Balcony Shoot #28 - Micro Stingers
Date: 2003-11-10
Description
Both devices were identical, 25 mm long, 9.5 mm ID tubes. 4 mm thick wax treated cat litter plugs, 1.8 mm nozzle, core, and spin vent. Propellant of straight meal powder. Fused with thin blackmatch glued in with meal-NC paste.
Launched from a spent sparkler wire attached to a gadget to allow it to sit in the rocket launch pipe as usual.
Comments
Both worked well.
Bloody loud, especially when you are only a few metres from them. I think I heard the first one land, I might try and recover it in daylight. Update: 1st device was recovered, post mortem pictures have been added. Note the impact with the ground appears to have chipped off some material from the nozzle. The hole fireproofing worked fairly well, but could be better. Note also the slightly off-tangent spin nozzle tract.
The second one made a strange effect as it fell. A silver flash, barely caught in the video (bottom middle of frame just before the comment). The cause is unknown, there was no Aluminium in the composition, so it could not be a delayed Aluminium flash, like a glitter.
In fact there was no metal in it at all, so the only logical conclusion is that it was a trick of light as the case fell, reflecting the full-moon back to the camera. Not only the camera, but I myself observed it, and I was about 2 metres away from the camera operator, although perhaps not at the same instant? If it was a moon-glint effect it probably came from the white clay end plug, the nozzle end would have been blackened by the exhaust products.
Echos can be heard in the audio, I am not 100% sure what was the reflector involved, the delay is too small to resolve from the spectrogram because of the broadness of the fundametal line (although the chirp is almost ideal for ranging and the brain can definately pick out the echo with ease).
The first device spun up to 1020 Hz, the second a little faster, to 1100 Hz before the doppler shift makes things much harder to see. The first stinger twisted up the launch wire, and the thermal effects hardened it so I had to use plyers to straighten it again. The second stinger probably benefited from this hardened pin.
Attachments
| title | type | size |
|---|---|---|
| Launch Video #1 | video/x-msvideo | 314.326 kbytes |
| Launch Video #2 | video/x-msvideo | 528.788 kbytes |
| Pre-Launch Picture | image/jpeg | 28.082 kbytes |
| Spectrogram #1 | image/gif | 135.041 kbytes |
| Spectrogram #2 | image/gif | 155.874 kbytes |
| Post-Mortem Picture #1 | image/jpeg | 39.595 kbytes |
| Post-Mortem Picture #2 | image/jpeg | 22.784 kbytes |