Effect of plasma confinement on laser ablation propulsion parameters by using external semi-elliptical cavities for Aluminum and Silver propellants

Abstract

Ablative laser propulsion (ALP) is a type of beam-powered propulsion in which thrust is produced by ablating a target using a high-intensity laser beam. In this research work, we calculated the ALP parameters momentum coupling coefficient (Cm) and specific impulse (Isp) by confining the plasma with the help of external semi-elliptical cavities. The cavity minor axis was fixed at 2.5 mm while the major axis varied to 7 mm, 9 mm, 11 mm, 13 mm and 15 mm. Silver and aluminum samples were used as propellants. A pulsed Q-smart Nd:YAG laser operating at 532 nm wavelength was used to ablate the target. A significant increase in the value of Cm and Isp was observed using confined ablative propulsion. The highest Cm and Isp were recorded for the 9 mm major axis cavity, for which Cm was increased from 5.01 × 10−5 N-s/J to1.75 × 10−4 nearly 249% for silver and from 3.4 × 10−5 N-s/J to 8.9 × 10−5 N-s/J nearly 161% for aluminum. Hence the use of semielliptical cavities is an effective technique for enhancing propulsion parameters. Cavity acts as a trap for plasma and shockwaves. Confinement of plasma and reflection of shockwaves from the cavity walls results in enhanced laser ablation propulsion parameters.