Unrealistic SCI-FI metals

[Darth Wong]

Hrmm. I understood that one of the main problems can actually be that the impactor may dislodge a "plug" of armour from the impact point; usually in pieces but sometimes as a single piece, which can travel into the hull to cause damage.

http://www.warships1.com/W-Nathan/index.htm

- That's where I've gotten most of my information.

Makes sense; high-velocity impacts tend to cause failure in a "shear plug" manner, so all you get is a shear plug with a hard base

Case-hardening in industry is not done to improve the crack resistance of the metal anyway; it is done to improve the wear resistance, which is a non-factor in military armour. The most likely use of case-hardening would be the hope that the hard surface layer causes the impactor to shatter, but that would only work briefly, until the weapon designers figure out ways to soften it up. Any of these "liquid metal jet" type weapons will soften up the surface and remove any case-hardening effects anyway, thus making it a wasteful exercise.

I'd been wondering if a sandwiching of Steel/Ceramics/DU in series might be effective on spaceships, not necessarily in that order and probably with multiple layers of each.

Sandwiching dissimilar material types is a well-known and highly effective method of stopping crack propagation, so I don't see why not. The principal problem is the aggravation of having to work with it, build it, etc. Not something most people care about when "designing" sci-fi ships.

Do you think that railgun shells would be built with an AP cap, and thus that efforts towards decapping would be worthwhile? I've always conceived of them (railguns), as being simply a space-usage gun; at least until you can get enough of a fraction of c behind them so that the KE can do the job on its own.

In real-life, I don't see railguns being more than a technical exercise. I suppose one might imagine that they're really useful in sci-fi, but honestly, nukes make a helluva lot more sense. If it were possible to build a hypervelocity railgun in a reasonably compact package (which I think it is not, but let's ignore that for now), stopping its projectiles with armour would be a lost cause. The hardness simply doesn't come into play when the projectile hits so hard that it simply overwhelms the tensile strength of the metal. Even if we assume the armour is mythical unobtanium with impossibly high hardness and strength, the projectile would simply vapourize itself from work-heating against the amour, and you'd end up with a big crater in your armour which probably breaches the interior.

[The Duchess of Zeon]

Sandwiching dissimilar material types is a well-known and highly effective method of stopping crack propagation, so I don't see why not. The principal problem is the aggravation of having to work with it, build it, etc. Not something most people care about when "designing" sci-fi ships.

One thing I'm thinking about, also, is that if you're defending against a nuclear detonation, you want it to happen as far away from your actual hull as possible. Assuming some form of shielding is impractical - though something magnetic may be feasable eventually I suppose - I like the idea of a light outer hull designed to trigger contact devices. There'd be ways to punch through it, of course, but there'd be things you could do, again, and armouring is always a race like that.

In real-life, I don't see railguns being more than a technical exercise. I suppose one might imagine that they're really useful in sci-fi, but honestly, nukes make a helluva lot more sense.

I have to agree with you. It seems to me that nuclear missiles would be the primarily combat weapon of choice no matter how advanced space technology gets; armour would be largely radiation shielding and sufficient layers to discourage use of lesser weaponry. Of course, you could probably armour a ship heavily enough to defend against several nuclear detonations (in the right places for the later ones), but the damage would be severe and only major combatants would be valuable enough to warrant it.

The primary defence would be the same defence we have for ships today: Stealth, Jamming, and CIWS. In a more exotic fashion perhaps some kind of shield, but I doubt it would be highly effective even then.

[Enlightenment]

I'd been wondering if a sandwiching of Steel/Ceramics/DU in series might be effective on spaceships, not necessarily in that order and probably with multiple layers of each.

Congratulations. You've just reinvented Burlington (Chobham) tank armor, as used on the M1A2HA.

What kind of projectile do you want your armor to resist? If you only want to keep out the small stuff then Burlington armor might be good enough but keeping out something like a 500kg KE warhead arriving at 200km/s is getting beyond the point of what can be expected from armor designs that are light enough to be moved by reasonable propulsion systems.

[Enlightenment]

The primary defence would be the same defence we have for ships today: Stealth, Jamming, and CIWS. In a more exotic fashion perhaps some kind of shield, but I doubt it would be highly effective even then.

