipple shield to resist hypervelocity impact is the best. On this basis, the proposal of the optimum design for ceramic coating on aluminum bumper was made.

The effect of waves rupture diaphragm on acceleration loads of projectile

The acceleration loads of projectile during launch process of two-stage light gas gun were studied by the developed computational fluid dynamics program. With the usage of LS-DYNA software, the diaphragm rupture pressure was calculated by finite element method. The influence of different waves rupture diaphragm on the maximum acceleration loads of projectile was analyzed, keeping the configurations of gun unchanged. It is found that the maximum acceleration loads can be reduced and the muzzle velocity objective can be achieved by choosing the ruptured wave appropriately and optimizing other operational parameters. Soft launch capability is provided for launching complex lifting configuration models up to hypervelocity.

Shock Compression of the New 47Zr45Ti5Al3V Alloys up to 200 GPa

Shock compression experiments on a new kind of 47Zr45Ti5Al3V alloys at pressures between 28 and 200 GPa are performed using a two-stage light gas gun. The Hugoniot data are obtained by combining the impedance-match method and the electrical probe technique. The relationship between the shock wave velocity Us and particle velocity up can be described linearly by Us = 4.324(±0.035) + 1.177(±0.012)up. No obvious evidence of phase transition is found in the shock compression pressure range. The calculated Us − up relationship obtained from the additive principle is different from the experimental data, indicating that the α → β phase transition occurs below 28 GPa. The Grüneisen parameter γ obtained from the experimental data can be expressed by γ = 1.277(ρ0/ρ). The zero-pressure bulk modulus B0s = 97.96 GPa and its pressure derivative B′0s = 3.68. The P—V—T equation of state for 47Zr45Ti5Al3V is given using the Vinet equation of state to describe the cold curve and the Debye model for the thermal contributions.

Shock-Induced Chemical Reaction between Iron and Enstatite

By using a two-stage light gas gun, two experiments of shock recovery experiments with initial sample of Fe+(Mg, Fe)SiO3 (En) were conducted between 78 and 113 GPa shock pressure (the corresponding temperature is estimated as 3000~5000K). The recovered samples were analyzed by X-ray Diffraction (XRD).The XRD observation at the middle section of two recovered samples illustrates the new composition of recovered samples is (Mg, Fe)2SiO4.Comparing with the recovery experiments of MgO+SiO2 ,we can infer that iron and perovskite react to form SiO2 and (Mg, Fe)O. The experiments result indicates that reaction between liquid iron and (Mg, Fe)SiO3 perovskite may occur at the core-mantle boundary in geological history. The reaction creates a very heterogeneous zone at the base of the mantle. Si and O dissolved in liquid iron are rapidly dispersed by the flow of the liquid outer core.

In situ diagnostics for a small-bore hypervelocity impact facility

New in situ diagnostic capabilities and improvements made to the previously reported 1.8 mm bore, two-stage light-gas gun facility located at the California Institute of Technology are described. The Small Particle Hypervelocity Impact Range (SPHIR) facility is capable of routinely producing launch speeds of 5–7 km/s for launch package masses < 6 mg, with maximum speeds exceeding 10 km/s. The facility features a comprehensive ensemble of in situ diagnostics that are available for simultaneous implementation in every impact experiment. A fast (150,000 fps) camera is used routinely to provide impactor velocimetry. A gated, intensified ultra-high-speed camera is used in conjunction with an optical technique to create shadowgraph images of hypervelocity impact phenomena with very short exposure times (25 ns) and inter-frame times (<1 μs). This technique uses a constant 532 nm wavelength laser to deliver a collimated, coherent illumination beam orthogonal to the projectile flight direction that provides a 100 mm diameter maximum field of view. The ultra-high-speed camera produces 8 images with exposure and inter-frame times sufficiently short to enable sharp visualization of impact features with little motion blur at the test speeds of 5–7 km/s. Additionally, a debris capture system is located behind the target configuration during every experiment. This system is composed of layers of closed-cell foam and plastic film and provides depth of penetration and trajectory measurement for debris particles thrown behind the target. Lastly, the SPHIR facility utilizes two additional high-speed cameras coupled with two spectrographs to characterize the light emitted by the impact event. One spectrograph and its high-speed camera records UV–visible emission spectra in the wavelength range between 300 nm and 850 nm. The other spectrograph uses a high-speed, infrared camera to capture a single full-field image of the near-IR emission in the wavelength range of 0.9 μm–1.7 μm. These two spectrograph camera systems provide both visual and spectral data of the hypervelocity impact emission; yielding information regarding the molecular composition of both the impact ejecta and debris. The extensive diagnostic capabilities and techniques described can be used with a wide variety of impactors, target materials and target configurations to address a wide variety of engineering and scientific problems.

