The remarkably energetic boron-water reaction presents potential for employing boron as a fuel additive in water-breathing ramjets (ram rockets), consisting of a rocket combustor augmented by external water from the surroundings. Such motors utilize the high velocity of the vehicle, resulting in a high ram pressure that enables the ingestion of water into the motor. When mixed with the hot combustion products of the propellant, the water boils, generating steam that increases the overall mass flow rate, serving as well as an oxidizer for hydroreactive metals such as boron, aluminum, and magnesium, thus substantially increasing the energetic performance and thrust. This paper presents, for the first time, a comprehensive thermochemical analysis alongside an extensive series of over 100 static firing tests, evaluating the performance of a water-ramjet utilizing boron as a fuel component. The results reveal that the combination of a section of high temperatures from the propellant combustion gases, followed by a lower temperature section due to water introduction, creates favorable conditions for boron combustion and its energy utilization. As a result, a maximum standard specific impulse of 510 s with a combustion efficiency of 90% is demonstrated. Compared to more commonly employed metals such as magnesium and aluminum, boron demonstrates a 10% improvement in performance across broad ranges of metal mass fractions and water-to-propellant mass ratios, thereby expanding the operational range of the motor.
Study of Boron Fuel in a Water-Breathing Ramjet
2025-05-01
Article (Journal)
Electronic Resource
English
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