Dielectric constant of plastic foams

A cubic lattice is used to form a simple engineering estimate of the dielectric constant of plastic foams of the type used to build target support structures for RCS test ranges. The estimate predicts slightly higher dielectric constants than an empirical estimate proposed by Cuming. The estimates provided by both methods are slightly lower than values deduced from scattering measurements of a collection of nine plastic foam cylinders. This may be because the gas within the foam cells has a dielectric constant slightly greater than unity.>