A hybrid rocket is a propulsion system that uses a combination of solid fuel and liquid or gaseous oxidiser (Sutton 1992). Hybrids have many advantages, including their relative safety, minimal impact on the environment, low cost as compared to other forms of rockets, and their ability to be throttled. At the University of Queensland the hybrid rocket project has now been running for three years. This year the 2004 test rig has been modified and used for all test firings. In 2005 a record thirteen successful firing were made from sixteen planned tests, of which ten had successful data acquisition. Thirteen days were spent on site for these tests. The maximum thrust gained from these tests was 370 N in test 1 and the maximum specific Impulse was 222 N in test 14. A long burn of 37 seconds was conducted, giving interesting data on the behaviour of solid hybrid fuels, and the benefit other injection methods may have. Most of the test were conducted to get data point for the development of PVC and PMMA as hybrid fuels. Four of the test directly related to this thesis – testing of vortex injection, axial injection and narrow port diameters. It was found that a vortex engine could not be created with the current mass flow rate of oxidiser. Further investigation was made into creating a vortex in a hybrid and much theory was covered; however a successful hybrid rocket vortex engine test was not conducted due to budget restrictions. A new axial injection design was made; however could not be tested due to the expiration of liquid nitrous on the final test day. This is also the reason why another long burn test could not be conducted.