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Armed forces typically have personal protective clothing (PPC) in place to offer protection against chemical, biological, radiological and nuclear (CBRN) agents. The regular soldier is equipped with permeable CBRN-PPC. However, depending on the operational task, these PPCs pose too much thermal strain to the wearer, which results in a higher risk of uncompensable heat stress. This study investigates the possibilities of adjustable CBRN-PPC, consisting of different layers that can be worn separately or in combination with each other. This novel concept aims to achieve optimization between protection and thermal strain during operations. Two CBRN-PPC (protective) layers were obtained from two separate manufacturers: (i) a next-to-skin (NTS) and (ii) a low-burden battle dress uniform (protective BDU). In addition to these layers, a standard (non-CBRN protective) BDU (sBDU) was also made available. The effect of combining clothing layers on the levels of protection were investigated with a Man-In-Simulant Test. Finally, a mechanistic numerical model was employed to give insight into the thermal burden of the evaluated CBRN-PPC concepts. Combining layers results in substantially higher protection that is more than the sum of the individual layers. Reducing the airflow on the protective layer closest to the skin seems to play an important role in this, since combining the NTS with the sBDU also resulted in substantially higher protection. As expected, the thermal strain posed by the different clothing layer combinations decreases as the level of protection decreases. This study has shown that the concept of adjustable protection and thermal strain through multiple layers of CBRN-PPC works. Adjustable CBRN-PPC allows for optimization of the CBRN-PPC in relation to the threat level, thermal environment, and tasks at hand in an operational setting.

Thanks to a new TNO test facility, it will soon be possible to shoot at armoured civilian and military vehicles in controlled conditions. The Multifunctional Vehicle Test Facility will consist of a 45 x 10 x 6-metre bunker with rotating and tilting platforms.

Conventional gun propellants exhibit the phenomenon of nitrocellulose (NC) decomposition. Besides an effect on thermal stability of propellants, decomposition of NC has an effect on the mechanical integrity of the propellant grains. Enhanced grain fracture may lead to unacceptable changes of the pressure build-up. The effect of ageing on NC molecular weight, mechanical properties and performance has been investigated for the main propellants of 155-mm cartridge-bags. Grain fracture appears to affect the peak pressure much more than the muzzle velocity. This effect is strongly related to the loading density and can for a great part be explained by internal ballistic simulations.

Conventional gun propellants exhibit the phenomenon of nitrocellulose (NC) decomposition. Besides an effect on thermal stability of propellants, decomposition of NC has an effect on the mechanical integrity of the propellant grains. Enhanced grain fracture may lead to unacceptable changes of the pressure build-up. The effect of ageing on NC molecular weight, mechanical properties and performance has been investigated for the main propellants of 155-mm cartridge-bags. Grain fracture appears to affect the peak pressure much more than the muzzle velocity. This effect is strongly related to the loading density and can for a great part be explained by internal ballistic simulations.

A special porous concrete has been developed by the Delft University in collaboration with TNO. The concrete has a static compressive strength of 45 MPa. It fragments at impact into small size debris relative to reference concrete. The porous concrete was developed at laboratory scale and tested at small scale. In collaboration with the Military Science faculty of NLDA a procedure was developed to upscale the production. Panels of 0.5m x 0.5m x 0.10m were produced at slightly lower strength than realized at lab scale. These panels were used to investigate the ballistic performance of the porous concrete. The ballistic resistance proved to be comparable to that of reference concrete. The instant crushing feature of the concrete causes additional damage at the front side but the damage zone was still limited in size. Spalling at the rear side proved to be limited in comparison to the reference normal concrete. To further improve the ballistic resistance of the porous concrete, it was infiltrated with a polymer. Tests showed a considerable improvement of the penetration resistance, relative to the noninfiltrated porous concrete. The paper first summarizes the characteristics of the porous concrete developed at lab scale. The ballistic test data are presented and analyzed. The ballistic response mechanism of the porous concrete is compared with the mechanism in normal concrete. From this analysis the alternative of filling the pores emerges. Finally the paper presents the initial ballistic results for the infiltrated porous concrete.

