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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.

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At least 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

A study of explosive-induced fracture in polymethyl methacrylate (PMMA)

The fracture response of geologic materials is of interest for applications, including geothermal energy harnessing and containment of underground explosions. To better understand the explosively induced fracture response of geomaterials, polymethyl methacrylate (PMMA) was used as a transparent rock surrogate to allow imaging of internal shock propagation and fracture growth processes. Experiments were conducted using high-speed shadowgraphy and photon Doppler velocimetry (PDV), which were compared to numerical simulations. Experiments measured fractures produced in 304.8mm × 304.8mm × 304.8mm PMMA cubes with two simultaneously initiated detonators. The cubes were subjected to varying amounts and directions of externally applied uniaxial stresses, including no stress, 2 MPa stress, and 20 MPa stress. The fracture radius as a function of time was extracted from the high-speed videos. Post-test images of the PMMA cubes aided in the determination of three-dimensional effects not directly imaged by the cameras. The surface velocity history and the shock response captured in PDV and the high-speed videos were compared to the simulated explosive-induced shock response. The simulation results indicate that the shock drives the fracture for the first 20 μs corresponding to a fracture radius of approximately 15 mm in the experiments. The gas-driven fracture extent was estimated analytically using an equilibrium stress distribution calculated after the shock wave propagation through the sample. Reduction in the gas pressure due to the leakage of the explosive products through the crack as a function of time was accounted for. In conclusion, the estimated fracture lengths were in agreement with the experimentally observed fracture lengths.

15 GEOTHERMAL ENERGY↗
DOE OSTI2012

COMPACT REMNANT MASS FUNCTION: DEPENDENCE ON THE EXPLOSION MECHANISM AND METALLICITY

The mass distribution of neutron stars and stellar-mass black holes provides vital clues into the nature of stellar core collapse and the physical engine responsible for supernova explosions. A number of supernova engines have been proposed: neutrino- or oscillation-driven explosions enhanced by early (developing in 10-50 ms) and late-time (developing in 200 ms) convection as well as magnetic field engines (in black hole accretion disks or neutron stars). Using our current understanding of supernova engines, we derive mass distributions of stellar compact remnants. We provide analytic prescriptions for both single-star models (as a function of initial star mass) and for binary-star models-prescriptions for compact object masses for major population synthesis codes. These prescriptions have implications for a range of observations: X-ray binary populations, supernova explosion energies, and gravitational wave sources. We show that advanced gravitational radiation detectors (like LIGO/VIRGO or the Einstein Telescope) will be able to further test the supernova explosion engine models once double black hole inspirals are detected.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

Simultaneous observation of a hot explosion by NST and IRIS

We present the first simultaneous observations of so-called “hot explosions” in the cool atmosphere of the Sun made by the New Solar Telescope (NST) of Big Bear Solar Observatory and the Interface Region Imaging Spectrograph (IRIS) in space. The data were obtained during the joint IRIS-NST observations on 2014 July 30. The explosion of interest started around 19:20 UT and lasted for about 10 minutes. Our findings are as follows: (1) the IRIS brightening was observed in three channels of slit-jaw images, which cover the temperature range from 4000 to 80,000 K; (2) during the brightening, the Si iv emission profile showed a double-peaked shape with highly blue and redshifted components (−40 and 80 km s{sup −1}); (3) wing brightening occurred in Hα and Ca ii 8542 Å bands and related surges were observed in both bands of the NST Fast Imaging Solar Spectrograph (FISS) instrument; (4) the elongated granule, seen in NST TiO data, is clear evidence of the emergence of positive flux to trigger the hot explosion; (5) the brightening in Solar Dynamics Observatory/Atmospheric Imaging Assembly 1600 Å images is quite consistent with the IRIS brightening. These observations suggest that our event is a hot explosion that occurred in the cool atmosphere of the Sun. In addition, our event appeared as an Ellerman bomb (EB) in the wing of Hα, although its intensity is weak and the vertical extent of the brightening seems to be relatively high compared with the typical EBs.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2021

