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Thread: Tipping Rocket on Launch

  1. #1

    Tipping Rocket on Launch

    OK this started today and its with rockets and setups I have used before. When I get to say about 10k to 15k sometimes lower but never higher my rocket wants to "tip over" like its top heavy.

    So here is what I did - first I checked my center of mass etc...all good right down the middle. I thought maybe it was just a payload. I added angled boosters to help stabilize on launch.

    Never ever got above 15k with the rocket tipping over (loosing control, top heavy feel)

    SO ok I was getting frusturated. I launched the same rocket with no payload and it did the same thing - ok so its the rocket not the payload i thought. Played around a bit still every time same thing.

    OK SO I launched a different rocket - did the same thing!!

    I launched my primary rocket I use for say 75% of my lifts empty, with payload I have launched before etc... same thing.

    I thought ok mechjeb? took it off - still doing it. SAS? still doing it. FAB?? took it out still doing it.

    Here is a picture of my primary rocket I use.

    Here is two launches with the same rocket with TWO DIFFERENT tops (to different size payloads) that I got up no issues.

    NOW here is the kicker... I don't have this problem with STOCK launchers ?!?!?

    I have even rebuilt my rockets with no success. I'm lost

  2. #2
    It even happens on short stubby rockets not just tall ones.

    Last edited by chrisjk24; 29th June 2013 at 16:15.

  3. #3
    Will science for food. UmbralRaptor's Avatar
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    1) How much tipping over are we talking about, and what guidance systems are you using? By default MJ will begin its gravity turn at around 5-10 km. If you aren't using the ascent autopilot, are you using ASAS and/or Smart ASS?

    2) I'm not familiar with the engines on the first stage(KW? Novapunch?); do they have thrust vectoring?

    3) What are the drag values for the fairing/nosecone?
    Basics of orbital mechanics and interplanetary transfers (OhioBob) | KSP orbital parameters and celestial parameters (Maltesh) | Semi-analytic stage sizing. (me)


  4. #4
    I wonder if you're simply going too fast?

    You're using FAR and they look like mighty powerful rockets for whats sitting on top of them. Try to keep the speeds down to 250m/s below 10,000m and below 1000m/s (ish) in the next upper atmosphere. Air resistance will build up if you go faster and any slight deviation from your velocity vector will be uncontrollable.

  5. #5
    Have an ASAS onboard, and Mechjeb but I do all my launches without autopilot. Just a note I did try MechJeb once and it tipped out of control. ASAS won't hold it.

    Tipping as it once I get to say 85 90 degrees pitch it 'falls' like its on a pendalem (sp?) and just spins around with or without thrust never to regain control. I get even get it to point straight down and hold.

    Drag for fairing and nosecone is .2 per half nose cone .3 per half fairing.

    All engines have thrust vectoring.

  6. #6
    8.2t is what I am currently launching into a 200km orbit. At around 10t with the first rocket configuration I have about 300 to 500 dv left once I release the payload. Enough to retro it back to the surface.

    I have tried different speeds, throttle controls etc... once it hits that 90 to 85 pitch it falls.

  7. #7
    From the pictures it doesnt look like you put you SAS on, if you go too fast this will cause a unbalance

  8. #8
    Oh im sorry i misread your comment sorry

  9. #9
    Try to put some winglets on a higher stage. I'm just guessing here, but maybe you lose the winglets you have to soon if you drop the stage you have, making it difficult to control

  10. #10
    Try lowering throttle. In MJ 2 you can add "Terminal Velocity" to your info windows. If your speed goes above it, lower the throttle. Note that your old heavy rockets become OP when you use FAR

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