Design and Analysis of a Reusable N2O-Cooled Aerospike Nozzle for Labscale Hybrid Rocket Motor Testing

Author

Daniel Joseph Grieb, California Polytechnic State University, San Luis ObispoFollow

DOI: https://doi.org/10.15368/theses.2012.7
Available at: https://digitalcommons.calpoly.edu/theses/692

Date of Award

2-2012

Degree Name

MS in Mechanical Engineering

Department/Program

Mechanical Engineering

Advisor

Joseph D. Mello

Abstract

A reusable oxidizer-cooled annular aerospike nozzle was designed for testing on a labscale PMMA-N₂0[1] hybrid rocket motor at Cal Poly-SLO.[2] The detailed design was based on the results of previous research involving cold-flow testing of annular aerospike nozzles and hot-flow testing of oxidizer-cooled converging-diverging nozzles. In the design, nitrous oxide is routed to the aerospike through a tube that runs up the middle of the combustion chamber. The solid fuel is arranged in an annular configuration, with a solid cylinder of fuel in the center of the combustion chamber and a hollow cylinder of fuel lining the circumference of the combustion chamber. The center fuel grain insulates the coolant from the heat of the combustion chamber. The two-phase mixture of nitrous oxide then is routed through channels that cool the copper surface of the aerospike. The outer copper shell is brazed to a stainless steel core that provides structural rigidity. The gaseous N₂O flows from the end of aerospike to provide base bleed, compensating for the necessary truncation of the spike. Sequential and fully-coupled thermal-mechanical finite element models developed in Abaqus CAE were used to analyze the design of the cooled aerospike. The stress and temperature distributions in the aerospike were predicted for a 10-sec burn time of the hybrid rocket motor.

[1] PMMA stands for polymethyl methacrylate, a thermoplastic commonly known by the brand name Plexiglas^®. N₂O is the molecular formula for nitrous oxide.

[2] California Polytechnic State University, San Luis Obispo