Sudden leaning motion on reentry

[eightiesboi]

Hey fellow kerbanauts!!

Can I get some quick input here? On I have an inline stack consisting of an OCTO core, a docking hatch, a command pod, a habitation module, and a heatshield (and a few surface attached items set to either x4 or x2 symmetry)  CoM is inside the habitation module. RCS build aid shows no torque on a straight line force. However, on reentry, the decelerating module will suddenly swerve to one side and hold that swerve. It doesn't matter how I am holding attitude, and it doesn't matter what side of my stack is facing up; I've tried hatch up, hatch down, and hatch to the side. Video linked here: https://onedrive.live.com/embed?cid=FE34D6542466878C&resid=FE34D6542466878C!1281022&authkey=AI3uMqjN4R0SNK0, screenshot attached. I'd love some input.

[Spricigo]

It seems that the craft is barely stable, at some point it just go past the limit and there is no coming back.

Maybe it is the CoM shifting back as ablator get consumed, maybe is some of those micro-wobbling going just a bit too far from progade.  In either case the solution is to move the heavy part further ahead and the draggy parts further behind, probably adding some heavy/draggy parts for this particular craft to work.

 

[eightiesboi]

1 minute ago, Spricigo said:

It seems that the craft is barely stable, at some point it just go past the limit and there is no coming back.

Maybe it is the CoM shifting back as ablator get consumed, maybe is some of those micro-wobbling going just a bit too far from progade.  In either case the solution is to move the heavy part further ahead and the draggy parts further behind, probably adding some heavy/draggy parts for this particular craft to work.

 

That could be it. I thought I had added additional weight to the bottom (heatshield) end, but it looks like the ablator mass getting, well, ablated, may be it. Don't know why I couldn't see it myself--I think I was fixated on the sideward motion and not thinking enough about stability. Thanks!

[Wobbly Av8r]

If it helps to understand the situation, here's a post from awhile back about the issue....