Night of Flying Spinners - 6.4 mm BP UFO
Date: 2006-01-09
Description
My first try at copying the consumer "UFO" device, but with a twist. Instead of 3/8" Pthalate/Ti whistles and an exotic BP to Barium Nitrate/MgAl/Phenolic lift driver this one was all BP.
Essentially two 1/4" saxon drivers attached to a third arranged as a lift driver. The lift driver was matched from both spin drivers at their mid-point. Ignition was establised at the ends of the spin drivers, so the lift driver would not be ignited until the two spin drivers were half consumed. As the lift driver was dual-surface burning it would be consumed in about the same time as the remaining half of the spin drivers.
A 6:1:1 BP variant was used, produced with commercial airfloat, giving an intermediate strength driver composition.
Blackmatch was used to all matching and fusing with meal/NC priming. Wax treated cat litter end plugs. Pyrotube 1/4" ID x 2" tubes hot-melt glued together once charged and punched with an awl, giving 2-3 mm nozzle holes. Masking tape "piping" on inter-driver matching.
Comments
Not so great.
I should have used high-performance BP meal. I suspected this would be an issue, the device weighed 14 g, which is a lot for a 1/4" BP saxon driver to produce for an extended period as its wall ablates.
However it did display excellent stability. It spun on the ground for about 2-3 seconds before the mid-point of the spin drivers was reached. Exactly as planned the three lift nozzles sprang to life and the device took off. It just didn't have the ompf to keep fighting gravity.
I am confident that using my higher performance BP meals for the lift driver alone will make this device work perfectly.
The spin drivers could remain as-is, or be modified to produce metal spark effects with little impact in performance. The Post-Mortem picture shows significant spin-vent erosion, likely due to the positive oxygen balance of the propellant, this should probably be fixed for best performance.
Attachments
| title | type | size |
|---|---|---|
| Test Video | video/x-msvideo | 6.788 Mbytes |
| Pre-Test Picture | image/jpeg | 50.505 kbytes |
| Underside Detail | image/jpeg | 41.464 kbytes |
| Unmatched Device Detail | image/jpeg | 34.358 kbytes |
| Post-Mortem Picture | image/jpeg | 78.587 kbytes |