To further our understanding of chemical reaction pathways occurring during shock loading (sub-detonative and detonative) of plastic bonded explosives (PBXs), post-shock/detonation product species were investigated. Using a contained firing vessel, charges of PBX 9501, PBX 9501/9502 and PBX 9501/TATB were detonated producing gaseous products as well as solid carbonaceous species. Gaseous samples were transferred to a collection vessel which were then analyzed by gas chromatography (GC) with a thermal conductivity detector (TCD). The measured concentrations of H2, N2, CO, CO2, N2O, and H2O for PBX 9501 and PBX 9502 and TATB are presented and are compared to predictions from Cheetah. Identity of these gases were confirmed using retention indices as well as mass spectrometry (MS). Solid samples collected from detonation of PBX 9502 and TATB were analyzed by liquid chromatography coupled to ultraviolet-visible absorbance and mass spectrometry (LC-UV/Vis-MS). Additionally, solid samples from sub-denotatively shocked PBX 9502 were also analyzed via LC-UV/Vis-MS. For both the detonated PBX 9502 and TATB as well as the sub-denotatively shocked PBX 9502, a trace amount of TATB was measured and multiple TATB decomposition products were identified.

Traditional slow detonation velocity (Dv) explosives components, such as Baratol (76% Ba(NO3)2 and 24% TNT), rely on dilution of a traditional explosive with a dense relatively inert material, while some utilize Ca(NO3)2, ZnO or BaCO3. However, our applications require solely CHNO-based formulations that exhibit slow Dv near theoretical maximum density. Given a target Dv of 6.5 mm/µs, ammonium picrate was chosen as a convenient explosive to be diluted with a high binder level (14-20%). Thermal equilibrium calculations were performed to determine the binder level to provide the desired Dv. Two formulations were produced, a molding powder with a polystyrene/dioctyl adipate binder, Dv = 6.45 mm/µs and a cast-cure using hydroxy-terminated polybutadiene/bis-(2,2-dinitropropyl)acetal-formal/MDI binder, Dv = 6.58 mm/µs. All formulations showed no sensitivity response or compatibility issues. The cast-cured formulation was chosen for further analysis, and cylinder expansion was performed followed by JWL parameterization. Detonation tests confirmed that cast-cured formulation would initiate and propagate unconfined at thicknesses above 12 mm. The ultimate test configuration of the formulation was a sweeping initiation from PBX 9502, with Proton Radiography (pRad) imagery to demonstrate the leading detonation front in the PBX 9502 and a lagging detonation front in the slower cast-cured formulation, as predicted by simulation.

Iron(II) tris(3-amino-6-pyrazolyl-1,2,4-triazolo[4,3-b][1,2,4,5]-tetrazine) perchlorate (FATP) is an energetic material that has low sensitivity to mechanical stimuli [impact, electrostatic discharge (ESD), and friction] and is also capable of being readily ignited with a low-level 1064 nm Nd:YAG laser pulse, making FATP a potential candidate as a photoactive initiator material. Previous studies have shown that FATP is capable of detonating a PETN acceptor charge. However, the detonability of FATP itself has not been reported. Additionally, low thermal stability has been observed in FATP in both differential scanning calorimetry (DSC) and vacuum thermal stability (VTS) measurements. Herein, we report a modified procedure for the synthesis of FATP that results in improved thermal stability and also report detonability studies of this material.

The development of additive manufacturing (3-D printing) has opened up avenues previously unexplored due to prohibitive cost and/or complexity. Printing of inert parts for use in shock property characterization has reached a new level by allowing high resolution (10's of mu m) wave shapers to be designed and employed at varying dimensions; the ability to save time on HE machining, casting, and cost of HE is undeniable. Herein, we report the design of a PolyJet-printed wave shaper paired with a cast-cure HE formulation to generate a planar output shock; guided by CTH simulations, the design was iterated to increase planarity. Lens fabrication followed guidelines by J. Fritz, using PMMA Hugoniot data as a substitute for the chemically similar 3D printed acrylates. Front curvature characterization of these minimal explosive mass, small diameter (2.54 cm) charges showed reliable planarity below 100 ns and optimized to similar to 28 ns. Following this characterization, the plane wave generators were used to launch flyers at varying materials to investigate shock and particle velocities and chemical reactions. In this fashion, US-uP curves were created and will aid follow-on gas-gun experiments.

