About Speed Limits of Rocket

Discussion in 'High Power Rocketry (HPR)' started by John Feller, Jul 17, 2019.

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  1. Jul 17, 2019 #1

    John Feller

    John Feller

    John Feller

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    Hi everyone!

    I am designed a model rocket and its maximum velocity is 0,83Mach. One of my friends said that after 0,8Mach is problem for rocket because this speed is rated as "Transonic speed" so my airframe can be damaged in the air. Is this argument true? Airframe is fiberglass .

    Thanks in advance!
     
  2. Jul 17, 2019 #2

    Bat-mite

    Bat-mite

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    Fiberglass can definitely handle transonic speeds. I've had a canvas phenolic airframe glued together with 30-minute epoxy go M 1.2 with no problem. If you get to supersonic, then carbon fiber is a better choice.

    Make sure your fins are sturdy and well-attached; downswept helps. Go launch!
     
  3. Jul 17, 2019 #3

    Zeus-cat

    Zeus-cat

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    Fins are more likely to have problems at high speed than the body. Fin flutter and stress on the fins could be issues.
     
  4. Jul 17, 2019 #4

    Nytrunner

    Nytrunner

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    And either fiberglass or carbonfiber will shred if improperly fastened/glued together
     
  5. Jul 18, 2019 #5

    mperegrinefalcon

    mperegrinefalcon

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    Transonic is a walk in the park for fiberglass tubes.
    I have flown thin wall fiberglass airframe to mach 1.7 before, and I will be flying a MD 54 with fiberglass tube to mach 2.4. I am not worried about the tube and neither should you.
     
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  6. Jul 18, 2019 #6

    heada

    heada

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    Paper tubes and plywood fins can work just fine in the transonic range. You have to use epoxy for attachments with good filets. Fiberglass and carbon fiber are good options but not required.
     
  7. Jul 18, 2019 #7

    OverTheTop

    OverTheTop

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    The definition of "transonic" is that somewhere the airflow near the rocket is supersonic, usually first in any turbulance created by disturbances in the smooth flow. There is no specific speed which defines transonic, but generally it is around 0.7-0.8M. It is nothing to be scared of and really just shows where drag, typically from wake turbulance can start, and progress from there to become significant on the rocket.

    Fiberglass will have no problems with that speed. Balsa fins might be problematic, but cardboard airframes and plywood fins are not a problem either.
     

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