Lightcraft Impulse Measurements under Vacuum

Under an EOARD contract, the DLR has conducted a series of comparative impulse measurements for two different lightcraft configurations with the same nozzle exit diameter of 10 cm: The German design (GL) is of the more conventional parabolical bell shape with a plasma breakdown region at the focal point of a parabola. The second lightcraft was supplied by the Air Force Research Laboratory (AFRL), and was designated as model 200-3/4. The experiments utilized the DLR multi-gas laser, running in CO(2) with a laser wavelength of 10.6 m. It was the goal of this investigation to extend previous atmospheric impulse measurements to a vacuum environment and to measure specific propellant consumption of the solid propellant Delrin in order to determine the exhaust velocity and the specific impulse for both lightcrafts as a function of the laser pulse energy at various pressures