SharkWhisperer
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Shockie hey there. I think we're straying far from the original thread's focus on exhorbitant rocket motor costs outside the US, but will answer this question and then suggest a new or different thread be opened if this topic deserves additional discussion. Some might, inappropriately in my mind because specific formulations are not discussed except in the vaguest of terms, opine that we require HPR L2 certification and be US citizens to discuss anything remotely "experimental". Alright, not my forum, not my rules. A bit overcautious perhaps but so be it.
I'd be super surprised if whistle wasn't listed as an LEx like BP in Germany, as it is here with BAFTE. Now getting over that 20g limit might take work--doubt it'll ever happen because restrictions on the hobby tend to tighten instead of loosen, particularly in the EU. They looooove their rules. Then again, they do have quite a large fraction of their population who might be worrisome to authorities if handling energetic compounds at all. For good, previously demonstrated, reason.
Wax and mineral oil (baby oil without the stink) and sometimes vaseline are used as phlegmatizers, which means they desensitize the comp. US military whistle uses mineral oil. How much? Dunno the data specifics. Does compression desensitize it? Sure it'll slow/standardize burn rate but for magic pressures used by the pros you'll need to find that info on a different forum that you frequent, to see if it's been tested and reported. Wax/oil phlegmatizers also helps to get decent compaction into propellant grains under usual pressing forces because of the lubricant properties. Might also reduce cardboard tube compression/expansion in both longitudinal (yes, thick cardboard tubes compress along their long axes) and cross-sectional axes during pressing, and subsequent propellent grain distortion when the tube relaxes from those high loading pressures. If that tube and propellant develop a gap between them, even the slightest, you're looking at a CATO. Besides also acting as a binder of some sorts (like the dextrin that Estes puts in their BP motors, whereas no fireworker would typically use that approach because: 1) dextrin modestly slows the burn rate, and 2) motors are typically used pretty quickly so not many worry about 20-year shelf lives. Higher pressures form denser grains that burn more slowly than lower density, but there's problems like grain fracture that are more likely with low-pressure loading.
In terms of hygroscopicity (not hydroscopicity--it's not a word--sorry, but terminology is important), BP components are differently water-loving. The oxidizer in my experience only absorbs perhaps 2-3% of it's weight in water. The carbon based fuel is the issue, and can easily absorb 20% of it's weight in water (that I've seen) while others report values as high as 50% of fuel mass. Which is why I bake my carbon fuel to dryness before making BP. And store with desiccant before use--otherwise it'll grab up a bunch of water again within days/weeks. The yellow burn temp lowering agent is effectively inert to water in my mind. That said, many (including it is strongly suggested), add 2-3% water to their mill dust before loading tubes, and if you wet granulate first and then dry it out before powdering and loading, some still add that extra water. It makes dusty powder handling a less-messy process, and some swear it increases burn rate (water, not high pressure). Yes, a pressed grain will provide some measure of barrier to atmospheric water entry over time, but cardboard tubes are good, but not perfect barriers and water can eventually migrate through a tube (or be absorbed into the tube from damp BP and arrive at some type of equilibrium. Some BP motor makers swear by prewaxing the inside of their rocket tubes, which supposedly reduces CATO likelihood by, again, preventing tube expansion/recoil effects after pressing to prevent gaps forming between the tube wall and fuel grain, and also possibly by acting as a barrier to moisture exit/entry. I've never had an issue with unwaxed tubes and doubt Estes uses that step--though simple and cheap for "research" purposes, it would certainly raise already high (my opinion) BP motor costs. But all of my "experimental" (they're really not experimental, but very well characterized) BP motors are stored in bags with silica packets if they won't be fired immediately.
I'd be super surprised if whistle wasn't listed as an LEx like BP in Germany, as it is here with BAFTE. Now getting over that 20g limit might take work--doubt it'll ever happen because restrictions on the hobby tend to tighten instead of loosen, particularly in the EU. They looooove their rules. Then again, they do have quite a large fraction of their population who might be worrisome to authorities if handling energetic compounds at all. For good, previously demonstrated, reason.
Wax and mineral oil (baby oil without the stink) and sometimes vaseline are used as phlegmatizers, which means they desensitize the comp. US military whistle uses mineral oil. How much? Dunno the data specifics. Does compression desensitize it? Sure it'll slow/standardize burn rate but for magic pressures used by the pros you'll need to find that info on a different forum that you frequent, to see if it's been tested and reported. Wax/oil phlegmatizers also helps to get decent compaction into propellant grains under usual pressing forces because of the lubricant properties. Might also reduce cardboard tube compression/expansion in both longitudinal (yes, thick cardboard tubes compress along their long axes) and cross-sectional axes during pressing, and subsequent propellent grain distortion when the tube relaxes from those high loading pressures. If that tube and propellant develop a gap between them, even the slightest, you're looking at a CATO. Besides also acting as a binder of some sorts (like the dextrin that Estes puts in their BP motors, whereas no fireworker would typically use that approach because: 1) dextrin modestly slows the burn rate, and 2) motors are typically used pretty quickly so not many worry about 20-year shelf lives. Higher pressures form denser grains that burn more slowly than lower density, but there's problems like grain fracture that are more likely with low-pressure loading.
In terms of hygroscopicity (not hydroscopicity--it's not a word--sorry, but terminology is important), BP components are differently water-loving. The oxidizer in my experience only absorbs perhaps 2-3% of it's weight in water. The carbon based fuel is the issue, and can easily absorb 20% of it's weight in water (that I've seen) while others report values as high as 50% of fuel mass. Which is why I bake my carbon fuel to dryness before making BP. And store with desiccant before use--otherwise it'll grab up a bunch of water again within days/weeks. The yellow burn temp lowering agent is effectively inert to water in my mind. That said, many (including it is strongly suggested), add 2-3% water to their mill dust before loading tubes, and if you wet granulate first and then dry it out before powdering and loading, some still add that extra water. It makes dusty powder handling a less-messy process, and some swear it increases burn rate (water, not high pressure). Yes, a pressed grain will provide some measure of barrier to atmospheric water entry over time, but cardboard tubes are good, but not perfect barriers and water can eventually migrate through a tube (or be absorbed into the tube from damp BP and arrive at some type of equilibrium. Some BP motor makers swear by prewaxing the inside of their rocket tubes, which supposedly reduces CATO likelihood by, again, preventing tube expansion/recoil effects after pressing to prevent gaps forming between the tube wall and fuel grain, and also possibly by acting as a barrier to moisture exit/entry. I've never had an issue with unwaxed tubes and doubt Estes uses that step--though simple and cheap for "research" purposes, it would certainly raise already high (my opinion) BP motor costs. But all of my "experimental" (they're really not experimental, but very well characterized) BP motors are stored in bags with silica packets if they won't be fired immediately.
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