Geometrical Nozzle Design for Wagtail Rockets

Rocket nozzle geometry optimisation can increase the efficiency of a rocket during its burn and can reduce the weight of this component. The University of Queensland Centre for Hypersonics' 'Wagtail' rocket project has produced small solid fuelled rockets motors for sounding rocket applications. The performance of an optimised nozzle contour has been compared with the Wagtail motor's current conical nozzles. An approximation of an optimised nozzle can be made using the guidelines of Rao, which has been used on three different motors. The equilibrium gas properties of the motors propellant have been calculated at various temperatures and pressures. These properties are then used in the CFD simulation of the nozzles. The results of the analysis shows that an increase in performance can be achieved for a lighter weight Rao nozzle compared with a conical nozzle. In addition, flow characteristics throughout the nozzle are found in the simulation, which cannot easily be measured experimentally.