My AI isn't launching to space.

I've been building this big ass spacecraft but the AI doesn't seem to want to pull up to reach its target elevation (minimum 2k). When I added helium pumps in the chambers it pulled out of the water but no higher, I know for certain it has the upward thrust required and the engine power but it just refuses. I've also manually went and set the controls of all the thrusters and it does use them to stay up and level.