Proxima Engine

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Rice Eclipse is Rice University’s student rocketry team, founded with the goal of designing, building, testing, and flying student rockets powered by a student-developed propulsion system. Hybrid rocket engine development has been a goal from the club’s very inception, beginning with the 50 lbf - thrust Mk 1.0 hybrid engine. Over several iterations spanning multiple years, Mk 1.0 became Luna. Large engine development on the club can also be traced back similarly far, ending with Titan II, a large 1200 lbf - thrust engine that the club has designed to fly at the Spaceport America Cup. To gather data for the design of such an engine, Luna was employed as an experimental engine, performing tests with new components and systems. However, Luna inherited many issues from the Mk 1.0 engine and was poorly suited as a small-scale analogue of a larger rocket engine; it had no pre- or post-combustion chambers, no way to operate in blowdown, and was damaged following several anomalies. Furthermore, much of the formal documentation surrounding the design of the engine was insufficient to gain a deep understanding of the engine, and procedures for firing the engine were often unclear or entirely absent. Given the club’s high turnover rate due to its nature as a student team, comprehensive documentation is crucial to ensure that future users understand the engine and its operation. Thus, the club determined that designing a new engine, Proxima, would be advantageous for three reasons.

First, the engine could be designed to provide more accurate data for large engine development while being easier to build and test. It resembles Titan II more than Luna by incorporating many of the components that Titan II has such as the phenolic fuel grain liner and the post and pre combustion chambers. Because of this, test data from Proxima provides better information for the operation for Titan II. The Proxima design utilizes more extensive instrumentation of the engine and has a higher thrust than Luna. This will ensure that adequate data is collected for any given test and that the effects of component or system changes can be more easily observed. It is designed with the implementation of a new control system in mind. Proxima has also been designed for ease of assembly to ensure that the engine can be fired multiple times in a single testing day. The design and implementation of specialized tooling to cycle fuel grains between tests will allow us to utilize test weekends more effectively.

Proxima has also been designed to be faster to machine compared to Luna by simplifying parts where possible and reducing the number of necessary mill and lathe operations. The components will also be more robust, meaning they are less likely to need to be replaced in the event of an anomaly. The club has conducted a thorough failure case analysis of Proxima to ensure that the failure point of the engine would be the bolts going through the injection bulkhead to the upper flange of the combustion chamber. These bolts have been sized to fail at 1050 psi during an anomalous overpressurization. To validate the results, a thorough FEA stress analysis has been conducted on the engine components to ensure that a factor of safety of 2 is maintained even in the case of failure. The club believes that in the event of a failure the vast majority of Proxima will remain intact, reducing the impact of any failure relative to that of Luna. Aside from various design and testing improvements, a redesign of the engine provides the opportunity to create a new set of documentation which records all necessary information for the engine and allows it to be better utilized by future members. Lastly, the design process of a new rocket engine is an invaluable engineering experience for all involved. The Proxima hybrid rocket engine detailed in this report is designed with effective testing in mind, emphasizing versatility and robust design.