Ammunition Safety Research Articles

Metrological analysis of procedures established in the current standards applicable to the calibration of piezoelectric transducers used in ammunition pressure tests

This work investigates the statistical methods used in the calibration of piezoelectric transducers, which are critical for measuring transient pressure in ammunition testing. These transducers play a vital role in determining internal pressure during the combustion of ammunition propellant, a key factor in assessing ammunition safety and performance. The study focuses on evaluating the significance of the intercept in the linear regression model used for calibration and compares the uncertainty of the fit with the linearity error, a parameter employed by NATO to classify the usability of transducers. Additionally, the study delves into the theoretical background of piezoelectric transducers, the calibration process, and the associated statistical methods. It underscores that NATO mandates the use of a linear regression model with a zero intercept for calibration. However, the study suggests that examining the significance of the intercept could reveal systematic errors or issues with the transducer. The research also explores whether the uncertainty of the fit could serve as an alternative to the linearity error in evaluating transducer usability. In summary, the article investigates the calibration process of piezoelectric transducers, with a focus on the significance of the intercept in linear regression and the potential of using fit uncertainty as a metric for transducer usability. The findings could lead to enhanced calibration standards and better assessments of transducer performance in ammunition tests.

Research on active/passive energy dissipation control method for thermal protection of ammunition battery

High-temperature excitation is the main hazard affecting ammunition safety, and thermal protection technology for batteries inside ammunition is important for enhancing ammunition safety. This study proposes a design integrating a MEMS bistable actuator and battery, and constructs a parallel energy interface between the two. The US military's insensitive ammunition fast cook-off test is then used to verify this design. When the driving current of the MEMS bistable actuator reaches 0.032 A, the actuator completes its own “OFF–ON” electrical conversion, achieving dissipation of the ammunition battery energy. The conformal design of aluminum–silicon aerogel and ammunition forms an energy coupling relationship between thickness and heat transfer efficiency, which reduces the heating rate of the battery in the ammunition. When the material thickness is 5 mm, the internal temperature of the ammunition is 435.5 K after 1200 s of heating, whereas the temperature reaches 423 K within 37 s without protection. The MEMS bistable actuator and aluminum–silicon aerogel realize active/passive thermal protection of the battery and provide technical references for improving ammunition safety.

Modified Arrhenius kinetics for double base propellant decomposition: Effect of water

Numerous studies have been conducted on the decomposition mechanisms of cellulose nitrate (NC), a polymer employed in double base (DB) rocket propellants. It is well known that storage temperature affects the lifetime of these energetic formulations. However, less studies have been published on the influence of water. This research examined the role of water on the stabiliser consumption rate during accelerated ageing of a DB rocket propellant, as well as the impact on the shelf life prediction of the energetic formulation. Different volumes of water (0.8, 1.6, 2 and 4 µl/g) were added to the propellant in sealed vials, which were then isothermally aged (70, 80, 90, 100 °C). Analyses of the stabiliser consumption showed a faster decomposition kinetics in presence of water which is indirectly linked to the shortening of the storage life of the NC based propellant by 35 %. For the conditions, an activation energy of 133 ± 4 kJ/mol was reported for the water catalytic decomposition mechanism. A numerical model that included water as a variable was reported to reduce the uncertainty in the determination of the service life of NC based propellant. International standards such as Allied Ordnance Publication 48 should not overlook the effect of water/moisture on the safety of ammunition containing NC and should implement a modified Arrhenius equation.

Design and process of force-electric fusion for electromagnetic driven Si based MEMS S&A

In order to meet the technical requirements for precise control of the arming time in high-dynamic environments and ammunition safety, this article proposes a silicon-based MEMS safety system force-electric fusion design scheme for small-caliber ammunition platforms. Modeling and computational analysis are conducted on the sensitive units in S&A. A mechanical equilibrium model is established to study the centrifugal overload and electromagnetic forces, followed by verification through dynamic simulation. The design aimed to achieve the safety and arming control of the MEMS security system using a plate-type electromagnetic driving scheme. A low driving energy electromagnetic coil model is designed, and the driving capability of the electromagnetic coil is analyzed. It is found that under the condition of a distance of 0.1mm and 8V, a driving force of 270mN could be achieved. Considering the complex operating conditions during the arming process, a low damping model is developed for the arming degree of the MEMS arming device. After the design is completed, the S&A and electromagnetic coils are processed and prepared using deep silicon etching and microcasting techniques. Finally, threshold verification is conducted for the recoil and centrifugal arming mechanisms of the S&A. The designed S&A ultimately achieved a size of less than or equal to ∅20mm.

