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At least 793 records · Page 44
All sourcesNASA NTRSDOE OSTI
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↗
DOE OSTI2013

Understanding Debris-Background Ion Interactions in High Altitude Nuclear Explosions

The Starfish Prime event produced many interesting nuclear, electromagnetic, atomic and plasma effects, which have led over the past 50 years to much research in understanding the overall phenomenology of high altitude nuclear explosions (HANE). At altitudes lower than Starfish, where collisional processes come into play, the physics of a nuclear fireball in the atmosphere is well understood. But at high altitudes, where collisions are much weaker, the fundamental issue how the ionized weapon debris is stopped in the ionosphere in order to produce a relatively localized debris cloud remains unresolved. In the last 30 years this issue has been investigated in the laboratory using high-power lasers to simulation the explosion and subsequent expansion of the debris plasma. While experiments that were carried out on the Helios laser at Los Alamos and then later on the Pharos laser at NRL were able to produce some plasma conditions representative of the HANE environment and obtained interesting results, they were not very successful in addressing the basic debris-air coupling problem in the collisionless regime. This problem is being revisited in a new DTRA-funded experimental program with the 500 J Raptor glass laser on the Large Plasma Device (LAPD) at UCLA.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2013

Probability Calculation of Grit-Grit Interaction on a Plastic Bonded Explosive During Glancing Impacts

Recent experiments indicate that frictionally heated grit can act as effective hot spots for the ignition of PBX 9501 (Parker et al. (2013)). The most common mode for hot spot formation is when a piece of grit is dragged by the explosive across a high melting point surface, such as steel. This leads to a hot spot with a temperature of the melting point of the surface. For high melting point surfaces this can be hot enough to lead to ignition. It is believed that an easy way to mitigate this is to use surfaces with low melting points, which means the hot spots formed cannot become hot enough to ignite the explosive during the duration of the impact (Bowden and Gurton (1948)). However, when surfaces have a similar hardness to the PBX (such as many plastics), hot spots of sufficient temperature for ignition can still be formed by the collision of two grit particles, one being dragged by the PBX with the other being stationary on the surface. In order to mitigate the probability of ignition it is desirable to know how clean the work surfaces need to be in order to minimize the acceptable risk of an event. Two cases need to be considered: first, what is probability that a dropped piece of PBX will contact one or more grit particles? This will lead to an estimate of how ”clean” a surface needs to be when working with unmitigated, high-melting point surfaces. Second, what is the probability that a dropped piece of PBX will lead to a collision between two or more grit particles? This will give an estimate how clean a surface needs to be when working with low melting point surfaces.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2013

Development of ab initio techniques critical for future science-based explosives R&D

Density Functional Theory (DFT) has emerged as an indispensable tool in materials research, since it can accurately predict properties of a wide variety of materials at both equilibrium and extreme conditions. However, for organic molecular crystal explosives, successful application of DFT has largely failed due to the inability of current exchange-correlation functionals to correctly describe intermolecular van der Waals (vdWs) forces. Despite this, we have discovered that even with no treatment of vdWs bonding, the AM05 functional and DFT based molecular dynamics (MD) could be used to study the properties of molecular crystals under compression. We have used DFT-MD to predict the unreacted Hugoniots for PETN and HNS and validated the results by comparison with crystalline and porous experimental data. Since we are also interested in applying DFT methods to study the equilibrium volume properties of explosives, we studied the nature of the vdWs bonding in pursuit of creating a new DFT functional capable of accurately describing equilibrium bonding of molecular crystals. In this report we discuss our results for computing shock Hugoniots of molecular crystals and also what was learned about the nature of bonding in these materials.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Ranchero Armature Test LA-19.4-CT-3: PBX-9501 Explosive with no smoothing layer. Firing point 88, 9/16/13