Statistical analysis of correlations in the x-ray induced Coulomb explosion of iodopyridine

Coulomb explosion imaging is a promising experimental tool to study individual molecules. Here, in this work simulation data for the x-ray induced Coulomb explosion of 2-iodopyridine is analyzed and the involved fragmentation dynamics are described. It is found that particular final ion momenta show correlations that reflect a collision of two atoms during the explosion. Variations of the proton kinetic energies can be associated with variations in the charge build-up time. Covariances of the forces during the explosion can be utilized to simplify the description of the dynamics in reduced dimensionality using only four collective coordinates.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2019

Rapid clay precipitation in explosion-induced fractures

Fractures within the earth control rock strength and fluid flow, but their dynamic nature is not well understood. As part of a series of underground chemical explosions in granite in Nevada, we collected and analyzed microfracture density data sets prior to, and following, individual explosions. Our work shows an ~4-fold increase in both open and filled microfractures following the explosions. Based on the timing of core retrieval, filling of some new fractures occurs in as little as 6 wk after fracture opening under shallow (<100 m) crustal conditions. These results suggest that near-surface fractures may fill quite rapidly, potentially changing permeability on time scales relevant to oil, gas, and geothermal energy production; carbon sequestration; seismic cycles; and radionuclide migration from nuclear waste storage and underground nuclear explosions.

58 GEOSCIENCES↗
DOE OSTI2018

Laser Simulations of the Destructive Impact of Nuclear Explosions on Hazardous Asteroids

We present the results of preliminary experiments at laser facilities in which the processes of the undeniable destruction of stony asteroids (chondrites) in space by nuclear explosions on the asteroid surface are simulated based on the principle of physical similarity. We present the results of comparative gasdynamic computations of a model nuclear explosion on the surface of a large asteroid and computations of the impact of a laser pulse on a miniature asteroid simulator confirming the similarity of the key processes in the fullscale and model cases. The technology of fabricating miniature mockups with mechanical properties close to those of stony asteroids is described. For mini-mockups 4–10 mm in size differing by the shape and impact conditions, we have made an experimental estimate of the energy threshold for the undeniable destruction of a mockup and investigated the parameters of its fragmentation at a laser energy up to 500 J. The results obtained confirm the possibility of an experimental determination of the criteria for the destruction of asteroids of various types by a nuclear explosion in laser experiments. We show that the undeniable destruction of a large asteroid is possible at attainable nuclear explosion energies on its surface.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2020

Improved Parametric Models for Explosion Pressure Signals Derived From Large Datasets

Accurate recording and characterization of explosion-induced pressure signals are key components of the forensic analysis of explosion events in the atmosphere. Parametric overpressure models based on several key waveform features (peak overpressure, positive pulse duration, and impulse) are widely used to estimate explosion energy in terms of trinitrotoluene equivalent yield. However, those models are often developed by a limited dataset, including only a few events or recordings at relatively short propagation distances. Here, we develop empirical waveform-parameter models based on a regression analysis of a large set of data curated from four chemical explosion experiments including 16 detonations. We measured peak overpressure and impulse for positive and negative phases from 1000 pressure signals recorded at local ranges (<20 km) with scaled distance up to 8000 m/kg 1/3 . Additionally, the measured waveform parameters showed large variation with respect to observing distances indicating the effects of atmospheric propagation. In this study, a second-order polynomial model was used in a least-squares regression to account for those propagation effects and to improve data fitting. In addition to model parameters for waveform features, we also determined range-dependent model uncertainties based on data variance. The model uncertainty represents the prediction error of our models and can be critical to evaluating the uncertainty of yield estimate.