Barring the discovery of physics as we don't know it, it's simply not possible to stealth spacecraft. The problem is heat emission: spacecraft must radiate heat (IR) or they will roast. If there was a need, we could build--now--IR sensors good enough to detect a heat source on the scale of the Space Shuttle's OMS rockets at the distance between earth and mars. Hiding a nuclear reactor or two from a determined adversary with multiple scattered sensor platforms is simply a nonstarter. It's not possible to jam blackbody radiation, either, so forget significant ECM.

Gun-based CWIS are already on the verge of being obsolete for surface warfare, look instead to missile-based systems (a la RAM) or better yet lasers. A sufficiently powerful X-ray laser would be quite capable of disabling targets at a range of a light second or more and would be effective both as an anti-missile system and as a primary weapon in close quarters battle.

[The Duchess of Zeon]

Barring the discovery of physics as we don't know it, it's simply not possible to stealth spacecraft. The problem is heat emission: spacecraft must radiate heat (IR) or they will roast. If there was a need, we could build--now--IR sensors good enough to detect a heat source on the scale of the Space Shuttle's OMS rockets at the distance between earth and mars. Hiding a nuclear reactor or two from a determined adversary with multiple scattered sensor platforms is simply a nonstarter. It's not possible to jam blackbody radiation, either, so forget significant ECM.

You're right, passive stealth is out, but there are other forms of stealth - for instance the French are working on active stealth devices and those may hold promise for dealing with spoofing heat detection, at least good enough to prevent it from being used for missile targeting.

Gun-based CWIS are already on the verge of being obsolete for surface warfare, look instead to missile-based systems (a la RAM) or better yet lasers. A sufficiently powerful X-ray laser would be quite capable of disabling targets at a range of a light second or more and would be effective both as an anti-missile system and as a primary weapon in close quarters battle.

Missiles and lasers both, probably. Possibly also particle beams depending on what we're talking about in terms of technology level. One interesting idea, perhaps, would be the use of railguns to accelerate flechettes for point defence - That might be where they're viable, perhaps? Just a random thought.

[The Duchess of Zeon]

Congratulations. You've just reinvented Burlington (Chobham) tank armor, as used on the M1A2HA.

Rather! *grin*

What kind of projectile do you want your armor to resist? If you only want to keep out the small stuff then Burlington armor might be good enough but keeping out something like a 500kg KE warhead arriving at 200km/s is getting beyond the point of what can be expected from armor designs that are light enough to be moved by reasonable propulsion systems.

Honestly, "nuclear bombs" is the confession I have to make. Though I'm trying to think of ways to make them detonate at a distance from the actual armour to give us a better chance of things.

What's a reasonable propulsion system, anyway? One of those uber-Orions might do, though the drive is vulnerable. I'd prefer something based on fusion; clearly the sorts of ships we're discussing, anyway, are a ways off: A century and a half, or two?

[AdmiralKanos]

The only way to detonate a nuke at a reasonable distance from the inner hull is to shoot it down in flight. No realistic double-hull is going to help you if a megaton-level nuke explodes right next to it.

[The Duchess of Zeon]

The only way to detonate a nuke at a reasonable distance from the inner hull is to shoot it down in flight. No realistic double-hull is going to help you if a megaton-level nuke explodes right next to it.

All you need to do in theory is keep the fireball from impacting the armour hull. The diameter of the fireball for a 1 megaton device is 700 meters, which would hold up nicely in the vacuum of space as a workable figure. The radius, what we need to worry about, is 350 meters - Or, an outer hull with a separation in excess of 350 meters from the armour hull could theoretically let you armour the ship to survive a nuclear impact from a 1 MT device.

For weight purposes the outer hull could actually be a latticework, as long as it was sufficient to trigger an impacting device.

This is obviously at the upper end, and probably a theoretical exercise - But assume a smaller outer hull. That would at least allow you to protect yourself against kT range nuclear devices, forcing the enemy to use MT range nuclear devices. That means they have to build bigger missiles and bigger warheads, which means that can carry fewer of each, improving your chances of shooting them down.

[AdmiralKanos]

All you need to do in theory is keep the fireball from impacting the armour hull. The diameter of the fireball for a 1 megaton device is 700 meters, which would hold up nicely in the vacuum of space as a workable figure.

