Bullet-Proof Sheets of Carbon Nanotubes

An anonymous reader notes a CNN.com report on Nanocomp Technologies, the first in the world to make sheets of carbon nanotubes. "In April, [CEO] Lashmore had a mechanical multicaliber gun shoot bullets at different versions of his sheet, each less than a fifth of an inch thick. ... Army tests show the material works as well as Kevlar. The military also hopes to replace copper wiring in planes and satellites with highly conductive nanotubes, saving millions of dollars in fuel costs."

Re:Escalation

[MancunianMaskMan]

Artillery projectiles need to be heavy, not hard. Lead is good, depleted uranium is better. Not obvious where carbon NT can improve that.

Re:Escalation

[Nadaka]

Kevlar and carbon nano-tubes are not particularly dense. The ideal projectile material is extremely dense, its why lead and depleted uranium are often used instead (or in conjunction with) of hard brass or steel.

Re:Escalation

[Wolvenhaven]

People also used leather as armor, but so far no one has dug up a leather sword. The physical properties of kevlar as used for armor are entirely different from the physical properties of a good bullet. Kevlar has very high tensile strength allowing it to spread the impact over a large area by deforming and pulling on all the threads around it. With a bullet, you want all the force located in one small, strong, pointy area for penetration; which is why armor penetrating rounds are jacketed or tipped in a metal much stronger than lead or copper(steel, tungsten, depleted uranium).

Re:"Mechanical multicaliber gun"?

[OrangeMonkey11]

All or most armor manufacturers use a table top mounted "test gun" that they can change out the barrel and receiver to fire different caliber to test the protective effectiveness of their product. I don't think anyone can buy one of these you have to get them specially built.

If you ever watch any History or Discovery channel show(s) about fire-arms chances are they show a few of these.

Re:Escalation

[clone53421]

you want all the force located in one small, strong, pointy area for penetration; which is why armor penetrating rounds are jacketed or tipped in a metal much stronger than lead or copper(steel, tungsten, depleted uranium).

Actually, the advantage of DU [wikipedia.org] isn't its strength but its density:

Depleted uranium is very dense; at 19050 kg/m^3, it is 1.67 times as dense as lead, only slightly less dense than tungsten and gold, and 84% as dense as osmium or iridium, which are the densest known substances under standard (i.e., Earth-surface) pressures. Thus a given mass of it has a smaller diameter than an equivalent lead projectile, with less aerodynamic drag and deeper penetration due to a higher pressure at point of impact.

Re:Escalation

[Tekfactory]

Hey Bruce...

Lightweight and hard (not necessarily strong) are not necessarily what you want in a bullet. Hard bullets destroy the rifling in the weapon. There are smoothbore guns, but not too many. Lightweight bullets don't retain their energy well over time.

The trend in artillery is for really heavy rounds, like Depleted Uranium or thin Tugsten spikes launched inside of a Sabot. If anything came from this in a prjectile I assume it would come from the Silver Bullet style like the high speed tugsten spike.

Re:Escalation

[johndiii]

A few years back, the trend in armor-piercing rounds was the teflon-coated brass round [wikipedia.org]. They are now banned, though not for the Teflon coating (which wears off in the barrel or peels away in flight), but because of the hard cores.

Re:Calling BS

[Raleel]

My guess is it's more about the weight. carbon nanotubes are about 1/7th the density.

Re:Calling BS

[Ephemeriis]

"Saving millions on fuel costs"

There is very little energy wasted in copper wiring, especially in airplanes! Moving to a material of higher conductivity will result in minuscule savings, and will be nowhere remotely close to covering the cost of the (extremely expensive) materials.

They aren't going to save fuel because it is more conductive. They aren't burning tons of fuel because of transmission losses from one end of the plane to the other.

They are going to save fuel because the nanotube wires will be lighter than the copper wires we use now. Less weight == less fuel.

