Re: [SG2][DS2] Gauss Weapons vs. CPR

Bell, Brian K wrote:

>A highly subjective question:
>What would be the materials used for a gauss flechette?
> 
>My assumption would be a high regidity, high temperature resistant
>metal (steel, titanium, iridium) 

Tungsten or DU in a steel matrix are quite likely. My only experience
with titanium is that it deforms quite easily (ie, has low rigidity),
but that may simply be because of the particular quality we used and
the environment we use it in <g>

>or highly magneticly sensitive (as opposed to magnetic itself),
>advanced ceramic.

The ceramics we have today tend to be extremely hard, but very brittle.
Unless some really radical break-throughs are made, I wouldn't use
ceramics unless I was absolutely positive that the opposition used no
hard body armour. A ceramic coating for a high-strength metal core to
reduce abrading and melting might work, though.

The flechette itself doesn't need to be magnetic or magnetically
sensitive if you have a sabot, driving disk or similar which is - and
which doesn't cause too serious disturbances when it is discarded :-/

>Softer metals such as lead,  would probably not stand upto the flight
>stress or impact stresses involved. (Yes, I know that the whole
>flechette would be pulled by the magnetic field until it leaves the
barrel, >but at the end of the barrel or gauss field, the rear of the
flechette would >still be pulled/pushed while the front of the
flechette would be pushed by >the air in front of the projectile
(acutally the flechette would be doing the >pushing, but you get the
idea)). 

The muzzle effects are rather minor compared to the lead melting due to
air friction in the trajectory and deforming beyond recognition when it
hits the target. You can design your gun to reduce the stresses on the
flechette as it leaves the barrel, but you usually can't design your
atmosphere to have less friction :-/ 

>Also, for the flechette to have any accuracy over distance, it would
>need to be stabilized. The force on the nose of the flechette would be
>greater than that on the other parts of the flechette. Any variance in
>angle, would cause the flechette to start to tumble. Tumbling would
>decrease both penetration and accuracy.

That's one way to put it. Another is "If the flechette starts to
tumble, it'll stop dead within a few dozen meters." <g>

>I see two ways to provide stabilization.
> 
>1. The flechette has fins or is a flattned wedge shape (that would act
as
>fins). Both of these have the disadvantage of an odd fit when in the
>barrel. A uniform shape would be much easier to force to the center of
>a barrel for firing. Also, if using fins, it would require a much
higher tech >base to manufacture these. And it would make the ammo
itself more >easily damaged while loading.

Today's flechettes usually have a slight bulge at the rear end, and
look a bit like streamlined pins. Very simple to manufacture, robust in
handling, don't abrade away nearly as much as a real fin would (ie, the
flechette will stay stabilized for a lot longer than it would have if
it used real fins), and has pretty much the same effect as real fins
for such small projectiles. The odd fit in the barrel is a problem, but
I suspect that that'll be a lot easier to solve than the alternative:

>2. The flechette is spin stablized. 

You don't want to know have fast it'd need to spin in order to stay
stable. The longer and thinner a projectile is, the harder it is to
spin stabilize... flechettes are *very* long and thin.

>I see three ways to do this also.
>a. Rifled flechette. The flechette, itslef, has rifling on it. As it
passes
>through the air the air is channeld through the rifiling channels and
>imparts spin. 

Hasn't worked very well in practise for existing ammunition, and is
extremely sensitive to abrading due to air friction (which the
hypersonic flechette already has a serious problem with).

>b. Rifle the barrel. This has the disadvanatge of generating lots of
heat
>(from friction) as the flechette leaves the barrel at hypersonic
velosity.

Heat + friction together means erosion, even though you don't have a
large amount of highly aggressive propellant gasses. Your barrel wear
will approach that of modern machine guns if you try this.

>c. Spin the flechette by magnetic force. The flechette would need to
be
>comprised of two materials. One that is magntically sensitive, and one
>that is not. The magnetic and nonmagnetic parts would be arranged in
>a symetric pattern along the long axis of the projectile. The barrel
of the >gun would use either alternating magnetic fields to impart
spin, or the >magnets would be arranged in a spiral pattern in the gun
(pulling the >magnetic parts of the flechette in a rifled path).

This could work, but manufacturing such flechettes in large amounts
would be a nightmare.

Regards,

Oerjan Ohlson
oerjan.ohlson@telia.com

"Life is like a sewer.
  What you get out of it, depends on what you put into it."
- Hen3ry