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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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Shock Response of Polymethyl Methacrylate (PMMA) Under Explosive Loading

Abstract The dynamic response of polymethyl methacrylate (PMMA) is well understood for one-dimensional planar impact shocks, but limited research has been performed on the response of PMMA under spherical shock loading. In this work, the shock decay of an explosively-driven shock wave into PMMA was experimentally measured. PMMA cubes of various geometries were explosively loaded with an RP-80 detonator to produce the explosive shock wave. High-speed schlieren imaging was implemented to measure the explosively-driven shock wave velocity throughout the PMMA cubes. Photon Doppler velocimetry (PDV) was used to measure the particle velocity imparted by the shock wave at the surface of the cubes. The material shock response was studied at distances from 21.91 to 133.3 mm from the explosive source. The particle velocity history measured by PDV was compared to the wave profile visualized in the high-speed images. The shock wave pulse amplitude decreased with increased distance from the source. The conducted experiments extend the PMMA shock Hugoniot relating to the lower shock and particle velocity regime.

Torres, S. M. (ORCID:0009000287177206)↗
NASA NTRS1977

Cratering motions and structural deformation in the rim of the Prairie Flat multiring explosion crater

Cratering motions and structural deformation are described for the rim of the Prairie Flat multiring crater, 85.5 m across and 5.3 m deep, which was formed by the detonation of a 500-ton TNT surface-tangent sphere. The terminal displacement and motion data are derived from marker cans and velocity gages emplaced in drill holes in a three-dimensional matrix radial to the crater. The integration of this data with a detailed geologic cross section, mapped from deep trench excavations through the rim, provides a composite view of the general sequence of motions that formed a transiently uplifted rim, overturned flap, inverted stratigraphy, downfolded rim, and deformed strata in the crater walls. Preliminary comparisons with laboratory experimental cratering and with numerical simulations indicate that explosion craters of the Prairie Flat-type generated by surface and near-surface energy sources tend to follow predictable motion sequences and produce comparable structural deformation. More specifically, central uplift and multiring impact craters with morphologies and structures comparable to Prairie Flat are inferred to have experienced similar deformational histories of the rim, such as uplift, overturning, terracing, and downfolding.

Roddy, D. J.↗
NASA NTRS2010

Ignition-and-Growth Modeling of NASA Standard Detonator and a Linear Shaped Charge

The main objective of this study is to quantitatively investigate the ignition and shock sensitivity of NASA Standard Detonator (NSD) and the shock wave propagation of a linear shaped charge (LSC) after being shocked by NSD flyer plate. This combined explosive train was modeled as a coupled Arbitrary Lagrangian-Eulerian (ALE) model with LS-DYNA hydro code. An ignition-and-growth (I&G) reactive model based on unreacted and reacted Jones-Wilkins-Lee (JWL) equations of state was used to simulate the shock initiation. Various NSD-to-LSC stand-off distances were analyzed to calculate the shock initiation (or failure to initiate) and detonation wave propagation along the shaped charge. Simulation results were verified by experimental data which included VISAR tests for NSD flyer plate velocity measurement and an aluminum target severance test for LSC performance verification. Parameters used for the analysis were obtained from various published data or by using CHEETAH thermo-chemical code.

Oguz, Sirri↗
NASA NTRS2022

Simultaneous 100-kHz Acetone Planar Laser-Induced Fluorescence and OH* Chemiluminescence in a Linear Non-Premixed Detonation Channel

Reactant mixing and combustion are investigated in an optically accessible, self-excited linear detonation combustor. The mixing field is captured using 100 kHz planar laser-induced fluorescence (PLIF) imaging of acetone as a tracer in the fuel supply, while 100 kHz chemiluminescence imaging of excited-state hydroxyl (OH*) radicals simultaneously resolves the evolution of the detonation wave. Time sequences are acquired over multiple detonation cycles in each test, with acetone-PLIF images collected along multiple orthogonal planes to reveal the complex three-dimensional topography of the fuel distribution. The instantaneous and phase averaged acetone-PLIF images enable measurement of key fuel injection characteristics, such as the injector recovery time, fuel jet velocity, and refill height for a range of operating conditions. Instantaneous and phase-averaged measurements of acetone-PLIF with the time-coincident OH* chemiluminescence images also reveal a number key features, such as fuel stratification and weak detonation in the injector near field, incomplete combustion and deflagration behind the detonation wave, vitiation and deflagration of reactants ahead of the detonation wave, and fuel and oxidizer recovery time mismatch leading to combustion inefficiency. These measurements significantly enhance the ability to obtain detailed information on the intracycle and intercycle spatiotemporal evolution of the reactant refill process and its coupled effects on the detonation wave structure and propagation.

