SOLVENTLESS EXTRUDED DOUBLE-BASE (EDB) PROPELLANT CHARGES—A REVIEW OF THE PROPERTIES, TECHNOLOGY, AND APPLICATIONS

Extruded double-base (EDB) charges are used mainly due to their efflux having minimum smoke, attractive oxygen balance, and low corrosivity. The propellant class also has desirable burn-rate characteristics since it exhibits plateau burning and has a low temperature sensitivity to burning rate (πk). External ballistic modeling results are presented that illustrate the performance advantages that EDB propellants can provide, compared to more energetic propellants that are also not minimum smoke. For rocket motors, the plateau behavior is generally achieved by the inclusion of lead salts as ballistic modifiers, although these have had increasingly restricted availability, and lead-free alternatives are not yet generally in use. The manufacturing processes, both traditional batch and continuous, are described, including that used for medium- and large-caliber solventless gun propellants. The inhibition methods for rocket propellant charges are discussed. Strengths and weaknesses are considered together with potential developments in processing and materials (e.g., synthetic/nano cellulose). Various current and recent applications for such charges are reviewed, as well as insensitive munitions (IM) aspects. Consideration is also given to the maturity and potential further implementation of other minimum-smoke propellants to predict the future opportunities for solventless EDB propellants in the next five years. This includes an assessment of some historical issues that have arisen when propellant and motor technology advances have been attempted. This paper focuses on topics that are either new or have not been included in previous reviews; it includes more than 65 references.