Energy absorption efficiency of carbon fiber reinforced polymer laminates under high velocity impact

In this paper, response of carbon fiber reinforced polymer (CFRP) laminates subjected to high velocity impact has been investigated by experimental and numerical methods. Experiments using a two-stage light gas gun were conducted to investigate the impact process and to validate the finite element model. The energy absorption efficiency (EAE) of CFRP laminates with different thickness was investigated. According to the results of experiments and numerical calculations, thin CFRP laminates have a good EAE under relative higher velocity impact; by contraries, a superior EAE is displayed in thick laminates under relative lower velocity impact. Subsequently, EAE of CFRP laminates was compared with that of 304 stainless-steel plates. In a specific impact velocity range, EAE of CFRP laminates is higher than that of 304 stainless-steel. Thus, CFRP laminates have a potential advantage to substitute the metal plates to be used in high velocity impact resistance structures under a specific impact velocity range.

Shock-induced phase transitions of α-Ce3Al

A series of shock compression experiments on hexagonal α-Ce3Al have been carried out using a two-stage light gas gun. No phase transition was observed in the recovered sample shock compressed at 23.5 GPa. However, as the shock pressure was increased to 27.3 GPa, a face-centered cubic Ce3Al phase was detected in the samples recovered at ambient conditions. Furthermore, a Ce2Al phase was found in the 37.1 GPa shocked sample with a space group Fd-3m and lattice parameter a = 8.26(1) Å. These Ce-based alloys may have potential industrial applications due to the heavy-fermion related properties.

A High-Spectral-Resolution Laser Raman System and Its Application in Shock—Compressed Benzene

Raman measurements play an important role in examining the molecular changes associated with shock-induced structural and chemical changes in condensed materials. We combine a high spectra-resolution Raman system with a two-stage light gas gun to provide better quality data than the transient Raman system used previously. Representative measurements are presented for the shock compression of benzene. The high spectral resolution data have provided an insight into molecular changes that could not be obtained from time-resolved methods.

Non-invasive timing of gas gun-launched projectiles using external surface-mounted optical fiber-Bragg grating strain gauges

Non-invasive detection methods for tracking gun-launched projectiles are important not only for assessment of gun performance but are also essential for timing a variety of diagnostics, for example, to investigate plate-impact events for shock compression experiments. Measurement of the time of passage of a projectile moving inside of the gun barrel can be achieved by detection of the transient hoop strain induced in the barrel of a light-gas gun by the passage of the projectile using external, barrel surface-mounted optical fiber-Bragg grating strain gauges. Optical fiber-Bragg gratings have been implemented and their response characterized on single-stage and two-stage light gas guns routinely used for dynamic experimentation at Los Alamos National Laboratory. Two approaches, using either broadband or narrowband illumination, were used to monitor changes in the Bragg wavelength of the fiber-Bragg gratings. The second approach, using narrowband laser illumination, offered the highest sensitivity. The feasibility of using these techniques to generate early, pre-event signals useful for triggering high-latency diagnostics was demonstrated.