Propulsion↗
DOE OSTI2020

Three-dimensional microstructure-explicit and void-explicit mesoscale simulations of detonation of HMX at millimeter sample size scale

Fully three-dimensional (3D) microstructure-explicit and void-explicit mesoscale simulations of the shock-to-detonation (SDT) process of pressed granular HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine) are performed. The overall size scale of the models is up to 3 × 3 × 15 mm3, with ∼30 000 grains and 206 265 voids. The models account for the heterogeneous material microstructure, constituent distribution, constituent morphology, and voids. Loading conditions considered involve piston velocities in the range of 600–1200 m/s or pressures in the range of 4–8 GPa. The focus is on analyzing the SDT process and the effects of microstructure and voids on the run-to-detonation distance (RDD). Companion two-dimensional (2D) simulations are also carried out to assess the differences between 2D and 3D. Statistically equivalent microstructure sample sets (SEMSSs) are generated and used for both 2D and 3D, allowing the prediction of the statistical and probabilistic Pop plots (PPs). The predictions are in general agreement with trends in available experimental data in the literature. It is found that both the microstructure (heterogeneous grain size, morphology, and size distribution) and voids significantly affect the RDD and the PPs. These effects are systematically delineated and quantified via the use of SEMSSs with different combinations of attributes. A recently developed probabilistic formulation for the PPs is used to characterize the results, allowing uncertainties in the relations between the shock pressure and RDD arising from material heterogeneities to be quantified. The probabilistic formulation is further used to quantify the confidence levels in the ranked order of influences of different combinations of microstructure and voids on the PPs.

Miller, Christopher (ORCID:0000000206844381)↗
NASA NTRS1982

A critical velocity interaction between fast barium and strontium atoms and the terrestial ionospheric plasma

A disk of barium and strontium vapor traveling radially outward, perpendicular to the geomagnetic field lines, may be created by the detonation of a high-explosive, radially shaped charge with a liner composed of the two metals in the upper atmosphere. Because of solar radiation resonance, both the barium and the strontium may be optically tracked. Observations indicate the early formation of the metal ions thus evolved into a disk-shaped, stellate structure with a dark hole at the center of a radial structure. The results of these experiments indicate that the process could occur on a cosmic scale, and that unconfirmed aspects of the theory relating to this process could be determined through variation of the parameters in future radial rocket experiments.

Deehr, C. S.↗
DOE OSTI2025

Seismic DAS Observations of a large underground chemical explosion in dry tuff

On 18 October 2023 a 16.3-ton TNT equivalent chemical explosion was detonated underground at the Nevada National Security Site, generating a seismic event (Meyers et al., 2024). The associated seismic wavefield was measured on a Distributed Acoustic Sensing (DAS) array with slant range distances from 27 m – 1123 m. The first arriving phase traveled at an apparent velocity of about 2640 m s -1 from 27 m to 420 m slant range and about 2470 m s -1 from 505 m to 1123 m slant range according to the first arrival moveouts on the DAS data. The first arrival from the explosion temporarily saturated the cable from a slant range of 27 m – 186 m and 0.009 s to 0.084 s post detonation. From 186 m slant range to 420 m slant range, peak strain rates of 5.6 x 10 6 nm m -1 s -1 were observed for the first arrival phase. For the first arrival from 505 m slant range to 1123 m slant range, peak strain rates reduced to 8.0 x 10 4 nm m -1 s -1 . A comparison of the scaled accelerations computed from DAS, the geophone pairs, and the measurements of co-located accelerometer pairs show common agreement at the scaled ranges of the single point sensors. This study adds to the body of work reporting near-source DAS observations of the seismic wavefields generated by underground chemical explosions. These results indicate that near-source DAS observations can refine interpretations of phase identification from single-point sensor observations. Phase identification could be one mechanism that contributes scatter to single point seismic measurements which would confound the performance of empirical relationships for small explosions. Removing that mechanism may therefore reduce interstation variability and increase empirical relationship performance for small explosions.