LA-19.4-CT-3 (CT-3) was the third camera test in a series beginning in 1/11, which diagnose the performance of 6 mm thick, 6061 T-0 Al Ranchero armatures. [The test LA-43-CT-2 (CT-2) is described in LA-UR-14-21983.] The goal of CT-3 was to verify that PBX-9501, with 18 mm point spacing and no smoothing layer, could be used for Ranchero generator armatures in place of PBXN-110, which had been used in all previous Ranchero applications. CT-1 and CT-2 both had 43 cm long slapper detonator systems imbedded in the cast PBXN-110 explosive, but manufacturing a charge for a similar 9501 test was not cost effective. Instead, a single cylinder of 9501, 19.368 cm long and 15.494 cm (6.100”)in diameter, had a groove machined to accommodate a row of 11 SE-1 detonators with 18 mm point spacing along the mid-plane of the cylinder. The expansion of the armature looks like a slapper assembly along almost ½ of the circumference, and provides adequate proof of concept. Removing the smoother from PBXN-110-driven armatures increased the armature velocity from 3.1 mm/μs to 3.3 mm/μs, as seen in CT-2, and the velocity measured on CT-3 increased to 3.8 mm/μs. In addition, the camera records show that the surface of the armature is smooth enough, and free from ruptures for an expansion of greater that 2X. The advantage of using 9501 is that it precludes concerns about blow-outs seen when bubbles are left in the cast material, and gives extra velocity. The disadvantage is that the machined explosives are more expensive.

42 ENGINEERING↗
DOE OSTI2015

Historical Survey: German Research on Hydrogen Peroxide/Alcohol Explosives

Discussion of HP/fuel explosives in the scientific literature dates back to at least 1927. A paper was published that year in a German journal entitled On Hydrogen Peroxide Explosives [Bamberger and Nussbaum 1927]. The paper dealt with HP/cotton/Vaseline formulations, specifically HP89/cotton/Vaseline (76/15/9) and (70/8.5/12.5). The authors performed experiments with charge masses of 250-750 g and charge diameters of 35-45 mm. This short paper provides brief discussion on the observed qualitative effects of detonations but does not report detonation velocities.

45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEF↗
DOE OSTI2016

Air Blasts from Cased and Uncased Explosives

The problem of a spherical blast in air is solved using the STUN code. For bare charges, the calculations are shown to be in excellent agreement with previous published results. It is demonstrated that, for an unconfined (uncased) chemical explosive, both range and time to effect scale inversely as the cube root of the yield and directly as the cube root of the ambient air density. It is shown that the peak overpressure decays to roughly 1/10 of ambient pressure in a scaled range of roughly 10 m/kg 1/3 at sea level. At a height of 30 km, where the ambient density is a factor of 64 less, the range to the same decay increases to 40 m/kg 1/3 . As a direct result of the scaling a single calculation suffices for all charge sizes and altitudes. Although the close-in results are sensitive to the nature of the explosive source and the equation of state of the air, this sensitivity is shown to virtually disappear at scaled ranges > 0.5 m/kg 1/3 .

42 ENGINEERING↗
DOE OSTI2016

Analysis of MINIE2013 Explosion Air-Blast Data

We report analysis of air-blast overpressure measurements from the MINIE2013 explosive experiments. The MINIE2013 experiment involved a series of nearly 70 near-surface (height-ofburst, HOB, ranging from -1 to +4 m) low-yield (W=2-20 kg TNT equivalent) chemical highexplosives tests that were recorded at local distances (230 m – 28.5 km). Many of the W and HOB combinations were repeated, allowing for quantification of the variability in air-blast features and corresponding yield estimates. We measured canonical signal features (peak overpressure, impulse per unit area, and positive pulse duration) from the air-blast data and compared these to existing air-blast models. Peak overpressure measurements showed good agreement with the models at close ranges but tended to attenuate more rapidly at longer range (~ 1 km), which is likely caused by upward refraction of acoustic waves due to a negative vertical gradient of sound speed. We estimated yields of the MINIE2013 explosions using the Integrated Yield Determination Tool (IYDT). Errors of the estimated yields were on average within 30% of the reported yields, and there were no significant differences in the accuracy of the IYDT predictions grouped by yield. IYDT estimates tend to be lower than ground truth yields, possibly because of reduced overpressure amplitudes by upward refraction. Finally, we report preliminary results on a development of a new parameterized air-blast waveform.

