Chaff

A discussion of the present-day use of chaff as a viable and cost-effective countermeasure considers the principles of microwave reflection by chaff, and chaff materials, applications, and payloads. Chaff is made of electrically conducting filaments which are cut to form dipoles that are resonant at particular wavelengths. The conductive coating of a cylindrical dipole should have a radius that is large when compared with the skin depth, and a requirement for low RF resistance has tended to limit the choice of metals to aluminum, silver, copper, or zinc. Chaff design must consider the operational characteristics of the dispenser and hardware contained with the chaff payload. The majority of chaff types are silver-coated nylon and aluminized glass. Three types of aluminum chaff are compared, and the differences in section of these filaments affect the flight motion and, hence, radar response of the dipoles. Various techniques employed in air and naval dispensers to decrease the time required for chaff clouds to achieve maximum RCS are also discussed.