Your answer is 4-ish inches. As ambient pressure decreases, the rocket thrust increases. Ae, the nozzle exit area, is the determining factor how big this effect is.I'm attempting some RasAero simulations. The simulation asks for a nozzle diameter. For the nozzle on the 6" rocket below, is the answer 0 inches, 6 inches or 4-ish inches?
+1, that would be my best educated guess as well, though I don't know how accurate it would be - the thrust plume must vary a lot based upon nozzle design, angle, etc. Also I wonder if there is a way to account for the smoke grain burning - on larger motors I would bet it also has an effect in lowering drag.I'd say it's 4 inches by the looks of it. I'm pretty sure RASAero is looking for the nozzle exit diameter to aid in calculating base-drag of the rocket when the motor is producing thrust and when it is not... I think the exhaust jet acts kind of like a boattail... All of this is what I think. I may be wrong or may have misinterpreted the question or just don't know what I'm talking about, so feel free to correct me!