Abstract: A hybrid rocket motor includes a solid propellant fuel grain component which incorporates fuel strengthening agents or mechanical retention devices. In one embodiment, the hybrid fuel formulation is a modified elastomeric polyurethane reaction product based on a liquid hydroxyl-terminated homopolymer of butadiene. A reinforcing agent is added which increases the tensile and tear strength of the grain by 50%. By so strengthening the grain, separation of the grain during the last portion of the burn is minimized. In a second exemplary embodiment, mechanical web stiffeners are provided in the form of a core configuration about which the fuel grain is cast. The web stiffeners are in the form of an open tetrahexagonal truss structure which mechanically traps and adheres to the fuel and becomes an integral part of the fuel grain geometry. In both embodiments, the integrity of the webs is maintained throughout the burn.

Abstract: A solid propellant component grain is supported in a combustion chamber. A liquid propellant component container is mounted forward of the combustion chamber. The liquid propellant component is supplied through conduits from the container into the combustion chamber, and ignited to form combustion gas which is discharged out the rear of the combustion chamber to generate thrust for propelling a rocket. A high pressure tank containing a non-flammable gas such as helium is at least partially embedded in the grain. A conduit leads from the tank into the container, such that the high pressure gas pressurizes the container and urges the liquid propellant component to flow from the container into the combustion chamber. The tank provides internal structural support for the grain, with the wall of the combustion chamber constituting a safety barrier in the event of structural failure of the tank after the tank is filled with high pressure gas.