45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEF↗
NASA NTRS1976

A stop-restart solid propellant study with salt quench

Experiments were conducted to gain insight into the unsatisfactory performance of the salt quench system of solid propellants in earlier studies. Nine open-air salt spray tests were conducted and high-speed cinematographic coverage was obtained of the events. It is shown that the salt spray by the detonator is generally a two-step process yielding two different fractions. The first fraction consists of finely powdered salt and moves practically unidirectionally at a high velocity (thousand of feet per second) while the second fraction consists of coarse particles and moves randomly at a low velocity (a few feet per second). Further investigation is required to verify the speculation that a lower quench charge ratio (weight of salt/propellant burning area) than previously employed may lead to an efficient quench

Kumar, R. N.↗
NASA NTRS1987

Pulsed source of energetic atomic oxygen

A pulsed high flux source of nearly monoenergetic atomic oxygen was designed, built, and successfully demonstrated. Molecular oxygen at several atmospheres pressure is introduced into an evacuated supersonic expansion nozzle through a pulsed molecular beam valve. An 18 J pulsed CO2 TEA laser is focused to intensities greater than 10(9) W/sq cm in the nozzle throat to generate a laser-induced breakdown. The resulting plasma is heated in excess of 20,000 K by a laser supported detonation wave, and then rapidly expands and cools. Nozzle geometry confines the expansion to provide rapid electron-ion recombination into atomic oxygen. Average O atom beam velocities from 5 to 13 km/s were measured at estimated fluxes to 10(18) atoms per pulse. Preliminary materials testing has produced the same surface oxygen enrichment in polyethylene samples as obtained on the STS-8 mission. Scanning electron microscope examinations of irradiated polymer surfaces reveal an erosion morphology similar to that obtained in low Earth orbit, with an estimated mass removal rate of approx. 10(-24) cu cm/atom. The characteristics of the O atom source and the results of some preliminary materials testing studies are reviewed.

Caledonia, George E.↗
DOE OSTI2025

Seismic DAS observations of a large underground chemical explosion in dry tuff

On 18 October 2023 a 16.3-ton TNT equivalent chemical explosion was detonated underground at the Nevada National Security Site, generating a seismic event with a magnitude of 1.7 (Meyers et al., 2024). The associated seismic wavefield was measured on a Distributed Acoustic Sensing (DAS) array with slant range distances from 27 m – 1123 m. The first arriving phase traveled at an apparent velocity of about 2640 m s -1 from 27 m to 420 m slant range and about 2470 m s -1 from 505 m to 1123 m slant range according to the first arrival moveouts on the DAS data. The first arrival from the explosion temporarily saturated the cable from a slant range of 27 m – 186 m and 0.009 s to 0.084 s post detonation. From 186 m slant range to 420 m slant range, peak strain rates of 5.6 x 10 6 nm m -1 s -1 were observed for the first arrival phase. For the first arrival from 505 m slant range to 1123 m slant range, peak strain rates reduced to 8.0 x 104 nm m -1 s -1 . A comparison of the scaled accelerations computed from DAS, the geophone pairs, and the measurements of co-located accelerometer pairs show common agreement at the scaled ranges of the single point sensors. This study adds to the body of work reporting near-source DAS observations of the seismic wavefields generated by underground chemical explosions. These results indicate that near-source DAS observations can refine interpretations of phase identification from single-point sensor observations. Phase identification could be one mechanism that contributes scatter to single point seismic measurements which would confound the performance of empirical relationships for small explosions. Removing that mechanism may therefore reduce interstation variability and increase empirical relationship performance for small explosions.

58 GEOSCIENCES↗
NASA NTRS1973

Nearly spherical constant power detonation waves driven by focused radiation

Shape and inner flow of a tridimensional spark are studied. The spark is created by focusing a laser beam in a gas. A second order fully non-linear equation is derived for the radial velocity on the axis of symmetry in the neighborhood of the origin. Solutions to that equation display the existence of a forbidden region near the focus, thus indicating the limits of applicability of a small perturbation solution.

