Hypervelocity Flechette weapons?


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Nightcrawler
March 7, 2006, 04:42 AM
I've heard repeated several times that once ballistic projectiles reach a certain velocity (higher than what current rifles are capable of), the achieve a wounding capacity far greater than their size would suggest, making bullet mass much less important.

I've heard elsewhere that when objects reach about 3,000 meters per second in velocity, they tend to hit with a force roughly equivalent that same amount of mass of TNT detonating on the target.

3,000 meters per second (roughly 9,482 feet per second) is a little on the high velocity side for a shoulder fired weapon. So let's set our velocity at 2,000 meters per second (6,561 fps). This is what David Weber uses for the pulser rifles in his Honor Harrington series of novels. These weapons use a small gravitic accelerator (believable in a society that has mastered anti-gravity and gravitic propulsion) to propell a solid or explosive dart to high velocity. Some of these weapons have three barrels and selective magazines and are capable of high rates of fire.

So, let's say Nightcrawler Tactical has made a breakthrough (okay, we stole it from some Japanese scientists) in room-temperature superconductors, and are using some next-generation power sources we stole from somebody else.

We can now make a magnetic accelerator rifle. That is to say, a coil gun.

The weapon we designed uses this electromagnetic coil to propell a tungsten flechette, long and finned for stability, 4.5mm in diameter, to 2,000 meters per second. The projectile weighs 20 grains.

According to this handy muzzle energy calculator (http://www.on-targetrange.com/energy.shtml), that would give us 1,912 foot-pounds of energy at the muzzle, or 2,600 joules for you crazy Metric types. The projectile would have a sectional density of 0.091.

For comparison, a 55-grain .223 round has a muzzle velocity of roughly 3,240 fps, for an energy of 1,282 foot-pounds (1743 J), with a sectional density of 0.157.

The only real modern attempt at a flechette rifle, the Steyr ACR, pushed a roughly 10 grain dart to a palsy 5,000 feet per second. I have serious doubts about the ACR's effectiveness and penetration, due to the lightweight projectile. I don't think the velocity hits the threshhold where velocity itself becomes a wounding mechanism.

Anydangway, I don't think the recoil of my flechette rifle would be anything close to being unmanagable. You could probably even up the grainage a bit and maintain the same velocity without it being uncomfortable. Even at high velocity, lightweight projectiles are ususally easy on the recoil. Note frangible, high-velocity handgun rounds for comparison.

So, am I understanding the physics correctly here? IS there a velocity threshhold where, once crossed, kinetic energy in of itself becomes a significant wounding mechanism? Would 2,000 meters per second be sufficient?

I know that this works in theory. Tank projectiles blow up enemy tanks without using any explosive. The kinetic energy turns the projectile to molten goo and roasts everything inside the enemy tank. But a tank projectile has a lot more mass and velocity than what I'm talking about here.

Oh, and not to be rude, but skip the obligatory comments about overpenetration. This would be a battlefield weapon, where being able to shoot through walls, cars, armor, and equipment is a significant advantage.

It'd also be extemely flat-shooting.

I wonder, though, would it be effective? If so, I think a 6mm heavy flechette rifle (probably semiautomatic only) might be in the works... :D

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pauli
March 7, 2006, 06:27 AM
i should think a 20grain projectile moving at a mile and a quarter per second is going to explode on impact, not overpenetrate. if it's fully automatic, you might dig a hole to something worth hitting, but at best you're maliciously wounding someone to death.

Nightcrawler
March 7, 2006, 08:20 AM
That's why I chose tungsten as the projectile material. You need something dense that will hold together. Depleted uranium might work better, but is more costly and adds all the hazards of DU handling to small arms usage. (The powder/dust residue can be quite toxic.)

You want the projectile to be hard without being brittle. Perhaps other materials would be better for this than tungsten? I mean, if we have a set weight for the projectile (20 grains, 4.5mm diameter), other materials might work. Hardened steel, even?

Preacherman
March 7, 2006, 08:24 AM
Nightcrawler, the obvious limitation in answering this sort of question is that we simply don't know - we've never been able to fire a suitable projectile fast enough to find out what will happen. We can calculate potential energy yields, etc., but that's not the same as testing something in the "real world". How will the projectile behave on impact? Will it disintegrate, or penetrate, or both? What about the shock-wave caused by its impact - will this be a minor bump, or a wave of seismic proportions, powdering bone and jellying flesh, organs, etc. for some distance from the impact site? We won't know until we try it.

