Search NASA⌕ Search

SEARCH · Search NASA

Results for “EXPLOSIVES”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 793 records · Page 44
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Coulomb-explosion imaging of concurrent CH 2 BrI photodissociation dynamics

The dynamics following laser-induced molecular photodissociation of gas-phase CH 2 BrI at 271.6 nm were investigated by time-resolved Coulomb-explosion imaging using intense near-IR femtosecond laser pulses. Furthermore, the observed delay-dependent photofragment momenta reveal that CH 2 BrI undergoes C-I cleavage, depositing 65.6% of the available energy into internal product states, and that absorption of a second UV photon breaks the C-Br bond of CH 2 Br. Simulations confirm that this mechanism is consistent with previous data recorded at 248 nm, demonstrating the sensitivity of Coulomb-explosion imaging as a real-time probe of chemical dynamics.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2020

High Explosive Ignition through Chemically Activated Nanoscale Shear Bands

Shock initiation and detonation of high explosives is considered to be controlled through hot spots, which are local regions of elevated temperature that accelerate chemical reactions. Using classical molecular dynamics, we predict the formation of nanoscale shear bands through plastic failure in shocked TATB high explosive crystal. By scale-bridging with quantum-based molecular dynamics, we show that shear bands exhibit lower reaction barriers. While shear bands quickly cool,they remain chemically activated and support increased reaction rates without the local heating typically evoked by the hot spot paradigm. We describe this phenomenon as chemical activation through shear banding

Chemistry - Inorganic↗
DOE OSTI2020

Characterization and differentiation of aluminum powders used in improvised explosive devices – Part 1: Proof of concept of the utility of particle micromorphometry

Abstract Aluminum (Al) powders are commonly used in improvised explosive devices as metallic fuels, a component of explosive mixtures. These powders can be obtained readily from industrial‐scale and consumer products, and produced using unsophisticated “kitchen chemistry” techniques. This research demonstrates the potential of automated particle micromorphometry for comparisons between known source and questioned Al powders recovered from IEDs, as well as for insight into the method of Al powder manufacture. Al powder samples were obtained from legitimate manufacturers, and 56 samples were produced “in‐house” from Al‐containing spray paints and ball‐milled Al foils. Transmitted light microscope images of Al powder particles were acquired using an automated stage with automated z‐focus; 17 size and shape parameters were measured for all particles. Approximately 37,000–2,500,000 particles/sample were analyzed using an open‐source statistical package with customized code. Dimensionality reduction was required for processing the large datasets: eight of the 17 measured variables were selected based on inspection of the correlation matrix. Data from four subsamples from each of the 56 samples produced using “in‐house” methods were analyzed using ANOVA to assess the within‐ and between‐sample variation. High within‐sample variation was noted; however, ANOVA and post‐hoc Tukey's honestly significant difference (HSD) tests demonstrated that the between‐sample variation was substantially larger than the within‐sample variation. Each sample could be differentiated from all other samples in the test set. Future experiments will focus on ways to reduce the within‐sample variation, and additional statistical and microanalytical methods to classify sources and confidently constrain the method of Al powder manufacture.

Baldaino, JenaMarie↗
DOE OSTI2012

Hyperspectral Microscopy of Explosives Particles Using an External Cavity Quantum Cascade Laser

Using infrared hyperspectral imaging, we demonstrate microscopy of small particles of the explosives compounds RDX, tetryl, and PETN with near diffraction-limited performance. The custom microscope apparatus includes an external cavity quantum cascade laser illuminator scanned over its tuning range of 9.13-10.53 µm in four seconds, coupled with a microbolometer focal plane array to record infrared transmission images. We use the hyperspectral microscopy technique to study the infrared absorption spectra of individual explosives particles, and demonstrate sub-nanogram detection limits.

(110.4234) Multispectral & Hyperspectral Imaging↗
DOE OSTI2025

Improved field assessments of chemicals and explosives using high-resolution gamma-ray spectroscopy with a tagged neutron interrogation system

A field-portable tagged neutron interrogation system is being developed for detection of explosives and chemical warfare agents by prompt γ-ray neutron activation analysis. The system combines an associated particle imaging deuterium-tritium neutron generator with a high-purity germanium γ-ray detector. Fine spatial resolution neutron and α detectors enable precise mapping of characteristic γ-ray emission distributions onto high-clarity neutron radiographic images. A narrow coincidence gate associated with each tagged neutron ensures a large signal-to-background ratio, thus significantly improving sensitivity to the chemical compositions of the items being assessed. Recent experimental results recorded from test objects involving mock explosives and other chemicals are presented.

