Experiments were conducted to simulate radiant heating of the propellant stream of a nuclear light bulb engine. The primary objective was to obtain high exit temperatures in the simulated propellant stream due to the absorption of large per¬centages of the incident thermal radiation. A high-power d-c arc was used as the radiant energy source and argon seeded with carbon particles was used to simulate the propellant. Unseeded buffer layers were used to prevent coating of the trans¬parent duct walls. Methods were developed for introducing micron-sized carbon seeds into the central region of a three-stream flow in an annular duct to simulate the propellant stream.nThe bulk temperature in the exhaust of a reference nuclear light bulb engine is expected to be 12,000 R. A long-range goal of the propellant heating experiments conducted in the laboratory is to obtain as high a value as possible of this bulk exit temperature in a configuration closely simulating that of the engine. The results of the first phase of these experiments indicate that simulated propellant bulk exit temperatures between approximately 3000 and 4000 R have been achieved. Based on thermocouple measurements at lower temperatures, it is inferred that local temperatures at points in the simulated propellant duct were substantially greater than the bulk temperatures. The maximum bulk exit temperatures achieved in the tests to date were primarily limited by the particular cooling configuration employed for the transparent wall adjacent to the radiation source and by partial vaporization of the foam material used at the propellant stream inlets.
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