Re:You missed one -

[GameMaster]

The only industry I've ever heard of that being the case in is with Memory and IC substrates and logical design. Wood, ceramics, iron, and cement haven't "advanced", significantly to keep their lead over the others. The reason that titanium, magnesium, and carbon fiber haven't overtaken them yet is that we haven't, yet, developed a super-cheap production method for them (similar to the Bessemer process that allowed steel production to become cheap enough for it to over-take iron and the Faber process that allowed Aluminum to stop being worth more, per pound, than gold).

Re:Calling BS

[Gravitron 5000]

It's not about resistive losses. It's about weight. Also carbon nanotubes haven't benefited from any economy of scale efficiencies, and hence the cost is likely to be much less once they are able to be manufactured in quantity. It's not like carbon is a rare material.

Re:Calling BS

[e4g4]

A 747 has approximately 190,000 feet of copper wiring - per this [copperinfo.com]. I would imagine that that translates to quite a bit of weight - if that weight were to be reduced significantly (by half or better) - the fuel savings would not be negligible. The other place suggested for their usage was in satellites - which is a market where the cost is per kilogram - and satellites, as they are now, I'm sure owe quite a bit of their weight to the wiring that makes them function.

Re:Escalation

[lwsimon]

For clarification, Teflon coating of projectiles is designed to reduce barrel wear, and has nothing to do with penetration.

Most ammo manufacturers now use molybdenum coatings - not sure if that is because it is more effective, or because of the dumb "Teflon-coated cop-killing bullets that go through a bullet-proof vest!" bullshit the Brady group shrieked about in the 90s. FWIW, most any rifle bullet will penetrate light armor, and there are several surplus rounds that can even penetrate level IIIa from a pistol - 7.62x25 Tokarev being the most popular, in the CZ-52.

Re:hmmm

[QuantumRiff]

You know, considering some of the bears you might be facing would be several hundred pounds, and several times stronger than you, maybe you wouldn't want a "bear suit" to be light weight. Just cause their claws and teeth couldn't puncture the suit, doesn't mean they couldn't throw you into trees, pin you to the ground, or knock you into the water. Sometimes weight is a good thing. Unless of course, you are trying to outrun the bear, which you can't do...

Re:Escalation

[mayko]

Well its really both it's density and hardness. The Brinell hardness of U-238 is 2,400, which is just shy of tungsten at 2,570. Iron is 490.

Also, DU has incendiary properties (somewhat similar to magnesium) which make it great as an artillery shell.

Re:thicker than I expected

[lwsimon]

It doesn't list the calibers used in TFA, so hard to be a judge. I shoot 1/4" steel plates all day with a .223 without much damage to them - though a lot depends on the bullet type. Lead bullets will splash, lead-nose jacketed bullets will shatter, steel-core will damage or penetrate. Step up to a .308 and good ammo, you're going to need 1/2" or more to have a chance of stopping it.

A .50? The only time I've shot steel with a .50 BMG, it penetrated the 3/4" steel plates I had like they were paper.

If I had to guess, they're talking about handgun rounds, though - in which case, it sounds pretty equivalent to Kevlar. Kevlar isn't just a "sheet", though, as a single sheet is easy to penetrate - its more about the way they interlock when layered, causing the bullet to apply its force to a greater surface area before penetrating.

Re:Escalation

[clone53421]

Pretty sure it's not under STP.

Re:Escalation

[Chrontius]

THV [cqbservices.com] rounds [nildram.co.uk] are banned by name and description as armor-piercing [recguns.com].

If you are NOT a (FFL) licensee under the Gun Control Act (an individual) It is:
ok to OWN AP ammo
ok to SELL AP ammo
ok to BUY AP ammo
ok to SHOOT AP ammo
NOT ok to MAKE AP ammo (18 USC sec. 922(a)(7))
NOT ok to IMPORT AP ammo (18 USC sec. 922(a)(7))

The definition of AP ammo is at 18 USC sec. 921(a)(17): "(B) The term `armor piercing ammunition' means- (i) a projectile or projectile core which may be used in a handgun and which is constructed entirely (excluding the presence of traces of other substances) from one or a combination of tungsten alloys, steel, iron, brass, bronze, beryllium copper, or depleted uranium; or[...]

