Balcony Shoot #40 - Better Bottle Rockets

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Date: 2004-02-15


These five devices are the result of many undocumented experiments following the previous bottle rocket shoot.

All five were made identically. Wet rolled A4 80 gsm thin paper casing, 5 mm ID, 40 mm long. Propellant of 6:1:1 blackpowder. 5 mm thick clay nozzle. 25 mm of propellant rammed well in 5 increments. Nozzle and core drilled with a 2 mm drill, 15 mm from bottom of rocket (10 mm into the grain). Bulkhead seal of hot-melt glue.

A bamboo kebab stick was glued on as a stabiliser. The rockets were fused with thin blackmatch glued in place with some meal-NC priming paste.


All five worked great.

They flew up rapidly to at least 30 metres, where they swam around for a second or two before burn out. All likely landed in the ocean, none were recovered.

As they were experimental no flash report was added as a terminating effect, but future devices will probably carry a pinch above the grain as indicated in the diagram.

Note how the casings are creased and twisted slightly by the ramming. That concerned me a lot, but none CATOed or wobbled violently in flight so the current thin casing seems sufficient to survive the punishment for the few seconds of device operation. Three other units in addition to these five were flown with no problems during tuning of the core length.

They take slightly longer to make than a crimed motor, but I think the performance improvement is worth it. They were all made in the space of about 15 minutes so are fairly quick and easy to make compared to the 9.5 mm motors. The little buggers achieve only slightly less altitude and accelerate somewhat faster, while taking much less propellant. Of course they can't carry much of a payload, but up to gram shouldn't be an issue, the motor weighs less than 2 g complete, the stick actually weighs over 1 g.

Note the tooling photo. I made a simple adjustable scoup from a piece of soda straw, large bamboo skewer, and sticky tape - in rather the same manner as my previous micro star pump. The 2 mm drill was attached to a piece of dowel for easy hand-drilling, and a simple funnel was made from a scrap of sparkler packaging. The stick-end of the powder scoup is used to encourage the powder out of the funnel and into the case. In the past I used a seperate wire tool, but just reversing the scoup is faster than picking up another tool.


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Rocket #1 Video video/x-msvideo 368.214 kbytes
Rocket #2 Video video/x-msvideo 355.496 kbytes
Rocket #3 Video video/x-msvideo 363.042 kbytes
Rocket #4 Video video/x-msvideo 340.444 kbytes
Rocket #5 Video video/x-msvideo 328.990 kbytes
Pre-Test Picture image/jpeg 75.705 kbytes
Cross-Section Diagram image/jpeg 50.862 kbytes
Rocket Tooling image/jpeg 73.997 kbytes