How does one build air launched rockets?

[SunlitZelkova]

I have tried launching rockets from aircraft and a dirigible (courtesy of HL airships + Heisenburg) but they keep flipping out of control when the engines ignite.

First I used a RT-10 as a first stage and then a similarly sized liquid fueled second stage. It flipped out of control before I could activate staging.

Then I used a single stage rocket in similar size to a RT-10. It also flipped out of control, causing it to lose altitude before running out of fuel.

[Vanamonde]

Got pictures of the craft? 

[SunlitZelkova]

It's a little hard to see, but hopefully this works. I already deleted the craft.

That's a Swivel engine, and it is fully loaded with fuel. It just has a standard nose cone with a probe core, no crew (I was still controlling the Zeppelin when I took this).

[jimmymcgoochie]

When the rocket separates, what direction does the navball face when you control it? If it’s attached via a radial decoupler then there’s a good chance that that radial decoupler becomes the root part facing the wrong way; SAS tries to point prograde but ends up facing the completely wrong way and it spins out of control. Setting the probe core on the rocket with an action group for “control from here”  would probably fix that.

Alternatively, the weight of the engine and fuel at the back could be making it unstable and at a relatively low speed the little fins might not be enough to counteract its tendency to flip heavy end first. Bigger fins or a longer rocket might solve it in that case.

[Vanamonde]

I would suggest putting pivoting fins on it in place of those, and although it's usually bad for a rocket to have fins at the front, I think they would help if you're launching that way. Some parts to make the rocket longer might help as well, since the fins would be exerting their force over a longer lever.