George, Y. H.↗
DOE OSTI2020

The Young and Nearby Normal Type Ia Supernova 2018gv: UV-optical Observations and the Earliest Spectropolarimetry

The nondetection of companion stars in SN Ia progenitor systems lends support to the notion of double-degenerate systems and explosions triggered by the merging of two white dwarfs. This very asymmetric process should lead to a conspicuous polarimetric signature. By contrast, observations consistently find very low continuum polarization as the signatures from the explosion process largely dominate over the pre-explosion configuration within several days. Critical information about the interaction of the ejecta with a companion and any circumstellar matter is encoded in the early polarization spectra. In this study, we obtain spectropolarimetry of SN 2018gv with the ESO Very Large Telescope at -13.6 days relative to the B-band maximum light, or ~5 days after the estimated explosion—the earliest spectropolarimetric observations to date of any SN Ia. These early observations still show a low continuum polarization (lesssim0.2%) and moderate line polarization (0.30% ± 0.04% for the prominent Si ii λ6355 feature and 0.85% ± 0.04% for the high-velocity Ca component). The high degree of spherical symmetry implied by the low-line and continuum polarization at this early epoch is consistent with explosion models of delayed detonations and is inconsistent with the merger-induced explosion scenario. Finally, the dense UV and optical photometry and optical spectroscopy within the first ~100 days after the maximum light indicate that SN 2018gv is a normal SN Ia with similar spectrophotometric behavior to SN 2011fe.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS2016

Rapidly Rising Transients in the Supernova - Superluminous Supernova Gap

We present observations of four rapidly rising (t(sub rise) approximately equals 10 days) transients with peak luminosities between those of supernovae (SNe) and superluminous SNe (M(sub peak) approximately equals -20) - one discovered and followed by the PalomarTransient Factory (PTF) and three by the Supernova Legacy Survey. The light curves resemble those of SN 2011kl, recently shown to be associated with an ultra-long-duration gamma-ray burst (GRB), though no GRB was seen to accompany our SNe. The rapid rise to a luminous peak places these events in a unique part of SN phase space, challenging standard SN emission mechanisms. Spectra of the PTF event formally classify it as an SN II due to broad H alpha emission, but an unusual absorption feature, which can be interpreted as either high velocity H alpha (though deeper than in previously known cases) or Si II (as seen in SNe Ia), is also observed. We find that existing models of white dwarf detonations, CSM interaction, shock breakout in a wind (or steeper CSM), and magnetar spin down cannot readily explain the observations. We consider the possibility that a Type 1.5 SN scenario could be the origin of our events. More detailed models for these kinds of transients and more constraining observations of future such events should help to better determine their nature.

SNLS06D1hc↗
DOE OSTI2023

The reactive flow evolution of the polymer-bonded explosive PBX 9502: Experiments and model validation in extreme pressure regimes

The shock-to-detonation transition properties of the triaminotrinitrobenzene based PBX 9502 high explosive (HE) are experimentally and computationally explored in extremely high input pressure conditions. These include both slightly sub-Chapman–Jouguet and overdriven input pressure conditions, namely, ∼25 and ∼31 GPa, respectively. Our experiments capture the transient buildup of a shock-induced reaction via measurement of HE and polymethyl methacrylate window interface particle velocity profiles for a variety of sample thicknesses for this insensitive HE. These observations necessitate extremely thin explosive samples, and the high rates of reaction provide a considerable challenge to optical diagnostics. Samples at these thicknesses also provide an opportunity for evaluation of potential micro-structure effects on the resulting shock-to-detonation-transition measurements. To address this, the thin samples are also characterized via x-ray micro-computed tomography. Finally, a pair of previously established continuum-level detonation performance modeling approaches for PBX 9502 were used to analyze the experiments. The employed model variants crucially differ in their definition of each model’s empirical reaction rate functional form, utilization of shock state quantities, and local flow variable dependencies. As a result, the present experiments provide a novel platform to evaluate the quantitative and qualitative consequences stemming from these modeling choices in a challenging initiation scenario, largely beyond the chosen calibration range of either model. This new experimental information will provide a platform for both improved physics and model parameterizations for this well-studied explosive.

