For JPC this year:

More testing on thermite. I knew it wasn’t going to light, but I needed some photos to prove it. So, bust out the compound, a sample tray, a blowtorch, and a camcorder…

Quite boring, really. But that’s a good thing. Working in energetics, I’d much rather have a “boring” day than an “overly exciting” one.

One of my friends here has been having some issues getting a clean, reliable start on a motor, so I suggested using a thermite igniter to get things moving quickly. Seeking some evidence to use for convincing the higher-ups, we did some high speed videos of a couple thermite igniters to see what goes on. We fired a standard copper thermite compound, as well as one based on manganese dioxide and aluminum. Each shot was 5 grams of material. The CuO igniter was filmed at 2000 frames per second, and the MnO₂ at 10,000 frames per second. I also sped up the MnO₂ video and stuck the shots next to each other, to allow easier comparison between the two types.
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In preparation for a series of static tests this week, I’ve been working on some miscellaneous details. I updated the small test stand today to use a load cell for thrust measurement, instead of the state-of-the-art bathroom scale that was previously used, but I’ll talk about that later. I also realized that I’m running horribly short on igniters, and being the cheapskate that I am, I didn’t want to use electric matches for these tests. I remembered reading about using low-watt carbon resistors as igniters somewhere, and a quick Google search confirmed my speculation.

The main theory for resistor igniters is explained in an excellent whitepaper by Bob Dahlquist, archived at Aerocon’s site. I’ve also taken the liberty to put this article into a pretty, portable PDF. Paul Kelly has also done some research using resistors as igniters, archived at Backyard Ballistics. Contrail Rockets also uses a resistive ignition system for their hybrids, so the idea seems to be feasible. I mean, all igniters are resistors in one form or another, right? Granted, I have nichrome and pyrogen. But nichrome is difficult to solder, and bridgewire igniters are quite fiddly to assemble consistently. I wanted something quick, cheap, and brainless.
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