Hybrid rocket motor technology and the use of hybrid rockets have gained increased interest in recent years in many countries. For many years' private and university based organisations have performed work on hybrid propulsion systems for various reasons. Hybrid propulsion systems have not achieved the same technical and developmental levels as solid and purely liquid based propulsion systems have. There are several reasons for this. One of the main reasons has been coupled to their relatively low-density impulse, low regression rate and poor combustion efficiency and sometimes stability. However, there are many well know benefits by choosing hybrid rocket technology compared to other chemical alternatives, which is believed to have influenced its renewed interest. A typical hybrid rocket consists of a tank containing the oxidizer in either liquid or gaseous state connected to the combustion chamber containing an injector, inert solid fuel grain and nozzle. The feed line between the tank and combustion chamber has typically some valves for controlling the flow of the oxidizer to the combustion chamber. A hybrid rocket may also be designed to work in the opposite way by using a fuel in liquid state and the solid grain containing the oxidizing material. Different institutes have tested various combinations of fuel/oxidizers over years. Nammo Raufoss A/S has for almost 40 years designed and produced high-performance solid propellant rocket motors for many military missile systems as well as solid propellant rocket motors for civil space use. In 2003 an in-house technology program was initiated to investigate and study hybrid rocket technology. The program is to be continued. The program focuses on literature study and to develop the design tools for calculating hybrid rocket motors. A tank system for gaseous oxidizer have been designed and manufactured. This can be manually and automatically controlled. Two modular heavy wall rocket motors of different sizes are designed and build, which also can be connected in series in order to achieve a third configuration. Finally, static test firings are carried out with various fuel compositions to investigate general hybrid performance parameters as well as regression rate and mechanical strength of the fuels. On 23 September 2004 the first in-house designed hybrid test rocket motor was static test fired at Nammo Raufoss Test Center. The oxidizer was gaseous oxygen contained in a tank pressurized to 10MPa, flow controlled through a sonic orifice into the combustion chamber containing a multi port radial injector and six bore cartridge-loaded fuel grain containing a modified HTPB fuel composition. The motor was ignited using a non-explosive heated wire. This paper will present what has been achieved at Nammo Raufoss since the start of the program.
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