Also, I remain doubtful that powered weapons for on-the-body carry will ever be able to achieve this sort of efficiency. I rather suspect that the demands of cooling, sustained power delivery, etc. will limit such weapons to crew-served or vehicle-mounted status for the foreseeable future. It will take some major breakthroughs in terms of power plant miniaturization, power storage via battery/capacitor, power delivery, etc. to achieve man-portable sizes and sustainability for such weapons.

There is also the question of countermeasures for such rounds. I would imagine that body armor proof against such ammo would be rather easier to craft than ammo proof against (for example) a .50 BMG round. Given that the mass of the projectile would be extremely low, the main "opponent" of the armor would be velocity. If one can stop the low-mass projectile on a hardened outer layer, one can dissipate the energy imparted by the velocity in many ways. One can design armor that will "crater" externally, while preserving internal integrity.

Nightcrawler
March 7, 2006, 08:46 AM
You know what the problem with trying to put stuff together for science fiction writing is?

Everything cool is impossible, and everything realistic is lame.

I mean, look at us today. We're at the dawn of the 21st century. Back in the 50s, people today were assuming that I'd be able to drive down to the space port, climb into my rocket, blast off, and land on the moon. With maybe a refueling, I'd be able to take the same rocket back to earth and land safely.

Instead, what have we got? An obsolete, worthless space program dedicated to television satellites. No laser weapons that actually work, no household robots, none of it.

What's our big achievement? The so-called information revolution. The internet. Six thousand years of recorded history, and our grand achievement is ALL YOUR BASE ARE BELONG TO US, Leeroy Jenkins, adolescents arguing with each other on anonymous web boards, using l33t-speak, and being able to look at porn while at work.

*sigh*

Anyway. So, if the projectile was too fragile, it'd be easy to protect against due to its own velocity. Perhaps something harder, and less brittle than metal? Some kind of ceramic composite? Synthetic diamond? Glass? (I've read about them trying to use types of glass for large structures. It can be very strong.)

HankB
March 7, 2006, 08:51 AM
That's why I chose tungsten as the projectile material. You need something dense that will hold together. Depleted uranium might work better,Iridium and osmium are the two densest elements - I imagine a projectile made of these would be effective, as both are quite hard. (They're also brittle in the pure state, so perhaps a little toughness could be had by alloying with platinum.)

As none of these elements are cheap, cost might be an issue . . . ;)

In terms of armoring against hypervelocity projectiles, I suspect that the mass of the armor would become as important as the tensile strength. Personal armor which would be proof against hypervelocity kinetic energy projectiles would probably be too heavy for personal use . . . unless powered armor as described in Heinlein's famous Starship Troopers became available.

And it just might - the enabling technology for both powered armor and hypervelocity personal KE weapons is an electrical power supply a couple of orders of magnitude better than today's best battery packs. If you can power a personal railgun or mass driver, you can power motorized armor.

dfaugh
March 7, 2006, 08:56 AM
Force = mass * speed...From all I remember of my college physics, this is strictly a linear progression. So, no there's not some magic threshold where a projectile instantly becomes more deadly.

Furthermore, a tungsten (or other hard material) that doesn't deform is just the OPPOSITE of what you want. You've got all this kinetic energy, and you need to transfer that to the target...I suspect a tungsten flechette is gonna zoom right on through, causing minimal damage, because it's not gonna give up any energy in the target.

Sorry.

TMM
March 7, 2006, 09:00 AM
I don't know much (nothing) of physics, so i can't be of much help. however, if you say that you have the machinery to make such a device, do it! then test it, see what happens, tweak it, change it, until it works. (or dosn't?)

It would be a fun project.

~tmm

Third_Rail
March 7, 2006, 09:24 AM
2mm dart guns firing VERY high speed projectiles are already possible. It's getting the dang barrel to last longer than a few dozen shots that's hard. :D

HankB
March 7, 2006, 09:42 AM
Force = mass * speed...No.

Force = mass * acceleration.

Momentum = mass * velocity

If you're up into the hypervelocity range, IMHO there will be hydrostatic shock effects, so a nondeforming projectile will be effective.

I would guess that the minimum velocity for reproducible hydrostatic shock effects would be somewhere around the speed of sound in tissue or water, a bit above 1500 meters/second. So you'd need a projectile impacting sufficiently fast and having enough mass to maintain this velocity over a fair distance after impact.

The SPIW system used a soft steel "dart" which was designed to deform into a "fish hook" shape and tumble after impacting soft tissue . . . but it would still penetrate today's "soft" body armor.

