Pyrotechnic booster separation

Discussion in 'High Power Rocketry (HPR)' started by Cameron Anderson, Sep 16, 2019.

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  1. Sep 16, 2019 #1

    Cameron Anderson

    Cameron Anderson

    Cameron Anderson

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    I've seen several threads that doscuss HPR booster separation but haven't seen any actual, workable designs or flights.

    The electronics to airstart and separate boosters pyrotechnically exist in several altimeters/flight computers so that is the relatively easy part. But the design/fabrication of the hinges/brackets/charge systems are still nebulous.

    My goal would be a ground-started 54mm long burn in a 3" airframe with 4x 38mm booster airframes with 29mm motors airstarted in pairs then separated.

    I have a few ideas but I would love to see any successful HPR booster sep designs that use pyro.
     
  2. Sep 16, 2019 #2

    boatgeek

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    I had a version on my Falcon Heavy that I liked pretty well. Tested really nicely in ground testing. Unfortunately, the flight wasn't successful, but the failures were not down to the SRB attachment method. Posts 4, 9, and 15 here have details.
     
  3. Sep 16, 2019 #3

    Cameron Anderson

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    Not sure how I missed that, but your pyro ejection is nearly identical to the one I planned. Your rear retention looks similsr to what I was planning too.

    If you had to do it again, how would you change your booster retention/separation plan?
     
  4. Sep 16, 2019 #4

    timbucktoo

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    There are some threads floating around. I will see if I can find them and/or find some pics of mine.
    Question - where are you planning on putting your separation charge electronics? I have three 2 stage rockets and put my electronics for separation charge in ISC. Have seen others put it in sustainer. Setup is pretty simple. I use 0.5 grams BP in all my rockets. Doesn't take much. BP & ematch are enclosed in finger tip of disposable nitrile gove. Ematch is then fed thru a small hole into ISC which is connected to electronics. Typically timing is based on booster motor burnout. I choose 0.5 seconds after burnout. Several altimeters have this feature. Perfectflite MiniTimer4 is pretty simple to use and probably cheapest on the market for this purpose.
     
  5. Sep 16, 2019 #5

    Cameron Anderson

    Cameron Anderson

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    My current plan is to keep all electronics in the center core, in a traditional e-bay on an av sled between the upper air frame/NC and the lower core/fin can. I want to light four Strap-on boosters in pairs of two...booster ignition will be done by channels 1,2,3, and 4 of an Eggtimer Proton. Channels 5 and 6 will be for core apo and main DD recovery. Core will also have a backup altimeter for main and apo (something just for redundancy, and small). Booster sep will be done with a Missileworks PET2+ timer with one event separating the first pair and second event taking care of the second pair. Strap-on igniter lines will use JST connectors so if the timer kicks a strap-on before ignites it won't ignite as it's floating down under chute. Strap-on recovery will be motor deployed and times individually. I want a CTI L265 core motor and LMS i205s in the boosters.
     
  6. Sep 16, 2019 #6

    boatgeek

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    If I do it again, I'd do booster retention and ejection the same way. This approach worked really well in ground testing, so I don't have any reason to change it. I might change it up after a successful flight, though... :)
     
  7. Sep 16, 2019 #7

    Cameron Anderson

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    Cruise missiles are fun, I enjoyed the video
     
  8. Sep 16, 2019 #8

    boatgeek

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    I would have been a lot happier with the cruise missile if it hadn't been destroyed by fire in the crash. :oops:

    Slightly more seriously, there are three kinds of flights:
    Good flights (your rocket does what it's supposed to)
    Bad flights (your rocket doesn't do what it's supposed to)
    Great flights (someone else's rocket doesn't do what it's supposed to)
    I'm pretty sure that before that flight, the LCO said that it was either going to be a good flight or a great flight.
     
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  9. Sep 16, 2019 #9

    Cameron Anderson

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    I am a believer in the good flight/great flight mentality.

    I'm bringing a bottle of champagne to BALLS for a big two-stage project I'm flying...i'm either going to celebrate a great flight or drown my sorrows.
     
