Armadillo Aerospace News: Self-Preheating, 125 second burn time

After the rather surprising preheat behavior with the spray nozzle injector head with the glow plug, we bought a bunch more glow plugs for experimentation. They are a different brand than the previous one, and we unexpectedly found that if they are left on for too long without any extra resistance, they will burn themselves out. We added some extra wire to cut the current a bit, but they still draw 15 amps each.
The easiest thing to try was to put the glow plug in a side chamber above the engine inlet. We have to avoid getting liquid splashed directly on it, which can cool it down too fast, but having it branched off the main flow path seemed to shelter it enough. We had hoped that the decomposed peroxide and vaporized methanol from the warmup pulses would find its way up through the spreading plate holes and off to our little side chamber, but there doesn’t appear to be enough vapor circulation for this to work. Read More