Remember, just because you can detect it doesn't mean you can defend against
it...
A while back, someone mentioned something about a dozen ships being adequate
to cover a planet. However, I cannot remember the distance at which these ships
were supposed to be operating from the planet. I am going to assume a distance
of 10 planetary diameters for this discussion, for three reasons: (1) ships
coming into the system will be 100 or more diameters out, so the protective
ships will be between the intruders and the planet, (2) ships leaving the
system will be unlikely to jump until they get at least that magical 10
diameters out (unless really foolhardy or desperate), so the protective ships
have time to intercept the target ships (such ships are usually smugglers or
escaping criminals), and (3) with 'x' ships, it means that the ships have less
of an area to cover, thus improving effectiveness, than if they were at 100
diameters. With this being said, with an earth-sized world, it will take a 6G
fighter over *2 hours* to get from the 10 to 100 diameter ranges. This is more
than enough time for the hostile ship to do what it wants way out there. A few
'first-line-of-defense' ships at 100 diameters might help, but unless you have
half the Sector Navy at hand, you won't be able to put more than a token number
of ships at the 100 diameter range (of course, a few Q-freighters would help).