Nondestructive Mapping of Hybrid Rocket Fuel Grains
The regression rates of solid fuels used in hybrid rocket motors are a critical parameter in the design and development of hybrid propulsion systems. Currently, it is difficult to measure fuel geometries accurately, thus causing difficulties in accurately describing regression rates, especially for smaller scale systems. Nondestructive techniques can solve this problem, as it is not necessary to get tooling into the ports. An apparatus that maps the fuel grain employing an immersed ultrasound transducer has been manufactured; its results will be the primary focus of this study. The full geometry of the fuel grains can be generated pre and post fire, which may lead to greater understanding of the way hybrid rocket fuels burn. Furthermore, previously undetectable defects, such as cracks and voids, may be identified. The study found that the method used to cast the fuel grains, spin casting causes thinning in wall thickness on average of 11.3% with a standard deviation of 1.2% from the end to the middle of the fuel grain. The generated data can further validate proposed analytical solutions (Cantwell, 2014) to the regression rate equations (Marxman and Gilbert, 1963) associated with hybrid rocket propulsion systems.
© 2016 American Institute of Aeronautics and Astronautics. Published Online: 22 Jul 2016. A. M. Costantino would like to thank the Summer Undergraduate Research Fellowship (SURF) with the aid of the donation from Mary P. and Dean C. Daily and funding from the Stanford aerospace and Astronautics Department. I also thank Stanford graduate student Pavan Narsai who guided and assisted me in my research over the course of the program as well as Javier Stober and Alexandra Ilic for their help in machining parts of the measuring device.