Temperatures From Spectroscopic Studies of Hot Gas and Flame Fronts in a Railgun

High-speed video (143 kframes/s) and optical spectroscopy (1-ms integration, 188-1100 nm) recorded light-emission events occurring at a railgun by aiming directly down the bore or at the backside of the breech. Blowback was marked by a wave of high-intensity light, smoke, a flame front, and glowing particles traveling back up the bore from the muzzle and lasting up to or beyond 60 ms after launch. Spectra taken down bore and during blowback had signature peaks for alkali metals, AlO, and CuO. Estimated radiation temperatures T_ER were determined by fitting a Planck distribution to the spectral backgrounds. In the bore, T_ER was between 3700 K and 3000 K at the start of travel and cooler (2500 K) at the muzzle blast. During blowback, T_ER ranged from 2400 K to almost 4000 K, the combustion temperature of Al particles. Some shots showed T_ER consistently around 3600 K during the entire blowback period.