You can estimate an intercept course with just range circles, assuming you know target course and speed. No calculators or outside references needed.
Time to Intercept Method:
1. Pick a desired time to intercept and draw a range circle around the target at a distance of Target Speed x Intercept Time. Draw an X on that circle where the target course intercepts it (cursor bearing from center of circle is displayed while you're drawing the circle). If you want a specific range other than zero at intercept, offset the X from the target course line at the desired distance (on your side of the course line obviously).
2. Draw a range circle from your sub that intersects the X, note the cursor bearing while it is on the X. That is your intercept course.
3. Intercept speed is the new circle radius divided by the Intercept time.
Speed to Intercept Method
Simplest method for this is to try different iterations of the Time to Intercept method, using shorter or longer intercept times, until you like the Intercept Speed calculated in Step 3. Once you do it a few times, you'll get a feel for where to start the iterations to speed up the process.
Admittedly, neither of these methods is likely to give the "exact" intercept course/speed for a given situation, but as others have said, with modern seeking weapons, you don't really need to be exact.
Mike
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