ssto keeps fliping

[Claw]

The problem is quite simple, I did different ssto in my career and I want to do a more advanced one that could go past LKO. Problem is, when I am reaching around 1200m/s, it flips. Any idea why?

http://steamcommunity.com/profiles/76561198079296946/home

[CATAO]

look if the center of trust is aligned with your center of mass

[Marshall]

And don't forget your center of mass "CoM" moves as you consume fuel. Leading to center of thrust "CoT" imbalance and flipping.
Try experimenting and seeing how it looks, by draining fuel tanks in the VAB, while watching the "CoM" vs "CoT"

[Claw]

center of thrust is a tiny bit higher.

[Claw]

Yea I think I see it, im going to try ading stuf on the front to balance it.

[Bubba Fett]

Do you have any pictures of it? If it's a spaceplane your wings may be too far in front of your center of thust.
One of the things that make spaceplanes so difficult is that in order to be properly balanced for low speed flight your center of mass should be just a bit forward of your center of lift.
Your center of lift usually provides a lot of drag at high speed and your center of thrust is behind it pushing hard against all that drag. Since your center of mass is so close to your center of drag, you don't get much directional stability.
Add to that how most planes are not vertically symmetrical and you've got a problem.
If you put air intakes or a vertical stabalizer on the top you're adding drag above the center of thrust. If you put your wings below the centerline of the craft, you're adding drag below the COT.
And if all that's not bad enough, drag works differently once you're supersonic.

Spaceplanes are hard. If you've got versions that work to LKO you're doing pretty good.

[=BB= Misophist]

Originally posted by marguerite100:

The problem is quite simple, I did different ssto in my career and I want to do a more advanced one that could go past LKO. Problem is, when I am reaching around 1200m/s, it flips. Any idea why?

http://steamcommunity.com/profiles/76561198079296946/home

Bad link?

[andylaugel]

His profile is set private, so we can't see his screenshots.

[=BB= Misophist]

Originally posted by andylaugel:

His profile is set private, so we can't see his screenshots. :sad_creep:

Ah.

[Claw]

oh, thanks, didn't know why it did that

[Claw]

Can you see it now?

[Azunai]

there's an awful lot of engine mass in the back and the aerospike and nerv engines have no thrust vectoring. when you get out of the denser parts of the atmosphere, the aero control surfaces won't do much (or nothing at all) and once the shiplash jet engines shut down, you lose their thrust vectoring. so the only control authority left at this point is probably the tiny reaction wheel in the cockpit.

which i guess is not enough to keep that extremely back-heavy design stable.

you can try and add some more reaction wheels and see if they are enough to keep the plane controllable. shifting the mass of the engines closer to the mid section of the plane would probably be a better design, though. the engines attached at the end of the main stack/fuselage can't be moved much, but the radially attached whiplash and nerv stacks (along with most of the wings) could be moved from the back to the center of the plane to make it a lot more inherently stable.

balancing an SSTO for both full and empty tanks is a delicate task. there are many techniques that can help, but simply moving some of those heavy engines from the back to the mid should help a lot already.

[andylaugel]

Originally posted by marguerite100:

Can you see it now?

I can see these pictures now.
http://steamcommunity.com/sharedfiles/filedetails/?id=723831843
http://steamcommunity.com/sharedfiles/filedetails/?id=723831859
I have to agree with what mkunz2 is saying.
Planes flip in atmosphere if their center of mass moves behind their center of lift. You can see where these are by clicking on those buttons in the lower left side of the screen, to the right of the cost and above the symmetry controls. You can also adjust how full the tanks are in the VAB and SPH by cllicking on the tanks.

[=BB= Misophist]

Originally posted by RoofCatA:

Airbrakes should be able to help with pitch/yaw. How exactly does it work I haven't tested yet, but they have got settings on them like on steering surfaces where you can enable or disable particular steering plane. Except those on airbrakes are inactive by default! I presume they are SAS connected as well? And having some on SSTO may be not such a bad idea anyway.
http://steamcommunity.com/sharedfiles/filedetails/?id=732349177
My airbrakes are probably facing the wrong way but they still wok on descent (drag is auto-retrograding) and don't mess up with anything on ascent. The thing is quite small to place and have them work properly at the same time. I know it's a joke of SSTO. Still it can both land from LKO orbit fully tanked with ~2 fuel units spent for landing last m more secure and launch back into LKO subsequently. So the joke is probably not on me.

I might actually use something like that for all those bs missions... Thanks for the idea