Ammonium perchlorate (AP) based propellants are used extensively throughout the Department of Defense (DoD) to deliver critical satellites to space and weapons to targets. However, both AP and its combustion products are hazardous to human health and the environment, and instances have been documented that show a strong link between the use of ammonium perchlorate and damage to the environment. The objective of this project is to advance an alternative technology concept – an integral hypergolic hybrid-supersonic ramjet motor – employing a developmental propellant combination that offers higher performance and poses fewer risks to human health and the environment. 

Technical Approach

To accomplish the objective, experimental testing and physics-based computational fluid dynamics modeling will be employed to develop and evaluate hypergolic hybrid rocket and solid-fuel ramjet combustors fueled with ammonia borane (AB)/nitric acid and AB/air (bipropellants), respectively. This project is designed to elucidate the combustors’ combustion dynamics, identify and resolve fundamental issues that might limit their performances, and establish their full operational capabilities. The effort should culminate in a validated dynamic fly-out model of integral hypergolic hybrid-supersonic ramjet motor. This model will provide a basis for establishing the performance potential of such motors versus the ammonium perchlorate-based solid propellant systems they seek to replace.


Upon successful completion of the project, the DoD will be able to evaluate both the environmental and performance benefits of an integral hypergolic hybrid-supersonic ramjet motor fueled with an AB-based propellant versus current systems. The performance benefits are expected to be quite substantial and include a potential 3.7 increase in total impulse, decreasing the time-of-flight, enabling ballistic flexibility – not available with current systems, and reducing vulnerability to various threats (improving insensitive munitions performance). Environmentally, AB is not considered to pose a concern, and its combustion products are likely to be benign. As such, only hazards associated with handling nitric acid will likely need to be addressed, but they are currently managed worldwide in many industrial applications. Additionally, detailed information about the combustion behavior of a very promising propellant combination will be made widely available, allowing industry, academia, and the private sector to fully evaluate its potential.