KnCalc
A utility to aide in the design of solid rocket motors.
It calculates the moving Kn ratio for three common grain types, Uninhibited, Outside Inhibited, and Bates grains.
To use it, enter the following:
Number of grains.
Easy. How many chunks of propellant did you load into the casing? It might be 1 or it might be a higher number.
Outside diameter
This is the outer measurement of the propellant itself, not counting any inhibitor that it might be contained within. If the propellant is in an inhibitor, be sure to subtract the thickness of the inhibitor from the diameter of the grain, twice.
Core Diameter:
What sized coring mandrel was used? Or better yet, measure several grain cores and take an average.
Length:
Exactly how long are the grains? If they vary within a motor load, enter the average length.
Note that if you hit the Neutral Bates button, the length of the grain is calculated for you, and appears in the Length box. this is the "ideal" Bates dimension for that diameter and core.
Nozzle throat diameter:
The diameter of the nozzle throat.