Re: Orion Drive space battle


Rhysy wrote:
OK, I should probably have determined the relative
velocities/distances.

This REALLY should have been the first thing you figured out.
Without a sense of scale, you might as well have space
fighters shaped like giant robots duking it out with beam
sabres and plasma axes. (Trust me, this looks REALLY COOL!
Do it!)

However I really don't find these tens of
thousands of kilometers distance or up to 100km/s velocities quoted at
all plausible. No-one's going to fight a battle if there's time to
dodge the enemy missiles, or even just leave the combat zone
altogether.

You don't just "dodge" enemy missiles. Missiles are guided.
If you make a maneuver, a missile will also maneuver, so it
hits anyway. This is the whole reason why today's missiles
can hit a target even after travelling hundreds of kilometers
to do so.

The 100km/s figures come from the fact that you're using
orion drives. Orion drives are capable of higher velocities
than chemical rockets or solid core nuclear thermal rockets.
What's the point of using Orion drives if you're not going
to use its capabilities? It's like making jet fighters
which only travel at a hundred miles per hour.

But the main thing driving up the speculated combat distances
is the plausible effective range of laser weapons. Even
with today's technology, lasers with a range of at least
4000km could be fielded (Space Based Laser). This sort of
range is potentially useful because it means a small number
of satellites could provide global coverage against
ballistic missiles. There's no real reason why today's
technology couldn't be scaled up to have an effective range
of tens of thousands of kilometers--it's just that we
have no current need for such long ranges. Earth just
isn't that big.

It makes no sense. At lower distances, the high relative
velocities I also find highly dubious as I doubt any system is every
going to be perfect to ever be able to accurately target anything at
those kinds of speeds.

Those speeds don't represent unreasonably high slew rates
when you're firing from tens of kilometers away. With
high velocities, it might actually be easier to hit the
enemy with a long range laser than with a self guided
short range missile.

With a self guided missile, hitting a fast incoming target
is very challenging. The target starts off as a miniscule
dot which is barely moving, and then as it gets closer that
dot blows up in brightness by the inverse square law (or
inverse r^4 with active radar!), while the apparent motion
blows up inversely (1/r). It is HARD to design a missile
sensor which can handle this wide range of behavior with
the necessary precision. From the perspective of the missile,
the target is a small unmoving dot until suddenly ZOOM--it's
a streak off to some side as the missile misses. It sounds
like an impossible problem to solve.

However, there's a neat little "trick" to give accuracy
to missiles, called "beam-riding". This is where a
guiding vehicle shines a conical beam at the target,
and the missile keeps itself centered on the beam.
In this case, there are no issues with inverse laws or
inverse square laws. The missile merely needs to be
able to maneuver with as much thrust as the target to
stay on target. This beam-riding "trick" is used a lot
in real life.

Strangely though, people have also raised issue with the unguided
weaponary (which only amounts to a few guns anyway - I barely even
mentioned it in the battle plan).

They figure quite prominently in the design of the
ships you propose. That they're even included at all
is a bit silly.

Yet others think that unguided ball
bearings are going to be devastating weapons !

No one who thinks unguided ball bearings are plausible
space weapons knows what they're talking about.

Note that Luke Campbell did propose a ball bearing
WARHEAD for long range MISSILES. He even proposed
a reasonable knife-fight range of 10km as a possible
warhead detonation range. This showers the target
area with a shotgun conical spread of ball bearing
fragments, and could be more effective than a nuclear
warhead.

Firstly, unguided
weaponary may have two uses : Actually causing damage, or causing the
opponent to expend resources to avoid it (either dodging at high
distances - which I find highly suspect - or using countermeasurs such
as lasers, or simply having to have lots of armour).

There's no need to dodge unguided weaponry, because
the chances of them even hitting if you don't dodge
is minimal. Just look at real life artillery. Here,
we're talking about really short ranges of maybe 20km.
An unguided shell at this range has more or less no
chance of hitting a point target. In contrast, a GPS
guided shell has an extremely high chance of hitting
a point target.

Secondly, this
idea of low-mass ball bearings being used to cripple warships is not
plausible in my opinion.

100g ball bearings being fired at 100km/s do have the KE of WWI
battleship shell, but weren't those filled with explosives too ?

Not much. Almost all of the mass of each shell was
dumb iron just to handle the shock of firing and to
penetrate the enemy's armor. A small explosive charge
was included because that's what would do the most
damage once the armor was penetrated--otherwise, the shell
would punch entirely through the target only depositing
a very small fraction of its kinetic energy.

The dynamics of hypervelocity collisions is very
different. There's no risk of "shoot through" with
a hypervelocity collision. The projectile and whatever
it hits is vaporized in a spectacular explosion. It's
like the effect of shell guns on wooden battleships.

IssacKuo suggest a full broadside. Unfortunately, no
design changes are possible at this stage

Pity. Oh well, I thought this was the most minor of
possible suggestions, as it wouldn't require you to
change your overall plan, scales, or chosen weaponry.

