Kerbal 1.x+ launching problems

[Scourge1979]

Ok, so Ive seen a couple of threads about this, but nobody has (to my knowledge) answered this properly. And please guys, read what I'm going to type, because it's almost as frustrating having to deal with off topic replies as it is the actual problem here

Ok, so ever since version 1.0 came out, I've been having massive issues launching (any) rockets.

What happens: The rocket starts its gravity turn and over turns, spinning completely round, sometimes more than once, thus wasting a tonne of delta V and fuel, not to mention looking stupid.

What I've tried: Launching with Mechjeb with countless variations on ascent path settings and so forth. Launching manually with no mechjeb with SAS on and SAS off (stupid, but I had to try). Adding control fins.

Come on guys, this is f(*&ed, what is wrong with this? I know there's a new aeronautics model in this version, but come on, this is starting to seriously .... me off. I never had this issue before it went full release.

Please help

[cybersol]

Here's my quick summary:

Spinning out of control essentially comes down to a contest between drag and control. When the drag overcomes your control authority, you go for a spin. You can decrease drag by staying closer to prograde and building a more aerodynamic rocket. You can increase control using engine gimbals, stabilizer wheels, and control surfaces.

Also note that drag increases significantly right around mach 1 (340 m/s). So you should stay pointed as prograde as possible at speeds around 280-400 m/s.

On a rocket control fins should be as low and outside as possible. If you are using control fins on more than one stage, the CoL needs to stay below the CoM at all times, even as the tanks empty.

[Tank Buddy]

There are tons of threads addressing this "issue" (Really it's just people not wanting to learn something new)

I don't feel like searching for the forum threads for you, but I assure you they are out there.

In order to stabilize your rocket you need to

a. Design your rockets so that the center of mass is far above the center of lift. This means putting fins/control surfaces on the bottom of your rocket. Gimballing engines also help.

b. Quickly and gradually initiate a gravity turn; you don't even need SAS. Don't let your attitude deviate to much from your (surface) velocity vector. It will take several tries to master.

c. Most importantly, experiment, research, and learn: there are tons of resources to help you. Just look a little harder. AND STOP COMPLAINING! - Good luck

EDIT: This guy is helpful:

and this guy @ 1:30

'

I found that tilting over 5-10 degrees immediately after launch, then reaching 45 degrees at 13 Km is a good flight trajectory. Don't worry about going below 35 degrees from horizontal above 35 Km.

Some helpful threads:

http://forum.kerbalspaceprogram.com/threads/122142-HOW-NOT-TO-FLIP-Some-Crazy-Things-I-ve-Gotten-to-Orbit-And-How

Edited May 21, 2015 by Tank Buddy

[Snark]

Also, besides putting fins on, make sure your payload up front is streamlined. Smooth pointy cylinders. If you're putting up something that's unavoidably draggy, put a fairing around it to reduce drag during atmospheric ascent, it helps a lot.

[heng]

you can get visuals of the forces acting on your craft during ascent if you hit F12. if you see a lot of red vectors pointing away from your rocket, you might want to adjust stuff...

[lincourtl]

Come on guys, this is f(*&ed, what is wrong with this? I know there's a new aeronautics model in this version, but come on, this is starting to seriously .... me off. I never had this issue before it went full release.

Well, KSP never had anything remotely resembling a realistic aerodynamic model before 1.0.

Would you care to share a screenshot or two, and your craft file? It's really hard to give advice without knowing what you're working with. Also, if you're using any mods, list them as well.

[Anglave]

The simplest solution for "old style" rockets with crazy non-aerodynamic shapes and/or unwieldy payloads, is to just launch straight up to 20km, then do the 45° turn the way you used to. With vectored engines, I find I generally don't need fins or extra reaction wheels or anything.

Keep your speed low (100m/s to 10km, then up to 300 m/s at 20km, full throttle thereafter).

If you try to turn by more than a few degrees from your direction of flight, while low in the atmosphere, in a rocket that's inherently aerodynamically unstable, you will not go to space today.

[Methusalem]

As others have mentioned, the issue is the drag at lower heights. You could:

- stay below a speed of 320ish m/s until you've reached a height of 15-18 km

- make sure to use fins for stabilization

- build the rocket very top heavy (like an arrow, the weight is in the tip and the feathers stabilize)

- for MechJeb: go into the Attitude control and change the values for Tf to min = 0.05 and max = 0.15. Then MechJeb will try to compensate quite a bit earlier.