Details
The Prometheus system is the Liquid Propulsion Laboratory's augmented spark torch igniter, comprising a fluid test bed, torch, and high-voltage spark system. It was redesigned and built to fire the torch, collect pressure data, and evaluate design changes.
The feed system includes three lines: GOX (576 psig), GN₂ (730 psig), and Jet-A fuel, replicating Atlas Prime feed conditions. Components are mounted symmetrically to a 0.125" aluminum plate for leak visibility and easy access through hand ball valve cutouts. Vents route upward and away from test conductors. Fuel is pressure-fed from a dedicated tank using GN₂, which also branches as a torch purge line. The system uses 1/4" tubing with AN fittings, check valves, inline particulate filters, and relief valves set to 1.5x MEOP. Tubing length and bends were minimized; measured pressure drop does not exceed 10 psi during cold flows. The fuel tank is supported by a custom 3D-printed mount. Inline solenoids are N.C. to cut propellant flow on power loss; vent solenoids are N.O. for automatic depressurization, defaulting the system to a safe state.
The torch operates at a mixture ratio of 1.5, delivering 3.2 g/s GOX and 2.1 g/s Jet-A. Chamber pressure is maintained above 410 psig, exceeding the Nomad engine's 350 psig via reduced throat diameter and adjusted injector flow rather than a choked GOX orifice. Injector stiffness of 35% limits backflow. The torch is a 1.45" x 1.45" x 2.00" 416 stainless steel block with inlets for GOX, Jet-A, nitrogen purge, and a pressure transducer. Tangentially offset inlets generate coaxial swirl mixing, achieving 418 psig chamber pressure. NPT-threaded orifices allow diameter changes as needed.
The spark ignition circuit uses a 20 kV AC boost circuit powered at 5V/4A, MOSFET-controlled via DAQ signal, with a spark plug positioned inside the chamber. The circuit is housed in a high-temperature SLA-printed enclosure.
