Design of target support columns using EPS foam

When making RCS measurements on a ground-bounce range, EPS foam columns are frequently used as target supports for test bodies and air vehicles. Since background subtraction is rarely used to suppress foam-column scattering in large-scale RCS measurements, the columns must be structurally sound while maintaining a minimized RCS signature over the aspect angles, and radar frequency band, of interest. The goal is to devise a column that is unnoticeable in the measured data, yet strong enough to support a specified weight. The major factor that contributes to EPS foam-column scattering is shaping, and finding the optimal shape for a particular test is not trivial. Part 1 of this paper describes methods in the design and construction of EPS foam columns. Subjects include determination of EPS material properties, mathematical specification of column geometries, accurate and efficient computation of column mechanics and scattering, and effective optimization of column parameters. Part 2 of this paper shows comparisons of predicted column RCS to column measurements performed at NRTF. These comparisons give credibility to the concept of foam-column modeling and ground-bounce range scattering simulations, and give range engineers confidence in the foam-column design process.