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Thread: Pyrogen Formula

  1. #1

    Unhappy Pyrogen Formula

    Thought I had it all figured out. Bought the wire, bought the black powder and acetone. Bought the ping pong balls. I made a batch of ignitors per the formula I found on this web ring (www.sparksrocketry.com/ignitors.htm) only to be told by one of the old hands that a black powder based ignitor was only good for igniting a black powder motor. He said the ignitors used on Aerotech reloads and the like need a pyrogen in order to ignite the composite motors. I haven't had the courage to try to light one of those expensive reloads since I was told that. He said that APCP lights due to pressure rather than the flame that my ignitors yield. I'd really like to pursue this since I found it rather enjoyable making the ignitors, but I don't know where to go next with this. Thanks for the help.


  2. #2
    Join Date
    26th January 2009
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    PCH
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    3,112
    David's igniters work well. I've seen 'em used to light both AP and BP based motors. Go ahead and try lighting an APCP motor, you've got nothing to lose. If the motor fails to light, try it using a different ignitor (e.g. a Magnelite or a Copperhead). Oftentimes, the igniter will light a small amount of the propellant, causing the chamber to pressurize and the motor to come up to full thrust. Most igniters do not produce the pressure required to bring an APCP rocket motor to full thrust instantaneously (with the exception of the blacksky Head-ends and the famous Copper Thermite igniters, both really only useful on K+ motors). Most HPR igniters are just like a big sparkler -- which it sounds like you've got.

    Give it a try, it just might (and probably will) work

    David Reese
    TRA 5590
    http://davidree.se

  3. #3
    I've made several batches of igniters with black powder only. They work fine. I haven't had 100% success but I'm still tweaking the process. I wouldn't use them to stage or for deployment but for getting ap going they work great.

  4. #4
    I got pyrogen from Al's Hobby Shop a couple of years ago. Just used the conductive primer recipe and the used the Firefox pyrogem mixture (sent in separate containers for shipping and regulation purposes) and have had 100% success with composites from E through I impulse. It's just a matter of a 2nd dip in the pyrogen.

  5. #5

    Re: Pyrogen Formula

    Originally posted by amtraktrekker
    Thought I had it all figured out. Bought the wire, bought the black powder and acetone. Bought the ping pong balls. I made a batch of ignitors per the formula I found on this web ring (www.sparksrocketry.com/ignitors.htm) only to be told by one of the old hands that a black powder based ignitor was only good for igniting a black powder motor. He said the ignitors used on Aerotech reloads and the like need a pyrogen in order to ignite the composite motors. I haven't had the courage to try to light one of those expensive reloads since I was told that. He said that APCP lights due to pressure rather than the flame that my ignitors yield. I'd really like to pursue this since I found it rather enjoyable making the ignitors, but I don't know where to go next with this. Thanks for the help.
    I'd give about five to three it's a case of someone assuming "uses" means "needs". From what I've seen, "old hands" are more prone to this than are those who'd ask the question.

    In science-speak, it's an empirical question. That is, the trying provides the real answer.

    "When a distinguished but elderly scientist says something is impossible, he is almost certainly wrong." -- Arthur C. Clarke

  6. #6
    amtraktrekker,

    Have you set one of these igniter off yet? If it burns for more than a second, and you have to sheild your eyes from the light, chances are you have nothing to worry about...seriously though, ground test.

    As mentioned before, if the igniter does not ignite the AP motor, then you will have your answer...if it does light the AP, then all that work you enjoyed so much will be worth it.

    note: do not ground test on loaded AP motor! Open air ground test only

  7. #7
    Thanks for the great advise, fellas. I'll do some more ground testing this weekend and hopefully light one up next weekend.

  8. #8

    Gary Purrington

    of Firefox enterprises has an excellent bunch of literature on just about every topic you could think of in pyrotechnics, including ignition of composite propellants and formulating igniter pyrogens.

    the main problem i can see is that while it is fairly simple to formulate a pyrogen mixture, there is some bit of danger since the oxidizers used in pyrogens/primers are typically more sensitive than the oxidizers used in propellants.

    the other problem is that for a few grams of pyrogen, you have to purchase about 7lb of chemicals.

    i'd suggest purchasing one of the kits sold for igniter construction from gary or one of the other vendors. that way there's no waste or toxic chemicals left over and you have a proven formula right off the bat with nittle to no testing needed.


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