The majority of methods to assess the behind armour blunt trauma (BABT) risk for ballistic helmets is based on plastic deformable headforms. An alternative, the Ballistic Load Sensing Headform (BLSH) can record the dynamic contact force between helmet back face and the skull. Helmet BABT methods are still under development and outcomes are highly sensitive to test procedures. A test method for the BLSH has been developed, as there was no method available, and evaluated in a round robin series performed by three laboratories, using the same procedure and their own headform, data acquisition and processing. Helmets were tested three times at front, rear and both lateral sides. Peak contact force is used as performance criterion. The peak force varies between 3.536 kN and 10.110 kN depending on location. This is to a large extend caused by a significant variation in stand-off which occurs despite the strict positioning procedure of the helmet. Results become more consistent by statistically correlating peak force and stand-off. However a significant spread within each laboratory remains, which needs further exploration. It is expected that peak force is too sensitive as it is a high frequency phenomena and the tested helmets are not designed to control nor optimize the BABT contact force. It appears that there is systematic difference between laboratories which is not understood. The helmet BABT risk assessment method needs further development to allow inter laboratory comparison and is therefore not acceptable for a test standard. However it is very useful for research purposes and helmet optimisation knowing the vulnerable and sensitive aspects. The scattered response requires a statistical approach and consequently multiple helmet test are required to allow for meaningful conclusions.

This poster describes the work done within the Category B joint research project under the European Defence Agency (EDA) on Future Flare Compositions [1]. Contributing members were Finland, Germany, United Kingdom and the Netherlands. The program was aimed to identify the technology gaps that apply to countermeasures against future IR/EO threats to flying platforms. The focus has been on new advanced flare compositions against the above mentioned threats. Also rapid design and analysis tools for spectral countermeasures for new threats were developed. Work defined were a literature study of the current state of the art, a workshop on spectral countermeasures with the focus on modeling and rapid design, next generations countermeasures by a selection of concepts and the manufacture of test flares, and full scale trials to test for suitability and correlate modeling results.

TNO has developed an alternative, more configuration independent ceramic test method than the standard Depth-of-Penetration test method. In this test ceramic tiles and ceramic based armor are evaluated as target without a semi-infinite backing layer. An energy approach is chosen to evaluate and rank the target materials penetration resistance. By measuring the armor material’s energy absorption, subtracting the residual projectile energy after penetration from the projectile energy before impact, an objective performance parameter for the ceramic or ceramic based armor is obtained. However, this parameter is still related to the specific projectile used in the test. The presented alternative testing method for ceramic based armor uses a high speed camera technique to determine residual velocity of target material fragments and of projectile remains. The residual mass of the projectile is determined, capturing the penetrated projectile (and ceramic fragments) in a water basin. Analysis of the projectile remains after the impact event, provides valuable information on the two projectile to target interaction stages, dwell and penetration. The test method and analysis method are described in this paper. Results on ceramic and ceramic based armor are presented and discussed.

Subgroup A Energetic Materials Team, SG/A (EMT), develops and maintains standards that are relevant to all life-cycle phases of ammunition/weapon systems. STANAG 4147 is the standard regarding chemical compatibility of explosives with munition components, and is a document of prime importance. Currently the 3rd edition of STANAG 4147 has been sent out for ratification. Several aspects of the assessment of compatibility are addressed in this paper, including test conditions (temperature and duration), the mixing ratio of explosive composition and contact material, and sentencing criteria. Future standard development may benefit from on-going research providing experimental data, and possible directions are indicated.

The introduction, analysis or development of soldier systems presents many questions regarding the optimum of possible combinations of burden, effectiveness and safety of the soldier system. The soldier is subject to a broad spectrum of physical loads as a consequence of the threats being encountered. Often, the individual burdens are treated and analysed independently, but the interdependence of the burdens require an integrated approach. In the future such a model can be used to e.g. guide decisions for procurement of clothing and equipment or to guide future needs for development. The initial steps in constructing such an integral model are presented here. The model is called COBESE (COst BEnefit model for Soldier system Evaluation). The focus for the current iteration COBESE model lies on the trade-off between mobility and vulnerability (i.e. the physical safety). COBESE aims to integrate existing models with expert judgement in order to model the influence of clothing and equipment (costs) on an individual soldier’s mobility (benefits). This integration qualitative and quantitative data is achieved using a Bayesian Belief Network (BBN) approach. This paper describes the choices, underlying structure and the implemented sub-models of the COBESE model. Furthermore, case studies are performed to demonstrate the functionality and benefits of the model.

