Found the correct Standard Impact Energy for cratering.
According to Fundamentals of Astrophysics (Hsu)
A 1 Megaton shallow buried blast will produce a crater about 1000meters
in diameter. This is about 4.2E+15 J or about 4.2E+9 MJ
So the diameter of your crater will be
D = 1000m * Cube-Root(IE/SE)
Where IE is the actual impact energy in MJ
SE is the standard energy 4.2E+9 MJ
Projectile impacts are going to through very high velocity debris well
beyond the circles of general damage I suggested a post or two ago.
The impact should be assigned a primary and secondary burst radius
accordingly outside the 2nd circle(Within 2nd circle=certain
death/critical injury)
Well gotta, hope to post on orbital bombardment with explosives and
submunitions tomorrow eventually leading to delivery systems. The point
of all this is to give rationale for some general standard OB weapons
I'll post next week as well as provide background for other interested
persons.
Tariq