IR flares

Infrared radiation is used for both civil and military applications. The military applications are target acquisition, surveillance, homing and tracking. IR flares are used in military applications mainly for two purposes tracking a missile and decoying enemy missiles [13, 14]. Depending on their applications, IR flares are classified into three different classes. 

An IR flare is a compressed pellet of fuel and oxidizer with suitable additives. 

The MTV formulation is the most common pyrotechnic formulation used for IR flares. The main reaction on combustion of Mg with Teflon is as shown in Equation 5.7 ... 

Some information on IR flares is available in the literature. Two pyrotechnic formulations consisting of Mg-Teflon-rosin and Mg-Ba(N03)2-rosin were formulated and studied for radiant intensity, mass flow rate, effect of combustion temperature by Gongpei and coworkers [15] and the gist of their findings is as follows ... 

The salient features of some IR flares and decoy flares burning time, IR output along with end use, are given in Table 5.6. 

Modern missiles employ counter-counter measures. Their advanced seeker heads use two or more spectral bands in an attempt to distinguish between the flare and the target. Trajectory discrimination may also be used by some seeker heads. The physical size of the heat source is more important as imaging seekers that can discriminate a spot target of IR flares, have been developed. Depending on their application, IR decoy flares can be further classified into ... 

The IR intensity of IR flares is measured by using a radiometer which consists of both optical and electronics systems. The radiometer uses the optical system consisting of mirrors and lenses to collect the radiation emitted by the object and focuses this radiation upon an IR detector which converts it into an electrical signal. This signal after amplification is processed by the computer system where it is stored. This stored data can be displayed on the monitor and printed. 

The set-up and method of measurement of IR intensity is similar to that of luminous intensity. The distance between the radiometer and tunnel is 82 m in this set-up. While carrying out measurement of IR intensity, the IR flare is mounted on the stand and radiometer is focused onto the flare. The fan is switched on and when it achieves a uniform speed, the flare is ignited and radiation emitted by the flare is received by the radiometer. The radiometer operates in two modes ... 

Bixon, E., Broad, R., DeSalvio, J., Gagliardi, F., Nagori, A., Poret, J. and Zimmer, A. (2008) Accelerated aging of the M206 countermeasure IR flare. 35th International Pyrotechnics Seminar, July 13-18, Fort Collins, CO,... 

Dillehay, D.R. and Leander, R.C. (1994) Cowles-dissolver fire involving IR flare mix. Proceedings of the 26th DoD Explosives Safety Seminar, Miami, EL, August 16-18. 

Perimeter Monitoring - The perimeter of a hazardous area or process unit can be effectively monitored for vapor release by IR beam arrangements on the edges. Theoretically they could be used to warn of open air combustible vapors approaching ignition sources in a reverse role, e.g., to the flare from the process area. 

The IR intensity of formulations based on Mg/KN03/hydrocarbons are equally high and are used in new decoy flares. These formulations are good for decoy... 

Results of a comprehensive study of the absolute spectral radiance of the infrared emissions from methane—air expins have been reported (Ref 44). The spectral growth of these expanding flames was recorded with a time resolution of one msec in the spectral range 1.7— 5.0 microns. Time resolved spectra were obtained as a function of stoichiometry, nitrogen dilution and Halon dilution. Similar data are also available for coal dust-air explns. Additional applications of rapid scan IR spectroscopy are discussed in Ref 50. In this work, flare spectra (Mk45, LUU-2B and LUU-2B/B) in the 1.7-4.7 and 9—14 micron regions were studied. The Mk-45 and LUU-2B/B showed similar spectral character with Na and C02 emissions superimposed on a gray body continuum, while LUU-2B flares demonstrated variable emittance properties... 

The terms decoy flare or countermeasure munition are used to denote a system, which imitates the IR signal of a plane and therefore ground-air, water-air or air-air rockets, so-called heat-seeking missiles, get lured away from their targets. One of the first and best-known IR seekers - Sidewinder was developed in China Lake (Fig. 2.20). 

The schematic construction of a IR decoy flare is shown in Figure 2.22. The main reaction between Mg and Teflon can be formulated as follows, where m > 2 ... 

The radiant intensity (I) is a measure of radiometric power per unit solid angle Q (Q = A/ r2), expressed in watts per steradian (W sr-1). The value of the solid angle Q is numerically equal to the size of that area divided by the square of the radius of the sphere. For hand-held NIR flares one wants a reasonable bum time (ca. 45 s), a high concealment index X which is defined as the ratio of the radiant intensity in the near IR region (/NIR, 700-1000 nm) over the radiant intensity in the visible region (IvIS, 400 700 nm) and high radiant intensities in the NIR regions /j(600 900 nm) and /2(695 1050) ... 

Mixtures containing 65% of tungsten with organic binders were developed as priming charges for surface flares [1]. Ignition of the dual metal-oxidant mixtures by IR irradiative heating was studied [2]. 

Enhancement of the radiation from the propellant exhaust of drones by target flares may be called visual signaling even though it is only for the benefit of a sensor in an attacking missile guided by IR radiation. 

The efficiency in terms of cp sec/g metal for flash charges is much inferior to that for flares. Since a much larger part of radiant emission is in that part of the infrared that can be made photographically useful with special IR sensitive film, efforts have been made along these lines. ... 

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