Spaceplane stability issues.

[thevegimobil]

Recently delving into building space planes I found that after I take off and pitch up the plane backflips and goes out of control... It always happens..it's symmetrical as far as I know and I just don't understand....it just flips ... Any help in building spaceplanes and sorting this issue out would be great

[Fuzzy Dunlop]

It would help if you could post pictures of your planes. Two general things that might be wrong. Firstly the centre of lift may be in front of the centre of gravity, which will make the plane spin. Secondly if you have to many fins and control surfaces at the front of the plane the plane will want to fly backwards (like an arrow the feathers always want to be at the back). Either way, try moving the wings back a bit?

[Markus Reese]

The backflip issue I am narrowing down myself, but still not 100% sure on the issue. A good example is a plane I built for a challenge had heavy flipping. I did 3 things to fix it. I will also point out that lift to c.o.g. were aligned.

First off, I removed some lift from the nose. I was using some wingbits to make a cool landing gear support, but it caused stability issue.

Second was it was a large plane and I decided to use delta wings for the tail fin. This isn't uncommon for me, but in this plane's case the tail was mounted well above the central longitudinal axis. I think the higher drag of my tail setup was causing an offbalance.

last, I actually brought some mass forward a little bit on the plane. I made it longer, but also added more nose mass. The lift to c.o.g. positioning remained the same, but the plane became alot more stable. Wish I could point out exactly what might cause it. Can you post up a screenie of your plane or two?

One theory might be when you get initial pitch, there is some sort of angular drag that throw off your lift and balance. By keeping drag centralized and your mass forward, it prevents a balance tip from occuring. This is probably why the issue is most common on large planes, but I find it rarely on my smaller ones.

[vexx32]

Just a note... if centre of lift is too close to centre of gravity, the craft becomes unstable. Ideally, you want the centre of lift to be a little ways behind the centre of gravity. The closer the centre of lift to the centre of gravity, the more maneuverable the craft is, but at the same time it becomes more unstable.

[thevegimobil]

To be honest I'm just trying to build a chase plane for when I launch my rockets.... Just want a stable fighter like craft.... I get cog and cot but I'm new to the sph so Co.lift is new to me.... And ideas with that in mind?

Vex thanks that helps a bit

[bsalis]

Ah, flipping. The great evil of planes in KSP. Many an SSTO design of mine suffered this.

There's all sorts of reasons for this.

* Center of lift in front of center of mass - this is the big one.

* Center of mass way to the back.

* Most or all of the control surfaces (elevators) way up the front.

* No control surfaces behind the thrust.

As an example, something like this cannot be flipped... Actually it's pain to change directions. That's because it's like a normal plane. With the elevator and rudder way to the back...

[thevegimobil]

Thank you...however the lift was behind the com... Any ideas how to stop a plane on a vertical launch from toppling?

[Markus Reese]

on vertical launch, use the launch supports to keep it vertical. Have them in the stage after your engines ignite. This will allow you to build thrust before decoupling. In actual space vehicles this is employed since it does take a small bit of time for initial thrust to build. It isn't instant like in ksp. That is why early rockets failed so much, they fell over while thrust built.

http://www.quora.com/Spacecraft/What-holds-a-spacecraft-in-a-vertical-position-during-a-rocket-launch

Clamping it while thrust builds when using plane engines is a must.