The fragmentation of ceramic tiles under ballistic impact has been studied. Fragments and aerosol (respirable) particles were collected and analyzed to determine the total surface area generated by fracturing (macro-cracking and comminution) of armor grade ceramics. The larger fragments were collected and the mass distribution was obtained from sieving. The aerosol particles were collected using a particle impactor device that counts the number of particles of specific ranges in size. From the total surface area of all particles was concluded that fracture energy is small compared to impact energy. The average grain size of the ceramic tiles did not lead to a specific peak in mass or concentration for that particle size. In fact, a large concentration of much finer particles has been obtained. The size of the aerosol dust ranged between 10 micron and 10 nanometers, indicating a lot of particle fragmentation (comminution) to have taken place.

In order use material models in (numerical) calculations, the mechanical properties of all materials involved should be known. At TNO an indirect method to determine the dynamic flow stress of materials has been generated by a combination of ballistic penetration tests with an energy-based engineering model. For visco-elasto-plastic materials, like clay, not only the dynamic flow stress is strain rate dependent, but also its Young’s modulus. Experiments using 7.62x39 MSC bullets have been performed on Roma Plastilina nr. 1 at several target temperatures. The dynamic flow stress and young’s moduli have been determined using an adjusted ductile hole growth engineering model for weak materials.

At TNO mind sized engineering models are created for specific penetration conditions. The models are energy based and calculate the energy absorbed by target deformation (strain energy) and displacement (kinetic energy). The input parameters are restricted to basic target material properties (density, Young’s modulus), impact velocity, mass and the dimensions of projectile and target. In this paper an engineering model for impact of blunt projectiles on metallic sheets is presented. During blunt projectile impact a shock phase precedes the global deformation of the target. It results in increasing membrane and shear deformation of the target, while the projectile deforms and is retarded. These effects are included in the model. When the conditions for shear- and/or tensile failure of the target material are met, the target fails and is penetrated. Calculation results on projectile deformation and penetration behavior are compared with experimental results.

TNO has developed an engineering model for flexible body armor, as one of their energy based engineering models that describe the physics of projectile to target interactions (weaves, metals, ceramics). These models form the basis for exploring the possibilities for protection improvement. This presentation describes how the main physical details of projectile to flexible weave (fabric) interaction can be modeled with a simple set of equations that are based on four well known relations for force, work performed, kinetic energy of a moving material and strain energy in a material and on the two relations for longitudinal wave velocity and cone diameter expansion. The evolution of an impact in the model is based on energy conservation, equal to the summation of kinetic energy in projectile and weave and the strain energy in the armor material. The effect of friction and delamination is excluded. The model allows plasticity of the projectile, strain rate effects on the fiber strength and fiber failure strength as a function of fiber damage due to transverse loading effects. The model is made time resolved, calculating projectile deceleration, weave displacement and straining in a series of calculation steps. The model has created a better understanding, how projectile kinetic energy is transferred into the flexible armour material and how fibre failure and energy absorption in the weave stack are shifted in time. The model has indicated that fibre failure in flexible weave under ballistic impact, is partly initiated by high lateral fiber stress at the location the projectile interacts with the weave stack. This phenomenon is currently investigated at TNO.

Depth, diameter and volume of dents in clay backing of soft and hard body armour are used to assess the protective performance of such vests. The characteristics of the dents are traditionally measured manually. Optical scan techniques are becoming more popular and provide an objective method compared to the manual method and it allows to archive the scans for later evaluation. However, commercial high end scanners, accuracy in 1-10 μm, are expensive and there is no software available to automatically determine the dent characteristics. Recently low end scanners, accuracy 0.1-0.5 mm became available. An automatic dent measuring method was developed using Matlab to control a DAVID3 Structured Ligth Scanner and process the scans of the clay backing to obtain the dent characteristics. This SLS dent scan system is presented in this paper. Accuracy of the scans is better than the most strict requirement of 0.5 mm. Scan and processing time to obtain the dent characteristics is less than sixty seconds. The traditional method takes about two minutes between each shot. The accuracy and precision is evaluated by comparison of the SLS scan method with a measurement of a dent by a high end but much slower scanner (accuracy < 0.05 mm). A comparison between the manual and SLS method is made by measuring dents for three clay trays with each five calibration dents and for a soft and hard armour BABT performance assessment. It is concluded that the accuracy of the SLS method is better than or equal to the manual method.