Actually, that radius is caused by atmospheric interactions. In vacuum, there is no fireball radius. All you get is a tremendous burst of hard radiation which will literally boil the outer hull away and then shoot through the vacuum layer to strike the inner hull. Your only saving grace is the inverse square law, which won't make much difference at a range of a few hundred metres. You'll still take a big enough blast on your primary hull that your spouse will be cashing in your life insurance.

[The Duchess of Zeon]

Actually, that radius is caused by atmospheric interactions. In vacuum, there is no fireball radius. All you get is a tremendous burst of hard radiation which will literally boil the outer hull away and then shoot through the vacuum layer to strike the inner hull. Your only saving grace is the inverse square law, which won't make much difference at a range of a few hundred metres. You'll still take a big enough blast on your primary hull that your spouse will be cashing in your life insurance.

Well, since all it would be is radiation (And I should have realized that would effect how the detonation occurs), why couldn't you put enough radiation shielding on the inner hull to protect the crew and vital equipment? (What sort of radiation levels from a, say, 500 kT device are we talking about in deep space?)

[AdmiralKanos]

Well, since all it would be is radiation (And I should have realized that would effect how the detonation occurs), why couldn't you put enough radiation shielding on the inner hull to protect the crew and vital equipment? (What sort of radiation levels from a, say, 500 kT device are we talking about in deep space?)

A 500 kT weapon is 2.1E15 J. At a range of, say, 400 metres, this is 1 GJ per square metre, which is enough to melt 0.1 metres off the armour. More realistically, it would vapourize a thinner layer violently off the surface and destroy all sensors, antennae, etc. This would not only blind the ship, but it would also produce a rocket-like propulsive effect and shove it away. The internal stresses produced by this acceleration could be seriously dangerous in their own right.

[The Duchess of Zeon]

A 500 kT weapon is 2.1E15 J. At a range of, say, 400 metres, this is 1 GJ per square metre, which is enough to melt 0.1 metres off the armour. More realistically, it would vapourize a thinner layer violently off the surface and destroy all sensors, antennae, etc. This would not only blind the ship, but it would also produce a rocket-like propulsive effect and shove it away. The internal stresses produced by this acceleration could be seriously dangerous in their own right.

But not indefensible, nor beyond the limits of the future to find a counter against - At least within the realm of a couple hits (Obviously you'd roll the ship after one hit to offer your undamaged side).

How much radiation shielding would be needed, though? That's what might kill a chance of viably defending a vessel against that sort of detonation, the weight of the radiation shielding (Which would presumably be around a still-smaller pressure hull, than as a component of the armour hull - If the components between them could survive the dosage. If not, the weight is, of course, regrettably increased).

[Warspite]

I apologize for the big picture, but if anybody wants, I can get bigger ones... (ducks and run out of the room... )

Well, since all it would be is radiation (And I should have realized that would effect how the detonation occurs), why couldn't you put enough radiation shielding on the inner hull to protect the crew and vital equipment? (What sort of radiation levels from a, say, 500 kT device are we talking about in deep space?)

A 500 kT weapon is 2.1E15 J. At a range of, say, 400 metres, this is 1 GJ per square metre, which is enough to melt 0.1 metres off the armour. More realistically, it would vapourize a thinner layer violently off the surface and destroy all sensors, antennae, etc. This would not only blind the ship, but it would also produce a rocket-like propulsive effect and shove it away. The internal stresses produced by this acceleration could be seriously dangerous in their own right.

Well, for a suitable designed military vessel, maybe the stresses could be minimized with enough structural strength, remember, both the designers and the operators know what they're facing, and so, they'll take the appropriate measures, minimising the blast effects as much as possible.
Question: wouldn't a (wide enough) ablative layer disperse most of the nuclear blast's energy? Like you said, the jet produced would be terrible, but if the proper measures could be applied to make that point moot?

I think nuclear blasts aren't necessary. Vacuum is a nasty thing, and it doesn't combine well with humans, so why use an expensive weapon, when a railgun can drill a hole through out much anything? And, when I mean railgun, it's not the electro-magnetic type, the good old nitro-cellulose acelerating an hipervelocity bullet can have devastating effects. At least, it's a much more cheaper option than a nuke, and more safe to store in space, no?