Exploring the thermal decomposition and detonation mechanisms of 2,4-dinitroanisole by TG-FTIR-MS and molecular simulations.

2,4-dinitroanisole (DNAN), an insensitive explosive, has replaced trinitrotoluene (TNT) in many melt-cast explosives to improve the safety of ammunition and becomes a promising material to desensitize novel explosives of high sensitivity. Here, we combine thermogravimetric-Fourier transform infrared spectrometry-Mass spectrometry (TG-FTIR-MS), density functional theory (DFT), and ReaxFF molecular dynamics (MD) to investigate its thermal decomposition and detonation mechanisms. As revealed by TG-FTIR-MS, the thermal decomposition of DNAN starts at ca. 453 K when highly active NO2 is produced and quickly converted to NO resulting in the formation of a large amount of Ph(OH)(OH2)OCH3+. DFT calculations show that the activation energy of DNAN is higher than that of TNT due to the lack of α-H. Further steps in both thermal decomposition and detonation reactions of the DNAN are dominated by bimolecular O-transfers. ReaxFF MD indicates that DNAN has a lower heat of explosion than TNT, in accordance with the observation that the activation energies of polynitroaromatic explosives are inversely proportional to their heat of explosion. The inactive -OCH3 group and less nitro groups also render DNAN higher thermal stability than TNT.

TECHNOLOGY FOR DETERMINING THE SAFETY OF AMMUNITION IN ACCORDANCE WITH NATO STANDARDS

September 2023 marks 60 years since NATO countries began implementing the principles of ammunition and explosives safety, which are now described in the AASTP and AOR series of publications. This issue is important and significant because during the preparation and operational process, ammunition is exposed to environmental factors that can change the initial parameters and properties of ammunition.
 Today, NATO member states assess the safety of ammunition on the basis of more than 45 NATO Standards that have been developed and implemented.
 The main guiding documents for determining the safety of ammunition are: Standard AOP- 15 Guidelines for the Assessment of Non-Nuclear Ammunition Safety and Suitability for Use by NATO Forces; Standard AAS3P-01 Evaluation Tests for the Safety and Suitability of Non-Nuclear Ammunition; Standard AASTP-3 NATO Guide to Safety Principles for the Classification of Hazards Associated with Military Ammunition and Explosives; Standard AOP- 62 Ammunition Operational Surveillance, General Guidance.
 The article proposes a technology for determining the safety of ammunition based on NATO standards. The proposed technology for determining the safety of ammunition includes two blocks: an assessment process and a program for determining the safety and suitability for use of ammunition: The presented process of safety and serviceability assessment is a specialized problem-solving process; one stage leads to another, taking into account the guarantees that the ammunition is safe and serviceable.
 The evaluation process also has several distinctive features that make it possible to apply it effectively in practice. It is possible to repeat the evaluation stages as often as necessary to achieve the desired results. The process can be applied at any level of system complexity, from the development of a general design concept to the final detailing of a subsystem or component design. It also involves making management decisions between the ideal and the most practical option. In this way, the assessment process provides results that meet the definition of system safety, ensures that the optimal degree of risk elimination is achieved within acceptable operational efficiency, time and cost. The program of safety and suitability testing developed on the basis of these factors should be introduced to the requirements for assessing safety parameters at the national operational level.
 The developed technology is a clear guideline, a step-by-step instruction for military specialists to determine the level of safety of ammunition and its suitability for use.

