Characterization and discrimination of large caliber gun blast and flash signatures

Two hundred and one firings of three 152 mm howitzer munitions were observed to characterize firing signatures of a large caliber gun. Muzzle blast expansion was observed with high-speed (1600 Hz) optical imagery. The trajectory of the blast front was well approximated by a modified point-blast model described by constant rate of energy deposition. Visible and near-infrared (450–850 nm) spectra of secondary combustion were acquired at ∼0.75 nm spectral resolution and depict strong contaminant emissions including Li, Na, K, Cu, and Ca. The O2 (X→b) absorption band is evident in the blue wing of the potassium D lines and was used for monocular passive ranging accurate to within 4–9%. Time-resolved midwave infrared (1800–6000 cm-1) spectra were collected at 100 Hz and 32 cm-1 resolution. A low dimensional radiative transfer model was used to characterize plume emissions in terms of area, temperature, soot emissivity, and species concentrations. Combustion emissions have ~100 ms duration, 1200–1600 K temperature, and are dominated by H2O and CO2. Non-combusting plume emissions last ~20 ms, are 850–1050 K, and show significant continuum (emissivity ∼0.36) and CO structure. Munitions were discriminated with 92–96% classification accuracy using only 1–3 firing signature features.