A Monte-Carlo-based simulation of jet exhaust nozzle thermal radiative signatures

Abstract

An important consideration in the design of military aircraft is observability, or how visible an aircraft is to hostile weapons. One area of great importance to overall observability is an aircraft’s infrared signature, particularly the infrared emissions from the exhaust nozzle and plume. This creates the need for accurate modeling of the infrared signatures from these sources as a design aid or for comparison of candidate designs.

To that end, a parametric model has been developed based on the General Electric F110-GE-129 jet engine. The basis of the model is a highly flexible Monte-Carlo ray-trace formulation which is capable of simulating real surface behavior, such as specular reflections, and allows for variation of input parameters such as temperature, surface properties, and geometry. For given input parameters, the model predicts the overall infrared signature due to surface radiation from the exhaust nozzle and interior components. It also indicates the relative contribution of each interior surface to the overall signature and predicts the image that would be seen using infrared imaging equipment. The basic principles of the simulation method and the theory behind the application are discussed. Results are presented, primarily in graphical format, and recommendations are made for further work.