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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 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Laboratory-scale Investigation of the Influence of Ageing on the Performance and Sensitivity of an Explosive Containing ϵ-CL-20

Here, the performance and sensitivity of aged composite explosives based on the epsilon polymorph of hexanitrohexaazaisowurtzitane (ϵ–CL–20) have been evaluated with the laser–induced air shock from energetic materials (LASEM) technique using only milligram quantities of material. The LASEM results demonstrated reduced explosive performance (i.e., lower estimated detonation velocities) and higher sensitivity to ignition with increasing ageing. Chemical analysis of the explosive formulation subjected to ambient and accelerated aging was conducted to help understand the LASEM results. The Fourier Transform Infrared (FTIR) spectra revealed no evidence for conversion to lower–energy polymorphs. Based on the desorption gas chromatography/mass spectrometry (D–GC/MS) results, the observed decrease in performance and increase in sensitivity for the explosive powder aged at 100 °C (relative to ambient and 70 °C aging) have been attributed to changes related to solvent inclusions in the molding powders.

45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEF↗
DOE OSTI2018

Analysis of Residual Explosives by Swab Touch Spray Ionization Mass Spectrometry

Swab touch spray ionization mass spectrometry, an ambient ionization technique, has been applied to the analysis of six explosives from various surfaces including glass, metal, Teflon, plastic, human hands and three types of gloves (nitrile, vinyl and latex). A swab, attached to a metallic handle, was used to sample explosive residues and acted as the ion source. The explosives, 1,3,5-trinitro-1,3,5-triazinane (RDX), 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX), and 2,2-bis[(nitrooxy)methyl]propane-1,3-diyl dinitrate (PETN) had an absolute limit of detection of 10 ng from all the surfaces except for PETN from the nitrile gloves (limit of detection 100 ng). Sodium perchlorate, 2-methyl-1,3,5-trinitrobenzene (TNT) and tetra-butylammonium perchlorate had limits of detection of 100 pg, 10 pg, and 1 pg, respectively from all surfaces. This study demonstrates the feasibility of swab touch spray ionization mass spectrometry for detection of a wide array of explosives from a variety of forensically applicable surfaces with disposable, commercial, tamperproof and individually-wrapped conductive swabs without complicated/lengthy sample preparations or extractions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Modelling the Fluctuations of Reactive Shock Waves in Heterogeneous Solid Explosives as Stochastic Processes

Although current phenomenological burn models are useful for describing the average or bulk reactive flow behaviour of heterogeneous explosives, one fundamental weakness inherent to these models is the loss of detailed microstructural information at the scale of the calculation. In order to include the effects of the microstructure, and in particular the underlying material heterogeneities that influence the build-up to detonation, a new paradigm is put forth for modelling sub-grid, reaction-induced fluctuations (i.e. “hot spots”) at the continuum level. This modelling approach assumes that the reaction rate is stochastic, rather than deterministic, and it uses Langevin-type equations with a mathematical framework built upon Itô calculus and Lambourn's CIM model for shocked heterogeneous explosives. This approach follows directly from our previous letter, Ref. [1], and is inspired by the probability density function (pdf) methods used in turbulent reactive flows. Here, the stochastic burn model is derived, implemented, and exercised far beyond what has been shown in previous work. New hydrocode simulation results demonstrate the role of stochastic fluctuations during shock initiation; these fluctuations are approximated by collections of discrete particles, that evolve with drift (i.e. deterministic) and diffusion (i.e. stochastic) coefficients. Furthermore, the particle values are propagated and averaged to calculate the heat release, yield strength, and material impedance in each computational cell. Hydrocode simulation results further show how the fluctuating hot spot energy may or may not be transmitted to the wave front, and result in a detonation wave-like structure. The fundamental stochastic nature of this model permits simulations to have varying outcomes with the same initial conditions; this allows for go/no-go estimation (e.g., marginal or failed detonations), which might possibly be calibrated using the statistical distributions from real materials. Mesoscale calculations of shocked heterogeneous explosives also show that these fluctuations are physically justified (i.e., Ref. [2]), and it is hypothesized that the pdf functions provide a link between the meso(grain) and continuum scales for practical engineering calculations. Hence, our approach is a paradigm shift for building efficient, reduced order continuum burn models, that represent the sub-grid stochastic behaviour of shocked heterogeneous solid explosives.