Medusa
March 7, 2006, 09:48 AM
mass times velocity gives impulse, not force, by definition, force is mass times acceleration, force times time gives mass times velocity. or ΔF x Δt = m x Δv. Energy the bullet has depends on velocity's square (twice the velocity, quadruple the energy). Yeah, there's a serious lack of empirical data, but as the coil gun seems to be a one way of research, then who knows, maybe someday the tests will be done.
Nightcrawler, you got it wrong on Steyr, Steyr IWS 2000 shoots 308 grain flechette (15.2 mm cal) 4750 fps. Now that's some, should shoot trough APC at kilometre (1000 yards or so) range.
http://world.guns.ru/sniper/sn46-e.htm

PS after sending, noticed that Hank the man made a comment on similar subject. sorry.

Nightcrawler
March 7, 2006, 09:58 AM
Holy crap. :eek:

0007
March 7, 2006, 10:19 AM
Somewhere I read that one of the DARPA groups had used a rail gun to slam through a 1/4 inch (I think) of aluminum(I think) with a 5gram plastic projectile. You can probably google it under rail gun darpa... The Russians supposedly are working with massive capacitors (charged from small nuclear power plants - relative term there) to fire much heavier projectiles through much thicker material at greater distances. Definately not man-portable yet, but all things in good time.

jason10mm
March 7, 2006, 10:57 AM
IIRC, Niven used something like this (hypervelocity coil gun, not the Styer) in one of his Man-Kzin Wars stories. The humans had pistols that shot hypervelocity glass beads. Were pretty effective in the story.

Personally, I doubt that there will be a suitable replacement for chemical propellant kinetic energy weapons in the near to mid future. The advances will come in the optical sighting and bullet design, not the propellant. Our atmosphere limits lasers, plasma, and hypervelocity, not to mention the durability and cost of those components.

With the advent of ceramic personal armor, we are entering an era much like the middle ages, when plate armor became proof against many melee and missile weapons. I predict an enventual return to large caliber rifle cartridges to defeat such armor, should it ever become widespread amongst our enemies.

Jim Watson
March 7, 2006, 11:09 AM
Without rereading a book or two, I recall that RMN pulsers are all full auto, even the sidearms, and the lower velocity fletchette guns for inboard use are basically shotguns. I don't think Mr Weber expects a whole lot of per-dart effect, he's stitching them full of holes.

The Swedes did a lot of work a few years back on hydrostatic shok in elg hunting. Called it the "pulsatile cavern" effect. They concluded that it showed up at 2650 fps impact velocity. Of course that was with a big old 6.5mm projectile, not a 4mm dart.

James T Thomas
March 7, 2006, 11:34 AM
I remember reading articles, I believe it was published in the middle fifties, about that weapon development. That was along with succeeding articles on personal rocket packs for the soldier to fly about the battlefield in futuristic wars.

Later the military developed in actuality the ultra high velocity sabot antitank rounds, the electric motor driven Gattling gun, and the shoulder fired, ultralight, corrosion proof, and "cheap" to mass produce, 5.56 mm dart gun which would inflict horrendous wounding on the enemy soldier. The multiple projectile, 2 mm concept having been abandoned for a single projectile weapon.
Thus placing enormous strain on the supporting infrastructure of an enemy army. Theoretically; that is, when facing nations who did hold human value for their fighting men.

The sabot antitank round, and the Vulcan gun were good developments.
Two out of three, I suppose, is acceptable.

Zak Smith
March 7, 2006, 03:04 PM
Let's not forget BC.

If you could drive a 0.2 BC bullet at 9000fps, it will lose half its velocity by 500 yards.

At 200 yards, it has lost 25% of its muzzle velocity.

Twycross
March 7, 2006, 03:08 PM
Wouldn't a projectile such as this have a very high BC?

Zak Smith
March 7, 2006, 03:13 PM
Wouldn't a projectile such as this have a very high BC?
It's going to be difficult to make a very light projectile have a high BC.

El Tejon
March 7, 2006, 04:36 PM
How dare you question the utility of looking at porn while at work, er, I mean, er, um, the Information Revolution.:uhoh: :D

RyanM
March 7, 2006, 05:16 PM
There's no bonus result at striking velocities above the speed of sound in tissue. Just a progression of more and more tearing due to temporary cavity, as they go faster and faster.

http://www.btammolabs.com/fackler/wounding_mechanism.pdf
http://www.btammolabs.com/fackler/wounding_mechanism_projectile_shape.pdf

A 20 grain, 4.5mm projectile would only need to be about 0.6" long if made of lead and cupronickel. A .177 x .6" cylinder is 25 grains, if the average density is 10.9 g/cm^3.

According to my equations, a 4.5mm bullet with a 90 degree cone tip, 20 grains, striking at 6500 fps, would penetrate 35" (assuming no deformation), crush a hole about .16" in diameter, and make a temporary cavity a maximum of 1.75" in diameter. In comparison, a plain old .45 should make about a 3.5" wide temporary cavity.

