On Fri, Dec 02, 2011 at 07:26:34AM +0100, Onno Meyer wrote: >Did I get the physics right?
Yes. The dV is the muzzle velocity, of course, which for anything modern will be quite small by comparison with low orbital speeds (1700m/s for a KEP tank round, says Wikipedia, compared with 7800m/s for a 100-mile orbit round Earth or 3100m/s for GEO). (I'm assuming circular orbits here.) However, that's enough. If you fire that tank round retrograde, it will impact Earth's surface even without considering atmospheric drag - in fact you only need 49m/s to assure this from 100-mile LEO, and 1500m/s from GEO. (Without atmosphere, or with something small and pointy enough to slip through without decelerating much, the more dV you put in, the harder and more vertically the impact will occur; with atmosphere, the huge dV from re-entry will predominate, and you probably want to skim the projectile along the edge of atmosphere to where it can be captured. In the latter case you certainly want some sort of terminal guidance if you want to hit a point target.) R _______________________________________________ GurpsNet-L mailing list <[email protected]> http://mail.sjgames.com/mailman/listinfo/gurpsnet-l
