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  1. #1
    Join Date
    1st February 2018
    Location
    Orlando, FL
    Posts
    5

    Chicken Heavy: Parallel staged, fully separating, BT80 monstrosity

    Back in fall 2016, I competed in a rocketry competition at my university where the objective was to carry an egg payload safely with the best apogee. Our team name was SpaceEggs, and naturally we named our rocket the Chicken 9.

    The logical extension is of course to make Chicken Heavy, a parallel-staged cluster complete with deploying side cores. And that's exactly what I'm doing.

    I am Level 1 certified with NAR (doing L2 attempt very soon) and I wanted a challenge that really forces me to step up my skills in design, construction, and electronics. The design of the CH isn't based exactly on the FH, but moreso on creating a Heavy version of the rocket we originally built for the competition. This forces me to work within some particular constraints, and believe me it was a challenge. The payload isn't an egg this time around, it's a miniature Tesla Roadster.

    Self-imposed constraints
    * The body tube must be thin wall BT80 and the nose cone must be the PNC80B, these were the supplies given in the competition
    * The body tube must be 36" long to match the original Chicken 9
    * Tail cone is required, as it was also part of the C9
    * The boosters must completely separate in flight while the center core is still under thrust

    Is this the easiest way to do it? No.
    Will it succeed? Maybe.
    Should I have gone for something smaller? Probably.
    Am I a madman? Yes.

    I should point out that I only recently joined this forum and just now (Feb. 4th) saw Cabernut's BT-60 FH. I haven't taken any inspiration from it, in fact the airframe is completely done as of the time I read his post and most of the design work was done months ago.


    The fins are laser-cut from 1/8" acrylic, because that's what we used on the Chicken 9 and because the engineering lab's cutter doesn't do lexan. Why, you may ask, is their shape so bizarre? The guy who made them originally has no idea why but they helped significantly improve our apogee, we think it had to do with aerodynamic interaction with the tailcone.

    I used my favorite method to align the fins, which is to half-notch the fins and centering rings for exact radial placement. Also a fin jig helps.



    Repeat with side core motor assemblies. After cutting fin slots, I shoved the whole thing in the body tube and secured it with epoxy.

    My method of attaching the side cores is just an upscaled version of the booster pod kit. I 3D printed hooks and seats (I don't know what else to call the bottom piece that it sits in) and used them to align the placement of the thrust rods, which transfer the load to the center core. I then epoxied the hooks and seats to the center core.

    What I did for the Roadster was cut off the bottom of the nose cone and epoxy in a ring through which the car and its mount fit neatly. Those two are attached to a bulkhead which screws into the ring.


    So as of last night, the airframe is complete and the Roadster is securely inside the nose.




    My flight plan is to have a slow-burning H45 in the center and two F44's on the sides. About two seconds into flight, the miniTimer4 will fire charges in the boosters, deploying the nose cones and allowing them to fall away under streamer. The center core will continue for about four more seconds before burning out, and the DDC-22 will trigger events at apogee and 600 ft for deployment of a drogue streamer and main 24" chute.

    Finding a way to trigger charges in the side cores while not having a permanent connection was an interesting challenge. I decided on using spring connectors that contact copper on the center core. The springs should also provide a small pushing force to encourage booster separation, even if it's only a little bit.

    I did learn about the OpenRocket dev version from Cabernut's post, so I made a rough version of the whole stack and it actually validates my sketchy hand calculations saying the rocket is stable.




    I fly with NEFAR, and to my knowledge a fully separating rocket like this hasn't been flown there in a long time so this should be an interesting one. I'm going to install an onboard camera as well to capture booster sep. The decorations will be pretty much the same as the original Chicken 9, all hand-designed stickers and decals. I may even add laser cut grid fins and paper model legs.


    I appreciate any advice you guys have, since this is my first cluster. If you think this is a disaster waiting to fly... it's too late now, the Chicken Heavy is closer to being done than it was when I started two days ago. In the words of someone who saw it, "God help us."

    Chicken 9 album


  2. #2
    Join Date
    26th October 2016
    Posts
    146
    Cool project. I've been following the Falcon Heavy build thread and am excited to see two parallel efforts towards a similar goal. Keep us updated as you build.

    NAR level 2: Mad Cow Super DX3

  3. #3
    Join Date
    12th September 2013
    Location
    SE Wisconsin
    Posts
    1,072
    Are you planning on having motor ejection of the booster chutes, after the flight computer blows the nose cones with a separate charge? Assuming the nosecone doesn’t pull out the chute.


    Sent from my iPhone using Rocketry Forum
    Charles McGonegal
    Ciderwright at AeppelTreow Winery & Distillery
    www.appletrue.com
    NAR #103560 L1 6/25/17 Estes Leviathan CTI H175-SS
    Ad Astra Tabernamque!