36 MATERIALS SCIENCE↗
NASA NTRSDate not supplied

Experimental and Computational Analysis of a Rotating Detonation Combustor

Rotating detonation combustor (RDC) research has progressed along parallel experimental and computational paths with limited opportunities for validation. Validation is a crucial step to ensure RDC simulations provide an accurate representation of the physical phenomena, and thus, can be used with confidence for design optimization in different applications. In this study, data from a quasi-two-dimensional computational fluid dynamic simulation in an annular RDC are compared with experimental measurements including particle image velocimetry at 100 kHz. Results show good agreement between measured and simulated dynamic pressures, Chapman-Jouguet speeds, and static pressure distributions. Velocity measurements at the annulus exit show good temporal and quantitative agreement with simulations including spikes from the passing shock.

Detonation↗
DOE OSTI2023

Chapman–Jouguet deflagration criteria and compressibility dynamics of turbulent fast flames for turbulence-induced deflagration-to-detonation transition

This work characterizes the compressibility dynamics in turbulent fast flames for a range of turbulent flame speeds. These turbulent fast flames experience increased effects of compressibility through the formation of strong shocks and may develop a runaway acceleration combined with a pressure buildup that leads to turbulence induced deflagration-to-detonation transition (tDDT). Simultaneous high-speed particle image velocimetry, OH* chemiluminescence, schlieren, and pressure measurements are used to examine the reacting flow field and flame dynamics. We examine flames with turbulent flame speeds ranging from 100 to 600 m/s. At lower turbulent flame speeds, the flame is not able to produce favorable background conditions for deflagration-to-detonation transition (DDT) onset, and thus flame compressibility and turbulence amplification are less dominant, resulting in a weaker acoustic coupling between the flame and compressed region. As the turbulent burning velocities exceed the Chapman–Jouguet deflagration speed, favorable background conditions are produced, as we observe flame-generated shocks and flame-generated turbulence with higher turbulent velocities and larger turbulent scales. At this regime, the flame is categorized to be at the runaway transition regime that leads to tDDT.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS1991

Demonstration of Hazardous Hypervelocity Test Capability

NASA Johnson Space Center (JSC) White Sands Test Facility (WSTF) participated in a joint test program with NASA JSC Hypervelocity Impact Research Laboratory (HIRL) to determine if JSC was capable of performing hypervelocity impact tests on hazardous targets. Seven pressurized vessels were evaluated under hypervelocity impact conditions. The vessels were tested with various combinations of liquids and gasses at various pressures. Results from the evaluation showed that vessels containing 100-percent pressurized gas sustained more severe damage and had a higher potential for damaging nearby equipment, than vessels containing 75-percent liquid, 25-percent inert pressurized gas. Two water-filled test vessels, one of which was placed behind an aluminum shield, failed by bulging and splitting open at the impact point; pressure was relieved without the vessel fragmenting or sustaining internal damage. An additional water-filled test vessel, placed a greater distance behind an aluminum shield, sustained damage that resembled a shotgun blast, but did not bulge or split open; again, pressure was relieved without the vessel fragmenting. Two test vessels containing volatile liquids (nitro methane and hydrazine) also failed by bulging and splitting open; neither liquid detonated under hypervelocity test conditions. A test vessel containing nitrogen gas failed by relieving pressure through a circular entry hole; multiple small penetrations opposite the point of entry provided high velocity target debris to surrounding objects. A high-pressure oxygen test vessel fragmented upon impact; the ensuing fire and high velocity fragments caused secondary damage to surrounding objects. The results from the evaluation of the pressurized vessels indicated that JSC is capable of performing hypervelocity impact tests on hazardous targets.

Rodriquez, Karen M.↗
DOE OSTI2021

Simulation of flame acceleration and deflagration-to-detonation transition with heat transfer in HE product and fractured HE

A simple heat transfer model has been developed for high explosives. For the gaseous high explosive (HE) product, the Smargorinsky eddy viscosity model has been adopted for estimating the turbulent thermal conductivity. Convective heat transfer in the fractured solid HE is modeled as the effective thermal conduction in the porous media, which is equivalent to the enthalpy flux carried by the velocity determined by Darcy’s law with Forchheimer term.Other features of the model include a multi-reaction chain, equation-of-state for each species involved, and a two-phase hotspot model. Test calculations are performed with various initial disturbances. Onset and progress of flame acceleration (FA) and chemical reactions are strongly affected by the heat transfer and initial disturbance. Staged development of FA also affirms the necessity of modeling based on a multi-reaction chain. When conditions warrant,e.g., stronger initial disturbance, FA evolves to deflagration-to-detonation transition (DDT),demonstrating automatic capture of the DDT.

45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEF↗