Heavy SSTO - unable to take off?

[selfish_meme]

Usually violent sudden pitch changes are due to drag or CoM change, so the nose drag increases with speed, the craft flips if it exceeds the rear. If the CoM shifts behind the CoL the craft again flips. It will be one or the other.

[March Unto Torment]

'Flip' isn't how I'd decide it - more a rapid swing from 10 degrees positive to 35 degrees negative. But I digress.

CoM change? Interesting. Do you have any suggestions for how to alter fuel load as so to ensure that the CoM moves as little as possible? And are there any tools/mods to dynamically display CoM and CoL while in flight?

[selfish_meme]

Aerogui and rcsbuildaid for in editor

- - - Updated - - -

Also as air runs out your wings lose control authority and your gimbal and sas are more important

[March Unto Torment]

No SAS on this thing - it's too damned big for that. They don't make SAS in this size

But I do have a few RCS thrusters, and some gimbal. But yeah, I did notice the control authority problem - I tried to pull up after the pitch change, and couldn't adjust altitude by the time I hit a few thousand metres, at which point the thing had so much heat that it exploded.

[March Unto Torment]

Alright, problem was solved by redistributing some mass and hitting rockets when engine thrust dips below 500kN per engine.

Still got a whole pile of issues (like how the .... I'm supposed to land this damned thing), but those are workable. For now, marking this as 'answered'. Thanks for your help, everyone!

[Captain H@dock]

Any idea what would cause it to pitch down like that? It was really sudden - the whole thing must've gone from 10 degrees positive to 35 degrees negative in two seconds or so.

Prograde stability assit engaged with the game automatically switching to target mode?