  4. #4
    Join Date
    1st February 2018
    Location
    Orlando, FL
    Posts
    5
    Quote Originally Posted by Charles_McG View Post
    Are you planning on having motor ejection of the booster chutes, after the flight computer blows the nose cones with a separate charge? Assuming the nosecone doesn’t pull out the chute.


    Sent from my iPhone using Rocketry Forum
    The streamers will be pulled out with the nose cones at the booster separation event. I'm looking into whether I need full parachutes for them once they're free falling, since they're light (~12-13oz each). One concern I have for putting in chutes is having them come out at booster sep, which could damage them or the boosters.

  5. #5
    Join Date
    12th September 2013
    Location
    SE Wisconsin
    Posts
    1,072
    Quote Originally Posted by SpaceEggs View Post
    The streamers will be pulled out with the nose cones at the booster separation event. I'm looking into whether I need full parachutes for them once they're free falling, since they're light (~12-13oz each). One concern I have for putting in chutes is having them come out at booster sep, which could damage them or the boosters.
    Yes, it could. I haven't tested my cheap solution.
    Charles McGonegal
    Ciderwright at AeppelTreow Winery & Distillery
    www.appletrue.com
    NAR #103560 L1 6/25/17 Estes Leviathan CTI H175-SS
    Ad Astra Tabernamque!

  6. #6
    Join Date
    1st February 2018
    Location
    Orlando, FL
    Posts
    5
    Quick picture of how the Roadster mount attaches to the nosecone.




    And here's what it looks like underneath the nose cone when it's on the rocket. Bear in mind it's not actually going to be that far up because the bulkhead it's attached to sits on the end of the nose cone shoulder. In this picture, I'm using a dummy bulkhead to keep it from sliding into the body tube.

    NAR L1 - Senate Launch System, H135, October 14 2017, NEFAR

  7. #7
    Join Date
    5th December 2013
    Location
    MD
    Posts
    7,143
    Very cool. I wish you much success. Please take video of the flight!

    John S. ---- NAR #96911 ---- TRA #15253 ---- MDRA #067 ---- BARC #028
    L1, 3/15/14: Aerotech Sumo, CTI H133BS
    L2, 6/21/14: Giant Leap Vertical Assault, CTI J240RL
    L3, 3/12/16: MAC Performance Radial Flyer, CTI M1101WH
    Altitude: 13,028', L3 flight; Speed: Mach ???, L3 flight

  8. #8
    Join Date
    15th October 2016
    Location
    Huntsville AL
    Posts
    2,042
    Fortunately the forumites in general take any imitation as flattery and the passing of knowledge instead of as theft of intellectual property.

    Heck, I'm basically using Eric Cayemburg's builds as the manual for my L2!
    "I'm at least 70% confident about whatever I say (90% of the time)"- college me

    NAR 101195
    Level 1: Big SAM, 9/10/16

  9. #9
    Join Date
    15th October 2015
    Location
    Minnesota
    Posts
    1,329
    That's perfect. I wonder if you could 3D print a little Starman to go in there. Or a chicken, keeping with the theme.
    NAR L1 - Optima 3" upscale/CTI H133 @ NYPower 20, May 28, 2016
    My YouTube channel

  10. #10
    Join Date
    1st February 2018
    Location
    Orlando, FL
    Posts
    5
    Quote Originally Posted by Cabernut View Post
    That's perfect. I wonder if you could 3D print a little Starman to go in there. Or a chicken, keeping with the theme.
    I'm not good enough with 3D modeling yet to make a little Starman in the appropriate pose, but I did find an STL file for this adorable Chicken Trump which I think I'll print and strap into the car.
    NAR L1 - Senate Launch System, H135, October 14 2017, NEFAR

  11. #11
    Join Date
    1st September 2010
    Location
    Tucson, AZ
    Posts
    1,077
    Quote Originally Posted by SpaceEggs View Post
    I'm not good enough with 3D modeling yet to make a little Starman in the appropriate pose, but I did find an STL file for this adorable Chicken Trump which I think I'll print and strap into the car.
    DO. THAT.
    NAR 96681
    L1 - May 29, 2014 LOC Norad ProMax, H120
    L2 - Feb 21, 2015 Fiberglassed Madcow Frenzy, J280

  12. #12
    Join Date
    27th December 2014
    Location
    Seattle, WA
    Posts
    846
    The only thing I'd worry about is whether the H44 has enough initial thrust to lift the whole stack off the pad safely if the side boosters don't light. You might think about a G64 for the core and maybe faster-burning side booster motors.

    NAR L1 "Cheeto Dust", scratch 54mm, H54R (before it became a G54), Mansfield, WA
    L2 "Arc Light", Madcow 2.6" Arcas, J285CL, Mansfield, WA, recovery by snowshoe

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