Journal of Pyrotechnics

Titles and Abstracts for Issue 23, Summer 2006

Computer Modeling of Flying Star Ballistics

Dayu Ding, Morimasa Higaki, Yozo Ooki and Tadao Yoshida
Ashikaga Institute of Technology, 268-1 Omae-cho, Ashikaga-shi, Tochigi 326-8558, Japan

Abstract: The burning time of stationary and flying fireworks stars was measured, the trajectories of flying stars were observed and the results were analyzed in this work. It was found that the difference in burning time between the stationary and flying burning stars was dependent on the kind of star. Modeling of flying star ballistics was applied to the trajectory of stars with shorter burning times and was found valid for this case.

Keywords: fireworks, burning time, exterior ballistics, modeling

Temperature Measurements within the Luminous Region of a Burning Ba(NO₃)₂/Al Mixture

P. J. Disimile, R. Prasad and N. Toy
UC-FEST, Department of Aerospace Engineering, University of Cincinnati, Cincinnati, OH 45221, USA

Abstract: Knowledge of the local temperature field associated with a pyrotechnic event has numerous implications, especially in the field of safety and survivability. These implications involve the development of sensors that are capable of detecting pyrotechnic events and that are used in part to eliminate or reduce a fire hazard. However, in order to be able to predict a possible fire scenario from a pyrotechnic event the temperature distributions and the thermal heat transfer are prerequisites. This experimental study discusses the temperature measurement methodology required to evaluate the transient temperatures associated with a small, commercially available, pyrotechnic device. Furthermore, the temperature distribution close to the surface of two devices, one commercial, the other fabricated, has been obtained, and shows that the temperature distribution away from the event is not uniform.

Keywords: temperature distribution, thermocouples, pyrotechnic facility

Ballistics of an Iron Bar Shot from a Mortar

Morimasa Higaki, Dayu Ding, Yuuzo Ooki and Tadao Yoshida
Ashikaga Institute of Technology, 268-1, Omae-cho, Ashikaga-shi, Tochigi-ken 326-8558, Japan

Abstract: An accidental explosion in 1848 in the USA became a trigger for the development of neuroscience. An accidental explosion of Black Powder took place in a borehole for blasting and the expelled iron bar penetrated the head of a young man. He was injured but survived for 12 years. The authors were asked to calculate the speed, impact pressure or energy of the explosion by the producer of a TV program. At the time we were carrying out similar experiments using a mortar and firework stars, and so a model experiment was performed. Here we report of the results.

Keywords: Black Powder, ballistics, iron bar, shot energy efficiency

Ballistics of a No. 3 Spherical Shell with Illuminant

M. Higaki, D. Ding, Y. Ooki, M. Higaki and T. Yoshida
Ashikaga Institute of Technology, 268-1, Omae-cho, Ashikaga-shi, Tochigi-ken 326-8558, Japan

Abstract: Shot experiments were carried out using a No. 3 spherical shell with an illuminant. The three dimensional trajectory of the flying shell was obtained by tracing the shell with two high-speed video cameras in different orientations and by analyzing the recorded video picture. The 3DSTAR1 computer code was developed for calculating the three dimensional trajectory of a flying shell with high accuracy. The optimal drag coefficient, wind speed and wind direction were estimated using the 3DSTAR1 code by fitting the calculated trajectory to the experimental one for a No. 3 shell.

Keywords: ballistics, no. 3 shell, trajectory

Effect of Particle Size on the Mechanical Sensitivity and Thermal Stability Aspects of Pyrotechnic Flash Compositions

S. P. Sivapirakasam, M. Surianarayanan, F. Chandrasekaran and G. Swaminathan
Cell for Industrial Safety & Risk Analysis, Chemical Engineering Department, Central Leather Research Institute, (Council of Scientific & Industrial Research), Adyar, Chennai , 600 020, India

Abstract: The mechanical and thermal sensitivity of pyrotechnic flash compositions consisting of mixtures of potassium nitrate (KNO₃), sulphur (S) and aluminum (Al) with varying particle sizes of KNO₃ and Al indicated that, irrespective of the composition of the cracker mixture, all the compositions were found to be thermally and mechanically sensitive. Although the impact sensitivity results reflected the change in the surface area of the particle sizes, the changes were within a narrow range of limiting impact energy (LIE) (7.5–9.1 J). Further it was difficult to pinpoint a particular sieve fraction as sensitive since the response to explosion depended not only on the flash composition and the particle size but also on the density and the compactness of the chemicals.