That sounds pretty crappy to me.

MAURICE
March 7, 2006, 05:33 PM
Oh come on, Nightcrawler.
100 years ago the airplane hadnt even been invented! Now look at where we are. Porn at work! Technology is advancing by leaps and bounds! Next we will have indoor lighting!

I have nothing to add to the discussion at hand. Sorry for thread drift.
Maurice

GunnyBob
March 7, 2006, 06:40 PM
NASA, as well as various Universities that have been given grants to research the subject, has for years been recreating meteor impacts, so this of course meant designing projectiles and the means by which to launch them. They have developed hypervelocity launch systems that you just KNOW the military must be keeping an eye on, and I'd lay odds that future weaponry just might come from what might otherwise be considered a totally different area of research. How hard does it hit, how can we simulate a ten-ton impact in a relatively small laboratory. Give the bright boys the time and the funding...all under the guise of examining what happens when extra-terrestrial materials are on a collision course with earth, so even the ultra left wingers cannot protest...and stand by to stand by.

Future fly-on-the-wall time: "Why yes, General, as a matter of fact Dr. Soandso HAS developed a vehicle that hurls 100 grain projectiles at upwards of 10,000 meters per second from a rather small, inexpensive, and easily carried launch system. Why do you ask?"

MajorPowerchord
March 7, 2006, 10:30 PM
I was stationed at Fort Knox a few years ago during a contractor "show your wares" gathering. I saw and handled the anti-tank sabot 'dart'. It was about 6 inches long and had fins. It was not shot through a barrel but was accelerated along a rail. The dart was encased (sandwiched) between 2 pieces of magnetically affected materials. Because there was no need for a barrel and no propellant, the cyclic firing rate was ridiculously high. The contractor stated that when the dart (cant remember what it was made of) hit a tank, the dart would deform (very quickly) and heat up. The Energy (mass x velocity squared) went from kinetic to heat (thermodynamics is our friend here). This essentially turned into a super hot, penetrating blob. As it traveled through the armor it created more blob. By the time it got to the inside, the blob splattered which acted like seering hot liquid bullets killing the entire crew. The weapon system needed LOTS of electricity so one obstacle was designing a new chasis for the weapon. YOu couldnt just pull off a tank turret and replace it with the rail gun system.

As far as hypersonic bullets go. If a low mass projectile was coming towards me at hypersonic speeds, it would almost be better to NOT wear armor as the armor allows energy to be transferred from the projectile to the armor and then go through you causing a hole and a crushing effect due to the hydrodynamic shockwave. If you arent wearing armor, you just get the hole. Not enough time to transfer energy to you because it goes through so fast it doesn't 'see' you long enough. Bottom line, if its going to go through you anyway, its better for it to go through fast than to go through slow.

Thats enough of my scientific BS for one day.

Fletchette
March 7, 2006, 11:47 PM
Nightcrawler, the obvious limitation in answering this sort of question is that we simply don't know - we've never been able to fire a suitable projectile fast enough to find out what will happen. We can calculate potential energy yields, etc., but that's not the same as testing something in the "real world". How will the projectile behave on impact? Will it disintegrate, or penetrate, or both? What about the shock-wave caused by its impact - will this be a minor bump, or a wave of seismic proportions, powdering bone and jellying flesh, organs, etc. for some distance from the impact site? We won't know until we try it.

It's been tried. It works. It just is to big too carry (yet?)

Ballistic technologies, utilizing a light-gas gun or a powder gun enable launching projectiles to velocities ranging from 1 to nearly 7 km/sec. (http://www.nasa.gov/centers/ames/multimedia/images/2005/comets1.html)

LAK
March 8, 2006, 04:11 AM
Third Rail2mm dart guns firing VERY high speed projectiles are already possible. It's getting the dang barrel to last longer than a few dozen shots that's hard.
Sabot projectiles solve this problem to a degree, but of course the problem of extreme heat at very high working pressures remains. They (they?) have been working on this for a long time, and most answers have or will come with new materials. Special ceramics for example might not have the tensile strength for receivers and whole barrels - but as a lining material for steel barrels might solve the barrel erosion problem quite easily. Higher yield propellants that burn at lower temperatures is another avenue.
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GrammatonCleric
March 8, 2006, 04:27 AM
Have any of you guys read the "Legacy of the Aldenata" by John Ringo? It's pretty good military sci-fi IMO. In this particular series the Terran ACS (Armored Combat Suit) battalions blast hostile aliens (Posleen) with 3 mm. grav guns that use anitmatter to propel 3mm. depleted uranium pellets at a sizable fraction of lightspeed. :eek: There is also a cool gun-nut character in the novels that some of you might identify with. I like it a lot.

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