Influence of pre-ignition technology on combustion and explosion characteristics of composite propellants

The slow cook-off test is widely used for analyzing the safety of propellants under accidental thermal stimulation. To examine the influence of the pre-ignition technology of a composite propellant on thermal safety and combustion characteristics, a quantitative evaluation experiment of slow cook-off reaction intensity of a typical composite propellant charge was designed and executed, considering hydroxyl-terminated polybutadiene (HTPB) and hydroxyl‑terminated block copolyether (HTPE) propellants containing ammonium perchlorate (AP) and aluminum (Al). The experimental method for quantitative evaluation of the slow cook-off reaction intensity is highly essential to investigate the safety of ammunition. The influence of pre-ignition on reaction intensity was analyzed at different temperatures, the combustion behavior of the heated propellant was studied using a closed bomb experiment, and the influence of pre-ignition on combustion evolution was analyzed. Finally, the process was characterized by theoretical modeling. The results show that the slider speed was 169.3 m/s when the HTPB/AP/Al propellant was ignited at 234 °C. The slider speed was reduced to 43.4 m/s and 61.8 m/s by pre-ignition at 120 °C and 214 °C, respectively. When the spontaneous ignition temperature of HTPE/AP/Al propellant was 212 °C, the slider speed was 110.5 m/s. Pre-ignition at 120 °C and 192 °C reduced the slider speed to 39.4 m/s and 43.7 m/s, respectively. Pre-ignition can effectively reduce the reaction intensity. Under the same conditions, the reaction strength of HTPE/AP/Al propellant is marginally lower than that of HTPB/AP/Al propellant. In the slow heating process before ignition, with the increase in ignition temperature, when HTPB/AP/Al propellant was pre-ignition at 120 °C and 214 °C, the pressurization time was 9.8 ms and 6.4 ms, respectively, while before ignition, the pressurization time decreased to 5.5 ms. At 120 °C and 192 °C, the pressurization time of HTPE/AP/Al propellant was 50.9 ms and 36.6 ms, respectively, while before ignition, the pressurization time decreased to 26.9 ms. The reduction in ignition temperature decreased the pressure growth rate of propellant during combustion and reduced the pressurization time. A calculation model of the propellant combustion process was established to characterize the growth process of the combustion pressure at different ignition temperatures. This model can effectively predict the combustion evolution of composite propellants after the slow cook-off ignition and aid in ensuring propellant safety.

Experimental Study on Motion Law of the Fragment at Hypersonic Speed

As a damage element, high-speed fragments have a significant effect on the ammunition safety. The impact from the fragments are also one of the basic problems of ammunition safety tests. To clarify the reaction characteristics of combustion, explosion, detonation, and so on, when hypersonic fragments hit insensitive munitions, it is necessary to carry out corresponding research on the deceleration law of hypersonic fragment in the air. In this paper, a 30 mm caliber gun with large chamber, small caliber, and large aspect ratio is proposed to drive high-speed fragments. According to STANAG 4496 standard, a near-cylinder steel fragment with Brinell hardness HB ≤ 270 and mass of 18.6 g was designed. The test system was composed of zone interception velocity measurement, chamber pressure sensor, trajectory tracking system, high-speed camera, and other equipment were also established to obtain the pressure variations in the chamber, the velocity of the fragment, and its flight orientation. From the video taken by the high-speed camera and trajectory tracking system, the fragment and the projectile sabot achieve effective separation after the fragment travels out of the muzzle. As time goes on, the distance between the fragment and the projectile sabot gradually increases. The fragment is always in the front of the sabot and steadily flies to the target. The muzzle velocity of the fragment is controlled by adjusting the propellant charge, and the flight velocity in the air is measured by the zone interception velocity measuring device in the range of 5 Ma to 7 Ma. The theoretical models of fragment deceleration and the models of flight orientation are also established according to the experimental data. On this basis, F test and least square nonlinear regression fitting were used to analyze experimental data. Finally, the deceleration coefficient of quasi-cylindrical fragments between 5 Ma and 7 Ma stipulated in STANAG 4496 standard is 0.009312, and the average drag coefficient in air is 1.109.

Design of a Double-Layer Electrothermal MEMS Safety and Arming Device with a Bistable Mechanism.

