Fins on Atlas V

[BenKerman]

Hi,

I made up my own little Atlas V in Realism Overhaul today.  It works a lot better than the early rocket models I made (Juno II, Mercury Atlas).  

I didn't include fins because the real Atlas V doesn't have fins.  This is in spite of the fact that my Atlas V's center of lift is far forward of its center of mass.  Why is this rocket stable?  I was so surprised that it flew so well.  Ordinarily I would add fins so that the center of lift is astern of the center of mass.  Why didn't I need to do that?

Thanks,

Ben

[GluttonyReaper]

I've not messed with RO in a long while, but if I had to guess I'll probably the general mass distribution of the rocket - the Atlas V setup has a more distinct second stage than both Mercury-Atlas or Juno II, which gives it that 'lawn-dart' configuration that's pretty desirable in rocketry. The Atlas V is also a lot heavier than the others, which means aero-effects generally don't matter quite so much, as cross-sectional surface area doesn't scale as fast as mass does. I'm not sure if you have FAR or anything else installed that might affect it, but the center-of-lift indicator in stock KSP is generally pretty useless for rockets - it doesn't take into account body lift and similar effects. The more important metric is center-of-drag... which KSP just doesn't display unfortunately.

I don't know how much RO models this, but the Atlas V also has a huge gimbal range on its main engine, which means you're getting a hefty amount of active stabilisation too if you're using it. It's actually enough that in reality it can stabilise itself enough that it can fly with a single SRB strapped to the side.

[BenKerman]

Thanks!