Shotline method for estimating aircraft infrared radiant intensity

Infrared (IR) emissions from aircraft are used to detect, track, and lock onto the target. For the analysis of IR signature, many parameters concerning aircraft configuration are flexible in the preliminary design stage. For candidate aircraft concepts, the accurate IR signature level is less important than relative IR values. Hence, in the preliminary design stage, a low-fidelity and quick-assessment method is needed. This research applies a shotline method, which is usually used to generate a line-of-sight description of an aircraft, and its components in vulnerability assessment to estimate aircraft IR radiant intensity. The aircraft is approximated using simple elements, such as quadrangles, boxes, cylinders, ellipsoids, and cutting planes. Each element is described by taking account of material emissivity, temperature, and radiant wavelength bands. By superimposing a planar or curved grid over the aircraft model and passing shotlines from a given detector aspect, the IR signature's masking or shielding among different elements could be analyzed, and the IR signature could be quantified by summing the radiant intensity that corresponds to each grid. Three examples show that the shotline method has flexibility in model approximation and computation time cost and is applicable for predicting IR radiant intensity for aircraft preliminary design.