From: acgetche@taco.engr.ucdavis.edu (Adam)
Newsgroups: rec.games.frp.misc
Subject: Guns (background information) 1 of 5
Summary: Background on hi-tech guns
Date: 11 Nov 92 22:54:40 GMT
Organization: College of Engineering - University of California - Davis

The Arms Race of the future:

	Modern firearms have developed a long ways from their cruder
origins.  Leaving aside potential developments that would make projectile
firing small arms obsolete (like, say, efficient batteries to make man
portable lasers of reasonable energy), I propose to examine the trends
in developing tommorrow's projectile weapons.	
	The first big improvement is caseless ammo.  Instead of using
conventional grainy propellant in a casing, form the propellant itself
into hard blocks with the round imbedded.  The original difficulty with
this concept was the flimsiness of the propellant block, but today's
caseless ammo is more robust.  Saves the weight of the brass casing, allowing
bigger clip sizes.  Also, since the action of the weapon doesn't have to cycle
the breech open to eject the case,you get higher rates of fire.  The Heckler & 
Koch G-11 has been around for some time, and is an example of this technology.
The G-11 can fire a 3-round burst so fast the muzzle hasn't lifted from the 
recoil of the weapon before the last bullet is out (~2000rpm).
	Next is the idea of liquid propellant rounds.  If you store the bullet
in one magazine and the propellant as liquid in another, then you can load a 
round into the firing chamber, seep the proper amount of propellant behind it,
and fire.  The advantage of this technique is ammo capacities get even bigger 
(now you need store only the bullet itself), and liquid propellants combust 
more thoroughly than solids, producing greater pressure and higher muzzle 
velocities.  Of course the disadvantage to this is that bottle of propellant 
on your weapon (one unlucky shot and BOOM!), but this can be gotten around by 
making a binary propellant mixture (a compound requiring two separate 
components which are individually inert but can mix to form your volatile 
propellant charge).
	The "ultimate" method for propelling bullets is via magnetic fields.
The so-called gauss gun or rail gun wraps a wire around the barrel; 
superconducting wire would be best of course.  Send a large current down
the wire and it will generate a very intense solenoidal field centered
along the bore, which will propel magnetic materials very fast and very
far indeed.  Most railguns being experimented with now fire in the 5-7
km/sec range, and are expected to exceed 11km/sec (making them useful to launch
cargos into orbit)  By contrast, a lagardly M-16 round makes 1000 m/sec.  A 
nice bonus to this method is lack of muzzle blast or other signature (the 
magnetic field is very localized and would require specialized detection gear,
namely a SQUID), and of course extreme accuracy.  A conventional explosive-
driven projectile weapon suffers inaccuracies where the bullet and barrel join;
gases seep past and tumble the round by giving it uneven thrust.  A gauss gun 
would shoot line-straight, subject only to the environment (wind, gravity, 
humidity, etc)  At the extreme velocities a gauss projectile would travel, 
this would be very small indeed. ("Battlefield zero" for the M1A1 firing an
APFSDSDU munition at 6,000 feet per second is over a mile, a rough rule of
thumb would be a second's flight time; therefore a gauss rifle would shoot
straight for ~10,000 meters)  
	The hangup, of course, is in the power supply and superconducting coils
(which need not be large but will be expensive).  The main limitation is power.
The rate of fire of the weapon would be entirely dependent on how fast the 
power recharges, the quality factor of the current waveform, and other things
like the "inductance memory" in the coils (hysterisis loops can be nasty).
	Another hangup is in the area of bullet design.  Extreme velocities
of this nature will generate intense heat in the round.  In point of fact,
the heating will be more pronounced than the heating occuring in, say, the
Space Shuttle, because the shuttle enters the upper atmosphere where the
density is negligible compared to sea-level atmospheric pressure.  If you
want a round to fly at 10,000 m/sec, you're going to have to engineer it
quite carefully.  For starters, you'll want as high a surface area to volume
ratio as possible.  A ring airfoil shape (c.f. below) might prove ideal.
You'll also need advanced composites which won't deform greatly under heat
(and hence are "brittle") but will retain shape integrity when penetrating
armor (hence "ductile" or "tensile").  Again, the best candidate would be
a memory plastic.  To propel such a round with a magnetic field, you'll
need a magnetic band (an alloy of "Alnico" would probably be best).  Such 
weapons will have a signature burst of plasma as the metal band vaporizes after
leaving the barrel (since the metal won't have the thermal properties of the 
plastic).
