Double Mean Machine

Discussion in 'Mid Power Rocketry (MPR)' started by Padseven, Aug 10, 2019.

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  1. Aug 10, 2019 #1

    Padseven

    Padseven

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    Double Mean Machine Drawing (1).PNG

    I had mentioned this project in another thread. Several expressed interest in the documentation of this project so I thought it best to create a thread. Please bear with me as this the first time I have attempted to create a thread.

    This project is for a build challenge hosted by my club. The challenge is to successfully design, build, fly and recover a gap staged rocket. I have been interested in gap staging since the first time I read G Harry Stine's book as a kid. I remember the book almost challenging me to build the longest gap staged rocket possible. I am hoping to test the limits of the gap stage by building the Double Mean Machine.

    The Double Mean Machine is just as it sounds, two Mean Machines staged. One as the booster, the other as the sustainer. The planned launch date for this will be mid September. I will post as the build progresses.
     
  2. Aug 10, 2019 #2

    mbeels

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    Wow. Awesome.
     
  3. Aug 10, 2019 #3

    Padseven

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    This idea has floated in head for several years now. When Estes re-released the kit I knew I had to try it. In February I final simmed the design and was shocked to see that it would fly on an E9. In April I pulled the trigger and picked a couple kits from AC Supply. Hopefully my nephew and I will begin the project in the shop Saturday.
     

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  4. Aug 10, 2019 #4

    neil_w

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    Are you going to ground-test the staging before flying?
     
  5. Aug 10, 2019 #5

    Padseven

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    Yes we will be ground testing the staging. One of the first things we plan on doing is building a special test stand.
     
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  6. Aug 10, 2019 #6

    GlenP

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    Good luck, will be interesting to see how this long a gap will work with the 24mm BP motor.
    I wonder if it might do better with a 29mm black powder E in the booster?
     
  7. Aug 10, 2019 #7

    BABAR

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    Ummmmmmmmm, what is the recovery plan for the booster? Cuz unless I am missing something, it is going to be accordion recovery.
     
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  8. Aug 10, 2019 #8

    Padseven

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    Couple points with recovery of the booster.

    We have a design that was already tested for deployment of a chute for the booster if necessary.

    However, years ago while flying a standard Mean Machine I had a separation event. The chute stayed with the NC and to my amazement the body backslid and then glided to a soft recovery. The recovery was actually really cool.

    I'm going to try to replicate that flight (I still have the original MM) and see what happens. I will make a decision on how to recover the booster after that test flight.
     
  9. Aug 10, 2019 #9

    BDB

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    I once had something serendipitous like that happen too. When flying my Magnum+ with an E16-0 booster, the engine casing was accidentally ejected when the sustainer ignited. The booster without the casing was apparently stable--it just glided away into the trees, never to be seen again.

    I've always wanted to make a booster with "maple seed recovery"--like the Estes Tornado. #rocketrygoals
     
  10. Aug 10, 2019 #10

    BABAR

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    Believe me, I am not trying to rain on your parade

    Regarding backslide recovery

    I have had this happen serendipitously on a few rocket models.
    Here is an article

    http://www.gorgerocketclub.com/wp-content/uploads/2017/03/Backslider.pdf

    You however have a chimney or stuffer tube running up the middle of your booster. That is going to add a good bit of mass. That is likely to bring your CG waaaaaayyyyy forward, especially with such a long booster to begin with. So I fear your booster is going to remain stable after separation.

    You MIGHT get away with horizontal spin recovery on the booster.

    https://www.rocketryforum.com/threa...nch-gap-stage-horizontal-spin-booster.149667/

    I am not sure if it will work with a booster as long as yours (but sure as heck wouldn’t hurt!)
     
  11. Aug 11, 2019 #11

    seth_cooper

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    There's going to be a lot of grumpy people if that "booster" (aka 95% of a mean machine) comes in ballistic in the spectator area.

    That's if it gets by the rso in the first place.
     
  12. Aug 11, 2019 #12

    BABAR

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    Easy enough to try it out with a 13mm 20 mm body tube combo before you go big on this

    Tip put a rolled-up piece of aluminum can inside your chimney just in front of the booster motor will keep it from burning through
     
    Last edited: Aug 11, 2019
  13. Aug 11, 2019 #13

    Padseven

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    I'm not to concerned with the CG moving. The stuffer tube will add weight but the mass distribution will be across the overall airframe distance equally.

    As for spectators there are none and I am the RSO lol! We will be test flying this in a 15 acre field with nothing around for a 1/2 mile, but I understand your concern!
     
  14. Aug 11, 2019 #14

    BABAR

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    One way or another, should be an entertaining flight!
     
