Chemical oxygen-iodine laser performance modeling

Abstract

We have developed a detailed engineering model for chemical oxygen-iodine laser (COIL) performance and design predictions. In this model, mixing between the primary oxygen and the secondary iodine injectant is treated using a two-stage/three-stream shear-layer model based on the flow characteristics of the transverse injection mixing scheme. Iodine dissociation, excited-state pumping, and quenching processes are treated using the Phillips Laboratory standard COIL kinetics package. Optical extraction from a stable resonator is described by a rooftop geometric optics model. These models have been incorporated into a two-dimensional Advanced Cavity Code for COIL (AC3). The detailed models in AC 3 have been systematically validated by comparing detailed code results reflecting a hierarchy of computational complexity with data from relevant experiments. The validity of the mixing, kinetics, and optics models has been corroborated by comparing the predictions of the code with iodine dissociation, laser small signal gain, and optical power measured in the RotoRADICL device. Selected small signal gain and output power measurements from the low pressure RotoCOIL were also reproduced by the model. Computational results showed good agreement with power measurements from the high efficiency RotoRADICL/JogRADICL experiments with different throat heights. Also, predicted results showed reasonably good agreement with the dissociation and power data obtained using the RADICL device and the baseline or Big-volume generator. Output power data obtained with Rocketdyne's closed-loop Mini-GDU device were excellently predicted by the model. The good agreement with the data obtained from various devices encompassing a broad range of experimental parameters lends credibility to this model. Without an elaborate CFD and wave optics model, the good agreement strongly suggests that the present model contains the essential physics for adequate modeling and prediction of COIL performance.