The battle between the defender and the attacker has a long history, and usually the attacker wins, since the defender is limited to a certain ammount of mass (or weight), that's why an Abraams is expensive as hell, but will get hammered by a 1000 lb iron bomb, or why the Yamato sinked, granted it took a shitload of torpedoes and a rain of bombs, but it sank. In space, the same problem exists, due to the vessel's mass, and the thrust of the engines and maneuvring thrusthers.
If we could get a powerfull enough propulsion and maneuvring system, then it would be possible to create an armour massive enough to withstand large nuclear blasts... But, only until the next big nuke... So, in ending this diatribe, the advantage is with the attacker, there will always be a bigger mallet to strike of the eggshell, and finding the ultimate defense is impossible.

[The Duchess of Zeon]

If we could get a powerfull enough propulsion and maneuvring system, then it would be possible to create an armour massive enough to withstand large nuclear blasts... But, only until the next big nuke... So, in ending this diatribe, the advantage is with the attacker, there will always be a bigger mallet to strike of the eggshell, and finding the ultimate defense is impossible.

Within a certain limit. What I was really thinking of was forcing the attacker to use larger nukes. That would reduce their payload, and thus make it easier for your anti-missile defensive systems to spoof/shoot down incoming missiles (fewer incoming to deal with).

So even though one incoming can still destroy you, your liklihood of being destroyed is reduced because your defensive systems have a better chance of shooting down the smaller number of missiles the attacker is forced to resort to, so that he can guarantee a kill.

[Warspite]

You could reverse that train of thought... It might work better.

The problem would be similar to the one faced by the US Navy during the bad old days of Cold War, they were always worried about facing a mass wave attack of anti-ship missiles by the Soviet Navy, both from air as well as sea. (That's one of the main reasons for the automation of CIWS, and the genesis of the AEGIS system.)

Big nukes are expensive, small ones are beautifull, and if you can swamp the defenses with a LOT of targets, the rules of probability can guarantee a certain ammount of damage. Worse, if more are decoys, then the defenders are literally toasted. And to destroy a target, a big nuke might be overkill, I refer to HMS Barham... one lousy torpedo, and bum!

Just another way of cracking nuts...


****EDIT****

Ooops, the Barham took 3 torpedoes... Oh, well, even then, it shouldn't have exploded when it went turtle.

[Sea Skimmer]

Barham was hit by three torpedoes. The range was so close the blasts appeared as one massive hit. This also happened was alongside the forward magazines and as she rolled they exploded, liky from torpedo spawned magazine fires which hit the charges as they fell out of there bins.

However three hits on one side would almost certainly be fatal to a Queen Elizabeth regardless of location. She would just take longer to sink.

[Sea Skimmer]

If we could get a powerfull enough propulsion and maneuvring system, then it would be possible to create an armour massive enough to withstand large nuclear blasts... But, only until the next big nuke... So, in ending this diatribe, the advantage is with the attacker, there will always be a bigger mallet to strike of the eggshell, and finding the ultimate defense is impossible.

Within a certain limit. What I was really thinking of was forcing the attacker to use larger nukes. That would reduce their payload, and thus make it easier for your anti-missile defensive systems to spoof/shoot down incoming missiles (fewer incoming to deal with).

So even though one incoming can still destroy you, your liklihood of being destroyed is reduced because your defensive systems have a better chance of shooting down the smaller number of missiles the attacker is forced to resort to, so that he can guarantee a kill.

You don't need a hard kill with your first hit though. A relatively small nuclear weapon might not wipe out the crew, but it will still fry one side's electronics. While the target is rolling to present its undamaged side your next salvo, good spacing is needed so one blast doesn’t kill the others, has a chance to get close once more. It then kills the other side.

At that point the target is at your mercy to fishing off with a single big missile, unless it has more sensors and weapons hidden under movable armor. That would however be very complex and require a much bigger hull then the standard fit.


I see little point to manned vessels though. Just send a hoard of missiles.

[NecronLord]

Here's something for the engineers to do, when they have the time.

Write me a description of all the processes needed to create an ubermatieral of doom from steel, then tell me how you implement that on a factory ship. (assuming plentiful raw materials produced by something along the lines of ST replicators)

[beyond hope]

This is going to sound unpardonably lazy, but can anyone point me in the direction of some good sites on materials strength, and the properties of railguns and directed-energy weapons?

