re: planetary invasion

> > Los wrote:
> > > OK I've noticed that many people on this list seem to assume that
> > > orbital strikes, ortillery and woning orbit means it's pretty much
all
> > > over for a planet, that it might as well roll over and die.
> > > I'd like to throw it back at everyone and ask, if you had to
design a
> > > planetary defense to counter such a situation what could be done?
How
> > > effective would be ground based wepons? Obviously they could be
very
> > > effective against atmospheric craft but what about Stuff in space?
> > > I know fixed defenses may be a problem but what about underground
> > > defense complexes connected by hundreds of kilometer of
underground
> rail
> > > where heavy weapons fuel with the vast power reserves available to
a
> > > planet could pop up shoot and scoot? Any ideas? I'm thinking about
> > > defensing the planet here not subjugating it.

i think that it is fairly obvious that a planet has more resources
available than a space fleet, in terms of power, room, environment
support, etc. burying huge class-ten beam batteries under mountain
ranges, with only the emitters poking through, would be pretty tough
(assuming that they can shoot through the atmosphere, and there are ways
to help with that, such as firing a smaller beam first to drive the air
out of the way for the main beam). missiles (MT and SML) could all be
sited in silos, on railway carriages, or on SSBNs. pulse torpedoes might
also work, but i'm not sure - PSB too high to tell. in fact, the defence
of a planet seems to be quite easy, much easier than capturing one.
we're back to medieval castles again, only on a bigger scale.

this applies especially in the GZG model of spaceflight, where a huge
ship is 10000 tonnes, the size of a modern heavy cruiser, and two
battleships, half a dozen cruisers and assorted escorts comprises a big
fleet. otoh, if you use a large-scale universe like star wars, where an
assault fleet may have ten immense (million-tone) star destroyers or
whatever, then things are a bit different.

so, for my part, i think that the tough part is figuring out how planets
can be captured at all! bear in mind that we are talking about capturing
the planet, with industry and population as intact as possible. this
means no/very few nukes/rocks.

i imagine that planetary defences would be situated away from major
urban centres, so that if an attacker does nuke them, or use other big
weapons, few civillians will die. otoh, they might put them in towns so
that an attacker will not use weapons of mass distruction for fear of
wiping out that which he wants to capture.

the main obstacles to decent planetary defence, then are:

- cost. if you have twenty planets to defend, then static defences are
going to cost a lot, whereas an ftl fleet which you can dispatch
wherever it is needed is going to be cheaper. probably.

- sensors. people have this idea that a planet will have better sensors
than a fleet. i'm not so sure.

the resolution of an instrument is determined by the size of the
aperture; i assume that all available sensors will be linked together to
form an interferometer, a virtual instrument where the aperture is the
size of the array of sensors.

a planetary interferometer can only be about 15000 km across (the
diameter of the planet), although it could be extended to the moon (if
there is one) or far-out satellites.

however, the fleet can spread out over as much space as it wants,
forming an interferometer potentially a million km across. it would have
less photon-gathering capability, but would have much better resolution.
not much good for astronomy, very good for atacking a planet.

if a planet did use far-out satellites to enlarge the array, they would
be vulnerable to destruction by the attacking fleet. could be a good
scenario - a destroyer detatchment has to knock out a far-orbit sensor
farm before an assault can go ahead.

i suppose civiliian/scientific instruments ould be commandeered - i can
imagine a footfall / id4 type movie where hubble is used as fire
control.

- gravity. projectiles fired from the planet will lose about 10 km/s of
speed climbing the gravity well. likewise, those fired from space at the
planet will gain 10 km/s. it is not too hard to deal with this by adding
big boosters or using a railgun.

the defenders have an asset in the speed with which the attacker can
land troops once he has interface superiority (ie space and air
superiority plus destruction of AA batteries).

i think the consensus is that the attacker will ferry troops down in
company- or battalion-size dropships (squad-size assault dropships being
used for landing marines to capture the planethead, suppress defences,
arrange landing strips, etc). this cannot be a fast process.

assume ten troopships with four LC's each, ech carrying a company of
troops, with a 15 minute drop-land-offload-launch-dock-load cycle. this
makes 80 companies an hour. actually, this is quite a bit. even if those
are brigade transports, the whole lot could be down in a day.

this brings me to another problem: even if they are brigade transports,
the attacker will only have around 100 000 men on the ground. in the gzg
universe, this is not so bad; i think a big planet might have 50 to 100
million people (remeber that the NAC capital world gets a population as
large as england, and that this is amazing; then allow for growth), and
so an army of around half a million (is this right? uk population is 60
million, our army is about 300 000, right? or am i way off message
here?).

these are still 5:1 odds, but the attacker has total air and space
superiority; he can call down naval barrages and airstrikes. if the
attacking fleet has 50 a-battery equivalents of firepower, then there is
roughly one a-battery per in-combat regiment. this is not a lot, unless
a-batteries are devastating and fast-firing (and there is an argument
that this is the case, if we go with the idea that a turn's firing in FT
is rastering a beam over the target's approximate location).

if your planets are bigger (one to ten billion people each, roughly like
earth), then the attacker is stuffed. there will be 10 to 100 million
troops waiting for him; this will require a biiig assault fleet, or some
unconventional tactics. those titanium rods (a la footfall) could come
in handy here.

brief historical comment: virtually all mass invasions have been by land
(eg germany vs russia) or across a short stretch of water (usually the
english channel) from friendly territory (eg uk vs germany; i think a
few us troops showed up for that one too :-).

so, in short, i think capturing planets is going to be bloody hard, and
that we don't need to spend too long figuring out how to make it harder!
the only anti argument i can think of which really holds water is the
cost one.

incidentally, has anyone considered using a nova cannon against a
planet? at range, it might be non-genocidal.

Tom

ps sorry about the length

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