Bucher, Brian [Idaho National Laboratory (INL)]↗
DOE OSTI2018

Uncertainty analysis for infrasound waveform inversion: Application to explosion yield estimation

While the acoustic waveform inversion method is increasingly used in geophysical acoustics to constrain source parameters, the inversion results are often provided without any uncertainty analysis. Here, this study presents a probabilistic representation for acoustic waveform inversion and method to evaluate the inversion uncertainty using ground-truth data. A posteriori probability distribution of source estimate is described by a priori waveform misfit covariance and the variance of acoustic source model. The probabilistic framework is applied to local explosion infrasound to estimate the yields of explosions and uncertainty. Estimated yields showed overall good agreement with the true yields (less than 25% errors). The uncertainty of the estimated yield is represented by the sum of the waveform inversion uncertainty and source model uncertainty. It is shown that the yield uncertainty attributed to local infrasound inversion (within 10 km) is as small as the uncertainty caused by 10% prediction errors in the acoustic source model. Finally, these results indicate that the acoustic source model uncertainty should also be considered for accurate yield estimation and that local infrasound can be a valuable tool to understand the magnitude of the source uncertainty.

58 GEOSCIENCES↗
DOE OSTI2012

Study of the core gaps formed accidentally during wire explosion

During wire explosion, along with striations (a regular structure with alternating lower and higher density bands), low-density regions the characteristic axial size of which differs substantially from that of striations and can reach 1-2 mm are also observed in the discharge channel. Such irregular structures came to be known as 'gaps' (D. B. Sinars et al., Phys. Plasmas 8, 216 (2001)). In the present study, the mechanism of the formation of core gaps during explosions of 25- and 50-{mu}m-diameter copper and nickel wires in air is investigated. It is shown that the specific energy deposited in the gap region substantially exceeds the average specific energy deposited in the wire material.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2015

Electric explosion of fine wires: Three groups of materials

Experimental data demonstrating differences in the structures of channels formed during nanosecond discharges through fine wires made of different materials are presented. In addition to the traditional two classes of metals and alloys (the copper and tungsten groups), a new class is proposed to which materials of the nickel type belong. Their properties combine the characteristic properties of the two traditional groups, due to which they occupy an intermediate position between the latter. This manifests itself in the unstable character of explosion, the type of which can change drastically when changing the ambient medium or other conditions. Most of the reported results were obtained at a small setup with maximum values of the current and voltage of 10 kA and 20 kV, respectively, the current rise time being about 300 ns. An attempt is made to construct a scenario of the development of a nanosecond explosion that would make it possible to qualitatively describe the formation of the discharge channel structure. The analysis is based on the recent experimental results indicating that the cores formed in the course of the discharge have a tubular structure.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2018

Study of Electric Explosion of Flat Micron-Thick Foils at Current Densities of (5–50)×10 8 A/cm 2

Electric explosions of flat Al, Тi, Ni, Cu, and Та foils with thicknesses of 1–16 μm, widths of 1–8 mm, and lengths of 5–11 mm were studied experimentally on the BIN, XP, and COBRA high-current generators at currents of 40–1000 kA and current densities of (5–50) × 10 8 A/cm 2 . The images of the exploded foils were taken at different angles to the foil surface by using point projection radiography with an X-pinch hot spot as the radiation source, the spatial resolution and exposure time being 3 μm and 50 ps, respectively, as well by the laser probing method with a spatial resolution of 20 μm and an exposure time of 180 ps. In the course of foil explosion, rapidly expanding objects resembling the core and corona of an exploded wire were observed. To this end, it is shown that the core of the exploded foil has a complicated time-varying structure.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2024

Codes for "Shallow Soil Response to a Buried Chemical Explosion with Geophones and Distributed Acoustic Sensing" DAG - 01101646

The codes reproduce the figures of the manuscript entitled "Shallow Soil Response to a Buried Chemical Explosion with Geophones and Distributed Acoustic Sensing" submitted to Journal of Geophysical Research - Solid Earth. Geophone data and Distributed acoustic sensing (DAS) data recorded during the Phase II of the The Source Physics Experiment (SPE) along a fiber-optic cable offshore were processed to understand the response of the shallow subsurface to an explosion. This Ground-based Nuclear Detonation Detection (GNDD), Low Yield Nuclear Monitoring (LYNM), and Source Physics Experiment (SPE) research was funded by the National Nuclear Security Administration, Defense Nuclear Nonproliferation Research and Development (NNSA DNN R&D).