  10. Sep 16, 2019 #10

    Nytrunner

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    Rockets and alcohol. At least the designers of the V2 thought that was a good combination

    Check out the advanced topics forum (staging/clusters/airstarts) for other builds also
     
  11. Sep 16, 2019 #11

    Charles_McG

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    Hey. I resemble that remark.

    I did a Space Shuttle stack with SRBs spring loaded against the booster, tethered in place, with a Quantum cutting the tether line. Build is here on the forum.

    Not directly usable with so many SRBs, but an adaptable idea.
     
  12. Sep 17, 2019 #12

    Cameron Anderson

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    After sketching out a few ideas, I think the biggest hurdle will be electrical connections to the boosters for igition. I'd prefer a streamline design but a 29mm MMT and 38mm airframe doesn't leave a lot of room.
     
  13. Sep 17, 2019 #13

    Nytrunner

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    Flattened brass tubing to thread the wires down?
     
  14. Sep 17, 2019 #14

    Cameron Anderson

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    Down the booster airframe sure, but between the core and booster, I think JST might be too big.
     
  15. Sep 17, 2019 #15

    Charles_McG

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    Why run the booster ignition through the booster? 54mm in 76mm airframe has a lot more room for running wiring chases. Out the bottom and loose wiring up, or out the side through a drilled hole, with a bent tube. I've run igniter wire across the vanes of outboard tubes (24mm mmt in 76mm frame) and a little masking tape keeps it in place fine.
     
  16. Sep 17, 2019 #16

    Cameron Anderson

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    My initial thinking was run the wire connection higher up on the booster with some sort of lipo connector as the quick disconnect because that would limit the chances of a booster getting hung up at sep.
    But a small JST 2.0 connector at the base with the wires run down the core and through a small hole in the side could work.
     
  17. Sep 17, 2019 #17

    Charles_McG

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    On my Shuttle (3.4" body, BT58 booster,s so on the border between low power and midpower) I made the upper support out of brass tubing. Hollow, so the tether could pass through, handily sturdy enough to lift the weight of the boosters under thrust. In the future (I have an Atlas 412 in mind), I'd change the build a bit to keep the release mechanism completely in the core, so the support didn't have a pass-through channel. The Shuttle boosters are pad lit.

    I have a midpower Titan IIIe, but don't like how the separation is done. It works, but is hard on the booster.

    My upscale NASA Pegasus is air-lit. I run the ignition wiring through the center body tube and out the aft centering ring and just twist and tape the wire leads. If I used a JST - it would be up by the avbay, so if the wiring was shorter than the shock cord, it would break cleanly at the connector.

    Running everything through the core gives more room to work - and really makes the boosters as simple as possible. And keeps the failure modes rooted in the core. As long as your boosters can ride along in all flight variations. If you light from the bottom, there's nothing to get hung up on.
     
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  18. Sep 17, 2019 #18

    Cameron Anderson

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    I think the main takeaway is keep the boosters as simple as possible, and I definitely think that's the right approach.
     
  19. Sep 17, 2019 #19

    boatgeek

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    If you have the booster igniter wires running out the bottom, I'm not sure you need a connector. When the booster lights up, it's going to spit the wire right out, leaving no connection. The trailing igniter wire will get fried up in the main motor exhaust, but that should cause any real issues.
     
  20. Sep 17, 2019 #20

    Cameron Anderson

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    Good point. I will still need a JST connection in my fin can to allow it to separate from my e-bay for DD recovery (Last two times I did twist and tape, it was too thoroughly connected and my streamer couldn't come out) but you're right, the igniters running from the aft end of the core into the booster motors will get cooked off.
     
  21. Sep 18, 2019 #21

    wrad

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    I tried using a headphone jack as the disconnect for the ignition wires to the av bay over the weekend, however it clearly wasn’t tight enough as it became disconnected in flight before ignition. As for the booster disconnect device I haven’t built anything for high power yet but am also very interested in doing so, I have a thread in the staging section for people to post there designs for strap on boosters which has a couple of methods posted so far, it would be great to see what you settle on. John Coker has a very interesting electronic separation method on one of his current builds on his website.
     
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