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]

Originally Posted by 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?

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]

Originally Posted by raketenjagdpanzer

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]

Originally Posted by pmulcahy11b

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]

Originally Posted by 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.

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]

Originally Posted by 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.

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!

[StainlessSteelCynic]

Originally Posted by Legbreaker

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

Don't laugh too hard, that's not too far from the way they make personal body armour!

[Webstral]

I think the final goal of carbon armor would be a single bonded sheet of whatever thickness was desired. In effect, the armor would be a single extraordinarily long molecule.

[Targan]

Originally Posted by raketenjagdpanzer

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?

This paradox has also been applied to the idea of matter transporters. Ones like those depicted in Star Trek scan the object to be teleported and store the information digitally. They then effectively disintegrate the target object and rebuild it atom by atom at the target destination. Essentially, the first time a person is transported in this way the 'real them' is destroyed and a perfect facsimile of them takes their place. The question is, if every single atom in your original body is destroyed is your facsimile really 'you'?

In my opinion the question is moot anyway because we don't retain the same matter throughout our bodies during our lifetimes anyway. We cycle through matter as our cells wear out, die and are replaced. It's really the 'pattern' of us that is us, not the individual atoms.

[raketenjagdpanzer]

Originally Posted by Targan

In my opinion the question is moot anyway because we don't retain the same matter throughout our bodies during our lifetimes anyway. We cycle through matter as our cells wear out, die and are replaced. It's really the 'pattern' of us that is us, not the individual atoms.

Right, but in the matter of a main battle tank, the question remains. You can argue that replacing the main gun and the needed suspension, drivetrain and powerplant rebuilds are all still under the category of "parts replacement" versus replacing the whole, but once you start talking about "replacing" the hull and turret for new armor...it's a whole new tank you're building. Just IMO.

[Legbreaker]

The parts removed and discarded are no longer considered part of the object.
The new parts installed are considered part of the object.
Over a period of time all parts may be replaced, but this is just evolution of the object.
In the EXTREMELY unlikely even the discarded parts are reassembled seperate to the "new" object, the discarded object should be viewed as a seperate object, or an earlier version. But how often are we ever going to see the same hundreds, even thousand of parts reassembled in the same order?

To avoid ANY confusion though, and as previously mentioned, the relevant overseeing bodies tend to place some kind of identifier on the major component, usually the chassis and/or engine. The identity of the object stays with that major peice.

If that major peice was to be melted down and recast into the same shape, it should be classified as a whole new item. The stresses it was subject to in it's previous incarnation are gone, "reset" in the recasting process. This "experience" is in my view at least part of what give the item it's unique identity.

[StainlessSteelCynic]

In everyday usage, the issue of a rebuilt tank (or anything else for that matter) is as Targan mentioned, a moot point. Simply because most operators don't really give a damn and neither does anyone else - as long as it does the job it's meant to, they don't care if it's factory original, maintenance depot rebuild or simply retrofitted.

The only times I have seen this being anything more than a philosophical discussion (and please don't think I am dismissing that side of things, I enjoy a good argument as much as the next person and my argument here is as much philosophical as it is practical) is as follows: -
1. For collectors. They want original spec because of the perceived value associated with an "original" object.
2. When an earlier model is upgraded/converted to the same specs as a later model e.g. a baseline M16 rifle being upgraded to the M16A3 version.

In this case, if the M1 MBT was retrofitted with nanotube armour, is anybody really going to care if the tank is considered the "original" tank. Personally I do not believe so, because we accept the idea that certain damaged parts of an armoured vehicle will be removed and replaced - including armour panels - in the normal course of combat. As long as the majority of the object survives in it's accepted form, we tend to consider it the "original" and as mentioned by Legbreaker, even if the tank was stripped back to the hull, it would be considered a rebuild and not a new build.

[raketenjagdpanzer]

I guess the rationale for starting on the "Ship of Theseus" matter wasn't so much that anyone would "care", but IRL it's kind of a matter to both the Army and defense contractors as to what constitutes a "new" tank.

[Tegyrius]

Back to Paul's original question...

Originally Posted by 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?

... what would the theoretical weight reduction do to the main gun's recoil effects on the vehicle (and its systems and crew)?

- C.

[Legbreaker]

Hmm, that's a good question. I'm thinking you'd have to modify the suspension and recoil systems to compensate for the reduced mass.
Or just use a completely diferent weapon with low to no recoil.

[Sith]

You can't really replace a tank's armor per say as they don't have a frame or chassis. The armor is the hull and turret, and everything else is just built on to those. The only way you could theoretically retrofit an Abrams with carbon nanotubes is to crack open the areas in the hull and turret that contain the ceramic pieces, then remove and replace them. An expensive process to say the least, and depending on where you cut, you could create weak points in the armor where it has become stressed. In total your weight reduction would not be that great as no steel would be replaced, although the armor protection would potentially be greatly increased.

For the sake of argument though, if you could craft an entire hull and turret out of carbon nanotubes you would probably get an eighteen (+ or -) ton vehicle with MBT level protection (assuming Targan's 1/4 rule). A 120mm cannon, however, can be placed on a twenty or so ton vehicle and work. A more practical weight though is around 35 tons.

I don't know about replacing other parts with carbon nanotubes as those are "working" parts. I don't know enough about this material to know how "wear and abuse" impacts it.

[StainlessSteelCynic]

Originally Posted by raketenjagdpanzer

I guess the rationale for starting on the "Ship of Theseus" matter wasn't so much that anyone would "care", but IRL it's kind of a matter to both the Army and defense contractors as to what constitutes a "new" tank.

Ahh I see what you are saying now, I was just thinking in terms of the end user and not the producer and buyer.
Yeah, in that situation I can see them arguing over what constitutes a "new" tank especially when some of those defence contractors believe that a major rebuild makes the vehicle "as new" and that will probably affect the price they can charge for the vehicle!

This is exactly the case with the Australian Army's M1 Abrams tanks. In no way are they "new" tanks because they have been rebuilt from earlier models (although with some significant improvements from the model they started as). As far as the defence contractor is concerned however, they are a new tank.

[pmulcahy11b]

Originally Posted by Tegyrius

Back to Paul's original question...



... what would the theoretical weight reduction do to the main gun's recoil effects on the vehicle (and its systems and crew)?

- C.

I suppose the best person to address that would be a former Sheridan crewmember.

[ArmySGT.]

Originally Posted by pmulcahy11b

I suppose the best person to address that would be a former Sheridan crewmember.

Check with the VA for all Sheridan Operators (or the 82nd Abn assn) whom have had a wrist rebuilt.

[Targan]

Originally Posted by Tegyrius

Back to Paul's original question... what would the theoretical weight reduction do to the main gun's recoil effects on the vehicle (and its systems and crew)?

Well, the M60-2000 weighs about 5 tonnes less than an M1A2 and seems to have little trouble firing the 120mm smoothbore. Five tonnes isn't much of a weight difference on a percentage basis though. I guess if an M1A2 weighed 1/3 less it migh have some problems. Still, maybe not. It's a very broad, low platform, inherently stable.

[Legbreaker]

With the mass it's likely to still have, I can't see there'd be too many problems a redesign/upgrade of the recoil systems couldn't deal with.