The ability to discover minute differences between samples or sample classes for gas chromatography coupled to mass spectrometry (GC-MS) can be a challenging endeavor, especially when those differences are not a priori. Fisher ratio (F-ratio) analysis is an apt technique to probe the differences between GC-MS chromatograms. F-ratio analysis is a supervised, non-targeted, discovery-based method that compares two different samples (or sample classes) to reduce the GC-MS dataset into a hit list composed of class distinguishing compounds. Three different F-ratio techniques, peak table, tile, and pixel-based were used to "discover" nine non-native analytes that were spiked into gasoline at four different nominal concentrations of 250, 85, 25, 5 parts-per-million (ppm). For the tile and pixel-based F-ratio calculations, a novel methodology is introduced to improve the sensitivity of the F-ratio calculations while reducing false positives. Furthermore, we use a combinatorial technique using null class comparisons, termed null distribution analysis, to determine a statistical F-ratio cutoff for analysis of the hit lists. The pixel-based algorithm was the most sensitive method and was able to "discover" all nine spiked analytes at a nominal concentration of 250 ppm albeit with one false positive interspersed towards the bottom of the hit list. The pixel-based software was also able to "discover" more of the spiked analytes at the lower concentrations with seven of the spiked analytes "discovered" at 85 ppm, four of the spiked analytes "discovered" at 25 ppm, and one analyte "discovered" at 5 ppm.

Erythritol tetranitrate (ETN) is a homemade explosive with high explosive performance which can easily be synthesized using widely available chemical precursors. Ascertaining the manner in which ETN is synthesized and being able to trace the ETN back to its precursor materials may aid in the forensic identification. As a proof of concept, seven different types of ETN were synthesized with laboratory grade materials as well as commercially available chemicals from the hardware store and grocery store. The seven different types of solid ETN and the reaction quenches were analyzed using high performance liquid chromatography (HPLC). Partial least squares discriminant analysis (PLS-DA) was used to probe the different classes of ETN and reaction quenches. Several PLS-DA models were produced with the seven different types of ETN and quenches having their own classification, ETN and quenches based on their acid source, and ETN and the quenches based on their nitrate source. Regardless of which classification manner was used, there were no differences found between the different types of ETN or their reaction quenches. Moreover, it is demonstrated that there is inherent variability in the synthesis of ETN making HPLC an unreliable method to determine the source of the synthesis materials. Elemental impurities were measured in seven solid ETN samples and their reaction quenches by inductively coupled plasma mass spectrometry (ICP-MS). No differences were found between the solid ETN samples, but there were trace metals found in the reaction quenches which were found to be identifiers of the source material.

Understanding solubility behavior of organic crystalline materials is critical in the development of slurry-formulated plastic bonded composites. In the field of high explosives (HE), a common method for obtaining high density, greater than 95% theoretical maximum density, is to encapsulate HE in a polymer matrix resulting in the formation of plastic bonded explosive (PBX) prills which can then be pressed to high density parts. Prill formation is highly nuanced and requires understanding of particle size distributions, solvent, antisolvent, and binder system as well as interactions thereof. In an effort to create mock-HE that mimics HE in density and mechanical strength, solubility of candidate molecules was compared to cyclotetramethylenetetranitramine (HMX) in binder solvents relevant to prill formation. The results indicate that the mock candidates chosen for this study have different solubilities compared to HMX in water and both organic solvents, 2-butanone and ethyl acetate, investigated. With these solubility differences known, prills to match PBXs based on HMX can be formulated, pressed and tested.

