Space Plane Re-Entry Trouble

[Bosun]

Hi All,

I've created a Mk 3 Chassis that is balanced both empty and full. I've balanced the COM and lift, and made sure thrust is centered as well on the fore/aft axis.

Here's the trouble - I can get it up to 20k meters, at 600m/s and accelerating. From there, all it wants to do is flip around. The same on Re-entry. I have RCS installed on it, and up until then it flies very stable. I've gotten it to orbit once (strapped to rockets, which defeats the purpose), and once in space it accelerates just fine as well.

So why, at between 40k and 20k meters, at speeds exceeding around 500m/s, does it want to just flip around?

[InterCity]

I'd have to see the plane to be able to help, but as you describe it, it's because it's tail heavy. I think it's because the plane is:

a) not totally empty as you return - KSP burns fuel from nose to tail - meaning that your CoM gets shifted.

balanced "too well" - generally speaking, you want your CoL slightly behind your CoM to get more stability. A good rule of thumb I use is to space them with about 5% of the length of the plane.

For more info, post a screenshot with CoL and CoM shown. I can help you further.

[Edax]

Sometimes the structure of the spaceplane generates too much lift at a certain angle. The best solution is to fly as prograde as possible, same with reentering.

[Pyromancer]

Fat planes with lots of thrust do that, possibly you don't have sufficient control surfaces for that altitude and drag from the parts overcomes it

[Warzouz]

Sometimes the structure of the spaceplane generates too much lift at a certain angle. The best solution is to fly as prograde as possible, same with reentering.

Yes, use airbrakes to slow down and renegage engines when speed is below Mach 2, if you are too far from the strip.