(bar 1, possibly, see later), however, I'm not
convinced that would be a good idea. Better to have all weapons
pointing towards the enemy if possible, it also helps protect the
vulnerable drive section.

The drive section isn't vulnerable--it's plausibly
the least vulnerable part of the entire ship. It's
got this sturdy chunk of metal designed to widthstand
nuclear explosions. If anything, you want to point it
at the enemy, so you can hide stuff behind it! Of
course, the enemy isn't going to just let you do that.
The enemy will space his forces apart so that there is
no single direction to defend against. That's just
common sense.

Anyway, superfiring centerline weapons can all fire
straight forward. In naval ships, superfiring is
limited by the fact that turrets high above the
waterline decrease stability and require heavy
armored support structures. In a space ship, there's
no such limitation on superfiring.

On the distances between ships, I fully agree.But they aren't going to
be that close in combat, I have already animated them seperating.
Having them this close at all is an artistic concesstion so that people
can see clearly, "Ah, a fleet of spaceships !" without needing to be
told it's a fleet. I admit it may be necessary to display the ships
closer together in combat than would actually occur - what would be the
point, artistically, in having them too far apart to see ? It would
only serve to add confusion.

As I said, you can display an entire fleet using a
tactical display, or by showing them as a collection
of flashbulb nuclear detonation "dots" maneuvering
together.

Think about what a tactical display is going to look
like. Is it just going to be a blank screen with
some tiny dots on it? No, each dot is going to be
associated with data about what it is. This isn't
air combat where there's a need to not overly obstruct
the pilot's view--that's why a jet fighter display
is made up of thin lines. There's nothing interesting
to obscure, so each "dot" will be replaced with a
zoomed in telescopic optical view of the target.

Can you explain in more detail why a line is preferred
to a plane ? I can't see much difference.

It depends on the tactical situation. In some tactical
situations, you'd want to space out your forces roughly
in a single plane. For example, if you want to enter
laser range simultaneously with all forces, you'd want
to arrange them all on the same sphere around the
intended target.

In other tactical situations, you may want to space
out your forces in depth (not all along a single line,
probably, because this allows the enemy to concentrate
its defenses along one axis). For example, if you're
using swarms of missiles it may make most sense to
send in your ships one at a time. A ship can expend
all of its missiles at once and then retire from the
battle (possibly by blowing through, or by getting
itself blown up by intense short range enemy fire).
The follow-up attacks can thus concentrate only on
whichever enemy ships have survived so far, rather
than wasting their missiles on redundant targeting.

There are missile turrets so that they can be pointed
towards the enemy and save -albeit slightly- on propellant.

It saves virtually nothing in propellant, but it
costs a lot of mass in magazine/loading systems.
Missile racks where the missiles simply get launched
straight out of their tubes weigh less than racks
where the missiles need to be shuffled around to load
into a launcher.

Dodging to avoid lasers is not so implausible I think - a moving target
is simply harder to hit. However that is something that can be changed,
if necessary.

Change it. The small angle adjustments necessary to
track a "dodging" target can be applied practically
instantaneously using the adaptive optics's servos.

"A chemical warhead to spread fragments may be far deadlier
than a nuclear warhead for anti-spaceship work. " - that's an
interesting point, but you'd have to somehow deliver the chemical to
the interior.

No. You don't understand. We're talking about a chemical
warhead which explodes before reaching the target.

See, a nuclear warhead produces a flash of radiation that
is deadly out to a certain range, but beyond which it
probably just causes some heating to the outer hull.
In contrast, the kill zone of a fragmentation warhead
extends over an unlimited distance--being further away
simply means a lower chance of getting hit by a fragment.

This can be very important, tactically. You may discover
in combat that the enemy's short range defenses have an
effective range of, say, 20km. If your missiles are
nuclear tipped, you're completely screwed. There's no way
they'll ever do damage to the enemy. If your missiles
are tipped with a chemical fragmentation warhead, you can
adjust your tactics to detonate the missiles from 20+km
away. Sure, you might be operating outside the ideal
range of the warhead, but you at least have a CHANCE to
kill the target.

" There's no good reason to wait until you're in knife range of the
enemy if you're
armed with a machinegun. " - but as you say the missiles may take an
hour to reach their targets, this analogy doesn't hold. A knife takes a
finite amount of time whereas a machine gun incapacitates instantly -
that's the whole point of the gun. The enemy isn't going to stand idlly
by for an hour being shot at.

Yes, the enemy isn't going to stand idly by. But what
exactly is the enemy going to do about it? Dodge? The
missiles simply follow anyway. Fire defensive missiles?
Sure...but they could do the exact same thing at short
range also. You don't gain anything by waiting around.

Laser fire? Okay, that's the big one. But for your
scenario to work at all, you need to assume that for
some reason the lasers are utterly pathetic.

Luke Campbell - haven't done the math on the lasers yet but I'll get
round to it.

