Its an old bug that is back, effecting mostly larger rockets, you have plenty of thrust, but the craft is stuck to the launch pad.. If you put stacked decouplers under the engines and activate them, then the craft takes off no issues.. It can effect smaller builds to. http://kerbalspaceprogram.com/forum/index.php?topic=4355.msg49281#msg49281 http://kerbalspaceprogram.com/forum/index.php?topic=3979.msg44572#msg44572