42 ENGINEERING↗
DOE OSTI2019

Hot Spot Chemistry in Several Polymer-Bound Explosives under Nanosecond Shock Conditions

Initial hot spot temperatures and temperature evolutions for 4 polymer-bound explosives under shock compression by laser-driven flyer plates at speeds from 1.5–4.5 km s -1 are presented. A new averaging routine allows for improved signal to noise in shock compressed impactor experiments and yields temperature dynamics which are more accurate than has been previously available. The PBX formulations studied here consist of either pentaerythritol tetranitrate (PETN), 1,3,5-trinitro-1,3,5-triazinane (RDX), 2,4,6-trinitrotoluene (TNT), or 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) in a 80/20 wt.% mixture with a silicone elastomer binder. The temperature dynamics demonstrate a unique shock strength dependence for each base explosive. The initial hot spot temperature and its evolution in time are shown to be indicative of chemistry occurring within the reaction zone of the four explosives. The number density of hot spots is qualitatively inferred from the spatially-averaged emissivity and appears to increase exponentially with shock strength. An increased emissivity for formulations consisting of TNT and TATB is consistent with carbon-rich explosives and in increased hot spot volume. Finally, qualitative conclusions about sensitivity were drawn from the initial hot spot temperature and rate at which the number of hot spots appear to grow.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Cookoff of Powdered and Pressed Explosives using a Micromechanics Pressurization Model

Cookoff experiments of powdered and pressed TATB-based plastic bonded explosives (PBXs) have been modeled using a pressure-dependent universal cookoff model (UCM) in combination with a micromechanics pressurization (MMP) model described in a companion paper. The MMP model is based on the accumulation of decomposition gases at nucleation sites that load the surrounding TATB crystals and binder. This is the first cookoff model to use an analytical mechanics solution for compressibility and thermal expansion to describe internal pressurization caused by both temperature and decomposition occurring within closed-pore explosives. This approach produces more accurate predictions of ignition time and pressurization within high-density explosives than simple equation-of-state models. The current paper gives details of the reaction chemistry, model parameters, predicted uncertainty, and validation using experiments from multiple laboratories with errors less than 6 %. The UCM/MMP model framework gives more accurate thermal ignition predictions for high density explosives that are initially impermeable to decomposition gases.

45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEF↗
DOE OSTI2024

In the nuclear explosion monitoring context, what is an anomaly?

Abstract In the early years of nuclear explosion monitoring, experts used downwind detections with meaningful ratios of radioactive species to identify an explosion. Today’s reality is sparse networks of radionuclide monitoring stations looking for weak signals. Analysts need to discriminate between industrial background radioactivity and nuclear explosion signals, even using the detection of one isotope. Aerosol and xenon measurements potentially related to nuclear tests in 2006 and 2013 announced by the Democratic People’s Republic of Korea and from worldwide civilian background radioactivity are considered when defining radionuclide detection anomalies to objectively guide the use of limited analyst resources and reduce the possibility of not detecting nuclear explosions.

Miley, Harry S.↗
DOE OSTI2026

A comparison of long-term 37 Ar and 39 Ar transport and implications for 39 Ar as a persistent indicator of underground nuclear explosions

Measurements were first made in 2016 of legacy 39 Ar gas from the decades-old Barnwell underground nuclear explosion site within the Nevada National Security Site. This has raised the question of the ubiquity of the radionuclide 39 Ar following underground nuclear explosions in general locations. This article presents a high-level evaluation of the scientific case for using 39 Ar as a long-term indicator of underground nuclear explosions. Assessment is made based on a broad set of assumptions to reasonably estimate the persistence of 39 Ar in the subsurface environment following an explosion to establish potential detectability years to decades after the originating event.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2017

Ion Mobility Spectrometry - High Resolution LTQ-Orbitrap Mass Spectrometry for Analysis of Homemade Explosives

The detailed chemical characterization of homemade explosives (HMEs) and other chemicals that can mimic or mask the presence of explosives is important for understanding and improving the performance of commercial instrumentation used for explosive detection. To that end, an atmospheric-pressure drift tube ion mobility spectrometry (IMS) instrument has been successfully coupled to a commercial tandem mass spectrometry (MS) system. The tandem MS system is comprised of a linear ion trap and a high resolution Orbitrap analyzer. This IMS-MS combination allows extensive characterization of threat chemical compounds, including HMEs, and complex real-world background chemicals that can interfere with detection. Here, the composition of ion species originating from a specific HME, erythritol tetranitrate, has been elucidated using accurate mass measurements, isotopic ratios, and tandem MS. Gated IMS-MS and high-resolution MS have been used to identify minor impurities that can be indicative of the HME source and/or synthesis route. Comparison between data obtained on the IMS/MS system and on commercial stand-alone IMS instruments used as explosive trace detectors (ETDs) has also been performed. Such analysis allows better signature assignments of threat compounds, modified detection algorithms, and improved overall ETD performance. .

