Open Rocket Help

Discussion in 'Low Power Rocketry (LPR)' started by Bruiser, Jan 20, 2019.

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  1. Jan 20, 2019 #1

    Bruiser

    Bruiser

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    Anyone know how to move the engine so it sticks out one inch from the rear of the engine mount tube?

    And, maybe someone could look this over and see if anything jumps out as just plane wrong?

    Thank you,
    -Bob
     

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  2. Jan 21, 2019 #2

    dhbarr

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    Motor tab
    This component is a motor mount
    Increase the Motor overhang
     
  3. Jan 21, 2019 #3

    Rex R

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    a question; do you really want plywood fins that are 5/8" (0.62") thick? or did you want 1/16" (0.0625")? (what I saw at a quick glance)
    Rex
     
  4. Jan 21, 2019 #4

    Bruiser

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    dhbarr, thank you. I was try to find it under the motor tab.

    Rex, thanks for catching that. I have it changed over to 1/16th now.

    I also saw that the body tube thickness had changed so I fixed that.

    Here's the updated version if anyone else could look it over.
     

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  5. Jan 21, 2019 #5

    Rex R

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    after a longer look, I notice that you are using non-standard size body tubes, this may cause problems finding things like nose cones and or centering rings, and as designed the rocket WILL descend much faster than open rocket says...evidently OR does not need a shock cord to connect the parts (like nose body + chute), real world does however. last bit, your chutes deploys 3 seconds early :).
    Rex
     
  6. Jan 21, 2019 #6

    Rex R

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    personally I would make the tube coupler a) one inch longer and b) give it a bulkhead. and move the chute down below the payload section. I think that I would limit the motor overhang to at most 0.5", but it isn't my rocket.
    Rex
     
  7. Jan 21, 2019 #7

    Rex R

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    I have made a couple small changes to illustrate how I might build your design. feel free to use (or not use) the suggestions :)
    Rex
    *edit*
    you will need some sort of launch guides, launch lugs for 1/8" rods would be easiest I think.
     

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  8. Jan 21, 2019 #8

    Bruiser

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    Ok, I'm busted. So this is the Tomahawk part of a Semroc Nike-Tomahawk. That's "why" the odd sized components. I am investigating making it a two stage rocket. As designed, it is a only a single stage.

    I am looking at using all the Tomahawk parts and using the motor mount tube that would be installed in the booster in the Tomahawk. All I need is some centering rings for it and the sustainer will be done. Oh, and I will probably use the chute that came with the kit in the sustainer (Tomahawk) after I either cut it down or cut out a spill hole in it.

    I need the motor to stick out 1" so that it can engage the booster. I was thinking of "flipping" the body tubes and using a longer coupler so I can turn the coupler into a baffle. I need to see if I have a longer one in my spare parts box. I like your idea of having the rocket split between the "motor" and "payload" sections. I'll play with that in Open Rocket :)

    I also enters an ejection delay, but I don't know how to ask it to tell me if a seven second delay is good or not.

    So the purpose of this exercise was to see if the sustainer could fly on it's own and it seems it can.

    I just moved the separation point and it still looks good.

    Thanks again for the help and ideas.

    Now I need help figuring out how to add the booster in.

    -Bob
     

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  9. Jan 21, 2019 #9

    Rex R

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    short answer is yes it is doable. I would suggest a 24mm motor mount in the booster, with a 12.5" long motor tube leading up to just aft of the upper stage motor(18mm), and 'gap' stage the rocket. hard part will be the streamer for the booster(lower) section.
    Rex
     
  10. Jan 21, 2019 #10

    Rex R

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    longer answer is that it would look something like this(see attached design file) :).
    rex
     

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  11. Jan 21, 2019 #11

    Bruiser

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    Yep, that is right along the lines I was thinking...

    So, one last question for the night. Does the program have a way to print the rocket blueprint out full size?

    Thanks,
    -Bob
     
  12. Jan 21, 2019 #12

    Rex R

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    not that I am aware of, think you're stuck with paper and pencil 2.0 for full size plans :).
    Rex
     
  13. Jan 21, 2019 #13

    Nytrunner

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    I'll rarely put shock cords in my sims since they have no bearing on the flight calculations. They get taken up in the mass balancing anyway

    When you run a sim, it will give "optimum delay time" in one of the columns
     
  14. Jan 22, 2019 #14

    Bruiser

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    So Rex, Why a "D" motor for the booster? I was thinking that too, but a "C" motor would give me more room for the booster recovery system... You know, it'll all need to fit in the space between the inner motor tube and the outer body tube...

    I haven't tried simming it on Open Rocket yet.

    -Bob
     
  15. Jan 22, 2019 #15

    Bruiser

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    So Rex, Why a "D" motor for the booster? I was thinking that too, but a "C" motor would give me more room for the booster recovery system... You know, it'll all need to fit in the space between the inner motor tube and the outer body tube...

    I haven't tried simming it on Open Rocket yet.

    -Bob
     
  16. Jan 22, 2019 #16

    Nytrunner

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    Likely to get you off the pad faster. Staged rockets are heavily and tend to weathercock easily.
     
  17. Jan 22, 2019 #17

    Rex R

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    Ding, Ding! we have a winner :). when you add in the weight off a 2nd motor and mount etc. that rocket will likely be over 5 ounces(or more), you're going to need the extra thrust at lift off and all the speed at staging that you can get to reduce weather cocking.
    Rex
     
  18. Jan 22, 2019 #18

    Charles_McG

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    A C11 would do the trick also. If you can still find some.
     
  19. Jan 22, 2019 #19

    Bruiser

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    All right, I'll go with the D12-0. I was just thinking of room for the chute and the altitude. Open rocket was showing 1762 with your design. Is that "doable" for recovering the sustainer with a chute without a dual deploy?

    Oh, I just realized I could launch with a smaller engine than a "C" in the sustainer to limit the altitude. I'll check that out in open rocket.

    Thanks again,
    -Bob
     
  20. Jan 22, 2019 #20

    Nytrunner

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    Depending on how heavy your sustainer is, a streamer is also an option
     
  21. Jul 27, 2019 #21

    James Irvin

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    Any fix for seeing images when you open help for open rocket in wiki. I opened help but pictures will not load?
     

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