Dynamic RCS Estimation of Chaff Clouds

We analytically investigated electromagnetic wave propagation through chaff clouds. The chaff fibers are assumed to be long and thin cylinders. The trajectory tracking algorithm was developed based on a combination of the six degree-of-freedom (6 DOF) equations of motion and the aerodynamic forces and moment acting on the chaff fibers. For the low Reynolds number flows around the chaff fibers, the normal force was obtained from a curve-fit formula offered by Sucker and Brauer, while an analytic solution offered by Curle is used to obtain the tangential force. The position and orientation of the chaff fibers as a function of time are thereupon obtained. As inputs of a generalized equivalent conductivity (GEC) method, this information is used to calculate the radar cross section (RCS) of the chaff cloud. The GEC method can estimate the RCS of a chaff cloud with an arbitrary orientation distribution for reducing computation time. The proposed chaff cloud model (CCM) can be applied to predict accurately the steady state response as well as the transient response before the RCS of the chaff cloud reaches the steady state.