Hybrid Orbital Propulsion System (H.O.P.S)

The H.O.P.S team aimed to develop a prototype hybrid rocket engine that could be used to maneuver a smallsat from the NASA Lunar Gateway to low lunar orbit. The team also sought to investigate the effects of tangential oxidizer injection over flat paraffin wax fuel plates.

Having come up with the idea to develop a hybrid rocket for smallsat propulsion, my team formed in September 2019. Over the next few months, the team tirelessly researched, designed, and analyzed all aspects of the rocket engine and its potential applications while also searching for project funding. After securing $4,800 in funding from the NASA PA Space Consortium and the Drexel MEM department, we began to order materials and manufacture components in January 2020. All fabrication was performed in the university machine shop and other labs. Unfortunately, just as we were preparing for our testing phase, the COVID-19 pandemic halted all university research activities, and we were forced to suspend physical project work. At this point, the team had completed the following items: hybrid rocket engine heavyweight first iteration, test stand with linear rail system and load cell mounting, DAQ and electronic control system with control box, piping and fluid systems, fuel disk molds, extensive structural, CFD, and thermal analysis.

The above pictures show the team at a poster session, the prototype engine, and a CAD rendering of the main test stand.

Shown above is a cross-section illustration of the H.O.P.S engine.

Test Stand and Areas of Focus

My main area of focus throughout the project was the test stand. In order to perform hot fire tests of the engine and collect data, I needed to design a test stand which would withstand the forces of the engine safely, be transportable, and allow for integration of all project subsystems. Taking all factors into consideration, I came up with a design that featured a large 48” x 36” x 0.25” thick aluminum sheet bolted to an 80/20 frame as a base support, as seen in the figure to the left. The hybrid engine sits on top of an aluminum plate which is connected to a linear rail and bearing. This allows the engine to press onto a load cell attached to a vertical steel plate during firing. I also designed a linear rail heat shield and a safety wall using leftover materials. To verify my designs, I conducted several static structural analyses in ANSYS which I discuss further below.

Wax Fuel Disks and Molds

Due to the unique tangential oxidizer injection design, flat disk shaped fuel grains were needed. In order to produce both the front and back grains accurately and quickly, I made two-part silicone molds. By using 3D printed positives of the fuel grains I could easily cast the negative molds. Making a fuel grain was then as simple as melting paraffin wax, pouring it in the mold, and letting it dry, as the wax easily releases from the mold.

Load Cell Geometry FEA

Performing FEA was critical in verifying the test stand design and ensuring tests could be conducted safely. The figure above shows the deformation plot of the load cell geometry analysis. In this analysis, bolt pre-tension was applied at all hole locations and a force of three times the theoretical engine max thrust was applied at the load cell location. The results from this analysis, and all other analyses performed, showed that the test stand was more than capable of handling all loads it might experience.

Virtual Final Presentation

This virtual final presentation gives a great overview and summary of the project.

Elevator Pitch Video

This is an elevator pitch style video that I created as part of the team's coursework requirements.

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