Considering the safety of ammunition, safety and arming (S&A) devices are usually designed in pyrotechnics to control energy transfer through a movable barrier mechanism. To achieve both intelligence and miniaturization, electrothermal actuators are used in MEMS S&A devices, which can drive the barrier to an arming position actively. However, only when the actuators’ energy input is continuous can the barrier be stably kept in the arming position to wait for ignition. Here, we propose the design and characterization of a double-layer electrothermal MEMS S&A Device with a bistable mechanism. The S&A device has a double-layer structure and four groups of bistable mechanisms. Each bistable mechanism consists of two V-shape electrothermal actuators to drive a semi-circular barrier and a pawl, respectively, and control their engagement according to a specific operation sequence. Then, the barrier can be kept in the safety or the arming position without energy input. To improve the device’s reliability, the four groups of bistable mechanisms are axisymmetrically placed in two layers to constitute a double-layer barrier structure. The test results show that the S&A device can use constant-voltage driving or the capacitor–discharge driving to drive the double-layer barrier to the safety or the arming position and keep it on the position passively by the bistable mechanism.

Constructional Aspects for Safe Operation of 120 × 570 mm Ammunition

This paper provides a characteristic of the design of 120 × 570 mm tank ammunition with particular reference to the cartridges in service in the Polish Army. The presentation of the design and technological details was primarily focused on emphasising their influence on the phenomena occurring or likely to occur during the process of ammunition operation, and to a much lesser extent related with the reference of the characteristics of the performance of the ammunition. Due to the sheer bulk of this subject matter, this paper narrowed the issues of ammunition primarily to the aspects of entry into service, transport, storage, and operation of the specified ammunition cartridges. During these operational stages, there was major focus on the issues of ammunition safety and reliable performance. Note that these aspects are not exhaustive for the topic; this paper also serves as an introduction to a future paper which will deal with safety issues during combat operation using the 120 × 570 mm tank ammunition cartridges.

Security Challenges and Air Quality Management in India: Emissions Inventory and Forecasting Estimates

The defense and peace literature have focused mainly on the military-growth nexus, with little attention paid to the environmental sustainability agenda, which is impacted by increased global arms transfers. The supply of lead-containing ammunition generates complex gas mixtures (including CO2 emissions) and particulates that harm the healthcare sustainability agenda. Based on the significance of the subject matter, the study uses the Indian economy as a case study, with a significant rate of arms transfers associated with higher carbon emissions. The study analyzed data from more than four decades, from 1975 to 2020. Data on arms imports, military personnel, and military expenditures are used to evaluate the ‘ammunition emissions function’. It corresponds to the three research hypotheses, namely, the ‘emissions-defense burden hypothesis’ (arms transfers increase carbon emissions), the ‘emissions-cleaner hypothesis’ (arms transfers reduce carbon emissions), and the ‘emissions-asymmetric hypothesis’ (positive and negative shocks of arms transfers either support the ‘defense burden hypothesis’ or ‘cleaner hypothesis’). The non-linear autoregressive distributed lag (NARDL) results confirmed the ’emissions-defense burden hypothesis‘ in the long run, as positive and negative shocks from arms imports increase carbon emissions. However, in the short run, positive arms imports increase carbon emissions while negative arms imports decrease carbon emissions. Furthermore, the findings supported the ’emissions-cleaner hypothesis‘ in the relationship between armed forces personnel and carbon emissions. The findings imply that the positive and negative shocks experienced by armed forces personnel reduce carbon emissions in the short and long run. Positive shocks to military spending support the ’emissions-defense burden hypothesis‘ in the short run; however, the results vanished when negative shocks to military spending supported the ’emissions-spillover hypothesis‘ (lowering military spending reduces carbon emissions and increases economic productivity) in the short and long run. The country’s unsustainable economic activities are viewed as a negative factor contributing to long-term carbon emissions increases. The negative shocks of armed forces personnel and positive arms imports would almost certainly have a significant long-term impact on carbon emissions. As a result, the ‘treadmill theory of destruction’ has been confirmed in a country. The study concludes that lead-free ammunition and managing ammunition safety are beneficial to a country’s environmental sustainability agenda.

