Ramjet thruster using ozone dissociation energy for high altitude operation

We present an innovative high altitude propulsion unit using the chemical energy stored in the typical chemical compounds (e.g.: ozone) encountered at higher altitudes within the atmosphere. The ozone enters the ramjet thruster through an inlet and within the thruster the ozone is determined to dissociate chemically in oxygen. The heat generated by the dissociation accelerates the resulted oxygen through an outlet, hence, generating thrust. The amount of thrust depends on the cross section of the ramjet and the energy density stored in the upper atmosphere. A thermo-chemical estimation that takes into account the enthalpies of input and output chemical substances is shown within the paper. The thermo-chemical calculation is then coupled with one dimensional gas dynamic equation of ozone flow through the ramjet thruster. Next, the paper presents the dynamics equation for the overall thruster taking into account gravitational force, aerodynamic force and thrust force all of them being functions of mass, velocity and geometrical dimensions. The thruster can produce thrust that can overcome aerodynamic force for a given ozone density and the difference between thrust and drag is also shown as a function of speed. Connecting the ozone density with altitude by using standard high altitude atmospheric models we derive the velocities attainable at 30,000 meters altitude. One of the big advantages of such a thruster is that it allows continuous operation at high altitudes without the need of a storable fuel onboard. The boost needs to bring the ramjet within the speed operating envelope for a given altitude and then the ramjet produces excessive thrust that maintains the burnout speed. Once the velocity is reached and the ramjet is activated, it can work indefinitely from the propulsion point of view. As a future development we propose a high altitude experiment to validate some of the theoretical models and refine the results for further technological developments. © 2009 Universitatea Politehnica Bucuresti.