Characterization of PAX‐21 Insensitive Munition Detonation Residues

Insensitive high explosives are being used in military munitions to counteract unintended detonations during storage and transportation. These formulations contain compounds such as 2,4‐dinitroanisole (DNAN) and 3‐nitro‐1,2,4‐triazol‐5‐one (NTO), which are less sensitive to shock and heat than conventional explosives. We conducted a series of four tests on snow‐covered ice utilizing 60‐mm mortar cartridges filled with 358 g of PAX‐21, a mixture of RDX, DNAN, and ammonium perchlorate. Rounds were detonated high‐ and low‐order using a fuze simulator to initiate detonation. Blow‐in‐place (BIP) operations were conducted on fuzed rounds using an external donor charge or a shaped‐charge initiator. Results indicate that 0.001 % of the original mass of RDX and DNAN were deposited during high‐order detonations, but up to 28 % of the perchlorate remained. For the donor block BIPs, 1 % of the RDX and DNAN remained. Residues masses for these operations were significantly higher than for conventional munitions. Low‐order detonations deposited 10–15 % of their original explosive filler in friable chunks up to 5.2 g in mass. Shaped‐charge BIPs scattered 15 % of the filler and produced chunks up to 15 g. Ammonium perchlorate residue masses were extremely high because of the presence of large AP crystals, up to 400 μm in the recovered particles.     

Investigation of Energetic Particle Distribution from High‐Order Detonations of Munitions

Military training with munitions containing explosives will result in the deposition of energetic materials on ranges. These residues contain compounds that may result in human health impacts when off‐range migration occurs. Models exist that predict the spatial and mass distribution of particles, but they have proven to be difficult to apply to detonating munitions. We have conducted a series of tests to determine if modelling results can be directly applied to simple detonation scenarios. We also command detonated several rounds to obtain an initial indication of high‐order detonation particle distributional heterogeneity. The detonation tests indicate that particle distributions will be quite heterogeneous and that the model used did not adequately describe the distribution of detonation residues. This research will need to be expanded to build an empirical database sufficient to enable the refinement of existing models and improve their predictions. Research on low‐order detonations should be conducted as low‐order detonations will result in higher mass deposition than high‐order detonations. Distribution models verified with empirical data may then be incorporated into range management models.     

Low-Sensitivity Explosive Compounds for Low Vulnerability Warheads

Looking for explosives for Low Vulnerability Ammunitions leads to an interest in explosive molecules less sensitive than the usual nitramines (RDX, HMX). If TATB is quite convenient in terms of sensitivity, its performance is too low. The researches described here are related to synthesis and use of NTO (nitrotriazolone), another insensitive molecule. The synthesis by nitration of TO (triazolone) is easy and the two steps from available starting materials have been optimized. A comparison of desensitivation of PBX either by TATB or by NTO have been made. The sensitivity levels were found equivalent while the detonation velocity of the NTO based PBX was slightly higher. Unfortunately in this case, the failure diameter would be larger. The last part relates to an extensive characterization in terms of performance and vulnerability to fast cook off, slow cook off, bullet impact, shock sensitivity and sympathetic detonation of a NTO and HMX based PBX. This PBX, B 2214, was one of the first examples of explosive composition showing no sympathetic detonation, even in 248 mm large diameter.     

Laboratory‐Scale Method for Estimating Explosive Performance from Laser‐Induced Shock Waves

A new laboratory‐scale method for predicting explosive performance (e.g., detonation velocity and pressure) based on milligram quantities of material is demonstrated. This technique is based on schlieren imaging of the shock wave generated in air by the formation of a laser‐induced plasma on the surface of an energetic material residue. The shock wave from each laser ablation event is tracked for more than 100 μs using a high‐speed camera. A suite of conventional energetic materials including DNAN, TNT, HNS, TATB, NTO, PETN, RDX, HMX, and CL‐20 was used to develop calibration curves relating the characteristic shock velocity for each energetic material to several detonation parameters. A strong linear correlation between the laser‐induced shock velocity and the measured performance from full‐scale detonation testing has been observed. The Laser‐induced Air Shock from Energetic Materials (LASEM) method was validated using nitrocellulose, FOX‐7, nano‐RDX, three military formulations, and three novel high‐nitrogen explosives currently under development. This method is a potential screening tool for the development of new energetic materials and formulations prior to larger‐scale detonative testing. The main advantages are the small quantity of material required (a few milligrams or less per laser shot), the ease with which hundreds of measurements per day can be obtained, and the ability to estimate explosive performance without detonating the material (reducing cost and safety requirements).     

