No, wait, is it Green / Purple? Aaarrrgggggh ...!

--- In sfconsim-l@yahoogroups.com, "Eric Henry" <ehenry@n...> wrote:
>
> Heathen! You only say that to disguise your own purpleness
>
> Long live Green!

Since it came up, as good a time as any to explain purple/green
arguments. Holy Grail reference aside, these are debates that come up
regularly on sfconsim, and are never finally resolved.

"Realistic" / operatic is probably the meta one, so to speak, never
resolvable because it's a de gustabus. Some others are battleships /
carriers; FTL comms / no FTL comms; for Ken and I, fission / fusion;
and so on.

THE purple/green debate, though, is missiles v lasers. Naturally this
happens more on the "realistic" side of things, both both weapons are
common in operatic techs as well, so it's good to know the basic
arguments. Which I'll summarize here. Mainly it is a tech arguments,
but with implications for tactics and game play.

I'm a partisan on the minority (missile) side. I'll try to be fair,
not worrying too much because if I load the dice the laser side will
zap back at me, big-time. :>


First, what (I think) both sides more or less agree on:

1) For a Really Effective laser, you need beam output power in the
megajoules. (4.2 megajoules = 1 kg TNT equivalent) This is
technically demanding. Ken describes weapon lasers as blast furnaces
that produce coherent light as a byproduct. I describe them as an
observatory telescope with a jet engine at the eyepiece.

2) Lasers Always Hit. If you can see your target you can shoot at it,
and in space you can almost always see it. There's no good excuse for
missing - certainly not missing at Nelsonian engagement range, like
Hollywood SF laser cannons do, at least the bad guys'. Aim precision
is determined by the same optics that focus the beam; if you can zap a
10-cm spot on the enemy ship's hull, that means your imagery pixel
resolution is also about 10 cm.

A five-meter telescope mirror - very expensive for a university
foundation, but not for the Pentagon - can do this in visible light at
1000-2000 km. UV will give you somewhat longer range (inverse to
wavelength). An X-ray laser can do *much* better, in principle, but
is extremely difficult to focus well.

3) For a Really Effective missile, you need something better than
chemical fuel. (AV is "tuned" so that chem-fuel missiles are still
just viable, but as a declining option.) This is also technically
demanding. Basically you have to make your ship drive, or something
comparable to your ship drive, small enough and cheap enough for a
one-shot weapon.

Some drive techs don't allow this, such as AV's NSWR (nuclear
salt-water reactor), which has a very large minimum size, probably
hundreds of tons. Early fusion drives might be even bigger; I've
handwaved that my drive can be squeezed down to about 10 tons.

4) Missiles (at least the Really Effective kind) have Stupendous
Range. If your ship drive can cross the Solar System, so can the
missile drive. Effective missile range is determined by the missile's
fuel supply. Unless it runs out of fuel, or is destroyed by defensive
fire, a missile should also Always Hit.


So, what is the Purple / Green argument about? Lasers have long
range. Missiles have nearly unlimited range, which should give the
missile the edge. But ... to nail you my missile has to reach you, or
at least get fairly close, penetrating through your defensive laser
fire.

The whole Purple / Green, missile v laser argument comes down to what
happens to the missile in the last few thousand or hundred kilometers
of its appointment with destiny, even if it went 100 million km to get
there.

The laser gang asserts that they can zap a missile before it ever gets
to kill range, even for a nuclear warhead. And do it every time - at
least so much of the time that missiles aren't worth firing. Even if
the missile fragments into 10,000 pieces of shrapnel (each with
substantial killing power), as my missiles do, tracking gear can
determine the fragments that will hit, and zap them before they reach
target.

The missile gang - which, on this board, may be only me :) - contends
that laser point defense can always be saturated. Fire a big enough
missile, or a salvo of missiles, coming in fast enough, and there will
just be more mosquitos than the bug zappers can zap in the short time
till impact.

One advantage to the laser is that it's reusable. If lasers are
dominant, it's also an offensive weapon to zap enemy ships, not a
purely defensive one. My response is that the missile can be fired
outside of laser range, and if it *does* penetrate point defense and
smoke your ship, your laser is no longer reusable. :>

That's the tech argument. It's really an argument about cost
effectiveness. Can you afford to carry point-defense lasers that can
stop my missiles? Can I afford to carry missiles that can penetrate
your point defense? Which is cheaper, purple or green?


There's also a tactical issue, which affects game play. Here I won't
try to be even-handed! Ken and I now are debating whether there can
be any real tactics in a long-range missile engagement. (It comes
down to whether you can afford to fire a missile on anything but a
certain intercept - this is also ultimately a matter of cost.)

The question for me is whether there can be any tactics to speak of in
a laser battle, or if it isn't just people standing at opposite ends
of a football field, shooting at each other with scope-equipped,
tripod-mounted sniper rifles. (Oh yes, and they're all crack
marksmen.)

Given equal quality lasers, if I can zap you, you can zap me. Given
laser ranges of at least a few hundred km, maybe a few thousand - or
maybe more! - how can ships maneuver? If they are slow, it will take
minutes to change position, meanwhile zapping away with multimegajoule
lasers. If they are fast, they'll hurtle past each other in a
drive-by, then take hours to swing around for another pass, unless
they have opera acceleration.

One solution AV uses is power management. Lasers aren't Hollywood
sixguns. They don't have to "reload," but the power supply has to
build up a charge, and they put out lots of waste heat that has to be
disposed of somehow - no handy rivers to use for cooling. This helps.

The other solution, used by AV and most laser concepts, is "facing" -
limitations on which guns can fire on what hull bearing; fore, aft,
port, starboard, etc. That way ships don't have to circle around each
other, or whatever, to get maneuver - attitude changes, especially
combined with even modest thrust burns, introduce an element of
tactical choice.

If you've been closing the range, but now want to hold present range
instead of closing farther, you have to swing around and fire a
deceleration burn. If no guns bear aft, you're in a jam.

This is fair enough in principle, but I have problems with it in
practice. Namely, it seems to presume that space warship designers
have forgotten things that 1910 battleship designers understood about
how to position armament for good firing arcs.

My optimal positions for laser cannons would be four "turrets," spaced
at 90 degree angles around the midsection of the ship. Each one can
train from straight forward to straight aft, 360 degrees around its
position, and straight outward ("up" relative to its position).

Now, if I am pointed straight at you (or directly away), I can bring
all four turrets to bear. On any "broadside" or "quarter" bearing, a
maximum 45 deg roll around my long axis will bring three turrets to
bear. (Just about the fastest and easiest attitude change to make.)
If a turret gets fried, another roll brings the remaining three to
bear. Unless I do lose a turret, I can always engage two enemy ships
in any relative position with two turrets, or one with three and the
other with one.

The hell of it is, this simple, sensible armament arrangement seems to
almost eliminate facing as a tactical element. Which, in a laser
engagement at any respectable range, just about eliminates tactics of
any sort.

Which is one reason I side with purple!

-- Rick