	A cheaper way to get many of the same advantages is ElectroChemical
Propulsion (ECP)  This method uses magnetic coils much like a gauss gun,
but the current load does not need to be as large.  Propellant is placed
behind the round (liquid propellant, c.f. above, would be ideal) and the
magnetic fields are used to ignite the propellant as the bullet travels
down the barrel.  This generates much higher velocities than a conventional
weapon because the round is accelerating the length of the barrel, instead
of just in the firing chamber.  Well, to be precise, the propellant gasses
*do* accelerate the round until it leaves the barrel.  The advantage to ECP
lies in continued momentum transfer from continued burn.  The rate of 
acceleration would also increase as more propellant gasses were produced.
	The "ultimate" version of this technique would be to use electric 
fields instead of magnetic fields to convert the propellant, a tungsten wire, 
directly into a plasma. (Tungsten is a good choice for the same reasons Edison
wanted; high heat capacity, high electrical resistance, high density -- 21 
grams per cubic centimeter.  This method might even beat out the gauss gun in 
projectile velocity.
	But why stop at propellant?  The guns of the future aren't only going
to be better than todays, they're going to be smarter.
	Laser, xenon flash, ultrasound -- all are nice ways of sighting the
weapon better.  The "smartgun" is the ultimate snapshooting combat sight--point 
the gun, and the image on your retina tells you where it'll hit.  But that's 
not the whole picture.  Computers in the M1 tank calculate vehicle movement,
target movement, wind velocity, humidity, atmospheric pressure and a dozen 
other variables to achieve one-shot kills travelling 60mph on hostile 
manuevering tanks up to miles away. In point of fact, the M1 has a smartgun
type system to damp out movement effects on fire: the gunner designates the
target, and the next time the bouncing, jittering barrel aligns with the
gunners point of aim the gun fires.  
	As the microprocessor shrinks, this technology is going to be common 
for personal weapons as well.  Interface expert computer systems with
Target Motion Analysis, a Tactical Map of the area, and a tactical database and
you've got the Tactical Computer.  Build one of these into the helmet (heavily
armored, by the way), include a camera with thermal imaging and low light
capabilities as well as extra-wide angle lenses.  Then you can program the 
computer compensate for the distorted image, track motion and shapes, send
IFF queries (via a radio or microwave system) and interface with the weapon
system of the soldier, or other troops in your platoon (want to see how the
point man bought it?  Link into his cameras and replay what he saw before his
sad demise).  With the tactical database overlaid onto a TMA and a
tactical map (5cm resolution should do) you can begin to make predictions
about probable enemy advance points, choke points, and unit distribution.
On the immediate level, if someone gets a shot at you the computer could
give "threat warning", as well as reactive fire suppression (program the
weapon to shoot a lot of rounds on someone zeroing in on you).
	Wait, I said program the weapon?  Well, a harness like in "Aliens"
is not a bad idea, but why make it "dumb"?  If you've already got a robotic
arm holding your weapon on gyrostabilized gimbals, you might as well add
servos so the computer can move the gun for you.  It might turn out to be
hopelessly antiquated to actually grab a pistol grip/rifle stock and point
the weapon, but I feel that human reflexes are significant at the infantry
level (else go join up with Armor).  The servos could work on a feedback
level, though.  Where the gunner is moving the gun, the weapon helps until
it is centered on the point of aim.  Then the weapon fires when the barrel
and point of aim are aligned.
	Okay, you've got a gunnery computer.  Well, with the propulsion systems
above, the computer can tinker with ballistic characteristics too.  If you are
pumping out a lot of lead (c.f., below), the computer can reduce recoil by
cutting velocity.  If you're setting up that long-range headshot, the computer
can kick up your velocity.  If you've got a hot enough computer, it can tinker
with the amount of bullet spin to give you all kinds of niftly effects.  The
aerodynamics of a spinning object can cause a lot of crazy things -- just like
a baseball.  How about a curve ball?  (Bullet going around corners)  Or a 
change up?  (Bullet velocity is lift-enhanced during initial trajectory, but
slows down as lift attenuates from rotational energy loss)  A blazing fastball
(use lift-enhancing principle along entire trajectory)  -- or a knuckleball 
(give round barely stable spin so that rotational energy greatly deforms the
trajectory upon impact -- the M16 uses this trick) -- or a slider (increase
bullet drop for "archery" purposes).  There are some neat tricks, if you know
how.
	Lead -- lets talk about bullets.  The classic bullet is snub-nosed,
flat-ended, and stumpy (meaning the ratio of length to width is low).
First, there's better materials than lead ... depends on what you want.  If
you're looking for maximum wound trauma, a soft material that expands is just
the ticket.  Traditionally lead has done fine -- memory plastic would be better.