Emphasis mine.

Re:Escalation

[SSJ_Ramon]

You're thinking of a shaped charge [wikipedia.org] round.

Re:Calling BS

[Ephemeriis]

But I dare say that military perspective is not on saving fuel costs. After all, why save money by putting in a smaller fuel tank when you can keep it the same size and use the fuel savings to fly further/faster?

It equals out to the same thing.

If you need to drop a bomb on someone 100 miles away, right now it costs you $100 in fuel to do it. If you replace all your copper with nanotubes and make the plane lighter you can do it for $90 in fuel.

If you need to drop a bomb on someone 110 miles away, right now it'll cost you $110 and you'll have to refuel somewhere along the line. Make the plane lighter with nanotubes and now you can do it for $100 in fuel and no refueling along the way.

Even if they don't make the fuel tanks smaller, they'll still be saving money.

Re:You missed one -

[Zerth]

Working raw titanium can be a pain. If you aren't careful, it will gall and go all lumpy.

It'll catch fire before it melts, unless it is in an inert gas environment. Far right on the periodic table inert, it'll burn in nitrogen.

On the plus side, you'll have lots of titanium oxide dust around. If you think FeO+Al is fun, try TiO+Al+Fluorite+Calcium Sulfate. It won't just burn through an engine block, it might keep going into the concrete @ 3800 F

Re:Escalation

[modecx]

The definition of AP ammo is at 18 USC sec. 921(a)(17): "(B) The term `armor piercing ammunition' means- (i) a projectile or projectile core which may be used in a handgun and which is constructed entirely (excluding the presence of traces of other substances) from one or a combination of tungsten alloys, steel, iron, brass, bronze, beryllium copper, or depleted uranium; or

(ii) a full jacketed projectile larger than .22 caliber designed and intended for use in a handgun and whose jacket has a weight of more than 25 percent of the total weight of the projectile.

It's important to note that this subsection relates ONLY to ammunition which can be loaded in handguns. There are few shops with CNC lathes which turn out solid brass bullets, supposedly of highly uniform density metal, which are sold to be hand loaded for long range shooters. Steel and tungsten core rifle ammo is commonly available--or at least it was before all the hoarding hullabaloo.

This is the reason why FN Herstal couldn't ship the 5.7x27mm cartridge with the SS190 Steel/Aluminum core bullet. It can be used both in their PS90 carbine and FiveSeven pistol. If they only marketed the carbine in the US, an argument could be made that they would be legally able to ship the SS190 ammo, as it isn't intended for handguns, and by definition isn't armor piercing ammo, per federal law.

Re:"Mechanical multicaliber gun"?

[Anonymous Coward]

Despite the fact that the .357 magnum fires both .357 and .38 "caliber" rounds, the reality is, it is not really multi-caliber. .38 caliber is actually .357 caliber. The difference between the rounds is not the width of the bullet, it's the powder charge. The reason .38 is called .38 despite only being .357 inches wide, is because it is a throwback to older days when they measured the width of the shell casing instead of the width of the bullet.

As for shell length, the .38 shells are mostly empty. The reason they are the length they are is because they were first made before smokeless powder was invented. Smokeless powder is far more compact, and so when they switched to the new powder, they didn't have to use anywhere near as much in order to get the same energy release. They kept the shell size to make sure older guns were still compatible with it. As for why you can't use a .357 shell in a .38 gun, it's because of pressure constraints; a .38 can't handle the energy of a .357 round, and would probably explode if you attempted to fire one. For that reason, and that reason alone, the .357 is about 1/8 of an inch longer; i.e. so that the round won't fit into a .38 gun accidentally.