Investigation of a Marine Water-Breathing Hybrid Ram-Rocket Motor

Abstract

This work presents theoretical and experimental performance studies and a general scheme of an innovative concept for propelling marine high-speed underwater vehicles, a water-breathing hybrid ram rocket. The water-augmented hybrid ram rocket enables obtaining superior performance relatively to a standard rocket and improved performance relatively to a parallel water–augmented solid ram rocket. In addition, it demonstrates improved safety and controllability due to the hybrid motor characteristics. The theoretical model incorporated data from a thermochemical program. The experimental investigation was based on static firing tests of hybrid rocket motors augmented by the addition of water during combustion. The study focused on the use of a non-water-reactive propellant combination, cured polyester as fuel and gaseous oxygen as oxidizer. Wide ranges of oxidizer-to-fuel and water-to-propellant ratios were considered. The experimental results showed a significant improvement (up to 70%) in specific impulse, relatively to a non-water-augmented hybrid rocket, in good accordance with the theoretical results. It is concluded that for standard chamber pressure of 6.9 MPa, corresponding to the ram pressure for cruising at , a specific impulse greater than 400 s can be achieved by a water-augmented hybrid ram rocket using a non-hydro-reactive fuel.