Thermal Stability Studies Comparing IMX‐101 (Dinitroanisole/Nitroguanidine/NTO) to Analogous Formulations Containing Dinitrotoluene

The 2,4,6‐trinitrotoluene (TNT) replacement, IMX‐101, containing 43.5 % 2,4‐dinitroanisole (DNAN), 19.7 % 3‐nitro‐1,2,4‐triazol‐5‐one (NTO) and 36.8 % nitro‐guanidine (NQ), has been certified for use as an insensitive munition. IMX‐101 has passed standardized performance, stability, and aging tests but in some categories was not necessarily an improvement over TNT or RDX. This study compared the thermal stability of DNAN and another low‐melting nitroarene, 2,4‐dinitrotoulene (DNT). When examined individually, DNAN was more stable; but formulated in IMX‐101 with NTO and NQ, the opposite was true. In two part mixtures, NQ had a similar acceleratory effect on the decomposition of both nitroarenes, while NTO had a greater impact on DNAN than on NTO. Ammonia, a reported decomposition product of both NQ and NTO, also accelerated the decomposition of both DNAN and DNT, with a larger impact on DNAN. The formation of dinitroaniline, potentially due to the interaction between the nitroarenes and ammonia, was detected by LC/MS as a decomposition product when either nitroarene was combined with NTO and/or NQ, indicating that this molecule may play a significant role in the decomposition mechanism. While not advocating the use of DNT in insensitive munitions formulations, this study addresses the importance of chemical compatibility as a criterion for selecting replacement components in formulations.     

NTO及其盐的制备、表征与应用(续)

2．2．2晶体结构 杨利等人、冯长根等人、马海霞等人对制备的NTO胺盐的晶体结构进行了研究,确定了它们的分子结构和晶体学参数,李加荣对一些早期的研究成果进行了概述,结果见表12。研究表明：目前制备出的NTO胺盐全部为离子型化合物,除ANTO和GNTO各含1分子结晶水外,其他NTO胺盐均不含结晶水。     

Partial Reparametrization of the BKW Equation of State for DNAN‐Based Melt‐Cast Explosives

DNAN‐based melt‐cast explosives are a type of new, insensitive munitions (IM) explosives. Quickly determining munitions’ explosive properties is extremely important during the formulation design stage. The aim of this study was to partially reparameterize BKW‐EOS (only β and κ were reparameterized on the basis of the parameters (α , β , κ , and θ ) of classical BKW‐RDX set and BKW‐TNT set) to more accurately predict the properties of DNAN‐based melt‐cast explosives. A new set of parameters β and κ was obtained (β =0.19, κ =9.81) according to measured detonation velocity and detonation pressure for ideal DNAN‐based melt‐cast formulations (DNAN/RDX and DNAN/HMX). For non‐ideal DNAN‐based melt‐cast formulations (DNAN/RDX/Al and DNAN/HMX/Al), aluminum oxidation degree was first determined according to the measured detonation heat; then, another new set of parameters β and κ was obtained in the same way as the ideal formulations (β =0.24, κ =8.5). The predicted detonation properties with BKW reparametrization for DNAN‐based melt‐cast explosives agreed with the measured data.     

From Synthesis to Formulation and Final Application

Meeting the requirements for insensitive munitions remains a complex route, where all the steps of the production process have to be addressed. NTO is a choice component, especially for large munitions. Various compositions have been optimized, which are now available, in pressed or cast PBX as well as melt cast formulations. Standard products such as RDX have been improved by the synthesis or crystallization methods, giving reduced sensitivity formulations. Some cast PBX can sustain severe shaped charge jet impacts, thanks to their large critical diameter, and are candidates as main filling of large munitions such as IM Mk82. The formulation step is addressing not only new binder principles, allowing an increase in the filler and thus energy contents, but also a bi‐component innovative method to get a semi continuous filling process where the pot life is no longer an issue. Finally a partial toolset for designing IM features is proposed with a recent example of successful application.     

