Description:
OBJECTIVE: To develop an alternative to the existing hexachloroethane (HC) and terephthalic (TA) smoke compositions that will produce a very low flame while maintaining a high smoke output. This composition should be similar in high performance as the M8 HC Smoke Grenade but with much less toxic materials and less incendiary hazards. New formulations should avoid hazardous materials to address toxicological concerns. HC smoke grenades produces toxic products such as zinc chloride. Some flame reductions could be achieved through hardware design, but improved chemical compositions are desirable. These devices intended for hand held devices to protect personnel, specifically the M8, but can also find use in the vehicle launched M83 grenade as well. Desirable specifications of the M8: provide a screen 3 meters high by 10 meters long; build up a cloud within 6 seconds,; having a duration of at least 90 seconds. Current TA smoke is a much less toxic and less incendiary smoke but is much lower in performance than the M8 HC smoke. DESCRIPTION: Currently visible obscurant grenades employ high explosives configured as a center burster to disseminate spherical powders. These devices offer very short dissemination periods, making it difficult to maintain protection for the soldier and equipment. Pyrotechnic smokes are composed of active fillers that typically consist of HC smoke mixtures (hexachloroethane/zinc) or TA smoke mixtures (terephthalic acid). In addition, Red Phosphorus is widely used to generate long duration visible obscuration. For all pyrotechnic or burning devices, there are many flame hazards associated with them that restrict their use. These items are avoided because they start brush fires in outdoor applications. They are very difficult to use for indoor applications and create hazards for personnel. The following is a list of performance metrics of various visible smoke grenades. 1. Red Phosphorous (RP) Yield factor of 4.8 at 10 degrees C, 50% RH. Extinction () is 3.5m2/g, Pack Density 2.0, FOM=21 2. Hexachloroethane (HC) Yield factor is 2.1 at 10 degrees C, 50% RH. Extinction () is 3.9m2/g, Pack Density 1.9, FOM=7.4 3. Terephthalic (TA) Yield factor is 0.28 at 10 degrees C, 50% RH. Extinction () is 4.9m2/g, Pack Density 1.3, FOM=3.4 PHASE I: Develop alternative formulations that when reacted, produce a yield factor of at least 2.0. Yield factor is the amount of grams airborne divided by the total amount of grams disseminate. New formulations should also have material extinctions of at least 3.5m2/g in the visible wavelength region. Flame fronts reduction should be at least 50% the HC M8 grenade, which is generally around 1ft at initiation. Ideally, no flame fronts are desired. Demonstrate a concept that can produce a similar amount of smoke as the M8 without using HC that can give Grenade Figure of Merit (FOM) of about 4.0. The FOM for a grenade would be the product of the extinction value, fill fraction, packing density and yield. One possible solution would be to produce hydroscopic species that can increase yield factors(FY). Improving the YF of the current TA smoke grenades (M83 and M90) from approximately 0.28 (or 28%) to something closer to the HC grenades will increase the Grenade Figure of Merit (FOM). Improvement in the how to fill and pack devices will improve the fill fraction and packing densities. New formulations should have higher than 4.0 extinction coefficients (with a high scattering component) in the visible region and be less toxic than the current M8 HC Smoke Grenade. Edgewood Chemical Biological Command (ECBC) has already focused on the ability to obtain a suitable reactions from the embedded chlorine with environmentally friendly oxidizers, as well as looked at finding other suitable fuels to replace the zinc in the old HC smoke composition. Tests can be performed at ECBC obscurant chamber to determine dissemination efficiency, extinction values, temperature and burn rates. At least 5 devices with different formulations should be delivered to ECBC for testing at the end of Phase I Toxicology is a complex and expensive field to evaluate. For Phase 1, a literature search should be provided to compare any new formulation to the existing HC formulation. In reference 6, the 15 minute exposure for HC smoke is given as 10mg/m3. PHASE II: Down select from the Phase I effort at least two formulations that show improvements in the grenade figure of merit and reductions in flame fronts on the M8 size device. Refine the design into two fully-functioning grenades. These must have the overall dimensions of the M106 or M8 handheld grenade. The second part of the Phase II effort is to design and produce using the previous formulations a larger size device with the overall dimensions of the M90 vehicle launched grenade. Scale up includes both hardware design and generation of material. An analysis of how the increase container size and material fills will effect the smoke production and dispersion. Finally, scale up production of the fill material and grenade hardware to be able to field test 60 (30 of each M8 and M90 size) devices at ECBC outdoor field testing areas to demonstrate improvements in smoke production (FOM) and flame reduction. PHASE III DUAL USE APPLICATIONS: The grenades developed in this program can be integrated into current military obscurant applications. Improved visual devices are needed to reduce current logistics burden in needing to carry countermeasures to protect the soldier and his equipment. Other dual use applications include markers for emergency rescue, signaling operations and aeronautic stunt planes. Improved dissemination techniques can be beneficial for all powdered materials in the metallurgy, ceramic, pharmaceutical and fuel industries. Industrial applications include electronics, fuel cells/ batteries, and solar energy. REFERENCES: 1. Bohren, C.F.; Huffman, D.R. Absorption and Scattering of Light by Small Particles; Wiley-Interscience: New York, 1983. 2. Embury, Janon; Maximizing Infrared Extinction Coefficients for Metal Discs, Rods, and Spheres, ECBC-TR-226, Feb 2002, ADA400404, 77 Page(s) 3. Clyens, S.; Johnson, W., The Dynamic Compaction of Powdered Materials, Materials Science and Engineering, 30 (1977), 121-139. 4. Schwarz, R. B., Kasiraj, P., Vreeland T., Ahrens, T. J., A Theory for the Shock-wave Consolidation of Powders, Acta Metall., Vol. 32, pp. 1243-1252. 5. Pyrotechnic Smoke Analysis Vol I, ERDEC-TR-129, N. Sordoni, W.Heard, W. Rouse, Dec 1993 6. Toxicity of Military Smokes and Obscurants, Vol 1, Committee on Toxicology, Commission on Life Sciences, National Research Council., ISBN 0-3090-56 166-3