58 GEOSCIENCES↗
DOE OSTI2020

Beirut Explosion Yield and Mushroom Cloud Height - Effects of the Source Environment

I use crater dimensions to estimate the yield of the August 4th, 2020 Beirut explosion to be equivalent to approximately 1.4 kilotons of TNT with a lower bound of about 0.7 kilotons. Based on the amount of ammonium nitrate reported to have been stored at the Beirut harbor, I assume an upper bound for the yield of 2.75 kilotons. However, it is highly likely that the yield was less than 2.75 kilotons, since reported values for TNT equivalence of ammonium nitrate are typically much less than one hundred percent. The crater-size based yield estimates are based on crater radius estimates from satellite imagery and empirical curves and data for scaled crater radius from past chemical and nuclear explosions. I present evidence that suggests that the relatively large crater radius is due to a high degree of coupling of shock wave energy to the surrounding medium and a reduction of the effective stress because of a high level of saturation of the geologic media beneath the explosion. I provide yield estimates based on seismic body-wave magnitude and crater depth as corroborating evidence. I compare preliminary estimates for the maximum debris cloud height, based on cell phone videos/images, with predicted maximum heights for this yield range from empirical formulas and numerical cloud-rise models. Based on a preliminary analysis of cell phone footage, the observed maximum cloud height appears to be approximately 1600 m. This is much lower than that predicted using standard empirical formulas and buoyant cloud rise models. I present results from a modified buoyant cloud rise model that more accurately predicts the maximum cloud height by allowing for the inclusion of a fixed amount of air and/or water into the fireball at the start of cloud rise. The amount of mass that needs to be added at the start, to reproduce the observed maximum cloud height, is relatively small compared to the total mass entrained during cloud rise. A much greater amount of dry air or debris is required, relative to water, for an equivalent reduction in maximum cloud height. The ammonium nitrate is one possible source for water in the fireball since it was being stored in a very humid environment and ammonium nitrate is known to be hygroscopic. The ground beneath the explosion, especially if it were saturated, and the nearby harbor could also have been sources for water or debris in the fireball.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2025

Designing Yield Grids for Airborne Nuclear Explosions to Maintain Decrements in Rayleigh Waveform Amplitudes

This document details a method for selecting grid points that sample the yields of airborne, low yield nuclear explosions that constrains the relative size of seismic waveforms sourced by explosions that are parameterized by this grid. In detail, we impose this constraint so that the vertical component of ground displacement that is sourced by explosions with a fixed height of burst (HoB) at grid point k change by a fixed factor of a when compared to the waveform amplitudes sourced by explosions at grid point k + 1, as observed at a fixed standoff distance. This gridding thereby preserves amplitude ratios along the grid so that they are agnostic to k. We assert that this method is useful in tests that apply algorithms against synthetic or augmented datasets for which the performance of the algorithm must be measured against source size, and waveform amplitudes must change uniformly (e.g., Berg et al, 2025).

58 GEOSCIENCES↗
DOE OSTI2017

The ALMA View of the OMC1 Explosion in Orion

Most massive stars form in dense clusters where gravitational interactions with other stars may be common. The two nearest forming massive stars, the BN object and Source I, located behind the Orion Nebula, were ejected with velocities of ∼29 and ∼13 km s{sup −1} about 500 years ago by such interactions. This event generated an explosion in the gas. New ALMA observations show in unprecedented detail, a roughly spherically symmetric distribution of over a hundred {sup 12}CO J = 2−1 streamers with velocities extending from V {sub LSR} = −150 to +145 km s{sup −1}. The streamer radial velocities increase (or decrease) linearly with projected distance from the explosion center, forming a “Hubble Flow” confined to within 50″ of the explosion center. They point toward the high proper-motion, shock-excited H{sub 2} and [Fe ii] “fingertips” and lower-velocity CO in the H{sub 2} wakes comprising Orion's “fingers.” In some directions, the H{sub 2} “fingers” extend more than a factor of two farther from the ejection center than the CO streamers. Such deviations from spherical symmetry may be caused by ejecta running into dense gas or the dynamics of the N -body interaction that ejected the stars and produced the explosion. This ∼10{sup 48} erg event may have been powered by the release of gravitational potential energy associated with the formation of a compact binary or a protostellar merger. Orion may be the prototype for a new class of stellar explosiozn responsible for luminous infrared transients in nearby galaxies.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2025

