RE: Planetary defenses

	I would like to think about your problem in a different angle.	

	If a race lives in the atmosphere of a given planet, then that
race
is very vulnerable to space attack for the purpose of obliteration.  All
that is required from an offensive force is to build devices that will
destroy the atmosphere.  In case of the earth, a large number of nukes
would
suffice to do the trick (think also about bio warfare).  After a number
of
years of war like that, not a living creature would be left in good
health
to keep fighting.  In this scenario, the offensive force is not planning
to
occupy the planet afterward.  Also, the offensive force does not have to
come close to the planet; it can lob those nukes from far away.  The
defense
system will stop some, but it would not take too many misses to wreck
the
planet.

	Second scenario, the offensive force wants to occupy the planet.
Now, this is a totally different game.	1) They must identify what to
shoot
at.  They can do this through intelligence or by getting close to the
planet.  2) They must be able to aim at the specified targets.	They can
do
this by getting close to the planet.  3) They must survive the attack. 
In
this scenario, the roles are reversed because the offensive force needs
to
get close to the planet while securing the artificial environment in
which
they live.  I will not discuss about the technological issues, but the
earlier observations (previous e-mail) on power requirement seem to
indicate
that the planet is better equipped to destroy all space installation
that
come too close.  In this scenario, the analogy with the air force makes
sense: even in the event that the offensive force win space superiority,
grunts are still required on the ground to take over the defensive
operations.

	Third scenario, the defensive force does not employ the
atmosphere
provided by the planet (like Moon Base Alpha in Space 1999).  Quickly,
this
seems to be a variant of the second scenario. (I must think more about
that
since destroying the planet based envrionment systems does not deny the
planet to the offensive forces)

	It seems to me that the most important factor is whether the
offensive forces are taking the planet over or if they are getting rid
of
rodents.

	JP