Beach Shoot #7 - Micro-Stinger #2

Date: 2003-10-28


Essentially identical to device #1, but instead of sealing the top with paper wadding and hot-melt glue I used hot-melt glue alone.


Worked too.

It is the device laying over on its side in the pre-test picture.

Very straight flight. I don't think it went as high as #1, but this may be because of a breech in the top-seal which you can see in the post-mortem pictures. Also note the very minimal spin-vent enlargment, and the almost identical slag flinging pattern at the lift nozzle when compared to the first micro-stinger device.

The device landed at my feet still spinning very, very fast and dug itself a little hole in the ground. It actually landed tail-first and was still upright, I guess the angular momentum wouldn't let it topple over as it fell back down. The flight was about 3-4 seconds long from spin-up to touch down.

The top-seal leak looked almost drilled out, I've never seen anything like it before. It was probably just the result of insufficient hot-melt glue. The wadding in previous devices probably prevented direct exposure of the glue to the internal pressures and temperatures. I think I'll try clay in future, it can be made thinner for the same sealing effect.

One interesting note is the change from charcoal to Aluminium effect near burn out. It is slightly noticable on the previous devices too, and my conventional rockets using the same propellant.

I have no clue what causes it, I've seen the same thing happen to saxons and ground spinners in the past as well but put it down to composition homogenity issues. Clearly it isn't, it is some kind of pressure or temperature related Aluminium ignition effect. The Aluminium is very fine (-325 mesh) but spherical, so it might be being consumed internally at higher pressures, or not igniting at all until some condition is satisified. It is definately not a delayed ignition like glitter and there is no delay agent in the composition anyway.

This device peaked out at 990 Hz or almost 60 kRPM. Still can't believe those figures, but it is clearly the fundamental on the spectrogram, unless there is some kind of frequency doubling going on, but I doubt that.


title type size
Flight Video video/x-msvideo 289.648 kbytes
Spectrogram image/jpeg 57.993 kbytes
Pre-Test Picture image/jpeg 48.738 kbytes
Post-Mortem Picture #1 image/jpeg 51.644 kbytes
Post-Mortem Picture #2 (bulkhead leak) image/jpeg 24.971 kbytes
Post-Mortem Picture (nozzle end) image/jpeg 24.114 kbytes