Monitoring of Solid Rocket Motors

As so-called wooden rounds, which are intended to sit stably in storage for extended periods and then function precisely as desired at a moment's notice, missiles would appear to be an ideal application for health monitoring. However, the solid rocket motors that serve as the propulsion system for these missiles present a number of unique challenges for the development of integrated vehicle health monitoring systems. Mechanical and chemical complexity, long service lives, aging materials, and designs with small margins are typical for solid motors, but the payoff for health monitoring is extreme as well. Maintaining a healthy and capable fleet—ensuring the viability of the missiles in the fleet, while not retiring or destroying good assets before it is necessary—could save as much as 50% in costs over a 50-year life cycle. In this article, a number of unique aspects of solid rocket motors are explored, the difficulties and successes in the development of sensors and diagnostic systems are discussed, and a path to further continue the development of these systems is proposed. Keywords: solid rocket motors; stress sensors; bondline; chemical aging; mechanical damage