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2018

Combined curing as a novel approach to improve resistance of ultra-high performance concrete to explosive spalling under high temperature and its mechanical properties

Highlights: • The combined curing can significantly enhance the resistance of UHPC to explosive spalling under high temperature. • The combined curing can improve the mechanical properties of UHPC remarkably. • Both further hydration of residual cement and pozzolanic reaction are activated under a high temperature steam condition. - Abstract: The influence of a combined curing composed of precuring in hot water and heating in dry air on mechanical properties and explosive spalling of ultra-high performance concrete (UHPC) subjected to high temperature was investigated in this experiment. Meanwhile, the microstructure of UHPC was determined by means of X-ray diffraction (XRD) with Rietveld method, thermogravimetric analysis (TGA), scanning electron microscope (SEM) and mercury intrusion porosimetry (MIP). The results indicate that the combined curing improves the mechanical properties of UHPC remarkably. More importantly, it is quite efficient to enhance the resistance of UHPC to explosive spalling under high temperature, which should be a novel approach to prohibit spalling occurrence, different from adding polypropylene fiber. During dry air heating in the combined curing, a high temperature steam environment is established in the dense structure framework of UHPC formed in the preceding hot water curing. Both further hydration of residual cement and pozzolanic reaction of mineral admixtures can be activated during the dry air heating, leading to not only the formation of a large amount of dense hydrates (such as C-S-H gels, katoite, tobermorite and xonotlite, etc.), which accumulate in the aforementioned existing framework, but also the consumption of most of internal free water. Therefore, both mechanical properties of UHPC and its resistance to explosive spalling under high temperature can be enhanced significantly.

36 MATERIALS SCIENCE↗
DOE OSTI2025

A novel ignition model for low velocity impact of heterogeneous explosives based on interacting hot spots

While numerous studies have focused on the ignition of explosives occurring in high velocity impact and the associated shock-to-detonation transition, there has been growing interest in developing computational models focused on low-velocity impact regimes. A predictive low-velocity impact ignition model will be important for analyzing high explosive safety and potential accident scenarios. This work introduces a novel ignition model based on the concept of thermally interacting hot spots to simulate low velocity impacted heterogeneous explosives where observed ignition times are on the order of milliseconds. The model asserts that relevant hot spots are micron-sized, the typical separation between neighboring hot spots is on the order of a hundred microns, and that neighbors interact thermally through heat conduction across the interstitial region between them. To achieve tractable numerical solutions, hot spots are assumed to form a periodic array as opposed to the highly irregular positioning in an actual explosive. This idealization allows a single two hotspot system to characterize the ignition process. Consequently, the model is referred to as the two hot spot Frank-Kamenetskii ignition model. In the present study, hot spots are modeled as constant heat sources terms, but this can be extended to include grain-scale phenomena like frictional heating of micron-sized growing cracks that are confined under high pressure. Because the micron-sized features are below the scale that can be efficiently resolved at a systems level, an efficient subscale scheme based on the Method of Weighted Residuals (MWR) is used to efficiently solve the equations. In conclusion, we carry out numerical examples and analytic predictions illustrating the accuracy and the functioning of the model.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2018

Formation of intermetallic structures at the interface of steel-to-aluminium explosive welds

