Spectral Flare Compositions

Wang et al. [34] have determined the rotational-vibrational temperature for gaseous species in a spectral flare composition given below... 

Koch, E.-C. (2007) Pyrotechnic countermeasures. Ill the influence of oxygen balance of an aromatic fuel on the color ratio of spectral flare compositions. Propellants, Explos., Pyrotech., 32, 365-370. 

The spectral efficiency of a flare composition is closely related to the combustion enthalpy of the flare composition, the plume temperature and the spectral emissivity of its combustion products as described in Eq. (10.18)... 

Payloads based on boron, PTFE, perchlorates and Viton have been proposed as both flare payloads for spectral flares and spectrally matched igniter compositions [55, 56]. Combustion of these materials yields significant amounts of FBO and CO2, both of which serve as spectral emitters [57] (see Figures 9.37 and 9.38). Typical compositions are given below ... 

A breakthrough discovery was reported by Sabatini (ARDEC) in the area of green illuminants. Formulations without any heavy metal can be based on boron carbide (B4C, fuel) with a suitable oxidizer (e.g. Iboron carbide (B4C) in pyrotechnical compositions. It can be seen that flares with 100% boron carbide as fuel show longer burn times and higher luminous intensity than the control barium nitrate based flare (M125 Al) while the spectral (color) purity is slightly lower. 

Long-burning formulations for infrared tracking flares typically comprise burn rate modifiers that extend the burning time. For this purpose, barium stearate has been proposed. Figure 10.20 shows the effect of stearate content on both normalized burn rate and spectral efficiency. Whereas the burn rate drops to levels of 20% of the unaffected composition shown below, the spectral efficiency climbs up to levels of 140% [28]. 

The radiant intensity profile for equal amounts of standard MTV decoy flare mix with the above composition is depicted in Figure 10.23. The spectral efficiency for the latter is about twice ( 2.03) in the 2-2.6 pm band. This is due to the much higher Mg content in MTTP formulation (66 vs 54wt% Mg). However, despite the high Mg content, the latter formulation shows a very slow rise in intensity, indicating a slower burn rate. Thus this material would require a different grain geometry to meet with operational rise time specifications. 

Herbage, D.W. and Salvesen, S.L. (1995) Spectrally balanced infrared flare pyrotechnic composition. US Patent 5,472,533, USA. 

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