Development of a Linear Implosion-driven Hypervelocity Launcher

A traditional difficulty with high-explosive hypervelocity launching techniques is that extreme loading generally causes hydrodynamic deformation of the projectile either incidentally or by design. The launcher presented in this study uses explosives to operate the pump tube of a two-stage light gas gun via continuous linear implosion. In this configuration, the projectile is cushioned from direct action of the explosives by a light driver gas. The launch cycle is therefore comparable to a conventional two-stage light gas gun but with the shock driven by the rapid linear implosion of the pump tube compressing the gas to a much higher enthalpy. A laboratory scale version of the implosion driven launcher has recently demonstrated the ability to launch a 0.7g projectile to 7.9km/s. This design has successfully been scaled up to launch a 15g projectile to 7.6km/s, a result comparable to large two-stage light gas guns. This study presents the experimental and computational work performed in the ongoing development of this device. The extreme launch conditions lead to a number of unique design considerations, including dynamic confinment of the driver and launcher reservoir, mitigation of the loss of driver gas, and in-bore projectile stability and survivability. These issues are addressed experimentally through a number of focused launcher trials, as well as through the development of a quasi-one-dimensional Lagrangian hydrocode. The development of advanced implementations that involve continuing explosives onto the reservoir and launch tube in order to maintain a high driving pressure are also considered. These “second stage” techniques offer the potential for achieving projectile velocities in excess of 10km/s.

Sub-millimeter Debris Impact Damage of Unmanned Spacecraft Structure Panel

This study investigated the damage caused by sub-millimeter debris impact on the structures of unmanned spacecraft owing to the increase in the amount of sub-millimeter debris in the low earth orbit. Panel structures are mainly made of honeycomb sandwich panels, and the chassis of electronic devices are mounted on the panel. Because damage to the electronic device strongly influences the mission success of a spacecraft, determining the damage to the chassis wall behind the structure panel is important in debris protection design. Hypervelocity impact experiments were performed on the sets of an aluminum honeycomb sandwich panel and an aluminum alloy plate. The aluminum alloy plate was installed behind the honeycomb sandwich panel, without a standoff distance. In the experiments, sub- millimeter steel spheres (diameters of 0.15-1.0mm) were accelerated up to 6km/s by a two-stage light gas gun. Impact angles were varied from 0° to 30°. The depths of craters on the aluminum alloy plate were measured after the impact. A crater depth equation that applies when impact angles are less than 16.1° was calculated empirically.

Using Time-resolved Wave Profile Measurements to Determine Elusive Phase Transitions in Molybdenum

The purpose of this study was to investigate the dynamic strength of molybdenum (Mo) at high pressures, particularly at the location of a solid-solid phase transition within Mo prior to entering the melt regime. The intent was to build on previous work by conducting both symmetric and non-symmetric impact experiments using a two-stage light gas gun and VISAR diagnostic system to examine molybdenum behavior up to pressures of 305GPa. The approach required compensating for the wave interaction due to the low impedance LiF window, but provided detailed information regarding the release state. The main effort consisted of a series of Mo symmetric impact experiments having a fixed ratio of impactor thickness (1mm) to target thickness (4.25mm) and variation of the impact velocity which resulted in changes in both shock and release wave velocity. Based on the geometry, any structural change resulting in a change in release wave velocity would be noticeable through changes in the amount of time at the Hugoniot state or dwell time. As expected, the shock velocity increased proportionally with increased impact velocity, but a noticeable change in dwell time occurred at approximately 190GPa. Additional analysis of the strength variation of Mo showed an increase in strength from 1.3GPa to 3GPa at approximately 190GPa the location of phase transition, followed by a dramatic drop in strength for stresses above 190GPa. Strength increased again for stresses of 300 and 305GPa. The data acquired in this effort indicate the phase transition occurs at a slightly lower pressure than previously indicated and there appears to be a mixed phase region. This paper describes the strategy, experimental method, and corresponding results which are used to draw conclusions about the dynamic strength of molybdenum at high pressure.

A New Cosmic Dust Detector with a Novel Method Using a Resistive Grid Sensitive to Hypervelocity Impacts

A new method is demonstrated to detect impacts of hypervelocity particles in real-time and to determine the size of particles. It uses a resistive grid on a thin substrate (here Duroid). Penetration of the substrate in an impact breaks lines on the grid, changing the overall resistance of the grid. The change in resistance is proportional to the width of the damaged area (i.e. number of resistive lines that are broken), which is in turn proportional to the impactor size. This method provides a large area, low mass, low power detector for measuring the flux of small dust particles in space. Based on experimental data (taken in a two-stage light gas gun), we show that impacts at 5km s-1 demonstrate that the principle works as described for particles 150μm and above and that in theory could work for impacts down to size scales as small as 50μm.