Highlights: • The interface of Fe-Al explosive welds was characterised by SEM/EDS and EBSD. • The intermetallics formed at the weld interface are rich in Al (Fe{sub 4}Al{sub 13}, Fe{sub 2}Al{sub 5}). • The presence of intermetallic phases on the interface deeply affects the weldability. • Al-rich intermetallics increase the solidification time of the weld interface. - Abstract: The formation of intermetallic structures at the interface of carbon steel to 6082 aluminium alloy explosive welds and their influence on the weldability of these two materials were studied. The morphology, the microstructure, the chemical and phase compositions of the welds were characterised by several types of microscopy techniques. The interface characterisation proved that explosive mixtures with a lower detonation velocity were revealed as being more suitable for achieving consistent welds since jet entrapment was prevented and continuous molten layers were not formed at the weld interface. It was also found that the physical properties of the intermetallic phases generated at the weld interface have a strong influence on the weldability of steel-to-aluminium explosive welds. Specifically, it was shown that the formation of aluminium-rich intermetallic phases at the weld interface increases the solidification time of the interfacial molten material, decreasing the weldability of these two materials. The formation of these intermetallic compounds should be avoided by reducing the interaction between the flyer and the baseplate as well as by avoiding excessive molten layers.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Single-Atom Doping at the Molecule–Metal Interface: How Rh Affects Surface Explosion Kinetics

Controlling chemical reactions at interfaces is central to many fields, including atmospheric, environmental, and biological chemistry as well as catalysis and corrosion. We performed a fundamental study of how catalytically active Rh atoms placed at and above a molecule-metal interface influence the surface reaction kinetics of tartaric acid (TA) decomposition. Specifically, TA decomposition on Cu(100) exhibits autocatalytic decomposition kinetics involving a slow initiation step followed by fast decomposition of the molecular layer. These so-called “surface explosions” are extremely sensitive to initial conditions, making it fundamentally interesting to study how the placement of reactive atoms affects the reaction rate. Temperature-programmed reaction (TPR) experiments reveal that Rh atoms embedded in the Cu(100) surface beneath TA (TA/Rh/Cu) or atop the TA layer (Rh/TA/Cu) reduce the decomposition temperature and modify the reaction rate constants. Isothermal TPR analysis reveals that Rh enhances both the initiation rate constant, k i , and the explosion rate constant, k e , facilitating explosive decomposition at lower temperatures. This result provides evidence that both the initiation and explosion steps occur at the metal-molecule interface and are accelerated by the presence of Rh at this interface. This study illustrates how small amounts of reactive elements may be used to control nonlinear kinetic processes at interfaces.

desorption↗
DOE OSTI2025

An In Situ , Automated High-Explosives Aging Method Utilizing Two-Dimensional Gas Chromatography–Mass Spectrometry

Understanding chemical changes that occur in high explosives as they age is of great importance to the safe employment and storage of these compounds. Traditional methods of aging high explosives even under accelerated aging conditions are time intensive with durations on the order of months to years. The nature of traditional aging analyses reduces each sample to a snapshot data point often separated widely in time, requiring many assumptions as to how the degradation products develop. Further complicating matters, several analytical techniques are typically employed for each sample analysis in order to ascertain an entire picture of the decomposition pathways. To address these shortcomings with existing methods, a new method of accelerated aging of high explosives utilizing comprehensive two-dimensional gas chromatography coupled to high-resolution mass spectrometry (GC × GC-HRMS) was developed using 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) as a model compound for method development. This in situ automated method reduces the time scale of aging to a matter of hours using the inlet of the GC × GC as the aging vessel. GC × GC in combination with HRMS allowed for the collection of both evolved gases and other decomposition products produced during the entire aging process in real time with HRMS providing far greater certainty in identification of explosives aging products. Additionally, this method allowed for a higher throughput of samples with greatly simplified sample preparation. Chemometric analysis of the GC × GC-HRMS data set via the alteration analysis (ALA) enabled discovery of statistically significant chemical changes providing insight into the variation of decomposition pathways with varying aging temperatures.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Discriminating Underground Nuclear Explosions Leading To Late-Time Radionuclide Gas Seeps

Utilizing historical data from the U.S. nuclear test program and freely available barometric pressure data, we performed an analytical barometric-pumping efficiency analysis to determine factors resulting in late-time radionuclide gas seeps from underground nuclear explosions. In this work, we considered 16 underground nuclear explosions with similar geology and test setup, of which five resulted in the measurement of late-time radionuclide gas concentrations at the ground surface. Additionally, the factors we considered include barometric frequency and amplitude, depth of burial, air-filled porosity, intact-rock permeability, fracture aperture, and fracture spacing. The analysis indicates that the best discriminators of late-time radionuclide gas seeps for these explosions are barometric frequency and amplitude and air-filled porosity. While geologic information on fracture aperture and spacing is not available for these explosions, the sensitivity of barometric-pumping efficiency to fracture aperture indicates that it would likely also be a good discriminator.

