Performance of Water-Augmented Metallized Hybrid Propellant Ram Rocket During Underwater Motion

This paper presents research on torpedo-like vehicles cruising underwater at very high speeds with water-augmented metallized hybrid propellant ram rocket motors (water-breathing ramjets), exhibiting superior energetic performance and thrust to that of conventional underwater rocket propulsion systems. Metal additives (aluminum and magnesium) within a polymeric fuel react with the ingested water, substantially increasing the specific impulse beyond that of non-hydroreactive fuels. A parametric investigation on firing tests of a submerged ram rocket vehicle during motion revealed the effect of additive type and contents (up to 40% mass fraction), oxidizer-to-fuel ratio, water-to-propellant ratio, and cruise speed on the standard specific impulse. Results demonstrated a specific impulse augmentation to 430 s, representing an improvement of up to 70% compared to conventional rocket propulsion systems and a 13% increase compared to fuels with non-hydroreactive ingredients, showing good correspondence to previous static firing data.