This thesis details sections of the design, construction and testing of a free-flying ramjet motor. This motor vehicle is based on previous projects conducted at the University of Queensland that involve the launch of a small ramjet motor payload mounted on a Zuni rocket booster provided by the Australian Space Research Institute (ASRI). These boosters have proven capable of achieving maximum flight Mach numbers of up to Mach 2.0 for payload weight of less than 20 kg. The target set for this project was to design a ramjet motor capable of being attached to a Zuni rocket that can produce thrust at least equal to its own drag under Mach 2 flight conditions. An additional goal was to make this motor a free-flying vehicle in its own right, that could separate from the Zuni booster stage and travel under its own power for at least 2 seconds and also be recoverable.
Within the scope of my work on this project was the structural design of the ramjet, and also the liquid fuel system, flight stability system (using fins) and parachute recovery system. The detailed design work that went into each of these systems is reported on and the major decisions made during this design process are explained. With the theory behind these subsystems of the ramjet motor vehicle explained, a discussion is given of how this was turned into a real vehicle through the construction phase of the project. Finally, a detailed description of the final flight test for the ramjet is given.
As part of the design stage of the project, motor performance and flight trajectory simulation models were made using the MATLAB programming environment. These tools indicated the ramjet could produce a theoretical maximum thrust of about 2.5 kN for an inlet air mass flow-rate of 3 kg/s. For drag forces or around 2.0 kN this was considered ideal, allowing the vehicle to stay at its design conditions while remaining within the Woomera LA9 Safety Zone.
Unfortunately, for a number of reasons detailed in the report the free-flying aspects of the design never made it into the final constructed ramjet payload. These and related subsystems are still discussed in this report, but the designs could not be tested during a real launch. Just prior to the final flight test there was a malfunction with the electrical system that prevented the use of the igniter spark plugs and much of the Data Acquisition System During the flight test, where the ramjet remained attached to the Zuni vehicle until the flight apogee, the fuel system injectors underperformed and the parachute failed. And while the results are not entirely conclusive, it appears that ramjet combustion did not occur.