Viens, Loic↗
DOE OSTI2024

Subsurface Spectroscopy of Thermal Degradation Inside an Inert Plastic Bonded Explosive (PBX) Simulant Using Feedback-Assisted Wavefront Shaping

We characterize the subsurface thermal degradation of an inert analog of high-explosive molecular crystals (Eu:Y(acac) 3 (DPEPO)) (EYAD) embedded inside of a plastic bonded explosive simulant using feedback-assisted wavefront shaping-based fluorescence and Raman spectroscopies. This technique utilizes wavefront shaping to focus pump light inside a heterogeneous material onto a target particle, which significantly improves its spectroscopic signature. We find that embedding the EYAD crystals in the heterogeneous polymer results in improved thermal stability, relative to bare crystal measurements, with the crystal remaining fluorescent to >612 K inside of the heterogeneous material, while the bare crystal’s fluorescence is fully quenched by 500 K. We hypothesize that this improvement is due to the polymer restricting the effects of EYAD melting, which occurs at 400 K and is the primary mechanism for spectroscopic changes in the temperature range explored.

Anderson, Benjamin R.↗
DOE OSTI2022

Raman Spectroscopy Characterization of Nuclear Materials and Soot from High Explosives

Vibrational and luminescence spectroscopy were used in the investigation of U and Pu-bearing compounds and soot from high explosives testing. Key spectroscopic signatures of UF4 and its hydrates, PuO 2 , and soot from different explosives will be presented. The United States Government retains and the publisher, by accepting this article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this work, or allow others to do so, for United States Government purposes.

Villa-Aleman, Eliel↗
DOE OSTI2016

Source spectra of the first four Source Physics Experiments (SPE) explosions from the frequency-domain moment-tensor inversion

In this study, I used seismic waveforms recorded within 2 km from the epicenter of the first four Source Physics Experiments (SPE) explosions to invert for the moment-tensor spectra of these explosions. I employed a one-dimensional (1D) Earth model for Green's function calculations. The model was developed from P- and R g -wave travel times and amplitudes. I selected data for the inversion based on the criterion that they had consistent travel times and amplitude behavior as those predicted by the 1D model. Due to limited azimuthal coverage of the sources and the mostly vertical-component-only nature of the dataset, only long-period, volumetric components of the moment-tensor spectra were well constrained.

58 GEOSCIENCES↗
DOE OSTI2018

Seismic Models for Near-Surface Explosion Yield Estimation in Alluvium and Sedimentary Rock

Seismic ground-motion data provide valuable constraints on explosion characteristics, such as yield and height-of-burst/depth-of-burial (HOB/DOB). In this study, we investigate a range of seismic amplitude features and their efficacy in minimizing errors associated with yield estimation. Using a set of explosion recordings from experiments conducted in alluvium and sedimentary rock geologies, we investigated the effectiveness of three different seismic feature types over a range of different frequencies. Using both velocity and displacement data, we investigated the zero-to-peak (ZTP) amplitude of the first arriving P wave, the peak-to-peak (PTP) amplitude of the first arriving P wave, and the P rms amplitude over various time windows starting with the P wave. These three basic features were measured on both vertical component only data and the vertical–radial vector sum. In total, there were 56 different combinations investigated. Our seismic models combine the effects of scaled range and scaled HOB/DOB on the observed seismic features. The results show that the vertical–radial vector sum of the ZTP amplitudes measured on displacement seismograms most consistently produce models with the smallest difference between predicted amplitude values and observed amplitude values when accounting for both alluvium and sedimentary rock lithology. The improvement in fit to the data when incorporating the difference in source lithology is significant. Lastly, if an alluvium lithology is assumed for a sedimentary rock lithology, the difference in yield could be up to ~3.0 times the appropriate yield in the far field.

