Axial Impulse Generation of Lightcraft Engines with ∼ 1 μs Pulsed TEA CO2 Laser

A twin Lumonics K922M pulsed TEA CO2 laser system (similar to 50 ns FWHM spike, with selectable 1.5 or 2.5 mu s tail-depending upon laser gas mixture) was employed to experimentally measure the axial impulse behavior of a family of lightcraft engine geometries, using a lightweight ballistic pendulum. Axial impulse performance in both airbreathing and solid ablative rocket (SAR) modes was examined as a function of: a) laser pulse energy (similar to 12 to 40 Joules); b) pulse duration (similar to 50 ns spike with 1.5 or 2.5 mu s tail); and, c) engine geometry. The four engines under investigation were the Lightcraft Types #150, #200 and #250, and a 11 cm parabolic bell. Lightcraft #200 axial C-M performance reached 250 N/MW, which is sharply higher than the 120 N/MW previously reported for the engine using long pulse (e.g., 10-18 mu s) CO2 electric discharge lasers.