dimovski Posted October 6, 2012 Share Posted October 6, 2012 So, this is my rocket So, the soviet anthem plays, the massive 7 mainsails and 6 BACCs start, seconds later the BACCs pop off just to be replaced by 12 new ones, after these pop off , we got about 3200 litres for each Mainsail, all fine and dandy,right? So i accelerate towards 2200 m/s , and then it happens, 8 LV-45Ts and a Poodle launch , and guess what, instantly it starts flipping over and rolling like mad, 8 RCS thrusters dont do anything ASAS either...so,i have to 1st coast ,then decouple the worthless fuel tanks n engines , and then,as a "reward" it goes "just" 45* in the wrong direction... and in the end... i feel that a simple "up to the mun" is impossible...;.; Link to comment Share on other sites More sharing options...
mustwinfull Posted October 6, 2012 Share Posted October 6, 2012 Welcome to the forums dimovski.Sorry I can't help more but I have no idea why it's tipping over, maybe too much mass and not enough support? (Struts).Maybe to test your rockets, you could get MechJeb and you can activate Smart ASS and click the "STOP ROT" button which stops the rotation for you, but of course this is a mod approach and I'm sure you would like a stock approach which someone else can help with.Have fun playing KSP and go blow up some rockets! Link to comment Share on other sites More sharing options...
Wayfare Posted October 6, 2012 Share Posted October 6, 2012 What's probably happening: near the end of your ascent stage, your craft is still quite heavy and your ASAS is fighting hard to keep it under control. When you drop that stage, your craft is suddenly much lighter. At the exact same time, your nine engines ignite. This gives you a very sudden boost in thrust-to-weight ratio while your ASAS still thinks it's trying to wrestle an elephant. It only takes a split second for the tremendous overcompensation to put your ship into an uncontrollable flip-over.Try cutting off your throttle and SAS before separating that ascent stage, then bring the SAS back online and gently throttle back up. Link to comment Share on other sites More sharing options...
Moltove Posted October 6, 2012 Share Posted October 6, 2012 your last stage wouldn't have the SAS forces to be able to control the decouple, and the thrust to weight ratio. Also try to turn off RCS as you decouple, that may help. Have fun! Link to comment Share on other sites More sharing options...
dimovski Posted October 6, 2012 Author Share Posted October 6, 2012 thx will try,but because this little gem took me already a week of computer time, id rather play some WoT now, will tell you the results later Link to comment Share on other sites More sharing options...
Vanamonde Posted October 6, 2012 Share Posted October 6, 2012 Your upper stage is very compact, making it easy for forces to induce a tumble around its axes. That's not a flaw, but it is a cause. Try moving the side tank/engine combos further down, even overlapping the central engine, to give the stage more rotational inertia. Perhaps even replace those eight 400-capacity tanks with one 1600-capacity big one and eight of the little 200-capacity tanks as side engine moutning points. That will give the stage identical weight, fuel capacity, and engine mounts, while making it longer and therefore more resistant to unwanted rotations. Also, since the gimballed engines are its strongest form of attitude control, try firing them immediately upon decoupling. I was just having a similar problem earlier this evening, and getting the engines on the job of resisting unwanted rotations right away did a lot to overcome it. You might as well save the RCS fuel and turn them off, by the way, since the current thrusters are not really scaled to be much use on the larger ship parts. Link to comment Share on other sites More sharing options...
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