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  1. #1
    Join Date
    20th January 2009
    Location
    Johnson City, NY
    Posts
    1,874

    Strange Rocksim results

    I've been working on a design and doing a few tweaks.

    I reran some existing simulations.

    Using the same motor I get a max alt of either 10182 or 10274 - no problem - expect some minor differences
    Max velocity of 1113 or 1114 - again no problem
    Time to apogee - 23.36 vs 23.48 - still good

    But max acceleration? 370 vs 1541 ft/sec/sec

    Say what? Over 4X the accel but every other number "matches"??? What is going on????

    File attached....

    ultimate_Darkstar_LRBb.rkt

    Rocket Addict
    More...more...I'm still not satisfied (T. Lehrer)

  2. #2
    Join Date
    30th January 2016
    Location
    US > OK > NE
    Posts
    2,613
    Acceleration jumps like this in OR as well, you can see it by making very short tubefins for instance.

    I haven't taken the time to file a bug report ( shame on me ), but it's fairly reproducible.


  3. #3
    Join Date
    7th February 2009
    Location
    Arlington, TX
    Posts
    1,207
    Rocksim does not limit itself to just the motor burn time when checking for maximum acceleration. Check your deployment settings.

  4. #4
    Join Date
    18th March 2009
    Location
    Wisconsin
    Posts
    3,169
    Quote Originally Posted by UhClem View Post
    Rocksim does not limit itself to just the motor burn time when checking for maximum acceleration. Check your deployment settings.
    You beat me to it. Likely a deployment event
    Mark Koelsch
    Tripoli 6155 L3
    Owner of http://www.rocketryfiles.com/
    Editor of http://www.thrustcurve.org/
    Keeper of the motor files

  5. #5
    Join Date
    20th January 2009
    Location
    Johnson City, NY
    Posts
    1,874
    OK - found it was the main deployment after coming down on drogue.

    The puzzling thing is I've made no changes in the drogue. So why did one simulation have one accel value and a different one have a much larger accel value when the main deployed?

  6. #6
    Join Date
    23rd July 2011
    Location
    Butte, MT
    Posts
    1,576
    What did you change?
    Steve Shannon
    L3CC, TAP, Director, Tripoli Rocketry Association

  7. #7
    Join Date
    18th March 2009
    Location
    Wisconsin
    Posts
    3,169
    Is it setup for drogue deployment at apogee and main at altitude, or was the drogue set to use motor delay?

    Mark Koelsch
    Tripoli 6155 L3
    Owner of http://www.rocketryfiles.com/
    Editor of http://www.thrustcurve.org/
    Keeper of the motor files

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