DSC studies on the effect of the Al particle size showed that a decrease in the Al particle size led to a second exothermic activity. This behavior should be viewed with caution when considering safety aspects.

Keywords: pyrotechnics, flash composition, fireworks, impact sensitiveness, friction sensitiveness, differential scanning calorimeter, potassium nitrate, sulphur, aluminum

Interrelation between Impact, Friction and Thermal Energy in a Pyrotechnic Flash Reaction

S. P. Sivapirakasam and M. Surianarayanan
Cell for Industrial Safety & Risk Analysis, Chemical Engineering Department, Central Leather Research Institute, (Council of Scientific & Industrial Research), Adyar, Chennai, 600 020, India.

Abstract: Firework chemical mixtures are sensitive to thermal and mechanical stimuli and lead to many explosive incidents. Experimentally determined thermal and mechanical (impact and friction) sensitivity data of a flash composition mixture are subjected to statistical and graphical analysis in order to understand the mechanism of triggering accidents. The interrelationship study reveals that irrespective of the nature of stimuli, explosion is the final event and occurs due to a thermal mechanism. This study shows that under severe impact thermal stimuli can occur. If the thermal stimuli are equal to or greater than the activation energy of the composition then ignition of the flash composition will occur.

Keywords: flash composition, fireworks, impact sensitiveness, friction sensitiveness, thermal sensitiveness, correlation analysis

Thermal Characterization and Kinetic Modeling of a Pyrotechnic Flash Composition under Adiabatic Conditions

S. P. Sivapirakasam, M. Surianarayanan and R. Vijayaraghavan
Cell for Industrial Safety and Risk Analysis, Central Leather Research Institute Chennai, 600 020, India

Abstract: A pyrotechnic flash composition consisting of 53% KNO₃, 30% Al and 17% S is subjected to Accelerating Rate Calorimetry (ARC) studies. The onset point for thermal explosion is 191 ºC resulting in the generation of a considerable quantity of gaseous products. The mixture is vulnerable to thermal hazards. There is good agreement between the predicted and experimental self-heat rates determined using adiabatic thermo kinetics.

Keywords: flash composition, ARC, fireworks, adiabatic thermo kinetics, thermal characterization

Communications :

Review by Christopher Pearce of Fireworks – Principles and Practice, 4^th Edition by Rev R Lancaster MBE

Selected Papers from the 2^nd Workshop on Pyrotechnic Combustion Mechanisms:

The Combustion Products of Novel High-Nitrogen Energetic Materials

David E. Chavez, Michael A. Hiskey, My Hang Huynh, Darren L. Naud, Steven F. Son and Bryce C. Tappan
Los Alamos National Laboratory, High Explosives Science and Technology, DX-2 MS C 920, Los Alamos, NM 87545, USA

Abstract: High-nitrogen energetic materials based on the tetrazine and tetrazole ring systems have shown unique and unpredictable combustion behavior. Unlike traditional energetic compounds, such as 2,4,6-trinitrotoluene (TNT) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), which derive their energy by the oxidation of the carbon and hydrogen skeletal atoms by the oxygen carrying nitro group, high-nitrogen materials typically have large positive heats of formation as their source of energy. This difference in the energy source may partly explain why the combustion chemistries of some high-nitrogen materials are unusual.