Solubility Determination of Raw Energetic Materials in Molten 2,4‐Dinitroanisole

2,4‐Dinitroanisole (DNAN) is an ingredient used in several insensitive munition formulations that have recently been qualified by the US Army. A phenomenon known as irreversible growth is found to occur during conditioning cycles of insensitive munitions (IM) that contain DNAN. A possible cause of the irreversible growth maybe the potential solubility of energetic components formulated with melted DNAN. This report documents methods development and procedures used to determine the solubility of energetic constituents in molten DNAN at 100 °C. High performance liquid chromatography and ion chromatography were used for quantitation. Solubilities (given as g energetic per 100 g DNAN) of RDX, HMX, NTO, NQ, and AP were found as 13.7, 3.02, 0.222, 0.448, and 0.088, respectively.     

Thermal Decomposition and Ignition of PBXN‐110 Plastic‐Bonded Explosive

Due to safety requirements, insensitive behavior in slow or fast thermal heating (cook‐off) conditions is a desired behavior for today’s munitions. The ignition time of munitions under slow or fast cook‐off conditions is an important parameter in the design of insensitive munitions. The critical temperature, which mainly depends on the chemical, physical, and the geometrical properties of the energetic material, is the determining factor whether the material will end up with thermal initiation or not, when it is exposed to an external heat source. In this study a slow cook‐off test setup is designed and developed and the tests for a generic munition containing PBXN‐110 plastic‐bonded explosive are performed in order to obtain temperature distribution in the test item, ignition time, ignition temperature, and ignition location. In this paper the development procedure and the experimental results of the slow cook‐off tests are explained. Moreover, the kinetic parameters such as activation energy and pre‐exponential factor for the plastic‐bonded explosive obtained from the TGA tests are presented.     

Reparametrization of the BKW Equation of State for the Triazoles and Comparison of the Detonation Properties of HMX,TNMA and NTO by means of Ab-Initio and Semiempirical Calculations

For some years, the research and the new composition development to low vulnerability make the many object works. In the perspective to realize new explosive formulation candidates to EIDS and more effective, the oxynitrotriazole(ONTA or NTO) is an interesting substance. Among melt cast formulations, the composition AFX-644, developed by the US Air Force⁽¹⁾, is considered as EIDS(Extremely Insensitive Detonating Substances) but its performances are too low. One of the possibilities to improve these formulations is to estimate detonation characteristics of these new substances by calculation codes so as to decrease the number of experimental tests and therefore to reduce the cost price. This paper describes the result of the reparametrization studies on the Becker-Kistiakowsky-Wilson(BKW) equation of state for the triazoles. The new set of BKW parameters(α=0.5; β=0.18; κ=11.8; θ=1850) give realistic values for the detonation properties and the predicted ab-initio F. BKW, semiempirical Kamlet and the experimental detonation celerities are in good agreement for each set of parameters for the Nitroaromatics, Nitramines and Triazoles.     

Cast PBX B2238 for Small-Calibre High Performance Insensitive Munitions

Generally speaking, today's small-calibre munitions, filled with conventional melt-cast or pressed high explosives, are classified in the 1.1 or 1.2 Hazard Divisions because they explode when exposed to various threats, such as fuel fire and sympathetic detonation. The RDX-based B2238 composition is a low-cost and less sensitive cast PBX originally developed by SNPE for the initiation of cast PBX main charges. While it is easily initiated with conventional detonators, B2238 offers the same degree of insensitivity as other cast PBXs used for main charges (HEXABU 88A or OCTORANE 86B for example) and does not explode when exposed to fire and/or bullet impact. Feasibility tests carried out on several types of small-calibre munitions have shown B2238 explosive filling to be an excellent solution in the design of small calibre insensitive munitions with a high performance (in terms of fragments and shaped charge jet) comparable to that of the most energetic conventional high explosives such as 98RDX/2wax. As a result, the new IM standards, currently being defined, should allow in the future to reclassify the small-calibre munitions filled with B2238 in Hazard Divisions other than 1.1 and 1.2.     

熔铸炸药研究现状与发展趋势

熔铸炸药是目前战斗部最主要的装药方式之一,但是现有以TNT为载体的熔铸炸药配方在能量、安全性、装药质量和力学性能等方面存在明显缺陷。本文详细综述了熔铸炸药连续相、高能量密度材料、综合降感技术、流变性研究和装药工艺5个方面国内外的研究现状,特别是归纳了以NTO、DNTF等为代表的新型含能材料的应用情况,提出了熔铸炸药在新型载体物质、高能钝感单质炸药、共晶炸药、功能助剂、高固相含量熔铸体系装药工艺等方面未来的主要发展方向。     