Recent experimental testing found that plastic-bonded explosives (PBX) can be initiated by metal-cupped detonators in a non-contact "standoff" configuration. Depending on the detonator type, and high explosive (HE) driver (e.g. PETN, HMX, or PBX 9407), a stochastic field of sub-mm fragments is generated which travel initially > 3 km/s. Determining the initiation mechanism in this scenario for the target PBX materials is difficult; the interplay between fragment size/shape, incident angle and velocity creates a highly complex variable set. Since each detonator cup breaks apart stochastically, each test potentially probes different initiation mechanisms; e.g. single large fragment versus multiple smaller fragments generating shock coalescence leading to detonation. To attempt to simplify this problem, and enable new hydrocode simulations, experiments were undertaken to design and parameterize a flyer system capable of launching multiple small flyers of a standardized size and shape simultaneously. 3D Simulations using reactive burn models in the CTH hydrocode were also performed to guide the experimental design and help analyze ignition criteria.

proposal lays out a new approach, requiring fewer, but more appropriate tests, for IHE Material qualification. One of these new tests is the Deflagration-to-Detonation Test. According to the redefinition proposal, the purpose of the new deflagration-todetonation test is “to demonstrate that an IHE material will not undergo deflagration-to-detonation under stockpile relevant conditions of scale, confinement, and material condition. Inherent in this test design is the assumption that ignition does occur, with onset of deflagration. The test design will incorporate large margins and replicates to account for the stochastic nature of DDT events.” In short, the philosophy behind this approach is that if a material fails to undergo DDT in a significant over-test, then it is extremely unlikely to do so in realistic conditions. This effort will be valuable for the B61 LEP to satisfy their need qualify the new production lots of PBX 9502. The work described in this report is intended as a preliminary investigation to support the proposed design of an overly conservative, easily fielded DDT test for updated IHE Material Qualification standard. Specifically, we evaluated the aspects of confinement, geometry, material morphology and temperature. We also developed and tested a thermally robust igniter system.

Multi-fragment impact of energetic materials can provide the impetus initiation and growth to detonation when shockwaves from these discrete fragments collide. The Sandia hydrocode CTH is used with reactive burn modeling to identify relationships between spherical fragment separation distances, variable fragment arrival timing, and initiability in energetic materials. This work demonstrates that detonation is most likely to occur is when multiple fragments collide with a surface simultaneously, because of the cumulative pressure rise of two equal colliding waves compared to the colliding waves generated by fragment impacts offset in time.

Detonators are fundamental to most explosive systems, yet the detonators themselves are rarely diagnosed to determine how well they function or why they fail. To remedy this, various electrical diagnostics were explored, including: Rogowski coils for high fidelity detection of changes in electrical current in explosive bridgewires and how they relate to detonator performance; and radio frequency (RF) antennas to detect any electromagnetic emissions associated with reaction and growth in the explosives. A new type of Rogowski coil is described and some interesting phenomena were detected with the radio frequency antenna.

Insensitive High Explosives (IHEs) increase safety in many types of uses. However, the safety comes at the cost of performance. Initiation of IHE requires large boosters and powerful detonators as well. Multipoint initiation is being utilized to exploit explosive wave interactions to create overdriven states, greatly facilitating the initiation of IHEs. This concept builds from recent explosive experiments where the minimum spot size for single-point initiation in PBX 9502 was determined. Below this threshold, PBX 9502 could not be initiated. This was then expanded to three initiation points, which were smaller than this threshold. Measurements of the velocity and pressure of the wave interactions were collected using Photon Doppler Velocimetry (PDV). Not only was initiation observed, but the resulting pressures at the double and triple points were found to be above the CJ state for PBX 9502. Based on these results, further tests were conducted to isolate and measure the longevity and pressure of this phenomenon using a series of cutback tests.

The inside cover picture shows the expansion of a copper cylinder containing hydrazinium nitrate based explosives, with and without deuterium substitution. Using high-fidelity detonation velocity and wall expansion velocity measurements, the kinetic isotope effect was utilized to probe reactions between Al and detonation product gases. By varying explosives with either H or D and including Al, data indicate that Al oxidation occurs on an extremely fast time scale, with post-detonation kinetic isotope effects observed in carbon containing formulations. Details are discussed in the article by Bryce C. Tappan et al. on page 62 ff.

