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  1. #1
    Join Date
    17th November 2015
    Location
    Cambridge, MA
    Posts
    68

    High Performance Pyrotechnics

    I've used 4F black powder for all my time in this hobby, but I'm working with a team on a high altitude rocket, and we're looking into a pyrotechnic gas-generator feeding a pneumatic piston for a deployment system, similar to Derek Deville's excellent Qu8k.
    Cleaning out the piston after every firing is a drag, and as an engineering student I'm inclined to assume that we can spend money and find an aerospace grade (overpriced and overperforming) solution to the problem. We do have an LEUP, so we can consider a wide range of materials.
    We're looking at Black Powder as a baseline material, but we're also considering nitrocellulose. We've eliminated sodium azide (too toxic), and APCP (thermal issues).
    Has anyone used anything other than black powder? Does anyone have any advice to share on the subject?

    Ad Astra per Aspera
    2016 Ns: 3525 (69% L)
    2017 Ns: 36984 (90% O)
    L3: "Artemis" 7,640 ft, MDRA, January 15, 2017

  2. #2
    Join Date
    30th January 2016
    Location
    US > OK > NE
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    3,484
    How do you feel about co2 systems? Check out cd3 & peregrine for powder activated, or life vest/raft inflators for mechanically activated.

    Check out Swiss Null B (0b) powder, it's even finer than 4fg. I don't think anyone still has stock of 5fg since Goex quit bottling it.

    Investigate 7fa or Meal XF powder. It's got more surface area per flake and isn't graphite polished, but I believe more susceptible to static and moisture.

    My current theory is that a thin layer of double base pistol tucked under a strata of meal xf in a lamp nipple would be an extremely fast and clean burn for a fantastic electronics bay support.

    Nobody that I know of has tried any of this; if you don't have an experienced firearms reloader to go with your LEUP you shouldn't try this.


  3. #3
    Join Date
    30th January 2016
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    US > OK > NE
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    3,484
    Oh, dirty piston. Duplex loads of smokeless pistol under black powder substitutes is where I'd take a look.

    Also airbag pellets, not all of them are azide based.

  4. #4
    Join Date
    23rd July 2011
    Location
    Butte, MT
    Posts
    2,273
    I looked at gun cotton years ago, which is just nitrocellulose that looks just like cotton. It burns very fast and very clean. Unfortunately itís affected by humidity over time and breaks down into something that was much less useful. It works well because it exposes so much surface area. Nitrocellulose powder might not work so well. Smokeless powder requires containment and when contained delivers very high pressures in a very short time, much higher than our amateur rocketry components can withstand.
    Iíve considered CO2 Systems and Iíve read about spring systems. I keep coming back to 4g black powder. Jim Jarvis had some recent posts on achieving more complete combustion that remove concerns about high altitude use of BP for me.
    Almost all of my rockets have used pistons. I have never had a problem simply wiping out the ďcylinderĒ. I have brushes up to three inches and my hand with a rag works above that.


    Steve Shannon
    Steve Shannon
    L3CC, TAP, Director, Tripoli Rocketry Association

  5. #5
    Join Date
    23rd January 2009
    Location
    NE Ohio
    Posts
    2,499
    Doesn't AP burn clean (no ash)?
    John Derimiggio NAR/TRA L3
    MarsaSystems

  6. #6
    Join Date
    30th January 2016
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    Quote Originally Posted by jderimig View Post
    Doesn't AP burn clean (no ash)?
    Yes, but they mentioned thermal issues there.

  7. #7
    Join Date
    23rd July 2011
    Location
    Butte, MT
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    2,273
    Quote Originally Posted by jderimig View Post
    Doesn't AP burn clean (no ash)?
    One byproduct is hydrochloric acid.


    Steve Shannon
    Steve Shannon
    L3CC, TAP, Director, Tripoli Rocketry Association

  8. #8
    Join Date
    8th December 2009
    Location
    CA
    Posts
    1,906
    The below links still use BP but use confinement methods for high altitude...

    http://www.google.com/url?sa=t&rct=j...k_0G5sFpeX2FXf

    http://www.rocketryforum.com/showthr...d-Ejection-Cap

    Tony

  9. #9
    Join Date
    26th November 2009
    Posts
    4,939
    Quote Originally Posted by Steve Shannon View Post
    One byproduct is hydrochloric acid.


    Steve Shannon
    Oh yeah, I forgot about that one. HCl acid might not be kind to the hardware and harnesses. Judging by the "heat blast" of a few pounds of APCP chips, bits and powder on the burn pile from 100 feet away after a group motor "machining" session,
    I'd say the thermal effects could lead to the flaming parachute recovery. Or a flaming rocket recovery if a cardboard rocker were tried! Kurt

  10. #10
    Join Date
    9th September 2013
    Posts
    54
    Quote Originally Posted by BlazingAngel665 View Post
    I've used 4F black powder for all my time in this hobby, but I'm working with a team on a high altitude rocket, and we're looking into a pyrotechnic gas-generator feeding a pneumatic piston for a deployment system, similar to Derek Deville's excellent Qu8k.
    Cleaning out the piston after every firing is a drag, and as an engineering student I'm inclined to assume that we can spend money and find an aerospace grade (overpriced and overperforming) solution to the problem. We do have an LEUP, so we can consider a wide range of materials.
    We're looking at Black Powder as a baseline material, but we're also considering nitrocellulose. We've eliminated sodium azide (too toxic), and APCP (thermal issues).
    Has anyone used anything other than black powder? Does anyone have any advice to share on the subject?
    Why even use pyrotechnics

    TP

  11. #11
    Join Date
    20th February 2009
    Location
    Cayuga, Indiana
    Posts
    12,899
    Quote Originally Posted by rocket_troy View Post
    Looks cool! But large, and maybe expensive.

    From the Ether...
    L3, TRA #11847
    Tripoli Indiana #132
    Tripoli Central Illinois #59
    Central Illinois Aerospace (NAR) #527
    Chicago Rocket Mafia, "Big Bucks" Dixon
    ___________________________________

    Quiet little voices creep into my head. -- We Were Promised Jetpacks

  12. #12
    Join Date
    9th September 2013
    Posts
    54
    Quote Originally Posted by dixontj93060 View Post
    Looks cool! But large, and maybe expensive.

    From the Ether...
    Yeah, probably not totally ideal for high altitude attempts where you want to optimise everything. Saying that, I have used it in airframes up to 4.5" diam which provides a modest intrusion to the available volume and mass.

    TP


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