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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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9 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Uncertainty Quantification Enabled by Automatic Differentiation for Hydrodynamic Simulation of Shock‐to‐Detonation Transition in High Explosives

Quantifying the effects of uncertainty in a reactive burn model on the run-to-detonation time in high explosives (HEs) provides a robust methodology for assessing the probability of an HE failing the IHE qualification standard. Moreover, uncertainty quantification helps evaluate whether the model calibration accurately represents data outside the calibration set. This study uses a specialized hydrodynamic simulation code for modeling detonation to determine the run-to-detonation time of the HE PBX 9502 for various impact velocities. To quickly approximate uncertainties in the model, a surrogate was constructed using a Taylor series expansion centered at the mean of the input parameters. To obtain the sensitivities required for constructing the Taylor series, HYP-percomplex Automatic Differentiation (HYPAD) was implemented. HYPAD is a methodology for infusing existing codes with automatic differentiation capabilities by augmenting variables with one or more imaginary units to compute step-size independent partial derivatives. These derivatives are accurate to machine precision with respect to the implemented numerical algorithm, meaning their accuracy reflects that of the underlying method (e.g., integration or discretization schemes). Using reduced order modeling techniques, the mean and standard deviation of the run-to-detonation time of a shock within PBX 9502 were computed for a number of initial impact velocities. A weighted least squares regression was then performed to obtain a best fit curve and prediction interval for the computed statistics. Historical data points from explosively driven wedge tests were utilized to validate the prediction interval, ensuring its reliability in predicting future outcomes. With this prediction interval and a known safety constraint curve, the most probable point of failure and the probability of failure for the HE PBX 9502 were determined.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2025

Equation of state measurement of detonation carbon condensates using optical microscopy and interferometry

Thermochemical models of detonation that estimate performance (e.g., detonation velocity, energy delivery, etc.), are based on assumptions that carbon condensates (soot) formed during detonation is largely similar to bulk carbon. However, soot constituents can range from amorphous carbon to nanodiamond and include other material phases. Since thermodynamic properties of the soot such as compressibility are imperative for accurate thermochemical modeling of detonation reaction chemistry, experimental measurements of the equation of state (EOS) which determine the compressibility are vital. Due to the mixed-phase nature of detonation soot, typical methods to measure the EOS (e.g., x-ray diffraction) are untenable. In this study, the high-pressure EOS up to 20 GPa was determined for detonation soot collected from PBX 9502, Composition B (Comp B), Hexanitrostilbene (HNS), and LX-21 high explosives by employing a direct volume technique using optical microscopy and interferometry in a diamond anvil cell. Comp B soot was determined to be the least compressible [K 0 = 57.9(17) GPa] with HNS soot [K 0 = 53.7(15) GPa], LX-21 soot [K 0 = 45.8(51) GPa], and PBX 9502 soot [K 0 = 28.2(27) GPa] being more compressible, likely due to differences in nanodiamond content as compared to amorphous carbon and graphite content.

Amorphous materials↗
DOE OSTI2025

Characterizing IHE Response to Multiple Shock Loading

The response of high explosives to shock loading is traditionally measured with a steady loading pressure. In many accident scenarios involving fragment impact, however, a loading duration that is shorter than the build up to detonation may occur. Fragments passing through multiple materials before reaching a high explosive charge may produce loading that is comprised of more than one shock wave. Additionally, the build up to detonation in high explosive corner turning loads the explosive a short duration pressure pulse, since rarefactions can often rapidly overtake the reactive wave. For these reasons, we have studied the response of the insensitive high explosive (IHE) materials PBX 9502 and LX-17 to complex loadings of varied intensity and duration. We refer to a single loading of limited duration as a “thin pulse”, whereas more complex scenarios were studied with an impactor that produces a double shock in the explosive. The following report presents experimental data and analyses of thin pulse shock initiation and double shock experiments designed to guide development of models of Insensitive High Explosives (IHEs) under controlled one-dimensional conditions relevant to accident scenarios and corner turning. Thin pulse shock initiation data on PBX 9502 and LX-17 were obtained under varied pulse duration, pressed density, and temperature conditions in order to probe various parameters essential for the development of a physics-based Cheetah reactive flow hotspot model. In situ pressure gauges provide insight into the degree of reaction in the explosive that are not obtainable with optical PDV measurements or distance measurements such as run to detonation. Double shock data was obtained to inform a Composition Aware Cheetah model which can be applied to any TATB-based IHEs. This model supports efforts to find a new IHE formulation and potentially incorporate new binders into IHE formulations. Simulations of each experiment are included to demonstrate the utility of these focused experiments to developing models of HE behavior. One-dimensional gas gun experiments are essential for characterizing shocked HE behavior and informing HE models.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Extrusion‐Spheronization of Energetic Materials

The prevailing method to produce plastic‐bonded explosive (PBX) molding powder, or “prills”, is a complex, multiphase, and bespoke process that was developed by the high explosives (HEs) manufacturing industry several decades ago. This work demonstrates the utility of a simpler, widely‐used mechanical process—extrusion‐spheronization—to produce PBX prills. We begin by detailing precautions taken to enable safe remote operation of extrusion‐spheronization equipment with HE. We then perform a study investigating the effect of lacquer solvent composition on the particle packing, pressed density, and compressive strength properties of a 95 wt.% TATB/5 wt.% polymer binder formulation akin to PBX 9502. It was found that increased composition of low vapor pressure solvents caused prolonged retention of the solvent, resulting in tackier materials that would agglomerate and form larger prills. The larger prills also led to lower poured density and tapped density of HE prills and compressive strength of pressed PBX articles. The samples prepared with a 75% propyl acetate/25% butyl acetate lacquer solvent composition exhibited the highest compressive strength. However, it is believed that the prill packing and compressive strength properties are primarily driven by the prill size rather than the chemical composition of the lacquer itself. Extrusion‐spheronization remains a promising method to reliably and repeatably produce HE prills that is less sensitive to feedstock or process variation than traditional methods.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Compatibility Screening of Explosive‐Inert Mixtures

Inert materials are necessary components in explosive devices and they must be tested for compatibility with the explosive materials to ensure that the device will function as expected over its lifetime in representative environments. True compatibility testing is time-consuming and expensive and so compatibility screening is often used as an early assessment. The screening is carried out with analytical methods run at temperatures exceeding those that the device will encounter in its lifetime. Shortcomings of this approach are discussed and improvements using a transient contact method and microcalorimetry are proposed. Typical screening results and microcalorimetry results are compared for a polyurethane adhesive—PBX 9502 combination.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Towards Robust Calibration of the AWSD Reactive Burn Model

Calibration of a reactive burn model for detonation of high explosive is an important step towards predictive hy drodynamic simulations of detonation. A typical calibration consists of varying model parameters (e.g., rate constants, activation energies) until results of hydrodynamic simulations match the experimental data for a certain set of ex periments. Hydrodynamic simulations of the dependence of steady detonation velocity on the radius of a cylindrical high-explosive charge - often used in such calibrations - can be computationally expensive. In this work, we propose a method where such expensive simulations are performed infrequently, and only to parameterize and refine a surrogate model for the dependence of the detonation velocity on calibrated parameters. The method is developed, implemented and applied to an example problem - calibration of the AWSD reactive burn model for important high explosive PBX 9502. Two different flavors of the surrogate model are investigated, and the calibration is performed successfully.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