New Design - Spartan Missle

[Slickwilly]

This is a 1960's ICBM killer.

Enjoy!!

[CPMcGraw]

Slick,

Watch out for the stability margin number. I just loaded up a D12-5 and the number fell below 1.00, to the point where the value was "marginal".

It needs either some tweaking of the main fin size (increase), or some ballast in the forward section, or a combination of both. Probably not much of either, just enough to get the loaded margin somewhere around 1.20, to be safe.

Addendum: Change the thicknesses of the two forward fin sets to 0.094" (3/32"), increase the size of the main fins by about 8%, and change them to 3/32" BALSA. This should give you a margin of about 1.25-1.30 when loaded with a composite E28-7. It has a Dv of 33 FPS, but at least it's not unstable and it didn't require any ballast...

More addendums: On this rocket, change the "Static Margin Reference" drop-down on the first tab sheet to "Max Frontal Diameter", instead of "NC Base Diameter".

With this engine, BTW, the predicted altitude is 1115'...

[CPMcGraw]

I'm posting my revision of Slick's plan so that anyone building it won't have to fight with the issue mentioned earlier. The plan has been updated with larger main fins than was originally posted. The new stability margin with an E28-7 loaded is 1.30. Dv numbers are marginally high, but with some simulation runs below 25 FPS.

Changes include:

Balsa main fins and central fins, 3/32" birch ply canards. Even with the "E" engine, balsa should hold up OK. This configuration places the heavier fins ahead of the CG and takes the place of ballast.