Mechjeb and heavy ships

[WatchDragon]

I am using the auto Ascent module in a very heavy ship trying to get to the Mun, when mechjeb hits 'Gravity turn' mode, the ship decides its time to become a missile. or when circlizing orbit, the ship will fall out of orbit, is it me doing something wrong or is that just how mechjeb works with heavy ships?

[Capt'n Skunky]

You probably need more control surfaces and devices like RCS. Put some fins on the bottom stage and add RCS thrusters at the top of the craft as well as near the bottom of each stage. The idea with RCS thrusters is to always have a set sitting at either end of the craft (the middle doesn\'t matter in this case) so the craft can be turned by applying force at the ends of the craft. BY putting at the bottom of each stage, when you separate you will still have a set at the new bottom of the craft.

Cheers!

Capt\'n Skunky

KSP Community Manager

[wired2thenet]

I regularly launch heavy ships, and the Capt\'n here is absolutely 100% correct. Note that the amount of thrusters on the top (at least it works best for me) is to add a few more than on a the middle and lower stages, to get the rocket moving just a little quicker. Also note that it is sometimes better to 'burst' RCS thrust, not leave it on constantly (ie, tap thrust, pause, tap thrust, pause) for the heavier ships.