Reshaping Rockets: Design, Testing and Construction of a Variable Geometry Rocket Nozzle

Abstract

The space industry was revolutionized when SpaceX safely landed the first stage of the Falcon 9 rocket in 2015. Since then, the cost of Low Earth Orbit (LEO) launch has dropped from over 10,000 USD/kg for the SLS to a couple thousand dollars per kilogram. Currently, the space industry relies on liquid rocket engines to achieve these low costs since they allow for landing control through precise throttling of the engines, yielding reusable first stages. However, these liquid engines require extremely complex cycles, delicate and high-pressure storage tanks for the propellant and LOX, are significantly more expensive to produce than solid engines for a given thrust, and cannot be stored for long periods of time.

As the aerospace industry grows, the demand for lower costs to LEO will increase. In order to keep up with the market, and lower down the cost of payloads to LEO even further, a two-load, solid rocket engine (SRE), reusable rocket design is proposed. This rocket would use the first load of solid propellant during launch while the second load would be ignited during the return and throttled to achieve a safe landing. Today, all the technology required to achieve this solid motor rocket design exists, except for the ability to throttle a solid rocket engine at the required scale.

In this thesis, I focus on the analysis, design, building, and testing of a variable-geometry rocket nozzle that uses the properties of compressible flows at subsonic and supersonic regimes to throttle a solid rocket engine by modifying the geometry of the rocket nozzle, particularly the throat area. The design and proof of this variable nozzle addresses the bottleneck issue of throttling this solid-engine, two-load, reusable rocket design, and could be a step towards the next big disruption that drives down the cost of LEO launches even further.