Primordial Black Hole Triggered Type Ia Supernovae. I. Impact on Explosion Dynamics and Light Curves

Primordial black holes (PBHs) in the asteroid-mass window are compelling dark matter candidates, made plausible by the existence of black holes and by the variety of mechanisms of their production in the early Universe. If a PBH falls into a white dwarf (WD), the strong tidal forces can generate enough heat to trigger a thermonuclear runaway explosion, depending on the WD’s mass and the PBH’s orbital parameters. In this work, we investigate the WD explosion triggered by the passage of a PBH. We perform 2D simulations of the WD undergoing thermonuclear explosion in this scenario, with the predicted ignition site as a parameter assuming the deflagration–detonation transition model. We study the explosion dynamics, and predict the associated light curves and nucleosynthesis. We find that the model sequence predicts light curves which align with the Phillips relation (B max versus ΔM 15 ). Our models hint at a unifying approach in triggering Type Ia supernovae without involving two distinctive evolutionary tracks.

Dark matter↗
DOE OSTI2017

The Magnetar Model of the Superluminous Supernova GAIA16apd and the Explosion Jet Feedback Mechanism

Under the assumption that jets explode core collapse supernovae (CCSNe) in a negative jet feedback mechanism (JFM), this paper shows that rapidly rotating neutron stars are likely to be formed when the explosion is very energetic. Under the assumption that an accretion disk or an accretion belt around the just-formed neutron star launch jets and that the accreted gas spins-up the just-formed neutron star, I derive a crude relation between the energy that is stored in the spinning neutron star and the explosion energy. This relation is ( E {sub NS-spin}/ E {sub exp}) ≈ E {sub exp}/10{sup 52} erg; It shows that within the frame of the JFM explosion model of CCSNe, spinning neutron stars, such as magnetars, might have significant energy in super-energetic explosions. The existence of magnetars, if confirmed, such as in the recent super-energetic supernova GAIA16apd, further supports the call for a paradigm shift from neutrino-driven to jet-driven CCSN mechanisms.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

Los Alamos Explosives Performance Key to Stockpile Stewardship

As the U.S. Nuclear Deterrent ages, one essential factor in making sure that the weapons will continue to perform as designed is understanding the fundamental properties of the high explosives that are part of a nuclear weapons system. As nuclear weapons go through life extension programs, some changes may be advantageous, particularly through the addition of what are known as "insensitive" high explosives that are much less likely to accidentally detonate than the already very safe "conventional" high explosives that are used in most weapons. At Los Alamos National Laboratory explosives research includes a wide variety of both large- and small-scale experiments that include small contained detonations, gas and powder gun firings, larger outdoor detonations, large-scale hydrodynamic tests, and at the Nevada Nuclear Security Site, underground sub-critical experiments.

42 ENGINEERING↗
DOE OSTI2021

Standing Shock Regulates Sparks in Explosive Flows

Electric sparks and explosive flows have long been associated with each other. Flowing dust particles originate charge through contact electrification and separate based on inertia, resulting in strong electric fields supporting sparks. These sparks can cause explosions in dusty environments, especially those rich in carbon, such as coal mines and grain elevators. Recent observations of explosive events in nature and decompression experiments indicate that supersonic flows of explosions may alter the electrical discharge process. Shocks may suppress parts of the hierarchy of the discharge phenomena, such as leaders. In our decompression experiments, a shock tube ejects a flow of gas and particles into an expansion chamber. We imaged an illuminated plume from the decompression of a mixture of argon and < 100 mg of diamond particles. We also performed hydrodynamics simulations of the decompression event that provide insight into the conditions supporting the observed behavior. The sparks occur below the sharp boundary of a condensation cloud. These results agree closely with the Mach disk shock shape and height in the simulation. This represents direct evidence that the sparks are sculpted by the outflow. The spatial and temporal scale of the sparks transmit an impression of the shock tube flow, a connection that could enable novel instrumentation to diagnose currently inaccessible supersonic granular phenomena.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Structural Effects of Postulated Hydrogen Explosions in Process Piping and Vessels - 20274