You'll do a LOT better by letting Luke Campbell do the
math for you. Seriously.

"Visually, you will not see any beam, but you will get a powerful green

flash (or continuous green flare, depending on the dwell time) where
the beam is incident on the missile. " - showing the beam is another
artistic necessity, I think. The audience needs to see clearly what's
happening, and OK, I like a nice lightshow. :)

You can get a nice lightshow just from the "muzzle flashes"
and the exploding targets.

Also, you can get visible beams near the target for real.
As part of the target gets blasted away, fragments and
vapor will be expelled in all directions. A high power
laser beam firing through this very thin "smoke" will be
visible (but far dimmer than the target spot).

Quick check (crossing fingers hoping not to slip up with the
calculator) : say the spaceship is made of steel for argument's sake.
The latent heat of fusion is 247 J/g. Let the nuke by 0.1kt (certainly
doable in a small missile or artillery shell - admittedly it could
probably be quite a bit higher). That's a total of 4.18*10^11 J
available, enough to melt 1.692*10^9g, or 1692 tonnes of steel - some
nasty damage but hardly anything like lethal.
[...]
I therefore sumbit that no plausible KE weapon under any remotely
plausible circumstances has any chance of causing a kill to warship of
specified design.

Damage is NOT done by melting the target. Damage is primarily
done by explosions causing physical shock and propelling
fragments through the ship. It takes much less energy to
punch through a plate of steel with a fragment than it does
to melt it.

Consider what any real life metal ship looked like when it
was destroyed. It might have been ripped into several pieces
due to internal explosions, but practically all of the actual
metal would still be there in solid form. It takes stupid
amounts of energy to melt it down. No one does it. There's
no need. Perforate a target with lots of holes, or rip it
apart...don't melt it to slag.

If you use the "does it have enough energy to melt the
target" criteria, then every weapon ever used short
of a nuke impossibly short on power.

You can simply toss all the missiles out, they'll float peacefully
alongside your ship until you give them the order to accelerate. Even a
ship with a lot of missiles, and few missile-launchers will be able to
have *all* it's missiles attack at the very same moment, if they so
wish." - this is a reasonable suggestion, although quite how my
proposal for faster launchers could be classed in any way as "extremely
silly" is beyond me. The end result - lots of missiles hitting rapidly
- is identical.

The thing which is silly is the idea that anyone would be
limited by a slow missile launch rate. You suggest that
somehow the guys with the faster launchers make up for
the fact that the other side has more missiles overall.
In fact, it's only plausible for the total number of missiles
to matter. Either side can launch them as fast as they want.

"Which would perhaps make it exciting, except that is *PRECISELY* how
99%
of the viewers will expect the figth to go, long before its even
started. D for originality." - There are a great many historial
examples of battles being won against seemingly overwhelming odds.
Salamis, Marathon, Guagemala, Agincourt, Rorke's Drift, Cannae,
Pharsalus, the Battle of Britain amongst many others. You want to argue
Julius Ceaser was "unoriginal" for defeating numerically superior
opponents by using superior armour and training... riiiight.

Julius Ceaser was unoriginal for doing that. It's a
cliche strategy which works. For a military leader trying
to acheive his objectives, originality takes a back seat
to military effectiveness.

To me, the damning thing about your scenario is that there's
no attempt on the part of either side to employ actual tactics.
In all of the historical battles you reference, the military
commanders made plans and made tactical decisions according to
the unfolding tactical situation and stratigic objectives.
It wasn't just a case of mashing two opposing forces against
each other and hoping for the best.

Here on rec.arts.sf.science, we tend to get caught up in
the technology and pay short shrift to tactics and strategy.
But the latter can be the really interesting story.
Imagine someone from the American Civil War era trying to
imagine what air combat would be like. He might imagine
fleets of "airships" lining up next to each other to exchange
"broadsides". Could he have ever imagined the tactically
rich scenarios of dogfighting maneuvers?

More recently, consider what happened when jet fighters
and guided missiles were developed. Based on the numbers,
a lot of smart technologically minded people thought that
dogfighting was dead. Opposing jets would simply make a
single high speed pass, loosing their missiles and then
returning home (if they survived). Sounds like a good
theory on paper, but what happened in real life? Dogfights.
It would be decades before the vision of BVR "push-button"
air combat would come true, and even now we don't discount
the possibility that dogfights will still occur.

In all of our speculations about what space combat would
be like, I always have the sneaking suspicion that we're
the equivalent of American Civil War era people trying to
speculate what aerial combat would be like. The way things
move around in space is so completely unlike the way
things move around in the air or water or land. I suspect
that whatever space combat is actually like, it will
involve more interesting tactics than anything we've
come up with.

The frustrating things to me is...the interesting tactics
of space combat will be entirely intuitive and obvious
to future generations. Just as we're intuitively familiar
with what air combat is like, future generations will
be intuitively familiar with what space combat will be like.
And today's speculative space warships will look as silly
to them as Land Battleships look to us.

Isaac Kuo

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