PH - Build
Project Hecate is an isopropyl alcohol(IPA) and gaseous oxygen (GOX) torch igniter. Igniter via a 1/4 - 32 hobby spark plug, this igniter was designed with the goal of being interchangeable with all kinds of propellants. Design work was done by both myself and a friend of mine.
Build Overview
The igniter was made up of a central combustion chamber which was slightly elongated into a snout which then converged to a throat section at the end. The combustion chamber had four total ports: two for IPA and GOX orifices (standard, from McMaster), one for the spark plug, and one for a pressure transducer. The spark plug would sit on the side where the counterbore is. Just to the left was the pressure tap and to its right was the port for the GOX orifice. The IPA orifice would be threaded on at the top.
Design
The design for the igniter used equations from Rocket Propulsion Elements and NASA SP 125. A few of the igniter's characteristics are given below:
Chamber pressure: 50 psi Chamber temperature: 2,114 C Exit Mach: 2
Thrust: 2.25 lbf Theoretical ISP: 234s Expansion Ratio: 1.94
The body of the igniter was modelled after a Hydrogen - Oxygen torch igniter from NASA, however, this design later proved to be incompatible with our IPA/GOX propellant combination (see PH - Test page).
Manufacturing
The igniter was made primarily using a lathe. Machined out of carbon steel, this igniter was run at an O/F ratio of about 2.5 to keep the material from melting. Additionally, threads were added to the igniter snout to make it easier to mount to the test stand. The final result was passivated to prevent corrosion damage, however, this process was omitted for the second igniter iteration.
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