Due to my schedule, and the fact my local rocket club doesn’t fly experimental motors, I only get to launch EX motors once a year, and Midwest Power in Princeton Illinois. EX motors are just that – typically a rocket propellant you whip up yourself in your garage, or basement. The big advantage of manufacturing your own motors is you can control a lot more variables. Want the flames to be red? add Strontium Nitrate. Need to speed up the burn rate of the propellant? Add Iron Oxide. Need an even thrust level through the entire burn? Try a Finocyl core geometry. You get the idea.
For the last few years, I’ve been trying to push the limit on making a slow-burning propellant. This is much more difficult than changing up the chemical composition because the longer the propellant burns, the more exposure the motor hardware, nozzle, and liner will have to the heat and pressure. Worse, the core geometries with the longest burn characteristics (endburner & moonburners) tend to keep the heat and pressure focused on a particular part of the case for an extended period of time. Once a formula is stable enough to flight test, I typically try them first in an oddroc saucer. They are very light – easy to lift of the pad, very stable – no fin alignment issues, and don’t fly very high – easy to recover just in case…..
In 2011, my longburn test ended in disaster. The propellant burn was so low, the rocket never got off the pad and eventually burned through the motor case, destroying the saucer, rocket motor, and the pad it was sitting on. All of this was caught on video at Midwest power 9 for your enjoyment
Needless to say, I spent a year with the nickname “firestarter” by everyone that witnessed this first attempt.
later, with dozens of changes and testing of the propellant formula, I returned to Midwest power in the hopes of a successful launch. The good news is the launch was successful – the saucer zoomed off the pad. The bad news is my nickname may now be permanent… After a successful flight, the rocket caught fire on decent and started a small field fire. Once again, I was left with a destroyed rocket and motor. Of course, my daughter caught the whole flight on her iphone while I was clicking away on the still camera. At least I have another year for research!
Saucer and 75mm EX motor ready for launch
And the recovery……
This is all I got back, some burnt carbon fiber and a ruined rocket motor