Testing N2O/CO2 oxidizer mixtures with paraffin based μaluminum fuels for Mars Ascent Vehicles

Abstract

The objective of this research is to perform experimental test of a hybrid rocket motor by using N2O/CO2 mixture as the oxidizer and paraffin wax as fuel with the addition of metallic powders such as micron size aluminum and magnesium. The impact of 3-micron size aluminum on key performance parameters such as specific impulse (Isp), regression rate (r), and combustion efficiency (ηcomb) has been studied experimentally using a lab scale hybrid motor with 70 mm grain length and 30 mm outer grain diameter. Thermochemical performance of the various propellants studied in this paper are evaluated using NASA’s Chemical Equilibrium Analysis (CEA) software. Numerous tests are performed with N2 O/CO2 mixtures as the oxidizer. CO2 as a saturated liquid is mixed with liquid N2 O between 8 to 30% by mass in order to measure the motor performance characteristics such as average regression rate, r and combustion efficiency, ηcomb. Experiments were performed in the blowdown mode using the self-pressurizing capability of the mixed oxidizer around 45-50 bar. Chamber pressure of the hybrid motor was in the 15-30 bar range. Successful ignition and motor operation of the mixed oxidizer is achieved all the way up to 22% CO2 in the mixture. Initial conclusion from this study indicate that mixing CO2 with N2 O is a viable method of burning CO2 in a practical rocket system for Mars missions.