58 GEOSCIENCES↗
DOE OSTI2022

Multi-Event Explosive Seismic Source for the 2022 M w 6.3 Hunga Tonga Submarine Volcanic Eruption

The eruption of the Hunga Tonga–Hunga Ha’apai submarine volcano on 15 January 2022 produced a variety of geophysical responses, including a significant seismic signal. We study the seismic source process of this event by inverting for moment tensors (MTs) using regional surface waves (Rayleigh, Love). By comparing inversion results for the eruption with eight nearby earthquakes, we show that it is possible to discriminate MT source types. Our inversion yields a shallow explosive source for the eruption and reveals the importance of trade-offs among depth, magnitude, and source type. We illustrate these trade-offs by representing the misfit variations over the eigenvalue lune. Finally, we invert for the source-time function of the sequence of explosions that occurred in the first minutes of the eruption. The multi-event source-time function comprises four subevents spanning ~270 s, with a total magnitude estimate of M w 6.34 ± 0.10.

58 GEOSCIENCES↗
DOE OSTI2012

High Energy-Density Materials with Fast Energy Release: Molecular scale shock response of explosives (DTRA Basic Research Final Report 2012)

The principle goal of this $\$$150K/yr, 3-yr. project was to experimentally measure the time evolution of shock induced chemistry in the explosive RDX. Since direct measurements of shock induced chemistry in RDX, or any other explosive, have eluded researchers for several decades, new techniques had to be developed. Transient absorption was coupled to laser shock loading to probe the possible role of electronic excitations in the chemistry of RDX. Transient absorption signatures turned out to be a good indication of the relative degree of chemical reaction versus time, but were not conclusive regarding whether electronic excitation was an important factor in shock initiation. Preliminary efforts to sensitize shock induced chemistry with ultraviolet pulsed excitation were performed, but are not yet conclusive. The bulk of the effort of the project was directed at development of femtosecond stimulated Raman spectroscopy (FSRS) as a diagnostic of temperature in the presence of chemistry. This effort was significantly more difficult than initially anticipated. While we had planned to apply the method to single shot laser experiments, the sensitivity achieved during the project duration was insufficient to measure the sub-nanogram amounts of material shocked. Despite the difficulties applying this measurement to our current small scale laser shock experiments, it shows significant promise for measurements where there is more volume of material shocked. We have established the theoretical framework and experimentally validated FSRS as a sub-picosecond molecular vibrational temperature measurement diagnostic. We have also followed the shock induced chemistry of RDX through transient absorption spectroscopy and established the shock stresses required to achieve sub-nanosecond reaction rates. The project led to 3 peer reviewed journal articles, 4 conference proceedings, 3 invited talks at conferences, 2 contributed talks at conferences, and a number of other presentations.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Ten Trials at Lower Slobbovia: Searching for Repetitive Electromagnetic and Seismoacoustic Signatures in Explosions

We performed a series of ten explosion tests, each test being a single 10-kg cylinder of Comp-B with a PBXN-9 booster. Eight of the tests were placed 2 m above ground level, one was at ground level, and one was 1 m below ground in a backfilled hole. The explosions were monitored by radio antennas to detect electromagnetic emissions and seismo-acoustic instrumentation. We found that certain aspects of the radiofrequency emission regimes repeated from test to test. Some features showed a systematic variation across tests, which we interpret as the effect of each detonation on the nearby ground. The radio emissions were probably from the high-temperature detonation shock, follow-on combustion, and frictional charging of dirt entrained by the blast. The below-ground test in particular generated an anomalously-high level of RF at both low and high frequencies, presumably due to the large amount of dirt and rock involved. The seismoacoustic observations clearly discriminate the buried shot from the table and surface shots, which appear as a single population. Seismoacoustic waveforms from repeating tests at local distances have highly self-similar waveforms but amplitudes are strongly dependent on atmospheric conditions. We show that we can correct for meteorological effects on amplitude for upward-refracting atmospheres, but that correction for downward-refracting atmospheric profiles requires a coupled correction for topography.

47 OTHER INSTRUMENTATION↗
DOE OSTI2013

The Biggest Explosions in the Universe [Poster]

While most supermassive stars formed in the early universe are expected to have collapsed to black holes, those with masses of ~50,000 solar masses are predicted to have exploded as extremely energetic supernovae. These explosions would have been ~10,000 times more energetic than most supernovae today, making them the largest explosions in the history of the universe. In addition to releasing enormous amounts of mechanical and thermal energy into their surroundings, they also enrich the primordial gas with the first heavy elements.

79 ASTRONOMY AND ASTROPHYSICS↗