The objective of the study was to obtain helmet-to-head contact forces from experiments, use a human head finite element model to determine regional responses, and compare outputs to skull fracture and brain injury thresholds. Tests were conducted using two types of helmets (A and B) fitted to a head-form. Seven load cells were used on the head-form back face to measure helmet-to-head contact forces. Projectiles were fired in frontal, left, right, and rear directions. Three tests were conducted with each helmet in each direction. Individual and summated force- and impulse-histories were obtained. Force-histories were inputted to the human head-helmet finite element model. Pulse durations were approximately 4. ms. One-third force and impulse were from the central load cell. 0.2% strain and 40. MPa stress limits were not exceeded for helmet-A. For helmet-B, strains exceeded in left, right, and rear; pressures exceeded in bilateral directions; volume of elements exceeding 0.2% strains correlated with the central load cell forces. For helmet-A, volumes exceeding brain pressure threshold were: 5-93%. All elements crossed the pressure limit for helmet-B. For both helmets, no brain elements exceeded peak principal strain limit. These findings advance our understanding of skull and brain biomechanics from helmet-head contact forces. © 2013.

The ballistic behavior of four different armor ceramic materials with thicknesses varying from 3 mm to 14 mm has been investigated. These are two types of alumina Al2O3 armor grades and two types of SiC armor grades produced by different armor ceramic producers. The ballistic study has been performed using the standard DoP technique with two types of AP projectiles. The microstructure and the mechanical properties of the armor ceramics are investigated with SEM (Scanning Electron Microscopy), X-ray microanalysis, impulse excitation methods and Vickers hardness method. The microstructures are characterized by the number and chemical nature of the phases, the grain size, the type of fracture mode identified from SEM investigation of fragments. The measured mechanical properties are hardness, fracture toughness, flexural strength and the speed of sound (transversal and longitudinal). The ballistic tests are performed with two 7.62 mm projectiles AP8 (WC core) at 930 m/s and APM2 (hard steel core) at 800 m/s. The mass efficiency factor has been determined for each of the armor ceramics. The difference in the ballistic performance of the two alumina types is marginal. The two silicon carbide types are indistinguishable from ballistic point of view. The gained knowledge can be used two-fold: first, to understand better the influence of the microstructure on the ballistic performance of armor ceramics and second, as reference material for the development of a new class of armor ceramics.

Damage containment is one of the key factors for optimising operational readiness of warships after an internal warhead detonation. Ship designers currently have no other option than to rely on state of the art solutions applied in vehicle and personal protection; mainly ballistic composites. These solutions are prone to being traded off during the design process due to cost of the bulk material. Areas to protect are in the order of magnitude of hundreds of square meters. This called for development of a cost efficient, but lightweight protection against fragments. TNO has teamed up with industrial partners to develop understanding of the physical phenomena involved in pre-layers on armour steels [1], in order to optimise protective solutions. Goal of the project was to assess the potential of using polymer coated armour steels in combination with blast bulkheads. The project consisted of three iterations of testing and analysis. The first test programme was aimed at understanding the physics explaining why armour steels perform significantly better against blunt projectiles when covered with an additional thin layer of a relatively soft material. Knowledge from the preliminary tests was applied to protective concepts for blast bulkheads. The pre-layer on the armour steel allows it to dissipate the energy over a wider area of the steel. In the experiments extreme stretching of the armour plate occurred and about twice the amount of energy is dissipated in the armour steel compared to the uncoated situation. The work resulted in protective concepts that fulfilled the mass requirements and are based on affordable materials. The project team considers this technology to be promising for future application in warships. Solutions from this project will be engineered further into a prototype concept. There is spin-off possible to other platforms like vehicles and offshore rigs, where mass and cost are equally important.

