Archive for January 2014

Visual and Near Infrared Mass Extinction Coefficient of Five Pyrotechnic Screening Smokes

Matti Harkoma

Abstract: The screening properties of five different obscurants were compared at relative humidities of 30%, 50% and 85% and mass extinction coefficients were calculated. The obscurants were five military smokes: 1) a traditional hexachloroethane, Zn powder and TNT based screening smoke, the HC smoke as a reference, 2) a potassium chlorite, Mg powder and azodicarbonamide based screening smoke, the KM smoke, 3) a Mg powder based HC smoke, 4) a potassium chlorate, lactose and terephthalic acid based white coloured screening smoke, the TPA smoke, and 5) a titanium oxide based HC smoke. The apparatus was a CCD (Charge-Coupled Device) detector based dispersive spectrometer with a sample chamber and a humidity generator. The wavelength region was 450 to 850 nm. The important variable in determining how a military smoke retains its screening properties over time is the mass extinction coefficient. According to the results, the Zn based HC smoke has the best screening properties at low relative humidity. When the relative humidity is high the Mg based HC smoke has the best screening properties at first, but the KM type smoke retains its screening properties well, being the best of these three smokes after 20 seconds. After 60 seconds, the mass extinction coefficient of the KM smoke is 33% higher than the mass extinction coefficient of the reference smoke, when the mass extinction coefficient of the Mg based HC smoke is 20% lower than the mass extinction coefficient of the reference smoke.

Keywords: Screening smoke, obscurant, extinction coefficient, infrared


Ref: JPyro, Issue 32, 2013, pp67-77 (J32-67)


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