A sharp impact on the plastic (like the bullet striking bone) and voila! the 
bullet flattens out to a pancake.  Semisolid fluids work well, too.  The Glaser 
safety round is a spoon point round with liquid teflon in the 'cup' suspending 
#3 birdshot.  It would violate the Stockholm Convention if it were used by
the Army, but the police can use it on civilians just fine.  'Gel' rounds of
liquid teflon would give maximum kinetic energy dump with minimal penetration.
	If, on the other hand, you want to blow through that punk's armor, 
there are a variety of ways.  High density, low cross-section rounds do best --
flechettes.  A uranium-cored shotgun slug also does the trick -- and combusts
with iron besides.  Kevlar bullets, with pointed tips, sloped sides, slippery
surfaces and a dense core whiz right through todays armor at ranges of 150m
or more.  If you're real exotic, a ring airfoil shape gives excellent range,
and if made of tough, slick Kevlar material, can out-penetrate a conventionally
shaped round (it also has desirable heat-shedding properties).  And while we're
at it, combining techniques isn't bad.  You can put a memory plastic coating 
around a dense tungsten penetrator, and delay the expansion of the memory 
plastic until the round encounters significant resistance (the front or back 
plate of armor, for instance).  Or put heavy spin on a flechette so that 
heavier resistance than air will tumble the round.  Another exotic technique is
to give the round a variable shape.  
	Example: the folks at Lawrence Livermore labs know that long-rod 
uranium/tungsten penetrators work better than the shorter rods in the M1A1, but
they also know that long-rods are difficult to fire (and store and load and...)
So, they designed a telescoping penetrator with a modified sabot.  Result: when
the new round fires, the sabot peel-away retards the velocity of the rearward
portion of the round, which extends and locks the round into place.  The
new sabot is 70% longer and suffers acceptable structural losses due to the
telescoping mechanism.  Pretty neat, huh?  Hey, that's old tech: 1992. Nowadays
we've got electrically deformable materials and quasisolids that make that old
telescoping trick look like ... well, an old telescoping flechette.
	We haven't even considered munitions rounds.  Exploding rounds are 
standard. Direct the blast into a cone, and you get a reprise on what todays 
tanks use to bust other tanks -- HEAT rounds.  Load the bullet with acid, or 
skin absorbant poison if you want to be sure of a kill.  Or white phosporous.
Or any hellish conconction of the company Biotech or Chemical labs.  If you
want to get exotic, you can use a combustion laser -- that's a laser driven
by chemical energy (combustion of jet fuel, lasing the fuel itself).  The pulse
will be very short, and very violent, and act like a HEAT round besides.
	The self-forging round is a pretty good trick.  If you carefully
shape explosives around the warhead, you can produce a shaped fragment much
like a long-rod penetrator upon proximity detonation.  Put a noisemaker in the 
round that grinds out 150db at 30-50 Hz.  Those frequencies are the bone-
shaking, teeth-chattering sounds of a jackhammer, and they carry through most 
solids besides (in fact, if the oppos holed up in an antique concrete building,
the concrete itself has a resonant frequency in the 50 Hz range -- meaning you
can powder it up good with your noisemakers).  Another one is a reprise on the 
flash grenade - with a twist.  Strobe bright lights at certain frequencies and 
you will produce a lot of epileptic siezures.  Just the thing to take down 
that crowd of squatters trying to mob your supply trucks.  Or if you like it 
simple, just flash enough candle-power to fry the retinas of anyone in line of 
sight.
	The bullets themselves can be modified, besides altering their material,
aerodynamic properties, and payload.  Put rockets on the round and a guidance
package and you've got a micro-missile.  The Army uses laser spotting with 
special shells that have a laser sensor in the nose and fins.  The shell adjusts
the fins in midflight until the laser pip is squarely centered.  And since 
you're already using a Smartgun with laser sighting, no hardware mods to the 
gun are needed.  You can do the same trick with ultrasound, or any frequency in
the electromagnetic spectrum.  A nasty one is to program the round to fly 
towards muzzleflashes.  Or movement.  Or some other marker characteristic of 
"bad guys". (Hear that, chummers?  Don't fire long bursts or you may be 
visited by a smart round or three.)

	Guns have always been hi-tech, even the primitive ones.  To quote
an old English Artillery captain, "...an automobile as efficient as a Maxim
machinegun would be the seventh wonder of the world..."

           -- Adam
+--------------+---------------------------------------------------------------+
|Adam Getchell |Surgery-Radiation Oncology    GETCHELL@radonc.ucdmc.ucdavis.edu|
| acgetchell   |ez000270@chip.ucdavis.edu        acgetche@taco.engr.ucdavis.edu|
+--------------+---------------------------------------------------------------+
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