Tests of Perchlorate Strengths
The following is a basic test of how different oxidizers affect sound and thrust in whistle rocket motors. Equipment and rocket motors similar to the ones used in the catalyst tests (here) were used in this experiment.
First Series of Tests
The following is a basic test of how different oxidizers affect sound and thrust in whistle rocket motors.
The four perchlorates tested were Firefox domestic ground perchlorate (standard purity - sort of an off-white/light yellow color), some good Taiwanese from another source, Firefox chunk domestic and high purity Chinese from Skylighter. At the moment, the exact purity of each perchlorate is unknown.
TaiwanesePeak Thrust: 1800 grams
Average Thrust for core: not evaluated yet
Average Thrust for non-cored area: 90-100 grams
Sound level: 131.1 dbDomestic ground
Peak Thrust: 1400 grams
Average Thrust for core: not evaluated yet
Average Thrust for non-cored area: < 10 grams
Sound level: 124.6 dbDomestic chunk
Peak Thrust: 820
Average Thrust for core: not evaluated yet
Average Thrust for non-cored area: < 10 grams
Sound level: 125.1 dbHigh purity Chinese
Peak Thrust: 1000 grams
Average Thrust for core: 850
Average Thrust for non-cored area: < 50
Sound level: 134.5 dbSome interpretation:
The result of the domestic chunk test supports what others here surmised - domestic chunk might best be used for non-whistle components.
The domestic powder is weak for sound although peak thrust was good. Average thrust was low.
The Taiwanese was very good for thrust and fair to good for sound.
The high purity Chinese was fair for thrust and very good for sound.Some backtracking:
These are preliminary results and would need to be validated by at least two more runs.
The process:
The Taiwanese and both domestics were run through a 'Magic Bullet' coffee grinder and then screened through a 50 mesh screen. The coffee grinder was cleaned between each run.
The motors were 5/8" and were made to the specifications shown at http://wichitabuggywhip.com/fireworks/rockets/whistletests.html. They all had a 25 gram grain.
The fuel for all tests was finely milled Potassium Benzoate. The catalyst for all tests was iron oxide. The ratio was 76/23/1 +3 mineral oil
Follow -on Tests
(aka - I need to get a life)
The following tests take into account the granularity of the perchlorate. Specifically, the perchlorates in all tests were reduced to -325 mesh. That is, the perchlorate powder was milled until it was less than 325 mesh. Perchlorate may clump and mechanically bind when milled so the measurements were done with a microscope. See pictures for examples of measurements. The fuel and catalyst were changed from a medium-low reacting combination (sodium benzoate and iron oxide) to a higher reacting mix during the experiment because it was found that low reacting fuels and catalysts tended to mask the strength of the potassium perchlorate - essentially with some low power fuel/catalyst combinations, no discernable difference could be seen between the perchlorates. Domestic perchlorate showed nearly the same strength as Taiwanese.
The perchlorates tested were Firefox domestic ground perchlorate (standard purity - sort of an off-white/light yellow color), some good Taiwanese from another source, high purity Chinese from Skylighter (also known as HP140), Spanish from Nitroparis (most likely still Chinese), Swedish donated by Tim Seekon, Reagent grade from a laboratory supply source, and cleaned domestic (recrystalized by Eric Hunkins). At the moment, the stated manufacturer purities for the common perchlorates are in doubt. The amount of impurities found in most commercial perchlorates exceed the stated purities by several percent. (See perhloratenotesv2.pdf)
The Data
The third attempt follows in video format. The first attempt showed differences but the perchlorates were not uniform in granularity. The second attempt used a low power whistle mix and the thrusts were hard to distinguish. This series use a high powered mix (as developed in the whistle tests). While at first glance, the third attempt seems to be a failure, it is not. These motors survived hundreds of tests using unmodified perchlorates. Now, with the perchlorates ground fine and a high powered catalyst/fuel mix, the results are ... well.. pyrotechnic. Also, the cleaned domestic perchlorate CATO'd while the normal domestic perchlorate did not. Take a look (wmv formatted movie):
Third attempt in video format
Fifth attempt
After another failed run (run 4), it was decided to run all end-burners and no cores so that our poor test stand wouldn't pop a cork. Here are the results of burns of two increments (about 10 grams) of each perchlorate after it had been ball milled for two hours in a 6" hobby ball mill, pressed to 6600 lbs in a 5/8" tube and fired on a small test stand.
Perchlorate Type Average Thrust in Grams Reagent Grade 90-95 (retest needed - this is probably wrong) Spanish 100+ Swedish (donated by Tim Seekon) 100+ (retest needed) Domestic Cleaned (by Eric Hunkins) 135 Taiwanese 113 HP 140 100+ Domestic 100