At Savannah River Site (SRS), preparations to startup new liquid waste operations and recent advances in understanding thermolytic hydrogen generation have led to several recent studies on the structural effects of postulated hydrogen explosions. This paper reports on seven representative piping and vessel cases that are evaluated for deflagrations, detonations, and deflagration-to-detonation transition (DDT) assuming the initial mixture is stoichiometric hydrogen and air. The evaluations are based on the approach used by the Department of Defense for analyzing structures subjected to accidental explosions and include inelasticity, dynamic structural amplification, and material strain-rate effects. Evaluation criteria consider the potential for repeated explosions causing fatigue but also consider that some degree of permanent plastic deformation is acceptable as long as rupture is prevented. Specific conclusions depend on the assumed pre-ignition pressure. If the pre-ignition pressure is atmospheric and if the components are designed to a code from the American Society of Mechanical Engineers, the components evaluated are expected to plastically deform but not rupture under the explosion scenarios considered. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2015

Advances in explosives analysis—part I. animal, chemical, ion, and mechanical methods

The number and capability of explosives detection and analysis methods have increased substantially since the publication of the Analytical and Bioanalytical Chemistry special issue devoted to Explosives Analysis (Moore and Goodpaster, Anal Bioanal Chem 395(2):245–246, 2009). We review and critically evaluate the latest (the past five years) important advances in explosives detection, with details of the improvements over previous methods, and suggest possible avenues towards further advances in, e.g., stand-off distance, detection limit, selectivity, and penetration through camouflage or packaging. The review consists of two parts. Moreover, Part I, reviews methods based on animals, chemicals (including colorimetry, molecularly imprinted polymers, electrochemistry, and immunochemistry), ions (both ion-mobility spectrometry and mass spectrometry), and mechanical devices. Part II will review methods based on photons, from very energetic photons including X-rays and gamma rays down to the terahertz range, and neutrons.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Waveform inversion of acoustic waves for explosion yield estimation

We present a new waveform inversion technique to estimate the energy of near-surface explosions using atmospheric acoustic waves. Conventional methods often employ air blast models based on a homogeneous atmosphere, where the acoustic wave propagation effects (e.g., refraction and diffraction) are not taken into account, and therefore, their accuracy decreases with increasing source-receiver distance. In this study, three-dimensional acoustic simulations are performed with a finite difference method in realistic atmospheres and topography, and the modeled acoustic Green's functions are incorporated into the waveform inversion for the acoustic source time functions. The strength of the acoustic source is related to explosion yield based on a standard air blast model. The technique was applied to local explosions (<10 km) and provided reasonable yield estimates (<~30% error) in the presence of realistic topography and atmospheric structure. In conclusion, the presented method can be extended to explosions recorded at far distance provided proper meteorological specifications.

45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEF↗
DOE OSTI2012

The challenge of improvised explosives

Energetic materials have been developed for decades, and indeed centuries, with a common set of goals in mind. Performance (as a detonating explosive, a propellant, or a pyrotechnic) has always been key, equally important have been the attributes of safety, stability, and reproducibility. Research and development with those goals has led to the set of energetic materials commonly used today. In the past few decades, the adoption and use of improvised explosives in attacks by terrorists or third-world parties has led to many questions about these materials, e.g., how they may be made, what threat they pose to the intended target, how to handle them safely, and how to detect them. The unfortunate advent of improvised explosives has opened the door for research into these materials, and there are active programs in many countries. I will discuss issues and opportunities facing research into improvised explosives.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