The simple one out of the way first:
Today, we can fit a 1-3 kiloton nuke in a 155mm
(6 inch diameter) artillery shell with ease. I've
seen actual (though prototype) football-sized ones.
There's really no point with a conventional fission
bomb to make it any less powerful than that; you reach
a point of inverse return where you have to design
it larger to get less power out of it... 8-) You can
extrapolate as you wish out to TL15; I suspect that
you could with gravitic imploders and less-stable
elements make very, very big hydrogen bombs in a
hand grenade sized package. Hell, if you can build
a moderately capable nuclear damper, just put a
kilo of Californium in a small damper container and just
turn the damper off to detonate it 8-)
On to Starports...
Adam Naylor seems to have slightly misunderstood
the position of a Starport. According to previous
published material, a starport is extraterritorial
in terms of local laws (imperial laws apply though),
but not for "ownership". There are references to
company-owned worlds where the corporation was investing
in upgrading "their" starport. In addition, there's
no good reason for the Imperial government to have
to be responsible for running them all. As long as
everyone follows the Imperial rules about how starports
are run, and that seems standard, then everyone can
go have their own if they want 8-)
- -george