Using the precursor 3,6-bis-(3,5-dimethylpyrazol-1-yl)-s-tetrazine (BDT), several useful energetic compounds based on the s-tetrazine system have been synthesized and studied. A number of these tetrazine based materials have shown to exhibit burn rates with low sensitivity to pressure, namely 3,6-bis(1H-1,2,3,4-tetrazol-5-ylamino)-s-tetrazine (BTATz), 3,6-bis-nitroguanyl-1,2,4,5-tetrazine (NQ₂Tz), the corresponding bis-triaminoguanidinium salt (TAG₂NQ₂Tz) and the N-oxides of 3,3´-azobis(6-amino-1,2,4,5-tetrazine) (DAATO3.5). A fifth compound of high nitrogen make-up, triaminoguanidinium azotetrazolate (TAGzT, is not prepared from BDT, but it also burns at exceptional rates with low pressure sensitivity.

The tetrazole-based materials, bis-(1(2)H-tetrazol-5-yl)-amine (BTA) and 5,5´-bis-1H-tetrazole (BT), are useful high-nitrogen energetic ligands for the preparation of metal complexes. While BTA, BT and their salts have been previously shown as possible energetic fuels for low-smoke pyrotechnic applications, some recent combustion experiments with the metal complexes of BT and BTA have proved to be even more noteworthy. These metal ion complexes have sufficient internal energy that they can burn under an inert atmosphere to produce the free metal, usually in the form of high-surface area foams or nano-sized particles. This highly unusual, reductive combustion chemistry may lead to efficient and controlled production of metal nanofoams.

The heat of formation (ΔH_f) of 3,6-diazido-1,2,4,5-tetrazine (DiAT), a highly energetic and sensitive energetic material (most notably to friction, spark and impact), was calculated to be approximately +1100 kJ mol⁻¹, or +92 kJ mol-atom⁻¹, using an additive method. Depending on the heating rate, DiAT can undergo pyrolytic decomposition to produce either carbon nanospheres or carbon nitride nanopolygons. With slow heating, leaf-like or rope-like forms of carbon nitride were the predominant products. With faster heating, carbon spheres with diameters on the order of 10 to 100 nm were produced. Such nanomaterials are of interest to the scientific community for a wide number of industrial applications.

Keywords: high-nitrogen, tetrazole, tetrazine, combustion, nanomaterials, propellant, foam
Reprint Information: Number of pages = 10.

Laser-Initiated Reactions of Energetic/Thermitic Composites

Jared C. Gump and Suhithi M. Peiris
Indian Head Division, Naval Surface Warfare Center, 101 Strauss Avenue, Indian Head, MD 20640, USA

Abstract: Researchers are attempting to prepare smaller (nano-scale) metal particles, and nano-scale thermitic (metal–metal-oxide) composites. When added to energetic compositions, these nano-materials could burn during or close behind the shock front produced by an explosive material. Therefore, investigation of their combustion kinetics is important, especially when the investigation technique requires only very small quantities of material that is initially prepared. This study uses time-resolved emission spectroscopy to measure reaction kinetics and mechanisms of micrograms of material initiated by a laser pulse. Results from nano-scale aluminum and the thermite-type compositions of Al + Fe₂O₃, Al + MoO₃, and Al + B₂O₃ are presented here.

Keywords: laser, nano-scale, composite, kinetics, time-resolved spectroscopy
Reprint Information: Number of pages = 6.

New Approaches to Model Pyrotechnic Reactions

Stefan Kelzenberg, Norbert Eisenreich and Volker Weiser
Fraunhofer Institut für Chemische Technologie, Joseph-von-Fraunhofer-Str. 7, D-76327, Pfinztal, Germany

Abstract: In most cases pyrotechnic mixtures are constituted from granular components. A theoretical study of such a granular system describes the temperature and concentration evolution in the energetic material by using hot spots as source terms for temperature and particles. The progress of the reaction is mainly influenced by particle properties which are size, melting and evaporation, gasification and surface reactions. In a first step the influence of the particle size ratio between fuel and oxidizer particles is investigated.

Keywords: hot-spot model, combustion, ignition, pyrotechnics, Green’s method
Reprint Information: Number of pages = 8.