  15. Aug 11, 2019 #15

    GlenP

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    Very cool concept, If this works out, you could probably get a Mean Machine booster to loft a mini Mean Machine sustainer also. This leads to other ideas like a three stage MDRM to DRM to mini Max, hmmm...

    Or a Centuri theme: 3 stages of THUNDER: ROC, to BIRD, to HAWK...
     
    Last edited: Aug 11, 2019
  16. Aug 11, 2019 #16

    Padseven

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    Update: The static test using 72 inches of gap was a failure x 3. The test was done with a PVC pipe acting as the "stuffer tube" using a B6-0 and an A8. Not sure what the exact issue was. 4 vents were drilled into the forward section. We started with one vent open and increased the number of vents until all were open. The next step here is to conduct the test with actual BT.

    We also tested the "glide" recovery of the Mean Machine booster. Flight used a C6-0 to simulate the lower altitude a typical booster ejection. At this lower altitude the body doesn't have enough velocity and time to get to a horizontal body glide recovery. It wanted to but ran out of air space and crashed 10 feet from the pad breaking a fin. So we will be using a chute for booster recovery.
     
  17. Aug 11, 2019 #17

    GlenP

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    Why were you testing an 18mm booster, aren’t you planning to use a 24mm booster? I would kind of expect the 24mm to throw a little more heat up the tube than an 18mm motor, maybe.
     
  18. Aug 11, 2019 #18

    BABAR

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    Good to see the testing. I have done 6 feet static, but failed my two attempts at dynamic at that length. I was using a 24mm D12 with a BT20 chimney.

    My 2 successful in flight staging 51 inchers were D12s.

    What was internal diameter of the PC?

    Where exactly are your vents?

    How are you deploying the booster chute? It gets a bit challenging because if it deploys immediately AT staging, you have a chute deploying from a rocket at or near max velocity. Been there, done that, ripped the shrouds off the chute.
    Options for delay include a seconds motor pod (internal or external) with a short delay motor that pops a chute 2 or 3 seconds post separation, vs electronics, vs something else?

    Streamers are more forgiving, could deploy out of the tail of the sustainer, should be plenty of room around the 18mm motor mount.
     
  19. Aug 23, 2019 #19

    jqavins

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    A couple of thoughts. First:
    The airframe CG will be about the same as without the stuffer, but the airframe overall will be heavier relative to the fins, motor mount, and motor. So the whole structure's CG will move up. Which, of course, is good for stability, and that leads nicely into the second point.

    The sustainer fins will move the CP of the launch configuration up a bunch. The stock MM has a very large static margin, but tall skinny rockets need that. If the combination's margin is reduced but still more than one or two calibers then one might think it's still OK; it is not. Because of the sustainer fins you may well need nose weight.

    And finally:
    From the OR screen shot, it appears the stuffer is BT-20. Maybe try BT-5; that has only about 1/2 the volume to fill.
     
  20. Aug 23, 2019 #20

    Bat-mite

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    Sounds like you are actually doing some rocket science, as opposed to recreational flying. Don't let people rain on your parade. Best wishes!
     
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  21. Aug 23, 2019 #21

    BABAR

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    Not saying DON’T go to BT-5, but if you do, definitely need some protection on the inside of the smaller tube just forward of the motor. The ejection gas is hot and concentrated during the first few inches forward of the motor. When your stuffer tube or chimney is the same diameter as the motor mount, the heat isn’t that concentrated. When you go down a tube size, it is. It will burn through the tube after a few flights, but because it’s internal, you won’t see it.

    Here is where a piece of rolled up aluminum can can save you. Yes aluminum is flammable (but so is paper tube!), it will hold up better during the short duration of the ejection flame better than regular tube.

    If you do downsize the stuffer, make sure you have good motor retention, as the back pressure is higher.
     
  22. Aug 23, 2019 #22

    Wallace

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    I'm just gonna take a wild a@# guess and say if you find a motor that'll give it enough kick to get off the pad straight it's gonna fold up on you, if it's just a cardboard coupler that is. How does it "feel" if ya give it a good shake?
     
  23. Aug 24, 2019 #23

    Red7Fifty

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    I could use the spare (left over) nose cone. LOL :)
     
  24. Aug 26, 2019 #24

    cerving

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    If you can't get the gap staging to work, this would be a real good candidate for electronic staging/deployment, just build an AV bay coupler "nose" for the booster and you can use the electronics to fire the sustainer and bring the booster down on chute. As a side benefit, you can use an AP motor in the booster... if you're staying with 24mm I think you'll need an F24 or F39 just to get this thing off the pad.
     
  25. Sep 2, 2019 #25

    AlfaBrewer

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    If electronics and AP are an option, there's also the 24/60 case - F35w, F51T, F62R, F63FJ. Plus Cesaroni has several 24mm options.
     

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