The handling of explosives and ammunition introduces a safety risk for personnel and third parties. Accidents related to storage, transport and transshipment may result in severe injury and material damage. Dispersion of structural debris is one of the main hazards resulting from detonations inside structures. Reliable prediction models for debris dispersion are essential for risk assessment methods. In this article we give a statistical description of the dispersion of explosion produced debris. The basis is a general expression for the projectile areal number density in the horizontal and vertical plane. Combined with engineering models for the launch conditions, predictions can be made. An analytical solution to the equations of motion may be used to allow for fast calculations. A parameter study shows consistent results. The model has been validated with internal detonation tests of bare charges in reinforced concrete structures. The validation clearly shows the prediction capabilities of the model for three loading regimes described in the literature. We give a thorough description of the validity and limitations of the model, and an outlook of current and future research. Examples are the failing debris mass distribution prediction for reinforced concrete in the shock overloading regime, and ricochet and roll and break-up at impact phenomena.

Exposure to signaling smoke is almost impossible to avoid, and may have adverse health effects. Hand grenades with signaling smoke are used during training and/or military operations. To obtain the most realistic results when estimating the toxicity of the smoke, not only the smoke–forming composition is ignited, but the whole hand grenade is used as it is used during military operations. The experiments are conducted by igniting colored smoke hand grenades, measuring the toxic effect of the formed smoke on the lung cells using the CULTEX® system, collecting samples for determining the mutagenic character by the Ames-test and analyzing the particle size (distribution) of the smoke particles and comparing the results. The toxic effect of the smoke for humans is not only dependent on the nature of the components present in the smoke, but also on the size of the formed particles and the exposure time. The migration of the particle into the lungs is dependent on the size of the particle. The smaller the particle the deeper it is able to enter into the lungs. Various techniques are used to determine the particle size and particle size distributions.

At TNO several energy-based engineering models have been created for various failure mechanism occurring in ballistic testing of materials, like ductile hole growth, denting, plugging, etc. Such models are also under development for ceramic and fiberbased materials (fabrics). As the models are energy-based they can be directly compared to experimental results of ballistic tests as the mass and velocities of projectiles are regularly measured. This allows the models to be validated, as has been done for the ductile hole growth model. Using AP-rounds on ductile target materials like many metals, clay and polymers, ductile hole growth (DHG) normally is the major failure mechanism during projectile penetration. When the core of the projectile remains rigid (which is often the case in ductile materials) the loss in kinetic energy of the core is easily measured from its initial and residual velocity. In the DHG-engineering model this energy loss is also calculated but requires that the flow stress at high strain rates is known. Using the experimental results in combination with this engineering model the dynamic flow stress of the target has been quantified. This procedure has been done for several material (metals, clay types and polymers) and allows the determination of dynamic material properties that are otherwise not easily measured. This method requires a rigid penetration of a projectile through a (thick) plate of the material to be characterized. Hence, no special sample shape or dimension is required. The dynamic flow stresses that are obtained have been compared to high strain rate (order 1000/s) strength values of the same materials determined by other techniques. As the values are very close to each other, this provides confidence in the approach to use ballistic test results of targets failed by DHG in combination with the engineering model for the characterization of materials at high strain rates.

The aim of this work is to demonstrate the manufacturing of a propellant by solvent-less continuous twin screw extrusion processing while maintaining gun performance characteristics of conventional JA-2 propellant. This is elucidated by explicitly researching the relationship between interior ballistic properties of the gun propellant and utilizing continuous manufacturing process using modeling and simulation codes. Processing conditions were established and the propellant was manufactured accordingly. The extruded propellant has the desired properties which resulted in a comparable gun performance as the conventional JA-2 propellant.

Strobes are pyrotechnic compositions which show an oscillatory combustion; a dark phase and a flash phase alternate periodically. The strobe effect has applications in various fields, most notably in the fireworks industry and in the military area. All strobe compositions mentioned in the literature were discovered by trial and error methods and the mechanisms involved remain unclear. Many oscillatory systems such as Belousov-Zhabotinsky reactions, cool flames, selfpropagating high-temperature synthesis have been observed and theories developed to elucidate their unstable behavior based on chemical interactions or based on physical processes. These systems are compared to experimental observations made on strobe mixtures. © 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