Equivalent Test Method for Strong Electromagnetic Field Radiation Effect of EED

The present study proposed the equivalent test method for the strong electromagnetic field radiation of electric explosive devices (EEDs) of the weapon equipment to satisfy the military requirements of the electromagnetic radiation safety test, as well as the evaluation of the electric ignition, the electric initiation ammunition, or missiles. Under stable conditions, the ignition excitation test and the bridge wire temperature increase test were performed to determine the ignition temperature of the EED. As radiated by the strong electromagnetic field, the relationship between the temperature increase of the bridge wire and the electric field intensity of the EED was developed based on the theoretical analysis and the experimental test. Given the ignition temperature of the EED, the radiation field intensity of the EED at 50% ignition was determined. As compared with the 50% ignition field intensity of the EED directly radiated by the strong electromagnetic field, an error less than 1 dB was caused. On that basis, the correctness of the equivalent test method was verified. Accordingly, this method was suggested to act as an effective method and technical means to test and evaluate the electromagnetic radiation safety of ammunition and missiles in unfavorable electromagnetic environments.

Crack Propagation Analysis of Damaged Solid Propellant under Impact Overload

The ammunition safety problem is particularly prominent when the storage and transportation launch box is airdropped and landed. A safety evaluation method of rocket air drop based on propellant damage evaluation is proposed. Based on the theory of fracture mechanics and the evaluation method of structural integrity of rocket engine, established a local finite element model of rocket engine with initial damage, the crack propagation analysis is carried out by using the propagation finite element method (XFEM). The results show that when the landing impact overload is 30g (25ms) that the airdrop equipment should be able to withstand, the modified double base propellant has produced the phenomenon of crack instability propagation. When the initial crack direction and load direction are 120 °, the propagation is the most serious and there are safety problems; when the solid propellant is airdropped, it is necessary to increase the buffer to reduce the overload.

Study on the Interference Process of Liquid Radial Reflux on the Stability of a Shaped Charge Jet

The process of liquid radial reflux interference during jet penetration in a liquid-filled composite structure is divided in this study into three stages: bottom plate reflection interference, side-wall reflection interference, and side-wall secondary reflection interference. The calculation model of the velocity interval of the disturbed jet and the residual penetration depth of the jet has been established through theoretical analysis. Results show that the liquid-filled composite structure can interfere with the high-speed section of the shaped charge jet. The accuracy of the theoretical analysis in this paper has been verified through numerical simulation, X-ray, and depth-of-penetration experiments. Among the results, those of the X-ray experiment show that the liquid-filled composite structure has interference on the tip of the shaped charge jet, which provides a possibility for the application of the liquid-filled composite structure to ammunition safety and other extreme cases.

Assessment of Ammunition Group Explosiveness in Destructive Effects Conditions and Ways to Reduce It

The ammunition placement in a small area creates the group explosion danger as a result of destructive effects. It is impossible to ensure the group explosive safety of ammunition, by increased distance between them, due to the limited volume in which they are placed. This can be achieved by using protective screens against the high-speed strikers impact. Another direction is the search for optimal ammunition placement schemes in storage that minimize the number of fragments falling into ammunition. The neutrons external background influence during the group storage of nuclear ammunition is also considered.

Calculation Model and Method of Target Damage Efficiency Assessment Based on Warhead Fragment Dispersion

There are many uncertain information and incompleteness factors on warhead fragments dispersion and the self-destructive factors of target damage. It is very difficult to scientifically give a target damage efficiency assessment calculation method of a proximity warhead fragments group. This article proposes a warhead fragments dispersion parameters’ measurement method using the intersection of two light-field cameras and a target damage efficiency assessment calculation method with a multiparameter correlation of warhead fragments dispersion under uncertain information. We research a correlation mechanism between warhead fragments parameters and target damage efficiency. Warhead fragments parameters are combined with the projectile burst location to establish a distribution density function under warhead fragments dispersion with uncertain information. The point trajectory rules of warhead fragments are utilized to set up the spatial position calculation model of warhead fragments hitting the 3-D surface of the target to give the calculation method of the target damage area caused by proximity warhead fragments. The damaged area combined with the damage characteristics of the target itself is used to establish a damage probability calculation model of warhead fragments dispersion to the target under the multi-intersection status of the projectile and target. Simulation analysis reveals the change rule of proximity warhead fragments parameters and target damage efficiency. Experimental results verified the calculation model of target damage efficiency of warhead fragments with uncertain information scientific. These research achievements can provide a scientific theory foundation for ammunition safety measurement, air defense campaign efficiency assessment, and smart ammunition damage efficiency assessment and have high scientific theory research value.

