atomic_fungus (atomic_fungus) wrote,
atomic_fungus
atomic_fungus

#1832: Dragonfly

In the 1990s I got back into model rocketry.

I'd liked it as a kid, and in my latter years of high school I'd gotten into the model building part of it. Some of this was due to the fact that my friends and I learned enough patience that we realized you had a much better chance of recovering a rocket on a clear day with little wind.

But of course we got interested in other things and model rocketry fell by the wayside; and in fact I don't remember what rekindled my interest in it around 1993 or so--only that I started buying kits and building rockets, and I built a launcher. I turned out some very nice-looking models and kept a log of all my flights.

One classic Estes kit is the Mosquito. It's essentially a body tube, a nose cone, and three fins, wrapped around an AT-size engine. It weighed next to nothing and it was tiny. The kit cost $1 for many years, and you never put a lot of effort into one because the damn things were impossible to find once launched. Even if you used the least-powerful engine Estes made, the thing went fsst! and transcended time and space as soon as you hit the "go" button. The only way you could possibly make a lighter rocket would be to glue the fins directly to the motor casing.

Anyway, in 1985 Estes came out with a kit--I can't recall the name--which replicated the dimensions of the Mosquito in a larger scale. It was a D-powered rocket--using 24mm engines--and its diameter was significantly larger than the motor cross-section. It gave me an idea for a real D-powered version of the Mosquito, one I called the "D-ragonfly".

I never built it...until 1994.

Like the AT-engined Mosquito, it was basically a body tube big enough to fit the engine, fins, and a nose cone. And it was nowhere near strong enough.

The prototype is the only version of the thing I ever flew. My launcher used two 9-volt batteries in parallel, guaranteeing that the ignitor would always (95% of the time, anyway) set off the engine. So when I put in the safety key and pressed the "go" button, it went.

It got about eight feet into the air before the fins began to oscillate--you could hear the hum--and it might have flown as high as twenty before aerodynamic loading tore them off the fuselage.

The fuselage with a partial fin still attached and part of another fin were recovered. That explained why the rocket didn't go out of control; the partial fin provided enough stability. The asymmetrical drag limited its aphelion, though, which is probably just as well.

I concluded that better materials and construction techniques would be needed, and abandoned the project. Plywood fins epoxied to a phenolic airframe would probably have done it, but it would have made the thing weigh as much as a larger rocket, thus offsetting the benefit of building such a minimalist rocket in the first place. At least I was able to say I'd tried it.

My other rocket science efforts worked better, such as my scale model of B-ko's Akagiyama missiles (from Project A-ko) and the Hot Potato, a rocket made from a Pringles can...but those are stories for another time.
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