During the interaction between a projectile and a target material the kinetic energy of the projectile is transferred into elastic and plastic deformation of both the projectile and target materials. Using a rigid penetrator the loss in kinetic energy is fully converted into energy absorbed by the target, both as kinetic and strain energy. Using optical high speed imaging the kinetic energy (e.g. velocity of fragments, plug and residual projectile) can generally be obtained. However, the strain energy remains invisible using high speed imaging. By thermal imaging using an IR video camera, the temperature distribution of the target material (on both the strike and rear face) can be obtained. In order to convert the camera recordings into a temperature distribution, the emissivity of the target material in the infra-red range of wave length needs to be known. For most armour materials the density, thickness and heat capacity are known, while the emissivity can be determined using the IR-camera and the target material at a known temperature. This enables one to calculate the amount of energy in the target that was dissipated by plastic and/or visco-elastic strain. Examples of thermal images will be shown for metallic, polymer and weaves/fabrics. From the temperature distributions the total thermal energy is obtained and compared to the total loss in kinetic energy of the projectiles. Thermal imaging provides a non-contact, remote measuring technique that can be used to directly see where and how much energy was dissipated by target materials. As the dissipated energy can be quantified, this technique is also of use for direct comparison with energy-based projectile-target interaction models.

The interaction of thin ceramic tiles with AP8 (WC core, 7,62 mm) at 1000 m/s velocity has been studied experimentally and numerically. “Thin” ceramic tiles refers here to ratio of the tile thickness (t) to the projectile diameter, (d), t/d@ 1, as they are both in the same order. The method applied to visualize the penetration dynamics has been described. It consists of two orthogonal X-ray sources each of 1.2 MeV, coupled to high-speed camera and triggered by aluminum foil, placed in front of the ceramic tile. The time resolution of the experimental set-up is ±1 microsecond. The spatial resolution is ±0.2 mm. The size of the tiles that permit very good image quality is 50 mm x 50 mm. The penetration dynamics of AP8 projectile in SiC tile with thickness of 8 mm has been studied both with and without backing to distinguish the different failure mechanisms during the penetration process. The normalized penetration versus time (P,t) and normalized length of the projectile versus time (L,t) curves have been generated. The penetration dynamics of AP8 in the tile with backing is a non-linear process and three different stages, each corresponding to different penetration velocity, have been identified and described. The penetration behavior in the case of stand alone tile (without backing) has linear character. The finite element code LS-Dyna has been applied to gain the spatial and temporal stress distribution and study the observed phenomena numerically. Both numerical and experimental approaches are set complementary to improve the current understanding of fragmentation and penetration dynamics in thin ceramic tiles.

Predicting potential consequences of Vapor Cloud Explosions (VCEs) has always been an important issue in safety assessments, because of the devastating damage that this phenomenon can create on (petro chemical) production sites. Although the TNO Multi-Energy method has been recognized as one of the best methods to predict blast overpressures of vapor cloud explosions, its application has been complicated by the required expert knowledge to choose a blast strength category and the congested fraction of the flammable cloud. In the GAME project (Guidance on Application of Multi-Energy, a contract research project for HSE), TNO already developed a quantitative method to derive the blast strength of VCEs, based on well-defined congestion area properties. Recently, this method has been extended and combined with dispersion models to derive a practical cloud coverage fraction, which is used to find the other important influencing parameter: the explosive mass of the congested part of the flammable cloud. This so-called "explosion regions" method can be used to determine the potential damage zones on a realistic site, with various potential sources of releases and multiple congestion areas or "receptors". The paper will give a full description of the calculation procedure used and provide potential benefits and drawbacks of its application.

Gun performance is usually affected by the operating temperature of the ammunition or weapon. This is caused by several factors, amongst which the temperature dependency of the propellant ignition and combustion processes. Compensation of temperature effects on weapon or ammunition performance is possible if these processes are controllable. As the output of plasma igniters depends on the delivered electrical energy, application of plasma ignition facilitates in principle the possibility to compensate for the temperature effects. Computer simulations show that compensation of propellant temperature effects can be achieved if the initial ignition conditions can be regulated. The feasibility of this principle was verified experimentally. A plasma igniter was designed and manufactured, and ignition experiments were carried out using a closed bomb and a gun simulator. The results show that application of plasma ignition results in a significant reduction of the level and variability of the ignition delay and that variation of the electrical energy results in the desired controllability of the ignition conditions. From the obtained results it is concluded that regulation of the combustion conditions, as required for compensation of weapon and ammunition conditions, can be obtained by the application of the developed plasma igniter. It is also concluded that RDX-based LOVA propellants, which are difficult to ignite by conventional primers, are easily and reproducibly ignitable by using this plasma igniter.

