Since I started using 1.3 my rockets flip out of control

[Enriched Uranium]

Since I started using 1.3, I have noticed my capsule and heat shield both create lift. I believe this is why all my ships flip out of control after dropping the first stage. I am keeping the Blue lift bubble below the yellow center of weight marker for all stages that will be used in the atmosphere. Does anyone have a tutorial on how to build stable rockets in 1.3? I can make it to orbit in smaller craft but If I try to build one to go to the Mun the craft always flips out of control when I drop the first stage.

PS: how does a heat shield or capsule produce lift when the surface creating the lift it is inside of a staging clamp where air can not get to it?

[Rodhern]

If you are on Steam try revalidating the game files. If you have mods, try temporarily removing them. I haven't noticed any major change to stock aero in 1.3.

[JonathanPerregaux]

I usually build giant rockets that test the limits of being able to fly. Flipping over is an old, annoying friend of mine. Here's what I do to keep him from showing up at my house.

• Watch your wet center-of-mass. As fuel burns, the COM moves. If you're not careful, though, the remaining fuel mass can pose a problem during your gravity turn, inducing a flip. With heavy lifters stacked on multiple tanks, I change the fuel priority so the lower tanks burn first. This shifts the COM towards the nose quicker than if I let all the tanks empty themselves equally (the default).
• Be wary of solid rocket boosters, as they have no gimbals. If they are too powerful compared to your liquid-fuel engines, you may lose just enough steering control to flip over. To compensate, I've either reduced the flow rate of the SRBs or added some Mk-55 "Thud" engines to the sides to add more thrust and gimbal.
• A little drag may help borderline cases. I've solved some flipping problems by ensuring I had adequate tail fins to keep the rear-end planted.
• Watch out when using non-cylindrical lifting bodies such as the MK2 for rocket fuselages. At speed, lifting forces will throw your rocket back and could flip it.
• Staging can suddenly drop a lot of mass, briefly throwing your COM into chaos. If your ship is not quite nose-heavy enough, or unstable structurally, it may not be able to survive this transition.
• Strengthen the ship using autostrut or, if geometries are complex, actual struts. Anything that wobbles won't be fuel-efficient. A wobble that grows into a resonance (especially during Max Q) may flip the rocket if steering overcompensates. I always autostrut each stage's main engine to the root part, unless I have pods sticking out. For outboard engines I usually try autostrut to grandfather part. If the ship twists itself to bits with this, I'll throw actual strut parts on there to hold her steady.
• Hide non-aerodynamic parts inside fairings if you can. You'd be surprised how much a set of exposed landing legs will cost you on ascent.
• Pay attention to Max Q (MechJeb is good at this) but be careful not to throttle down too much or you may lose control and flip.

[Cpt Kerbalkrunch]

@Enriched Uranium, a problem like what you're experiencing can best be diagnosed with a screenshot. Otherwise, you'll only receive very general advice that might not be relevant to your specific situation.

That being said, I'll make a very general recommendation: it sounds to me like you don't have enough drag on your second stage. Dropping your first stage is causing a very rapid change in the aerodynamics of your rocket. Fins or winglets usually solve this problem without a redesign. Couldn't say for sure without seeing it, however.

[HebaruSan]

3 hours ago, Enriched Uranium said:

I am keeping the Blue lift bubble below the yellow center of weight marker for all stages that will be used in the atmosphere.

Unfortunately, the lift indicator doesn't show what you need to see, which is the center of pressure, that is, lift plus drag. Only certain parts generate lift, but all parts generate drag. The easy solution to aerodynamic instability is always to move the center of mass further forward and/or add fins at the back.

[Enriched Uranium]

Ok I think i have it worked out now, thanks for some answers.  I can't allow my nose beyond 5% from prograde when I drop my 1st stage SRB's. Once the second stage starts accelerating the rocket becomes very stable. again thanks yall

ps I guess this ends rockets with no fins at all. 

Edited August 15, 2017 by Enriched Uranium

[Gargamel]

I don't know if there is a stand alone mod for it, but MechJeb has settings that will allow you to show both the CoL/D and the CoM on the ship while in flight.  You could use MJ for testing purposes, and then remove the MJ part for your normal flight if you are disinclined to use MJ.