Shaped‐Charge Jet‐Initiation of Covered RDX‐Based Aluminized Explosives and Effect of Temperature

AbstractUnderstanding the shaped‐charge jet‐initiation mechanism of covered explosives and the effect of explosive temperature is important for ammunition safety. We devised a method of using a shaped‐charge jet‐penetrating cover to shock‐initiate heated explosives. This method achieves uniform temperature control of explosives via heating the upper and lower ends and preserves heat on the side of the explosive charge. We experimentally tested the method on hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine (RDX)‐based aluminized explosives (61 wt.% RDX, 30 wt.% Al, 9 wt.% binder) at different temperatures and cover thicknesses. The jet‐penetration behavior and explosive detonation‐wave growth were observed via X‐ray photography, and the effect of explosive temperature on jet initiation was analyzed. A numerical model of the shaped‐charge jet‐initiating explosive was set up by considering the temperature change of the explosive and analyzing the detonation‐wave growth and initiation thresholds of different explosive temperatures under jet shock initiation. Under a thin cover, the explosive showed prompt impact initiation by the jet; the initiation occurred very near to the explosive surface. However, for a thick cover, the explosion was initiated by a bow wave formed at a certain distance from the upper surface of the explosive, and a retonation wave was observed. The temperature of RDX‐based aluminized explosives affects the two jet‐initiation mechanisms. The shock sensitivity of the explosives to the jet decreased with increasing temperature, but the shock sensitivity increased when the temperature exceeded a certain value. A simulation method was established that can be used to predict shaped‐charge jet initiation at different explosive temperatures. We obtained the relationship between the cover thickness and run‐to‐detonation distance under jet shock initiation, which provides a theoretical basis for safety analysis and evaluation of a warhead charge that is attacked by a shaped‐charge jet.

TATB Sensitivity to Shocks from Electrical Arcs

AbstractUse of insensitive high explosives (IHEs) has significantly improved ammunition safety because of their remarkable insensitivity to violent cook‐off, shock and impact. Triamino‐trinitrobenzene (TATB) is the IHE used in many modern munitions. Previously, lightning simulations in different test configurations have shown that the required detonation threshold for standard density TATB at ambient and elevated temperatures (250 C) has a sufficient margin over the shock caused by an arc from the most severe lightning. In this paper, the Braginskii model with Lee‐More channel conductivity prescription is used to demonstrate how electrical arcs from lightning could cause detonation in TATB. The steep rise and slow decay in typical lightning pulse are used in demonstrating that the shock pressure from an electrical arc, after reaching the peak, falls off faster than the inverse of the arc radius. For detonation to occur, two necessary detonation conditions must be met: the Pop‐Plot criterion and minimum spot size requirement. The relevant Pop‐Plot for TATB at 250 C was converted into an empirical detonation criterion, which is applicable to explosives subject to shocks of variable pressure. The arc cross‐section was required to meet the minimum detonation spot size reported in the literature. One caveat is that when the shock pressure exceeds the detonation pressure the Pop‐Plot may not be applicable, and the minimum spot size requirement may be smaller.

The Safety Analysis of Shipborne Ammunition in Fire Environment

The safety of Ammunition has always been the focus of national military science and technology issues. And fire is one of the major safety threats to the ship’s ammunition storage environment, In this paper, Mk-82 shipborne aviation bomb has been taken as the study object, simulated the whole process of fire by using the FDS (Fire Detection System) software. According to the simulation results of FDS, ANSYS software was used to simulate the temperature field of Mk-82 carrier-based aviation bomb under fire environment, and the safety of aviation bomb in fire environment was analyzed. The result shows that the aviation bombs under the fire environment can occur the combustion or explosion after 70s constant cook-off, and it was a huge threat to the ship security.

Numerical Simulation of Cook-Off for Passive RDX

For passive RDX, fluent software was applied to simulate the cook-off for explosive of different charge density at heating rates of 1, 5, 10k/min to improve thermal safety in the ammunition storage, transport and battle. The results show that the heating rate has great effect on ignition time and position for passive RDX. Charge density also has great influence on ignition time but no influence on ignition position. The ignition time decreases and ignition position moves from the center to the two ends of the cylinder edge with the increase of the heating rate. The ignition time increases with the increase of charge density under the same condition. Therefore, increasing the charge density can effectively improve the thermal safety of ammunition.