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Ridiculous Richard

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Posts posted by Ridiculous Richard

  1. I was firing them up to 100.7km with I think less than 100m variation between repetitions.

    If you are interested im my results from this I have typed them in below

     

    The test vehicle used:

    Nose assembly

    RC-001S

    FL-R25 ballast tank to approximately even out the weight between nose cones (ballast figure is amount of RCS fuel loaded)

    HammerSRB

    2xElevon 1 for stability control

     

    Modus operandi:

    Throttle full, SAS on (+ open/close intakes), launch, no time acceleration in the atmosphere, get peak hight from F3 once vehicle starting to descend

     

    Results for 4.2t 1.25m tests

    Nose assembly Ballast Added Peak altitude with 40% thrust limit Peak altitude with no thrust limit except for survivability
    Fairing 2 section 0 122km 69.5% thrust => 145km
    Fairing 1 section 25 116km N/C
    Fairing shortest possible 50 55km N/C
    FL-A10 NC 50 98km 100% => 102km
    Aero NC 75 79km 100% => 79km
    Shielded clamp-o-tron 50 66km 100% => 59km
    Heat shield 0 52km 100% => 42km
    Advanced NC 50 105km 71.5% => 121km
    Closed shock cone 50 101km 93% => 117km
    Open shock cone 50 101km 93% => 117km
    Tail cone A 25 108km 71% => 128km

    The accuracy of this comparison is limited by the VAB mass readout in steps of 0.1t. Adding ~0.1t to the Fairing 2 section reduced the 40% altitude from 122km to 105km so it is hard to measure the difference between the following with confidence

    * Fairing 1 or 2 sections

    * Advanced Nose cone

    * Tail cone A

    If you want to be more accurate then you need to control the test vehicle mass more closely. Or do something like the suggestions in http://forum.kerbalspaceprogram.com/index.php?/topic/129655-what-options-are-there-in-ksp-for-quantitatively-determining-the-drag-produced-by-parts/

    From the above experiment I have gone with a 1 section fairing over a shielded clamp-o-tron for it's much lower drag and higher temperature limit.

     

    Regards,

    Richard

  2. Hello,

    I have been performing some simple nose cone drag test measurements (affix nose cone to test vehicle, ballast out mass differences, launch and see what peak altitude is achieved).  Although this has been successful for a simple part like a nose cone it is labour intensive, very sensitive to part mass (a different mass means different accelerations are caused and different speeds obtained) and positive feedback (less drag => more acceleration => higher speed => get to higher altitudes quicker => increased engine thrust => higher speed .......) and isn't a direct measure.

    Is there a better way to get quantitative drag vs speed information?

    The unrealistic ideal would be a set of drag (and lift for relevant parts) vs speed curves as functions of altitude and angle of incidence (but that would probably be far too complex to measure/calculate)

    Thanks for any suggestions,

    Richard

  3. As part of some nose cone testing (put nose cone on a Hammer SRB with minimal control surfaces and ballast to even out weight differences and see how high they go) I noticed that a shock cone appears to have the same drag regardless of being open or closed (the test vehicle reaches the same height).

    Has anyone else observed this or is there something screwy with my test?

     

    Thanks,

    Richard

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