45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEF↗
DOE OSTI2017

Notes on the ExactPack Implementation of the DSD Explosive Arc Solver

It has been shown above that the discretization scheme implemented in the ExactPack solver for the DSD Explosive Arc equation is consistent with the Explosive Arc PDE. In addition, a stability analysis has provided a CFL condition for a stable time step. Together, consistency and stability imply convergence of the scheme, which is expected to be close to first-order in time and second-order in space. It is understood that the nonlinearity of the underlying PDE will affect this rate somewhat.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2017

New Source Model for Chemical Explosions

With sophisticated inversion scheme, we recover characteristics of SPE explosions such as corner frequency f c and moment M 0 , which are used to develop a new source model for chemical explosions.

45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEF↗
DOE OSTI2017

Trends in Nuclear Explosion Monitoring Research & Development - A Physics Perspective

This document entitled “Trends in Nuclear Explosion Monitoring Research and Development – A Physics Perspective” reviews the accessible literature, as it relates to nuclear explosion monitoring and the Comprehensive Nuclear-Test-Ban Treaty (CTBT, 1996), for four research areas: source physics (understanding signal generation), signal propagation (accounting for changes through physical media), sensors (recording the signals), and signal analysis (processing the signal). Over 40 trends are addressed, such as moving from 1D to 3D earth models, from pick-based seismic event processing to full waveform processing, and from separate treatment of mechanical waves in different media to combined analyses. Highlighted in the document for each trend are the value and benefit to the monitoring mission, key papers that advanced the science, and promising research and development for the future.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2017

Comparison Between Surf and Multi-Shock Forest Fire High Explosive Burn Models

PAGOSA1 has several different burn models used to model high explosive detonation. Two of these, Multi-Shock Forest Fire and Surf, are capable of modeling shock initiation. Accurately calculating shock initiation of a high explosive is important because it is a mechanism for detonation in many accident scenarios (i.e. fragment impact). Comparing the models to pop-plot data give confidence that the models are accurately calculating detonation or lack thereof. To compare the performance of these models, pop-plots2 were created from simulations where one two cm block of PBX 9502 collides with another block of PBX 9502.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2018

Metallurgical Failure Analysis of A2 Tool Steel Die Set from High Explosive Pellet Pressing Event

On 2 April 2018, a high explosive violent reaction (HEVR) occurred during routine pressing of a 1-in -diameter cylindrical pellet of PBX 9501 high explosive. Fragments of the die set (die body and stemples) involved in the event were sent to Sigma Division for metallurgical analysis. A handheld x-ray fluorescence alloy tester confirmed the die set material to be A2 tool steel. Light optical microscopy revealed what appear to be pre-existing flaws on the inner diameter of the die body. Scanning Electron Microscopy could neither confirm nor exclude the presence of fatigue cracking in the vicinity of these potential flaws. Energy Dispersive Spectroscopy indicated the presence of a carbon-bearing residue on fracture surfaces; nitrogen-bearing residue was also found. Optical microscopy revealed that the microstructure of the stemple and inner diameter of the die body contained large stringers and non-uniform grain size; this was distinct from the relatively clean and uniform microstructure seen at the outer diameter of the die body, and also other A2 tool steel stock (pedigree unknown and with no known connection to any HE pressing hardware) that was examined for additional comparison. Rockwell hardness testing indicated the material was heat treated properly. Metallographic analysis alone could not positively identify the root cause of the event, but, coupled with accounts provided by the operator and the successful history with the particular lot of HE involved in the event, points to ward mechanical failure of the die set due to pre -existing flaw as the most likely precipitating event. Suggestions for additional analyses and future qualification techniques are discussed.

36 MATERIALS SCIENCE↗