Strobes are pyrotechnic compositions that emit bright flashes of white or colored light at regular time intervals. The strobe effect has applications in various fields, most notably in the fireworks industry and in the military area (signaling – missile decoys – crowd control). However, the chemical and physical mechanisms involved in this curious combustion phenomenon remain unknown. This study investigates parameters that influence the strobe effect (frequency, sharpness of flashes). Variations were applied to the fuel particle size and weight fraction of the ternary composition ammonium perchlorate, magnalium (fuel) and barium sulfate. Both parameters are related to the heat generation and transfer within the composition. The light emission was recorded with photodiodes and a high speed camera (5000 fps). The experimental results served as input for a model to explain the strobe behavior based on layer-by-layer combustion. Moreover, it was established that the flash frequency is dependent on a delicate balance between heat generation in one layer and heat transfer to a next layer. The model gives new insights into the behavior of pyrotechnic strobes and enables a better control of the flash frequency by variation of the size and content of the metal fuel particles.

Work is proceeding within NATO toward establishing STANAG 4686, which would define the performance levels of armoured vehicles' active protection systems. This would be in addition to the existing, well-established standardisation agreements embodied in STANAG 4569 on the levels of ballistic protection of armoured vehicles and the threat of blast mines to them. The new STANAG has been ratified recently in principle and the first three of its eight volumes are now being ratified but details of it all remain to be released. In the meantime, Czech magazine ATM has reported that tests have already been carried out in the Czech Republic according to STANAG 4686 with the Czech Explosively Formed Axe (EFA) active protection system. The tests were conducted against RPG-7 rocket-propelled grenades and, in keeping with STANAG 4686, took into account not only the failure of the grenades to defeat their targets but also how little, if any, collateral damage the active protection system caused. So far, only the EFA's developers have agreed to have their system tested in accordance with STANAG 4686. However, its tests represent a significant contribution to the efforts of the NATO working group to finalise the new standard. The chairman of the working party has been Ricolt Boeschoten of the Netherlands' TNO research organisation and he, together with a group of international observers, attended the Czech tests.

A recent study was dedicated to relate the behaviour of Insensitive Munitions (IM) to an operational context. At TNO, a toolbox with a series of engineering tools is under study. These tools focus on the mechanisms that occur due to a range of IM threats and that transfer the effects from a reacting (donor) munition article to the neighbouring (acceptor) munition articles, focusing on sympathetic reaction. The consequences of this mechanism could be devastating, resulting in a mass detonation of large quantities of munition in storage on a compound, aboard a ship or in a vehicle. However, by using Insensitive Munitions and mitigating structures these effects and their operational consequences could be limited. In order to quantify this limiting effect and the consequences of such an event in an operational context, a case study has been performed on an Out of Area compound. Attention is given to the effects and consequences of a detonation of an munition storage facility on the war fighters and infrastructure on the compound in terms of probability of injury and damage. At a higher systems level a translation is made to the Essential Operational Capabilities of the compound. This evaluation puts the benefits of Insensitive Munitions and mitigating measures in the right perspective and challenges research institutes in finding new solutions in Insensitive Munitions technology.

This paper describes the development of a diagnostic prognostic health management tactical solid rocket motor demonstrator and provides results of deployment of two of these demonstrators in different environments. The demonstrators were exposed to different realistic environments in a controlled laboratory setting to cover a broad range of loadings. Next to an overview of some of the deployment results, some of the diagnostic evaluations based on sensor output are given. Prognostic algorithms will be further evaluated in future work based on the outcome of the current study.

The study describes recent simulation results for underwater explosions in close-proximity to rigid targets. Simulations are performed using Chinook, an Eulerian computational fluid dynamics (CFD) code. Predicted target loadings are compared with measurements taken from a series of experiments conducted under an international collaboration between Canada, The Netherlands, and Sweden. The simulations of the rigid target tests focused on themodelling of gas bubble collapse andwater jetting behaviour. Both two-dimensional and three-dimensional simulations were performed. It was found that the two-dimensional analyses produced good bubble periods and reasonable impulse loading compared to experimental data. The time of arrival of the bubble collapse and water jetting were found to be very mesh dependent and refining the mesh did not always produce better results. The two-dimensional approach provides a good initial understanding of the problem for a reasonable computational effort. The three-dimensional simulations were found to produce improved impulse predictions. The numerical gas bubble radii time histories are also compared to empirical time histories.