Someone build this for (any reason other than) the summer contest

Discussion in 'Scratch Built' started by neil_w, May 4, 2016.

  1. Jul 22, 2018 #61

    modeltrains

    modeltrains

    modeltrains

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    Now that I'm reading through all 3 pages of the thread, Yes.
     
  2. Jul 23, 2018 #62

    BABAR

    BABAR

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    Actually that makes a lot of sense. With seven attachment fins and your conversion of the ring fins to standard fins my spider sense has calmed and the robot voice ceased.

    Thanks
     
  3. Jul 23, 2018 #63

    neil_w

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    The fact that it makes sense doesn't make it correct. :) But in this case I hope it is.

    As long as this build would indeed keep the CG fairly far foward, there should be enough stability provided by the rings to make the whole things fly.

    I'm still waiting for someone to volunteer to build it, or else I'm gonna get stuck with it. :eek:
     
  4. Jul 23, 2018 #64

    BABAR

    BABAR

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    Call it the USS Vaxinator!
     
  5. Jul 23, 2018 #65

    neil_w

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    That's not bad.

    After modeltrains' recent post I was thinking "Chronic Illness". Also "Fuel Injector" also popped into my head recently.
     
  6. Aug 10, 2018 #66

    jqavins

    jqavins

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    Orbit Injection. (After K'Tesh's inadvertent(?) suggestion.)

    RocSim does ring fins. My computer is packed up and on a moving truck or I'd sim this, but surely there's someone reading who can do it.

    Also, if the bottom of the plunger - where the thumb pushes on a real syringe - is a solid plate rather than a ring then you benefit from base drag. There was an article in Peak of Flight years ago about simulating that effect by adding a cone that sticks out the back. Make it a conical transition with no shoulders; 1 mg mass, because RocSim doesn't allow zero; 10 µm forward diameter, because RocSim doesn't allow zero; aft diameter equal to the base diameter; and length, if I remember right, equal to the base circumference, i.e. π times the diameter. Search the archive topic index for "short fat" and you should find it.
     
  7. Aug 10, 2018 #67

    neil_w

    neil_w

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    I think this was addressed previously. Putting a plate at the back would add base drag stability, but I don't think it's necessary for this design, and it would kill performance. On the other hand it would look more "realistic". I've experimented with the base drag correction cone in the past; seems to work OK but I get nervous that the results end up being overly optimistic. But that's just my brainsim getting in the way of (alleged) reality.

    Of course anyone who builds this (still no takers?) could do it however they like, but if it ends up being me then it'll be a ring until proven impractical. Although I'm not one to generally shoot for max altitude, and this rocket will never be a competition flyer, I've also found that rockets that are *too* draggy and basically don't go anywhere aren't much fun to fly. So I try not to go too crazy with the excess drag.
     

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