AP burning questions

Does lit AP continue burning if moved underwater?

Once wet, will it burn after drying? If so would the rate or efficiency change?

Building a rocket submarine? Build thread!

An APCP motor will burn underwater but will not light when exposed to water. The water acts as a heat sink, preventing enough heat transfer from the igniter to start combustion.

jsdemar said:

An APCP motor will burn underwater but will not light when exposed to water. The water acts as a heat sink, preventing enough heat transfer from the igniter to start combustion.

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So hypothetically, an igniter sealed in ( hot glue? ) would get the job done. Optimal nosecone shape for an MD torpedo ( steel cable through eye bolts )? If I had a largish pond, I'd be Tempted by Science.

jsdemar said:

An APCP motor will burn underwater but will not light when exposed to water. The water acts as a heat sink, preventing enough heat transfer from the igniter to start combustion.

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Thanks! Should a delay grain? I thought it was plain AP, as in the oxidizer without fuel, but when I tossed it into a pond it went right out.

I wouldn't think that plain AP would burn very well at STP, let alone underwater. All oxidizer, no fuel; with what is it reacting?

watermelonman said:

Thanks! Should a delay grain? I thought it was plain AP, as in the oxidizer without fuel, but when I tossed it into a pond it went right out.

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If it was in a case with pressure forcing the exhaust gas out of the nozzle, then it would stay lit. But just a burning grain put into water will not stay lit (that's why we have fire extinguishers at rocket launches).

We don't have rain dates on a few of the fields we rent so we show up to launch unless it's absolutely impossible to. Our late club president Bill Spadafora once brought 2 micromax rockets and a deep vase and launched them from 1' underwater. When the video played back 10x slower than actual event, the audio actually sounded like a full scale rocket. Amazingly even though the rockets only apogee at 75', one of the two was not recovered....

[video=youtube;mtgCd3Uoopc]https://www.youtube.com/watch?v=mtgCd3Uoopc[/video]

Bob

jd2cylman said:

If it was in a case with pressure forcing the exhaust gas out of the nozzle, then it would stay lit. But just a burning grain put into water will not stay lit (that's why we have fire extinguishers at rocket launches).

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erm, actually the plan is to let the grains burn out and then use the extinguishers to put out anything that's burning, or contain the fire to around the grains. I don't think you'd get a grain out.

I don't think any bottles are getting these guys out-


For this fire after a CATO, we actually just went out and kicked dirt on everything.

Not AP, but there's this:

[youtube]74FIY3SGd4k[/youtube]

Multiple unrelated questions here, and some details missing in the underwater launch example.

BP is easier to light than APCP, in general.
You need to seal the motor to get it to light underwater, BP or composite. Some wax at the nozzle for BP works. A sealed cap on a composite motor will work.
APCP out in the open, not under pressure in a motor, can be extinguished with enough water to remove heat. Taking away oxygen with a fire extinguisher doesn't do anything.
AP alone needs fuel to burn. But it will detonate under extreme shock.

jsdemar said:

Multiple unrelated questions here, and some details missing in the underwater launch example.

BP is easier to light than APCP, in general.
You need to seal the motor to get it to light underwater, BP or composite. Some wax at the nozzle for BP works. A sealed cap on a composite motor will work.
APCP out in the open, not under pressure in a motor, can be extinguished with enough water to remove heat. Taking away oxygen with a fire extinguisher doesn't do anything.
AP alone needs fuel to burn. But it will detonate under extreme shock.

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Thanks, these are exactly the sort of answers I seek.

Do you know if delay grains are truly AP without fuel, or is it simply a different mix of much less potent fuel?

watermelonman said:

Thanks, these are exactly the sort of answers I seek.

Do you know if delay grains are truly AP without fuel, or is it simply a different mix of much less potent fuel?

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Delay grains are typically a slow APCP formula.

If it's AP held together with some sort of rubber, then it has some fuel.

Tony

tfish said:

If it's AP held together with some sort of rubber, then it has some fuel.

Tony

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I think some people are incorrectly referring to AP as the composite propellant. When I see/hear "AP", I think "ammonium perchlorate powdered oxydizer" alone without a binder. "APCP" refers to the composite propellant containing AP, a binder, and possibly other ingredients.

APCP propellent does burn in zero atmosphere and under water. However, igniting in those conditions is not easy...

Came upon this thread and reminded me of past relations w/ PSU/ARL.
Heres a paper from one of the researchers, I find interesting. Water Motors

Note: Do not even think of using nano-particles in amateur rocketry w/out the use of a qualified lab.

another one, AIAA, from same person, though unrelated, again interesting, using CO2
Magnesium Bipropellant Rockets for Martian Ascent Vehicles

NASA + AFOSR launched an ALICE ( Al , ice ) rocket in '09, haven't heard much since then.

Burn stability issues, IIRC. More of a proof of concept.

There are lots of combinations of things which can be used to make a rocket propellant if one really wants to. The issues are one wants it predictable, reliable, not too easy and not too hard to ignite, impossible to make truly detonate as a high explosive (burn at sound speed of the material), shock insensitive, not too poisonous to make or too poisonous exhaust and other residue, thermally stable over a wide range, humidity insensitive, not particularly chemically reactive, good long term storage, not too expensive to produce...

Gerald

APCP fuel additives for making effects would be good to know, especially the blue thunder, dark matter and red line types. What Chemicals are employed for making these effects?

midpower_madness said:

APCP fuel additives for making effects would be good to know, especially the blue thunder, dark matter and red line types. What Chemicals are employed for making these effects?

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Probably a better question for the restricted forum section

midpower_madness said:

APCP fuel additives for making effects would be good to know, especially the blue thunder, dark matter and red line types. What Chemicals are employed for making these effects?

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Blue propellant uses copper compounds.
Sparky motors uses titanium, larger mesh in larger motors. Some use steel or brass.
Red flamed propellant uses strontium compounds.
Green flamed propellant uses barium compounds (some more toxic than others, all toxic in the exhaust).

I have a burn mark in the bottom of my swiming pool to prove it burns under water

This should help; https://en.wikipedia.org/wiki/Pyrotechnic_colorant

The color also depends upon flame temperature. Too hot and the blackbody radiation will wash out the ionic coloring.

g zilla said:

I have a burn mark in the bottom of my swiming pool to prove it burns under water

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Lol- and does that burn mark come with a side of pride or embarassment? We just finished the pool at our house, I should ask the builder if fire damage is covered under the pebble warranty...and then get a picture of his face as he tries to imagine how that could happen.

g zilla said:

I have a burn mark in the bottom of my swiming pool to prove it burns under water

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You can't tell us that without telling the story

amell said:

You can't tell us that without telling the story

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lol....
+1...
Sounds like something I would do...

Teddy

I knew about the metal compounds. I do wonder about the super thunder propellent - I'm guessing it is core geometry and Ox to fuel ratio? Just saw my first H550 the other day and man it was fast!