Lifter issues

[Im The One]

So my recreated delta II has run into an issue that upon doing a gravity turn flips out of control. I have only sent one succesful load to the mun but required it to do its gravity turn at 20km up.

rocket with specs (load to mun)

previous nine booster setup but the same thing happens with 3 booster setup

Edited July 28, 2015 by Im The One

[scifi6546]

you have to do a very slow gravity turn, start the gravity turn right after you launch.

[Tex_NL]

Go slower and start your gravity turn sooner. 45 degrees at 10km is a hopelessly outdated strategy.

[Im The One]

So I retested after the suggestions so far (thank you for being fast btw), and it still flew out of control right at booster separation is when it flies out of control. To me it is almost like as if aero grabs it and just pulls it over

[FancyMouse]

Cyan arrow is a sign that you turn too much.

[Gaarst]

What has been said above.

Also, edit your rocket or fairing to remove that "bulge". It basically one of the worst things you can do with a fairing: never have a fairing wider than its base, it will ruin the behaviour of your rocket in atmosphere.

EDIT: never get the heading of your rocket out of the prograde circle, just follow it gently while staying inside.

EDIT2: and going >400 m/s at 6km is WAY too fast, your should be passing Mach 1 a bit before 10km (~320 m/s at this altitude)

Edited July 28, 2015 by Gaarst

[Im The One]

thank you guys it now works (though I wish i could keep that slight bulge similar to the in real life delta II but i can do with out it), once agian thanks

[Norcalplanner]

You may want to try fuel tanks plus. It has a double-length orange tank that largely eliminates the flipping caused by a two-tank design.

And then tick the "limit angle of attack" box if you keep using MJ.

Edited July 28, 2015 by Norcalplanner

[Tex_NL]

Your MechJeb Ascend Guidance turn shape is set WAAAAAAAAAAAYYYYYYYYY too high. 100% is lethal. Set it to no higher than 30 to 40%. That will give you a much smoother turn and less aerodynamic stress.

And activating the AoA with a max angle of 10 to 15 degrees is also a good idea. This will prevent MechJeb from trying to turn no matter what. Again giving you a smoother turn.

Edited July 29, 2015 by Tex_NL

[Ripper2900]

Another trick is to do fuel transfers on the way up. Once the top tank start to have some empty space, put sas on attitude or prograde hold, then alt-click on the two orange tanks and fill the top tank from the bottom one. That shifts center of gravity forwards, and keeps your rocket more stable.

[Chaos_Klaus]

All your pictures show you flying at a high angle of attack at high speeds. Of course that makes you flip.

Start your gravity turn right when you leave the pad and reach 50m/s. Turn a few degrees and then turn veeeeery slowly, staying inside the circle of the prograde marker.

Stay below transonic speeds (270m/s) before you reach 10km.

You can have your bulge, no problem.

You have two orange tanks stacked and the upper one empties first. You can change that by using a fuel line from the bottom tank to the upper one. That way the lower tank drains first and the center of mass shifts upwards, making you flight more stable.