I LOVE this program!
I especially like how you can watch onscreen as the CG and CP locations shift as you're altering fin dimensions.
When I think I have it right, I can select a commercially available motor, find one that gives an appropriate apogee, run a simulation, and see what delay increment I need. Then I can build a motor that matches those specs. This is going to take so much trial and error out of development I can't believe it!
Now I have another question, but first a little background on my launch site and testing procedures:
Other than the PGI Convention, I launch all my rockets on my own property on the bank of the Mississippi River. It is over 1/2 mile wide at that point.
Second, if I've built a motor to lift a size/weight of shell I've not done before, I make up a dummy to the same dimensions, filled with the appropriate amount of bentonite clay cat litter, and observe the results.
Third, I launch at an angle that insures that the rocket will always be over the water. Displays are at dusk or later, when there is never more than a light breeze. Testing is on days where the forecast predicts winds of less than 5mph.
For safety, I launch out of HDPE pipe that is larger than the outer fin diameter of the rocket. If a motor CATOs, the HDPE pipe contains it without damage.
The HDPE pipe I use for my largest rockets is 6" ID and 7 feet long. Here's my question: What should I shoot for as a stability factor when designing a rocket, or minimum velocity when the back of the fins exit the launch pipe (or what have you) in a simulation, to ensure a good flight?
Attached is an OR file for a rocket carrying a payload of 3 pounds of cat litter. I'd like an apogee of 350 to 450 feet. Simulation (using the default settings) with an Aerotech G55-5 motor shows stability 1.64 cal., velocity off rod 24.9 FPS, altitude 433 feet, optimum delay 3.7 seconds.
Is stability of 1.64 cal too low for safety, much higher than needed, or what?
Comments?
JR