Beach Shoot #15 - Core-Burning Rocket with 25 mm Canister Shell
Date: 2003-12-05
Description
The rocket motor was one of my standard 9.5 mm ID, 50 mm long, 2.5 mm nozzle, RP propellant core-burners. This design has displayed excellent success, none have failed, so it was chosen to lift the 23 gram 1 inch shell. A job for which it was somewhat under-powered.
The canister shell was made from 2 turns of chipboard, some thick chipboard end disks, and several turns of light kraft all pasted with dilute PVA glue. A small piece of lance tube and some blackmatch sticks provided the passfire from the rocket motor to the centre of the burst charge.
The unpunched disk was placed first and the kraft cut down and folded with more paste to close the end. A piece of match pipe was used as a canulle during loading. D1 Glitter stars, pumped to 8 mm cylinders were carefully cut with a scalpel and mallet into roughly 4 mm wedges (8 from each star) and placed around the match pipe.
The match pipe canulle was filled with -20+40 mesh KP burst. About 3 teaspoons of KP were shook into the spaces between the stars and the canulle removed carefully by twisting and tapping to release the KP it was filled with into the gap as it was withdrawn.
The top disk with attached lance tube was then put in place and the kraft cut and folded down to seal the canister. The shell was then spiked lightly with match making twine.
Finally some sticks of blackmatch were slid into the lance tube, some KP burst placed in the top recess of the motor and the shell glued in place with hot-melt.
The motor was fused as usual, with thin blackmatch and meal-NC paste priming. A long, thick bamboo kebab skewer was hot-melt glued to the motor casing for stability.
Comments
Worked OK.
It achieved reasonable altitude considering how overloaded the motor was. The rocket arced over before the shell burst, the apogee was probably 30-50 metres, the rocket and shell remains landed close together and were recovered about 75 metres down range.
The break wasn't very good though, the unpuched end disk blew out snapping all the spiking twine which remained largely fixed to the shell casing. There was also a small burst out of one side at the punched end disk. The chipboard canister walls were totally unharmed.
The use of KP burst instead of BP pulverone was the basis for this test. The KP clearly burns slower and forms a weaker break than the previous pulverone shells for the same containment. Perhaps with better containment it would be usable, or for larger shells, I think I'll stick of pulverone for smaller shells.
Better spiking twine may have helped, a good pasting of kraft after spiking may have helped contain the spiking better during the burst as well.
Attachments
| title | type | size |
|---|---|---|
| Test Video | video/x-msvideo | 1.267 Mbytes |
| Pre-Test Picture | image/jpeg | 62.092 kbytes |
| The Shell Before Attachment | image/jpeg | 39.369 kbytes |
| Canister Construction | image/jpeg | 56.762 kbytes |
| Post-Mortem Picture #1 | image/jpeg | 64.976 kbytes |
| Post-Mortem Picture #2 | image/jpeg | 37.861 kbytes |
| Post-Mortem Picture #3 | image/jpeg | 22.512 kbytes |