Presence and Persistence of White Phosphorus On Military Training Ranges

The use of obscurants is a common practice by militaries worldwide. One of the most effective of these is white phosphorus (WP). WP is the elemental form of phosphorus that does not occur in nature and is highly toxic. The use of WP rounds on training ranges has led to a number of die‐offs of grazing land animals and dabbling waterfowl, the first recorded in 1930. In the 1980s, thousands of waterfowl were dying annually at an impact range in Alaska, leading to the first large‐scale investigation of WP as a lethal range contaminant. Tests were conducted at an upland impact range in New York to determine the quantity and persistence of WP in a typical environment. At all sites cited in this paper, WP was persistent for months to years following the detonation of WP munitions. At the Eagle River Flats range in AK, WP was identified from rounds fired in the 1950s, persisting over 45 years in a non‐saturated environment. In New York, dispersal of gram quantities of WP occurred at detonation, and high concentrations of WP were found in the detonation craters a year after firing. Caution needs to be exercised when using white phosphorus munitions on ranges.     

A Novel Cocrystal Explosive of HNIW with Good Comprehensive Properties

In order to improve the safety of the high explosive 2,4,6,8,10,12‐hexanitrohexaazaisowurtzitane (HNIW), we cocrystallized HNIW with the insensitive explosive DNB (1,3‐dinitrobenzene) in a molar ratio 1 : 1 to form a novel cocrystal explosive. Structure determination showed that it belongs to the orthorhombic system with space group Pbca. Therein, layers of DNB alternate with bilayers of HNIW. Analysis of interactions in the cocrystal indicated that the cocrystal is mainly formed by hydrogen bonds and nitro‐aromatic interactions. Moreover, the thermal behavior, sensitivity, and detonation properties of the cocrystal were evaluated. The results implied that the melting point of the cocrystal is 136.6 °C, which means an increase of 45 °C relative that of pure DNB. The predicted detonation velocity and detonation pressure of the cocrystal are 8434 m s⁻¹ and 34 GPa, respectively, which are similar to that of the reported HNIW/TNT cocrystal, but its reduced sensitivity (H₅₀=55 cm) makes it an attractive ingredient in HNIW propellant formulations.     

Characterization of Granular and Polymer‐Embedded RDX Grades: Floret Tests

In an attempt to further contribute to the characterization of explosive compositions, small scale Floret tests were performed using four RDX grades, differing in product quality. A Floret test provides a measure – by indentation of a copper block – of detonation spreading or the initiability and shock wave divergence and is applied in particular to explosives used in initiation trains. Both as‐received RDX and PBXs (based on the AFX‐757 composition, a hard target penetrator explosive) containing these RDX grades were tested in the Floret test set‐up. It was found that the Floret test method, when applied to granular, as‐received RDX, was not able to discriminate between the overall RDX product qualities on the basis of the resulting volume of the indentation in the copper block. For the Floret test data of the PBX samples, a division into two parts, where one of the RDX lots shows a lower dent volume compared to the other RDX lots tested. Based on the results presented in this paper with granular RDX and a PBX composition and earlier results with a different type of PBX (based on PBXN‐109, an insensitive high explosive used in a wide range of munitions), the Floret test could be developed into a screening test for shock sensitivity and product quality, without the need for complex and large volume casting of specific PBX compositions.     

Particle Size Modification of Thermally Stable Secondary Explosives for IM Applications

As well as improving the survivability of weapons and platforms, insensitive munitions (IM) reduce both casualty rates and mission losses. Their use also leads to improved safety during storage and transportation. For a munition to fulfil IM criteria, each of its energetic sub‐sections must be IM compliant. The initiator and explosive train are the most critical of these sub‐systems as their safety and reliability are of paramount importance if the weapon is to be suitable for service use, yet they are generally the most difficult part of a weapon to protect from inadvertent initiation. As part of an ongoing study into initiation methods suitable for use in IM systems, an investigation into the behaviour of energetic materials when impacted by laser‐driven flyers was performed. Laser‐based detonators exhibit increased safety characteristics over conventional initiation methods as they can be based on insensitive secondary explosives rather than sensitive primary explosives. Also, they are less susceptible to accidental initiation due to an external hazard threat. Single pulses from a high‐powered Q‐switched Nd:YAG laser were used to launch flyers from substrate‐backed aluminium films to velocities up to 6 km s⁻¹ across a short stand‐off to impact explosive targets. Several novel energetic materials have been selected for investigation as potential candidates for inclusion within flyer‐based initiation systems and explosive train applications. The materials are of interest due to their increased thermal stability and power output over conventional explosives currently in service. Attempts were made to increase the flyer responsiveness of the materials by tuning their particle size using ultrasound. The effect of particle size on the initiation threshold energy was investigated for three materials.     

