  A computational model is developed to assist the design of the first hybrid
rocket engine of the McGill Rocket Team, using liquid nitrous oxide as an
oxidizer and solid paraffin wax as a fuel. The model is developed in three
phases: In the first phase, a steady-state model which neglects transient
performance decrease of the hybrid engine is considered. The steady-state model
considers: a constant oxidizer mass flow rate; a combustion chamber in chemical
equilibrium; a one-dimensional isentropic nozzle; and a one-dimensional
constant-thrust rocket ascent. The steady-state model is used to conduct
parametric studies on engine performance as a function of design parameters
such as: oxidizer mass flow rate, fuel grain dimensions, and nozzle dimensions.
The engine design point is selected to optimize specific impulse, given
physical and structural constraints of the system. In the second phase, an
unsteady model incorporating transient performance decrease of the hybrid
engine is considered. The transient model considers: a self-pressurizing
oxidizer tank in quasi-steady liquid-vapor equilibrium; a combustion chamber in
quasi-steady chemical equilibrium; a one-dimensional non-isentropic nozzle; and
a one-dimensional rocket ascent model. The transient performance profile of the
engine is established, and the unsteady model is used to predict propellant
requirements for the launch vehicle, given a target apogee of 3048 m (10,000
ft). In the third stage, the unsteady model is compared to hot fire testing
data of the McGill Rocket Team. Semi-empirical parameters used in the
formulation are calibrated against testing data, and the validity of the model
is assessed.
