Ablation of Liquids for Laser Propulsion with TEA CO2 Laser

Time-resolved force sensing and intensified charge-coupled device (ICCD) imaging techniques were applied to the study of the force generation mechanism for laser ablation of liquids. A Transversely Excited at Atmospheric pressure (TEA) CO2 laser operated at 10.6 micro-m, 300 ns pulse width, and 9 J pulse energy was used to ablate liquids contained in various aluminum and glass vessels. Net imparted impulse and coupling coefficient were derived from the force sensor data and relevant results will be presented for various container designs and liquids used. ICCD imaging was used in conjunction with the dynamic force techniques to examine dependencies on absorption depth, irradiance, surface curvature, and container geometry. ICCD imaging was also used to determine whether surface or volume absorption should be preferable for laser propulsion using liquid propellants. Finally, ballistic experiments were conducted in order to verify the dynamic force data and lend additional evidence to the predominant methods of force generation. Presented at the International Symposium on Beamed Energy Propulsion (4th), held in Nara, Japan, on 11-14 Nov 2005. Prepared in collaboration with Propulsion Directorate, Air Force Research Laboratory (AFRL), Edwards AFB, CA.