[SyntaxVorlon]

The reason for ceramic armor is that it takes a buttload more energy, laser, nuclear, or plasma, to destroy, and assuming energy weaponry this would make the best choice for an outer hull as most metals would melt much too easily.(If you think hot fast moving gas[this is all that plasma is] can shatter fortified ceramic armor, then you can go and get a blow torch and see how long it takes for thick terracotta to break)
If, however, railguns or rocket propelled weaponry is in employment then steel or some denser material is in order. But remember steel transfers heat very well, if you want an example go take a pair of metal tongs and put on a flame, leave them part way in for a while, then touch the furthest part from where they were in the flame, it will sting.
A ceramic hull will stop a laser by not letting the heat transfer to anywhere else that is why ceramics are good against heat based weaponry, they STOP heat.

[Darth Wong]

The reason for ceramic armor is that it takes a buttload more energy, laser, nuclear, or plasma, to destroy, and assuming energy weaponry this would make the best choice for an outer hull as most metals would melt much too easily.

I suggest a materials science textbook. Per unit volume, ceramics actually take less energy to destroy, particularly with high intensity. Their specific energy is not so much higher that it compensates for their low density or feeble thermal conductivity.

(If you think hot fast moving gas[this is all that plasma is] can shatter fortified ceramic armor, then you can go and get a blow torch and see how long it takes for thick terracotta to break)

Try the same thing with a refractory tungsten or nickel-based superalloy and get back to me with the comparative results.

If, however, railguns or rocket propelled weaponry is in employment then steel or some denser material is in order. But remember steel transfers heat very well, if you want an example go take a pair of metal tongs and put on a flame, leave them part way in for a while, then touch the furthest part from where they were in the flame, it will sting.

High thermal conductivity is good when dealing with energy weapons; it spreads out the impact rather than allowing it to build in one spot. I've said this three times now; are you suffering from some kind of reading comprehension problem, or is this ceramics superiority notion of yours some kind of dogma for you?

A ceramic hull will stop a laser by not letting the heat transfer to anywhere else that is why ceramics are good against heat based weaponry, they STOP heat.

No, a ceramic hull will be destroyed because it can't conduct heat away from the impact site, so the impact site will be explosively vapourized. You've got it completely ass-backwards; the ideal hull against energy weapons is thermally superconductive.

[aerius]

The reason for ceramic armor is that it takes a buttload more energy, laser, nuclear, or plasma, to destroy, and assuming energy weaponry this would make the best choice for an outer hull as most metals would melt much too easily.(If you think hot fast moving gas[this is all that plasma is] can shatter fortified ceramic armor, then you can go and get a blow torch and see how long it takes for thick terracotta to break)

A blowtorch burns at what, a few thousand degrees at most? The temperature for plasmas is in the range of tens of thousands to millions of degrees. By the same token I can shoot a cinder block with a BB gun and do no damage, but a .50 BMG round will blow it to little pieces. Get me an industrial cutting laser and you'll see that terracotta of yours shatter into pieces from the thermal stress.

[SyntaxVorlon]

I could have sworn that last time I checked it was easier to melt metals than it is ceramics.

Try the same thing with a refractory tungsten or nickel-based superalloy and get back to me with the comparative results.

You don't seem to get that I'm not saying that ceramics are superior, I'm just saying that they won't shatter.

When high intensity energy is being thrown around steel will melt, because it is getting throw quickly, the speed at which it transfers heat is slower than the speed at which it will melt in a high intensity energy battle. The fact that a ceramic armor does not transfer heat is it's strength. When hit by a high intensity beam it will vaporize but it will not have transfered as much heat in the time alotted, leaving the surrounding area virtually un harmed. This gives the hull time and a smaller area which will be affected. This means that the hull gets a pock mark but holds. If the energy beam is low energy over a long time then sure a superconductive metal will reflect the heat away, but when a lot of joules are moving fast then there is instant vaporization and you don't want that heat moving to far because then a larger portion of the hull will be affected. That is what I mean by stop, isolation, keeps the beam from getting past, even at the expense of a few inches of armor. A super conductive metal would conduct waste heat into more of the hull thus leaving a greater impact.
If you're dumb enough to sit there while an enemy laser drills into your hull on one spot then you are done for. But a ceramic hull will stop the heat from traveling from one spot. The metal will spread the heat through out the hull giving whatever enemies you have a larger area to shoot at with their weapons.
Ceramics mean you can get hit several times, losing some armor in several places but still not be dead. Steel will transfer that heat and if a second volley of energy hits nearby then a lot more energy is in that same area and a lot more armor in that area will be lost.
Also you presume that all ceramics must be low density, why is this?

