Feasibility Studies on the Cooling of Hybrid Rocket Nozzles Using Supercritical Nitrous Oxide

The fundamental requirement in the development of Single-Stage-To-Orbit (SSTO) system is to implement a nozzle contour with altitude compensation characteristics which leads to increase in aerodynamic efficiencies. Also, the reusability of the SSTO is another challenge due to the thermal fatigue loads experienced by the launch vehicle. To overcome such challenges, cooling of the throat of the hybrid aerospike nozzle becomes essential as the nozzles experiencing greater heat fluxes at the outlet. In 2009, Patrick suggested the use of nitrous oxide (N2O) in sub-critical regime as an active coolant for the nozzle component cooling. However, using sub-critical N2O causes more complications by introducing multi phase flow and heat transfer characteristics. The science of supercritical fluids is the only possible solution which consists of homogeneous single phase chemistry. So, in the present study, Supercritical N2O (TC=309.58K, PC=7.254 MPa) is proposed as an active coolant for the cooling of aerospike nozzles. Thermophysical properties of N2O are compared in both sub-critical and supercritical state and also an attempt has been made in order to correlate some of them as a continuous function of temperature and pressure. Statistical parameters are used to ensure the accuracy of developed correlations.