This is the short story of how two amateur rocket scientist couldn’t make a working bottle rocket.
A week or so ago my buddy, and fellow amateur rocket scientist, make a batch of Dragons Breath propellant. Old time readers of this blog may recognize the propellant name, it was what I used for my Stunt monkey piloted rocket named Norbert I flew at balls in 2007. The propellant is an AP based propellant with a bit-o-titanium to add sparks. After many weeks of experimenting and testing it has become a well characterized propellant and works in a predictable manor on most high power rocket configurations from G to L class. The propellant is normally cast into paper casting tubes, which in turn slide into a phenolic tube called an insulator. This is then slid into an aluminum tube, with end caps and a nozzle, this along with some o-rings and some other bits, make a working rocket motor.
For some reason due to either distraction, a lack of sleep, or maybe not enough coffee, Elvis accidentally cast the propellant into 1″ insulator tubes rather than casting tubes. This kind of mistake is irreversible. Normally a mistake in casting is saved to add a bit of spice to an otherwise ordinary and rather boring camp fire. I, however, had another idea. I happen to have some heavy walled paper tubing with a one inch inside dimension, perfect fit for the 1″ insulator tube this got me to thinking…. Maybe could make a rather largish bottle rocket using Dragons Breath propellant. Hmmmmm, Unorthodox to be sure, but is it possible? Elvis did some calculations to determine the proper nozzle size, grain geometry, and propellant burn temperature, and I got to work making up some tubes and creating a nozzle out of Durham’s water putty.
A good question came up. How much pressure can a paper tube handle? We could have easily spent the next few night pressurizing paper tubes with nitrogen and watching them explode while recording the rupture pressure, and I plan on performing this test in the future as a public service. But time was running short, and we only had a few days before our access to a proper testing facility would expire. Then we would have to wait for a month or so. I pulled a number out of my… ear, 250 psi sounds good, because it was a nice round number and well, I don’t think paper tubing can hold much more, I could be wrong.
We gathered the parts together and a nice long stick and headed to a proper licensed testing facility where we can legally assemble and test our creation. We arrived just in time to view a few tests of some ghost mines; a light green color was the objective. We had to wait for a bit until the testing was completed before we could try out our Dragons Breath bottle rocket.
Its tough work but someone has to do it.
It was finally time to light the fuse and test out our new toy. The device dimensions are one and a half inch in diameter by seven inches long with a five foot stick for stability. If all goes right it should blast off in a shower of sparks and quickly ascend to about a thousand feet.
Things didn’t go exactly as planed….
The first attempt chuffed and puffed then lit for a second (Sideways) then blew itself out.
The second attempt went better, but still did this un-predictable chuffing without enough thrust for a nice stable vertical flight. Ugh.
Yes we did find the rockets, and yes we did perform an autopsy to determine the cause of the chuffing and puffing that caused the erratic performance. No results as of yet.
Elvis and I both found it ironic that we can make a rocket motor work perfectly well on an expensive and carefully constructed rocket with hundreds of dollars in electronics and parachutes, but fail to make a simple bottle rocket that we do not care if works exactly to specifications. It’s like the more that is on the line the better they work. Counter intuitively rocket science didn’t hold up to the ancient skills of the old time rocket makers from China. We launched a few bottle rockets and they worked just fine, good quality control and consistant flights. Damn.
We are not discouraged.
We will prevail.
Some day our Dragons Breath Rocket on a stick will fly, just as well as Norbert did at balls.
Maybe it was the stunt monkey that made all the difference.
Hmmmm, Capt Danger…. Want to go for a ride?