Static Tests - Bottle Rocket Motor Static Tests
Date: 2006-01-07
Description
Similar to the previous static testing experiment. A number of bottle rocket motors were charged and test fired on a mechanical diet scale, the results videoed for study.
One SBR motor was constructed for comparison purposes on Steve Majdali's Super Bottle Rocket tooling and NEPT tubes using my Contaminated Meal batch. The remainder being on Rich Wolter tooling, using Pyrotube casings and charged with various propellants.
This time I secured my 1/4" tube testing stand to the scale with some blu-tac to prevent failures like those previously experenced.
Comments
Interesting results.
Some good figures for the SBR were recovered. Assuming I can ignore the impulse response of the system and I correctly interpolated the scale readings *and* my trapezoidal integrator hack I wrote in AWK works correctly then the motor would be classed as a 1/2A2-2.5. Its total impulse is 823 mNs and has an "average" thrust of 2 N. It end-burnt its delay section for 2.5 seconds. I think that is quite reasonable performance for a 1/4" motor using fairly weak propellant.
Unfortunately the last motor tested, the Nozzleless Benzolift unit, exploded with unprecedented violence! The scale mechanism was written off, and the 2 oz rocket tube off-cut that made up the testing stand was split open in a suprising manner befitting a Wile E Coyote cartoon.
The report was enormous for such a tiny device, my camera operator had hearing protection on and still described it as painful. My ears rang for several minutes after. The sound was very sharp, like a "crack". The video shows that the motor went from all there to pieces in far less than 1 frame (33 ms). There were no pieces of burning propellant thrown out, none of the usual CATO events, it was as if the entire grain detonated. Some pieces of cardboard made it 5 metres from the test stand.
A new scale will need to be purchased before more experiments can be made.
Attachments
| title | type | size |
|---|---|---|
| Pre-Test Picture | image/jpeg | 36.503 kbytes |
| Post-Mortem Picture | image/jpeg | 32.346 kbytes |
| Damaged Test Stand Picture | image/jpeg | 40.064 kbytes |
| Damaged Scale, Stand and Motor Bits | image/jpeg | 37.074 kbytes |
| Benzolift CATO Frames Loop | image/gif | 549.318 kbytes |
| SBR Contaminated Meal Video | video/x-msvideo | 2.925 Mbytes |
| 6:3:1 BP Video | video/x-msvideo | 2.869 Mbytes |
| 7:3 Sulfurless BP Video | video/x-msvideo | 2.431 Mbytes |
| Chrysanthemum #6 Video | video/x-msvideo | 3.110 Mbytes |
| New Rocket Meal (aka Bunnings 15:3:2) Video | video/x-msvideo | 3.098 Mbytes |
| RP Video | video/x-msvideo | 4.162 Mbytes |
| Nozzleless KP Red Video | video/x-msvideo | 9.327 Mbytes |
| KP Red Video | video/x-msvideo | 9.454 Mbytes |
| Nozzleless Benzolift Video | video/x-msvideo | 3.282 Mbytes |
| SBR Thrust Curve | image/gif | 23.785 kbytes |