Changes in Pore Size Distribution upon Thermal Cycling of TATB‐based Explosives Measured by Ultra‐Small Angle X‐Ray Scattering

Hot‐spot models of initiation and detonation show that voids or porosity ranging from nanometer to micrometer in size within highly insensitive energetic materials affect initiability and detonation properties. Thus, the knowledge of the void size distribution, and how it changes with the volume expansion seen with temperature cycling, are important to understanding the properties of the insensitive explosive 1,3,5‐triamino‐2,4,6‐trinitrobenzene (TATB). In this paper, void size distributions in the 2 nm to 2 μm regime, obtained from small‐angle X‐ray scattering measurements, are presented for LX‐17‐1, PBX‐9502, and ultra‐fine TATB formulations, both as processed and after thermal cycling. Two peaks were observed in the void size distribution: a narrow peak between 7–10 nm and a broad peak between 20 nm and about 1 mm. The first peak was attributed to porosity intrinsic to the TATB crystallites. The larger pores were believed to be intercrystalline, a result of incomplete consolidation during processing and pressing. After thermal cycling, these specimens showed an increase in both the number and size of these larger pores. These results illuminate the nature of the void distributions in these TATB‐based explosives from 2 nm to 2 μm and provide empirical experimental input for computational models of initiation and detonation.     

Preparation and Properties of An Insensitive Booster Explosive Based on LLM‐105

A new insensitive booster explosive based on 2,6‐diamino‐3,5‐dinitropyrazing‐1‐oxide (LLM‐105) was prepared by a solvent‐slurry process with ethylene propylene diene monomer (EPDM) as binder. SEM (scanning electron microscopy) was employed to characterize the morphology and particle size of LLM‐105 and molding powder. The mechanical sensitivity, thermal sensitivity, shock wave sensitivity, and detonation velocity of the LLM‐105/EPDM booster were also measured and analyzed. The results show that both mechanical sensitivity and thermal sensitivity of LLM‐105/EPDM are much lower than that of conventional boosters, such as PBXN‐5 and A5. Its shock wave sensitivity is also lower than that of PBXN‐5 and PBXN‐7. When the density of charge is 95 % TMD, its theoretical and measured detonation velocities are 7858 m s⁻¹ and 7640 m s⁻¹, respectively. These combined properties suggested that LLM‐105/EPDM can be used as an insensitive booster.     

Development of Aerosol Monitoring Instrument and Results from Monitoring Emissions of Contained Detonations

To determine the airborne emissions that occur when conventional munitions are destroyed by open burn/open detonation (OB/OD), munitions shots were carried out in a large underground (4650 m³) chamber. Carrying out the tests in a chamber allows the total emissions to be measured, which is not possible in open-air testing. We report here the development of an instrument to measure the time-dependent mass concentration and aerosol size distribution of respirable aerosols (< 10 μ m) from detonations of artillery projectiles in the underground chamber. The instrument incorporates an on-line diluter and real-time cascade impactor for aerosol monitoring. Design, flow modeling, construction details, and results from the instrument are given.

Particulate emissions from detonations of twenty four 155 mm artillery projectiles, with a total of 377 lbs net explosive weight, were monitored. Aerosol measurements from the two duplicate tests were very similar. Aerosol mass concentrations showed rapid decreases from 37,000 and 65,000 μ g/m³ for the first samples for the two tests, 14 and 17 min after detonation, to near 20,000 μg/m³ at 20 min after each detonation. Thereafter the concentration decreased less rapidly to several thousand μg/m³ at 90 min after the detonation. Aerosol mass concentrations peaked in the 0.3–0.6 μm diameter range during the first 30–60 min of sampling and shifted to smaller particles (< 0.3 μm) toward the end of the sampling period (90 min) as turbulence decreased in the detonation chamber and large particles settled out.

The data were highly reproducible between the two tests, indicating that the instrument performed satisfactorily. The data will be used to help determine the characteristics of dust emitted from OB/OD shots for munitions demilitarization and will provide a baseline for designing future studies to monitor the airborne emissions from full-scale open-air munitions demilitarization tests.