Augmented Spark Igniter

Project Goal

To design, manufacture, and test an augmented spark igniter (ASI) that will serve as an igniter for a liquid-fueled rocket engine.

My Role(s):

Propulsion subteam co-lead, responsible for the design, manufacture, assembly, and testing of the ASI combustion chamber assembly from a propulsion system standpoint.

Technical Skills: Non-technical Skills:

CAD (OnShape) Project management
Mechanical design Leadership
Machining/manufacturing Communication
Diagnostics, testing, & troubleshooting Collaboration

Results

Successfully designed and constructed the ASI assembly which saw two successful static fire tests with 1-3 seconds of combustion. The combustion chamber withstood the projected chamber pressure of 100 PSI and the projected temperature of 2300 kelvin.

Key Takeaways

The test campaign was a massive success for the club. The combustion chamber performed beyond expectations and allowed us to feel more comfortable with pushing for longer burn durations.
Although the static fires were successful, there were consistency issues: the system couldn't repeatedly fire in close succession. This is the next major step in refining the ASI system for use in a full-scale engine.
The chamber survived the test conditions without any issues, but improvements could be made to the data collection mechanisms. Our current chamber pressures and temperatures are based on theoretical calculations, but we plan to integrate effective and accurate sensors into the chamber to characterize the real-world performance of the ASI.

CAD Model of the ASI subassembly

Full ASI assembly with the copper chamber located on the right

Image of the ASI static fire

Overview & Process

As the co-lead of the Propulsion Subteam in the Yale Project Liquid, I worked with my co-lead in supporting the technical design of the combustion chamber, leading the manufacture and assembly of the system, and collaborating with other subteams to conduct a successful testing campaign.

Design: We began by obtaining the combustion properties of our propellants at various O/F ratios from the NASA chemical equilibrium analysis (CEA) website. Next, we selected certain target parameters (chamber pressure, thrust, etc.) and used the isentropic flow equations (see here) to size the chamber. We accomplished our goal of reducing thrust as much as possible by eliminating the diverging section of the nozzle.

Manufacture: The combustion chamber was made of copper due to the element's ability to absorb and dissipate heat. I led the manufacturing of the combustion chamber, delegating tasks to provide learning opportunities for other members while picking up on the workload whenever necessary. The manufacturing process involved several operations using tools including lathes, CNC mills, and drill presses.

Assembly: the chamber is connected to the fluids supply system through two o-ring boss (ORB) ports followed by 1/4" teflon-covered NPT fittings. The spark plug screws into the rear end of the chamber and creates a pressure seal with the built-in crush gasket. Finally, the chamber is secured to a supportive plate on the test stand using four screws.

Facts and Figures

Thrust: 0-3 lbf
O/F ratio: 4
Chamber pressure: 100 PSI
Chamber temperature: ~2300 K
Maximum burn duration: 3 seconds
Propellant inlet pressure: 150 PSI
Oxidizer: nitrous oxide (gaseous)
Fuel: ethane (gaseous)
Ignition mechanism: electric spark plug

A team member (foreground) and I (background) machining two combustion chambers on the lathes

Testing

Stress Analysis: we calculated a pressure rating for the ASI before conducting any tests to ensure that the chamber assembly was a robust pressure vessel. I was responsible for running the stress analysis on the combustion chamber, and the detailed procedure and results are documented here.

Leak testing: to validate our assembly, we conducted leak tests of the system. We threaded the outside of the combustion chamber and manufactured a leak test cap to screw over the nozzle and plug the end. Then, using a portable air compressor, we pumped pressurized air (up to 150 PSI) into the system and tightened any loose joints where leaks showed up. This test allowed us to verify that our oxidizer inlet, fuel inlet, and spark plug connection point were pressure-tight.

Static fire: We conducted successful static fires of the ASI at Stony Creek Quary in February and May of 2024. Working with other subteam leads, the project leads, and Yale Environmental Health and Safety, I supported the setup and commencement of the test. I also contributed to the diagnostics and troubleshooting of our first (unsuccessful) attempt which led to a successful fire on the second try. The video below is a montage of our February static fire test, produced and edited by a member of our team.

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