Drag - how to compare for different radius rockets?

[The_Rocketeer]

I'm looking into nose configurations with a view to options for low drag, but I'm having trouble finding a way to compare the drag of different-radius fuselages. When comparing two different noses on the same radius, it's easy - you add a ballast tank to null out any difference in mass, and just swap the relevant nose parts, keeping the same fueltanks and engine. When comparing the drag of different radius rockets, you can't be consistent with the engine since it obviously no longer matches all the rocket sizes. (Edit: so you get un-occluded drag from the engine/tanks).

There's probably a mathematical solution to this but I'm not a strong mathematician and I'm not sure where to find or make sense of the necessary drag data anyway.

I'm not just looking for the lowest drag configuration either - depending on the mission profile, it might be preferable to use a slightly draggier nose to give larger cargo bays or more crew capacity etc. What I'd really like to be able to do is make a comparison table for the best 2 or 3 options for each radius, but that may not be possible.

Edited October 26, 2015 by The_Rocketeer

[Red Iron Crown]

Install AeroGUI, it gives summary drag data. Compare at various speeds.