Just a Weird Question to Throw Out

[pmulcahy11b]

If you had the technology to manufacture enough carbon nanotubes or buckyballs, how much weight could you save on an M1 Abrams or Challenger if you replaced the steel armor with it

[Targan]

The volume to mass ratio of carbon is roughly one quarter that of steel (different grades of steel have slightly different volume to weight ratios), so that'e the simple answer if the same volume of carbon nanotube armor is required to provide the same protection as steel armor.

I know that carbon nanotubes have a far greater tensile strength than steel but I don't know anything about it's strength in other applications. I suspect if very long bucky tubes are interwoven to create plates like carbon fibre is used for it is probably much tougher than steel, even moreso if the molecular bonds are occurring between the fibres of the layers.

I think carbon insulates against heat much better than steel as well. And it won't form the same sort of molten shrapnel or spall like steel does when it's hit by a shaped charge or a hypervelocity, highly dense penetrator.

[cavtroop]

Im WAY over my head in this discussion, but bucky tubes look awesome. Is there any possible use of them in personal body armor, too Imagine the weight savings there for a foot grunt

[pmulcahy11b]

Im WAY over my head in this discussion, but bucky tubes look awesome. Is there any possible use of them in personal body armor, too Imagine the weight savings there for a foot grunt

I've heard of speculation for the future that entire military or police uniforms could actually be made of woven carbon nanotubes. Wear that, plus an even tougher vest of thicker carbon nanotube fibers, and you could get a rather unstoppable trooper. I do wonder how hot such a uniform would be to wear, however; I don't know if carbon nanotubes would make very breathable fabric.

Another thing I've heard is on the horizon for the future is body armor made of artificial spider silk -- that would be a lot tougher than Kevlar.

[pmulcahy11b]

I know probably no one can give a definitive answer to this one because its classified, but IIRC there are tankers on this board who might be able to estimate an answer: what percentage of an M1's weight is the steel part of its armor And what other parts of an M1 might possibly be candidates for replacement by carbon nanotubes or bucky balls in this hypothetical scenario

And I wonder: would carbon nanotube or buckyball fabric make a good antispalling liner

[raketenjagdpanzer]

Is the Abrams' armor "replaceable" though Don't you get into a "Ship of Theseus" issue there

[pmulcahy11b]

Don't you get into a "Ship of Theseus" issue there

I would guess you couldn't actually replace the steel with carbon nanotube armor; it's more a hypothetical question than anything else (M1A5, anyone).

I'm not familiar with the Ship of Theseus story; I'll have to look that one up.

[Legbreaker]

Welding would be out of the question so you might have to go back to something like rivets or bolts to hold it all together too. That comes with it's own problems as found in the early WWII era tanks.

[raketenjagdpanzer]

I would guess you couldn't actually replace the steel with carbon nanotube armor; it's more a hypothetical question than anything else (M1A5, anyone).

I'm not familiar with the Ship of Theseus story; I'll have to look that one up.

If it helps:

The Ship of Theseus paradox goes like this: Theseus sails into the harbor with a storm-damaged ship and asks the shipwright to repair it, but he wants his ship, not a new ship. So the shipwright removes all the planks down to the keel and replaces all of them, and stacks the wood aside knowing he can use it to build another ship. Is the repaired ship Theseus' ship or a brand new ship

And another curve: a man wanting a ship comes to the shipwright and asks for seasoned wood to be used, so the shipwright takes the planks he removed from Theseus' ship and builds a ship for the new customer. Is that ship a new ship, or is it Theseus' ship

Where this applies to our tank armor discussion is, at what point is a "rebuilt Abrams with new armor" a rebuilt Abrams and not an entirely NEW Abrams I mean, consider the S120/M60-2000 - is it an M60 any more It has an Abrams turret and everything associated, an Abrams powerplant, abrams-style armored skirt...all that's left of the original M60 is the cast armor hull.

[Legbreaker]

For me it's all about the chassis, the drive train and suspension. That's the core of the vehicle around which everything else is built. Replace that with anything except an identical piece, and it's new (unless it's just an upgrade of the drive train or suspension).
I believe this is basicaly the same definition used by most regulatory authorities too - vehicle chassis are stamped and numbered to identify the vehicle.

[StainlessSteelCynic]

I don't think the Ship of Theseus paradox is really much of a problem because you are going to have to rebuild the armour panel or make new ones anyway.

Most modern Western tanks use hybrid armours consisting of a sandwich of steel, ceramic and other materials (including depleted uranium for some). All you would be doing is replacing one of those materials with the carbon nanotubes/buckyballs - or instead of replacing, maybe adding to it.
(As I recall, these armour panels retain an outside coat of steel to mount the other armour materials to it - plus it helps stop the nicks and scratches of everyday wear & tear.)

However, this is something that would have to take place at the armour manufacturer's plant - after that you'd ship the armour panel off to the tank plant to be used for hull or turret in the normal manner.

[Targan]

Welding would be out of the question so you might have to go back to something like rivets or bolts to hold it all together too. That comes with it's own problems as found in the early WWII era tanks.

Ah, but this is where you're playing to carbon nantubes' strengths. Given the phenomenal tensile strength of buckytube filaments, you wouldn't rivet or bolt the sheets/plates together, you'd sew them. With continuous (and therefore molecularly bonded) bucky string.

[manunancy]

Logically carbon nanotubes would used as a replacement for kevlar and similar synthetic fibers. Teh'yre very strong but they behave like fibers and will bend easily.

That means spall liners inside the hull and fragment-catching panels within a composite armor. You can also probably use them into an epoxyde or similar matrix, (think epoxyde laminates - fiberglass panels in an epoxy resin matrix).

Modern composite armor is roughly ceramic (very hard, to fragment incoming projectiles) / kevlar or similar (to catch the fragments of ceramic and projectile) / steel (to soak the impact without too much deformation). Add layers until the desired resistance is reached or the chassis can't take more weight. The outer face is usually armor steel (very hard face and high tensile strength) to soak minor hits and shrapnel without degrading the composite - composite armor is somewhat ablative in behaviour.

Modular armor is that sort of panels strapped onto a 'base' hull of armor steel (very hard face, high tensile strength) which provides structural integrity and holds the various bits and parts together, acting like a car's frame along with providing some armor.

[pmulcahy11b]

Welding would be out of the question so you might have to go back to something like rivets or bolts to hold it all together too. That comes with it's own problems as found in the early WWII era tanks.

Carbon fiber parts are often glued together using a type of epoxy -- carbon nanotubes might be like that, with protective metal armored sections at the joints.

[Legbreaker]

I can see it now. The tanks of the 22nd century are held together with superglue and high tech shoelaces!