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Gas phase absorption of solar radiation has been suggested as an energy source to power space propulsion systems. The absorbing gas could be an expendable propellant or could be used in a closed cycle, exchanging heat with an expendable propellant. This study was conducted in order to develop basic data and understanding useful for the evaluation of such a system with the absorbing gas being a halogen or an interhalogen. Experiments and analysis were conducted to characterize the absorption of ultraviolet and visible radiation and subsequent energy release in chlorine gas, iodine monochloride vapor, and mixtures of hydrogen gas and chlorine gas. Xenon flashlamps were used to provide the radiation. Measurements included lamp electrical and optical characteristics, light energy absorbed, pressure rise in the closed reactor and reactants remaining after the reaction. Analysis included detailed kinetic modeling of the single shot experiments.

This report describes experimental and analytical efforts conducted to develop a new chemical laser nozzle concept, the tri-stream (or three-stream) chemical laser nozzle. This nozzle expands the cavity fuel and the fluorine atom (combustor effluent) flows through the same nozzle. The fluorine and cavity fuel streams are separated by a layer of diluent flow to inhibit intermixing and reaction of the fluorine atom and cavity fuel in the nozzle. These three streams (fluorine atom, diluent, and cavity fuel) form a basic unit, or element, of the device, and the number of elements per unit length of nozzle is the most important parameter affecting the achievable performance. Tri-stream nozzles were designed, fabricated, and tested in 2.5-inch-long by 0.4-inch-high nozzle exit configurations. Laser power tests of the tri-stream nozzles were conducted in a free-jet test facility capable of pumping to cavity pressures as low as 2.5 torr. The maximum specific power achieved with DF* lasing using all helium diluent was slightly in excess of 80 kJ/lb. The maximum DF* specific power achieved with N2 nozzle diluent was approximately 60 kJ/lb.

The purpose of this program was to investigate experimentally the performance characteristics of high-pressure recovery, high-performance, advanced nozzle concepts for supersonic chemical lasers. Tests were conducted at small-scale (1 by 3 inches) sizes using scanning mirrors and a high-spatial-resolution IR spectrometer to examine performance. A small water-cooled pitot probe was used to scan the flowfield at the cavity exit to measure potential pressure recovery. A large-scale version of one of the nozzle configurations was designed and fabricated during this program and tested at the Mesa facility by the Aerospace Corporation. The Mesa results provided size scaling data for projecting Laser Engineering Test Facilities (LETF) results to larger sizes. Screening tests were performed on an advanced nozzle concept which provides increased mixing rates, larger throat dimensions, and decreased fabrication time and cost. The results of the screening tests indicated that the nozzles performed as predicted.