Road flare rocket

The road flare rocket details could go on for a few pages to explain sufficiently, but since your not going to 'try this at home' - here’s just the jist:
If you have never seen/built an Estes model rocket then you may not get the whole desire of doing the road flare rocket. If you have had the privilege of inserting igniters, packing in wadding and mostly paying good money of .4 seconds of watered-down gunpowder propellant labeled as ‘engines’. I was passing an auto accident while riding my bike one day and stopped to look at the string of road flares marking off the crumpled cars. What fascinated me was the amount of energy spewing from the end of each flare and the duration of its burn. After a quick trip to Trak Auto, I was in the back yard striking my first road flare which burned uniformly upwards and to the sides, through the thin waxy paper. "Hmm- rocket engines channel all that thrust through a tiny hole and".. . As an avid model rocket enthusiast I knew a few fundamental constraints had to be met for even a partial lift-off.

Thrust has to exceed mass by a great margin.

The center of gravity has to be near the burn line for stability, before the fins kick in.

Given: A single automotive road flare weighs approximately 1lbs, while an average model rocket weights about the same as a pack of 'Tick-Tacks'.
Assumed: The total output of a flare is comparable to an Estes 'C6-0' engine, unconfined. Again assumed.
Concluded : There’s no way that the thrust can lift the full weight.
Task : Derive the max weight and chop the flare off, with the remaining being well lighter than the max.

The weight determination was done by gluing an engine to a toilet paper roll, then filling it with a handfull of quarters. A series of firings/coin reduction were blasted to until the burnt cylinder jumped off the pad. A new flare was hacked to a length leaving the remaing flare well lighter than the weight of the quarters.

The fun part in a nutshell. The flare was wrapped in two layers of aluminum foil and one layer of hi-temp model airplane fiberglass(w/resin).

Weight was rechecked and, obviously, the flare was re-chopped to attain the correct weight. One inch of the flare material was scooped out and leveled with an X-Acto knife, then refilled with JB-Weld – a metallic based automotive epoxy. The output jet(venturi) was carefully formed by carefully inserting a high-tech #2 pencil into the uncured expoy - then clamped until hard.

Fins were glued on all four side and mounted on a coat hanger launch rod. *** The ( do not try this at home ) launch: Getting the ol’ feeling of future trouble, I decide to launch at nighttime at the local school

baseball diamond. Just after dark, I set up the pseudo-rocket around second base and inserted a length of dynamite fuse in the veturi( the little port made by the pencil ).

After a few heart pounding strikes of the matches the fuse burst into a fiery hiss, "RUN AWAY!!!!". Watching, watching.. the fuse crept into the bottom of the night-cloaked rocket and starting an new sounding hiss. First the sound, then billows of white smoke and finally a razor sharp red line burning downwards - illuminating the whole cloud. Oh no! It just sat there teetering back and forth causing all the dogs in the neighborhood to go berserk. Attempts to extinguish the rocket with sand was futile and I didn’t want to knock over so I just watched it.

Five minutes into the burn, or after half its weight in fuel was consumed, it started creeping up the pole until it popped off. With a 4 foot laser-like blaze shooting at the ground the rocket lazily hovered perfectly still for a few seconds. It started swaying like a cobra, slowly in a four foot circle at first, then more violently- not unlike a loose firehose except BURNING and at MY height for at least 20 seconds! It finally crept higher and higher, the side-to-side gyrations got less and the red burn started to pick up speed. To make a long story short( too late ), the red dot climbed for an amazing duration getting smaller and smaller - barely visible. I could just see it burn out. "Wait, that means it has to come down. RUN AWAY!!!!!!!!!!"