To better understand how solid carbon forms and evolves during detonation, we have prepared Composition B-3 (Comp B) with C-13 and N-15-labeled 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX) and 2,4,6-trinitrotoluene (TNT) in order to trace the formation of soot from the carbon and nitrogen atoms in these explosives. Isotope-labeling of explosives has been performed in the recent past for a variety of reasons, including environmental remediation and reaction mechanism studies. Because it is expensive and time consuming to prepare these materials, and our detection equipment only requires trace amounts of isotopes, we have prepared fully-labeled materials and substituted them into unlabeled RDX and TNT at less than the 1% level. We will discuss the preparation and full characterization of this labeled Comp B, the detonation tests performed, along with the results of the post-detonation soot analysis. Various detonation models predict differing amounts and forms of carbon and nitrogen; these isotopically-labeled precursors have allowed these models to be tested.

3-Picrylamino-1,2,4-triazole (PATO) is a thermally stable explosive invented at Los Alamos National Laboratory (LANL) almost half a century ago. Despite a rapid and high yielding synthesis, performance data for this promising explosive are scant. We prepared material using Coburn's synthesis, and discovered that the particle size distribution and morphology leads to difficulty in pressing formulations to high density. Three formulations were made using glycidyl azide polymer (GAP), FK-800, and Estane 5703/nitroplasticizer (NP) as binders. The maximum pressed density of these formulations was 89 % of theoretical maximum density (TMD). We determined detonation velocity and, for the FK-800 formulation, detonation pressure. The performance of PATO is similar to TATB at equivalent pressed density.

Making high explosives that possess insensitivity on par with TATB-based plastic bonded explosives (PBXs), while outperforming them, has proven to be a difficult challenge. Many molecules that have challenged TATB have fallen short in either small-scale sensitivity (impact, friction), thermal stability, or possess a shock sensitivity that is either too high or too low. Recently, an alternative approach to single-molecule-based PBXs has been blending and/or co-crystallizing explosive molecules to address shortcomings of individual components. With this approach in mind, characterization of formulations of 1,1-diamino-2,2-dinitroethene (DADNE or FOX-7) or 3,3'-diamino-4,4'-azoxyfurazan (DAAF) with 3-nitro-1,2,4-triazole-5-one (NTO) were investigated. Two mono-molecular explosives and mixtures with binders were also evaluated, 5,7-diamino-4,6-dinitrobenzofuroxan (CL-14) and 1-nitroso-3,5-dinitro-1,3,5-triazacyclohexane (M-RDX or mononitroso-RDX) A new method for the production of M-RDX was discovered. The previous procedure was improved by economizing to a one-pot method involving two high yielding steps. The overall yield for this reaction was 80% with minimal RDX contamination. Half-scale (12.7 mm inner diameter) copper cylinder expansion testing was used to investigate the detonation performance of DAAF/NTO, FOX-7/NTO and CL-14 formulations. Small scale sensitivity tests were also performed on CL-14, M-RDX and NTO based formulations.

Two energetic materials identified for relatively high energy, but little to no response to impact, spark or friction stimuli are 3-nitro-1,2,4-triazole-5-one (NTO), and 3,3' diamino-4,4'-azoxyfurazan (DAAF). More of an outlier in performance versus sensitivity, DAAF illustrates insensitivity by small-scale sensitivity tests, yet has a failure diameter estimated to be 1.25mm and a short run length to detonation. Because of this unusual behavior, DAAF is an ideal material to formulate with NTO to obtain tailored shock sensitivity and critical diameter, with detonation velocities and pressures higher than PBX 9502. Here, we present detonation properties of Kel-F-(R) bonded formulations with ratios of 20-70wt.-% DAAF added to NTO. All formulations were evaluated for detonation velocity, aluminum flyer acceleration at jump-off, and via the cylinder expansion test.