Innovative Solid Formulations for Rocket Propulsion

Abstract

Solid rocket propulsion enjoys several unique properties favoring its use in space exploration and military missions still for decades to come, in spite of being by far the most mature propulsion technology among those currently employed. Yet, solid rocket propellants also suffer a limited performance in terms of gravimetric specifi c impulse. Although many high-energy density materials have been identifi ed, most of them are far from being practically usable in the short range due to a variety of severe diffi culties, including cost considerations. Presently, no integrated vehicle designs make use of these potential propellant ingredients<br />and formulations. Work is continuing worldwide and a broad overview will be discussed in this paper based on a joint international editorial effort just completed. After a quick historical survey, the current situation in terms of advanced solid oxidizers, metal fuels, and binder systems is scrutinized. Particular attention is paid to Ammonium Dinitramide (ADN)-based formulations to overcome the limitations of the currently used ones based on Ammonium Perchlorate (AP). The latter imply not only a limited gravimetric specifi c impulse but also a negative impact on the environment because of copious emissions of hydrochloric acid (HCl) as well as personal health because of perchlorate competition with iodide in entering the thyroid gland. Based on recent experimental investigations, due to its intrinsic ballistic properties, it turns out that ADN-based dual-oxidizer systems with Albased dual-metal fuels and inert or energetic binders are promising solutions for a variety of solid rocket propulsion aiming respectively at minimizing environmental impact (ADN + Ammonium Nitrate AN) or maximizing performance (ADN + AP). Yet, a lot of work remains to be done in order to upgrade these formulations to industrial applications. In particular, adequate analyses of manufacture, mechanical, and hazard properties are required.