The opposite is also true. I've been flying lots of altimeters in lots of model rockets over the last year or so. I typically see more than double the altitude A to B and B to C on what one might consider small to medium sized models. I actually have the most data on a BMS School Rocket with optional payload section.
My theory about why this is (I have not done the calculations to verify it) is that a greater proportion of the total impulse of the smaller motors is used just getting the thing moving at all as opposed to continuing to accelerate it as the motor burns longer at somewhere near the same sustained thrust. Or, to look at it another way (and looking at time-thrust curves for the most common Estes motors - A8, B6, C6), the initial spike that gets things going takes a much larger portion of the total from the A than from the C.
The case that edwinshap1 mentions just above also can happen - and I see that with the very same sorts of rockets going from a C6 to a (composite 18mm) D10. At that point the drag rise appears to be overcoming the further doubling of total energy delivered and the delta between the C apogee and the D apogee is less than double the C apogee.
Last edited by BEC; 1st July 2011 at 08:51 PM.
NAR 89040 L1