Roger replied to me: > >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.)
Hello Roger, I'm thinking of firing "outward" on an elliptic orbit. After the projectile travels out through the apogee, it swings back to a perigee which happens to be on ground level. The benefits? * Delayed impact. That could have tactical advantages ... "We neutralized the last BattleSat days ago. How long will this go on?" * Used differently, the delay could be varied to create one big time-on-target salvo. * Unexpected direction of the attack. Regards, Onno _______________________________________________ GurpsNet-L mailing list <[email protected]> http://mail.sjgames.com/mailman/listinfo/gurpsnet-l