[Darth Wong]

I could have sworn that last time I checked it was easier to melt metals than it is ceramics.

Most metals are selected for ease of processing, not high-temperature use. Didn't you ever wonder why high-temperature high-stress applications like jet aircraft enginer turbine blades are still made from metal? There are lots of metals which are optimized for high-temp use. Refractory ceramics are good because their melting point is high, so the laws of thermodynamics mean that they will take zero energy once they reach thermal equilibrium with a molten metal of lower melting point (this is why they're good for storing molten metal). However, you should not assume that this means they take more energy to damage; there is much more to this than simple melting point.

Try the same thing with a refractory tungsten or nickel-based superalloy and get back to me with the comparative results.

You don't seem to get that I'm not saying that ceramics are superior, I'm just saying that they won't shatter.

Against a laser, they will. I've seen lasers destroy bricks and I've seen them destroy metal. Bricks shatter, metal melts.

When high intensity energy is being thrown around steel will melt, because it is getting throw quickly, the speed at which it transfers heat is slower than the speed at which it will melt in a high intensity energy battle. The fact that a ceramic armor does not transfer heat is it's strength. When hit by a high intensity beam it will vaporize but it will not have transfered as much heat in the time alotted, leaving the surrounding area virtually un harmed.

Wrong. The vapourization of a small region will create stresses in the surrounding material, ie- physical shock. That will shatter the brittle ceramic.

This gives the hull time and a smaller area which will be affected.

You actually think it's good to allow the enemy to do precisely what he wants, ie- focus his energies more effectively in one spot? Have you given this serious thought?

This means that the hull gets a pock mark but holds.

No, it means that the enemy's weapon punches right through your hull because it doesn't spread the energy around. He gets to accomplish precisely what he wanted; high-intensity concentration of his attack on a single spot of your hull. Rather than having to heat up a huge mass, he now only has to heat up a very small mass.

If the energy beam is low energy over a long time then sure a superconductive metal will reflect the heat away, but when a lot of joules are moving fast then there is instant vaporization and you don't want that heat moving to far because then a larger portion of the hull will be affected. That is what I mean by stop, isolation, keeps the beam from getting past, even at the expense of a few inches of armor. A super conductive metal would conduct waste heat into more of the hull thus leaving a greater impact.

You're not thinking clearly; if a laser has enough energy to melt the entire hull's mass (ie- making a thermally superconductive hull useless), it will certainly annihilate the small core of ceramics it needs to in order to punch through to the interior.

If you're dumb enough to sit there while an enemy laser drills into your hull on one spot then you are done for. But a ceramic hull will stop the heat from traveling from one spot. The metal will spread the heat through out the hull giving whatever enemies you have a larger area to shoot at with their weapons.

As I said, you've got it ass backwards. The metal is more likely to melt on the surface and spread the heat around, while the ceramic will explode at the point of impact, shattering nearby material and probably allowing penetration because the laser need only heat a miniscule mass of material rather than a huge mass of metal.

Ceramics mean you can get hit several times, losing some armor in several places but still not be dead. Steel will transfer that heat and if a second volley of energy hits nearby then a lot more energy is in that same area and a lot more armor in that area will be lost.

After the first hit, a ceramic hull is most untouched except for a small area which is blasted away, and there are dead people inside. A high-conductivity metal hull has a big ugly-looking melted area on the surface, but the people inside are OK.

You have obviously never seriously studied failure mechanisms in engineered structures; you want to absorb and spread out energy. You never want to concentrate energy in one spot unless you're the guy designing the weapon, not the armour.

Also you presume that all ceramics must be low density, why is this?

Because they are. Close-packed metallic lattice structures stack atoms more efficiently than ionic or covalently bonded ceramics, so metals tend to be denser unless the atoms themselves are very lightweight. The densest solid materials are metals. Didn't you learn about this in high school?

[aerius]

You still don't get it do you? The thermal stress from the laser/plasma/heat cannon will shatter that ceramic into little peices. Ever taken a glass from the freezer and dunked it hot water? It cracks and shatters into pieces, and that's only a change of around 100 degrees C. Also with ceramics, they have nasty crack propagation issues, get a crack started and it ain't stopping. You're gonna have huge chuncks flaking off with every hit.