58 GEOSCIENCES↗
DOE OSTI2023

Global Nuclear Explosion Discrimination Using a Convolutional Neural Network

Using P-wave seismograms, we trained a seismic source classifier using a Convolutional Neural Network. We trained for three classes: earthquake P-wave, underground nuclear explosion (UNE) P-wave, and noise. With the current absence of nuclear testing by countries that have signed the Comprehensive Test Ban Treaty, high quality seismic data from UNEs is limited. Even with limited training data, our model can accurately characterize most events recorded at regional and teleseismic distances, finding over 95% signals in the validation set. We applied the model on holdout datasets of the North Korean test explosions to evaluate the performance on unique region and station-source pairs, with promising results. Additionally, we tested on the Source Physics Experiment events to investigate the potential for chemical explosions to act as a surrogate for nuclear explosions. We anticipate that machine-learning models like our classifier system can have broad application for other seismic signals including volcanic and non-volcanic tremor, anomalous earthquakes, ice-quakes or landslide-quakes.

58 GEOSCIENCES↗
DOE OSTI2026

Predicting multiphase flow and tracer transport for an underground chemical explosive test

Detecting radionuclide gas seepage from clandestine underground nuclear tests is central to nonproliferation explosion monitoring research. Yet, early-time (<6 day) gas transport driven by the explosive pressure wave remains poorly constrained due to scarcity of field data. We simulate multi-phase gas transport in the vadose zone using pre-shot data from a recent chemical explosion in P-Tunnel at the Nevada National Security Site, USA. Despite using a simplified 2D-radial model, predictions of tracer arrival matched observations within one order-of-magnitude. Our results show how transient blast forcing rapidly mobilizes gases from the cavity into surrounding rock – critical for optimizing sensor placement and test planning. This unique integration of field data and modeling represents a significant improvement in our ability to predict gas migration from underground explosions. More broadly, it offers insights into the coupled dynamics of pressure waves and contaminant transport in the vadose zone, with implications for monitoring and hazard assessment.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2019

X-ray radiography of the overheating instability in underwater electrical explosions of wires

We introduce the measurements of the development of striation like instabilities during the electrical driven explosions of wires in a water bath. In vacuum based wire explosion experiments, such instabilities have long been known. Yet, in spite of intense research into the explosion of wires in liquids, the development of these instabilities has either not been observed or has been assumed to play a minor role in the parameters of the exploding wire due to the tamping of the wire's explosion. Using synchrotron based multiframe radiography, we have seen the development of platelike density structures along an exploding copper wire. Our measurements were compared to a 2D magnetohydrodynamics simulation, showing similar striation formation. These observed instabilities could affect the measurements of the conductivity of the wire material in the gas-plasma state—an important parameter in the warm dense matter community. The striations could also act as a seed for other instabilities later in time if the wire is in a dense flow of material or experiences a shock from an adjacent wire—as it would do in experiments with arrays of wires.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2019

Scaled experiments on cavity confined explosions in limestone and poly(methyl methacrylate)

A scaled experiment comprising a laser-driven explosion in a cavity is used to characterize the coupling of mechanical energy into the surrounding solid material. Experiments are performed using poly(methyl methacrylate) and dry Salem limestone as the explosion containment blocks materials, in which are milled scaled spherical cavities of various dimensions. Measurements of the coupled shock, taken with fiber optic probes at the cavity wall, show the critical radius where wall deformation transitions from plastic to elastic deformation. These measurements also provide a diagnostic of the air blast, which is validated against GEODYN simulation code. The measurement of the coupled shock amplitude taken farther from the wall in the linear region indicates increased coupling efficiency in small cavities over the range of scaled cavity radii from 6 to 20 m/kt 1/3 , a phenomenon not previously observed in experiments. A comparison of results taken in this experiment with a parallel experiment using high explosive (HE) as the source shows that coupled shocks generated with HE are characteristically different with much larger amplitude than those produced by a high energy density laser-driven source with the same yield. This experimental technique potentially provides a rapid and cost-effective method to analyze the consequences of a full-scale, low yield, buried explosion.

58 GEOSCIENCES↗