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Old 06-13-2018, 11:14 PM   #1
Johnny1A.2
 
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Default Maximum possible DR...

Generally speaking, the limits of physical strength of materials are bounded by the interaction strength of electron bonds. Of course 'strength' is complicated, there's penetration resistance, melting/vaporization point, hardness and toughness which are different things, tensile, shear, and compression, etc.

But broadly speaking, about what would be the scientifically reasonable maximum theoretically possible DR material, in terms of conventional matter, say in the former of a uniform layer of the stuff an inch thick, or 2.54 centimeters if you prefer.
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Old 06-14-2018, 02:23 AM   #2
malloyd
 
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Default Re: Maximum possible DR...

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Originally Posted by Johnny1A.2 View Post
But broadly speaking, about what would be the scientifically reasonable maximum theoretically possible DR material, in terms of conventional matter, say in the former of a uniform layer of the stuff an inch thick, or 2.54 centimeters if you prefer.
Theoretical yield strengths probably top out around 150 GPa, which is 200 to 300 times the measured value for moderately strong steels, so perhaps something on the order of DR 15000-20000 per inch. For *real* materials, the usual rule of thumb is you can't expect more than 10% of the theoretical strength out of a macroscopic sample of anything, but magic nanotech is often assumed to be able to ignore that.

Though I suppose that would be more like HP, or at best ablative DR, since it isn't going to redistribute forces over its entire volume. It'd also be directional, for a 3D network I suppose it's about 70% of that.

Stressing "reasonable" bit more than the "theoretical" one getting a non-ablative DR above 1000 or so is starting to look a little doubtful to me, but higher values might be reasonable enough approximations in some cases - sure the actual surface might start to show inch deep pits from multi-thousand hit point attacks, but if it's a thick enough plate on a huge object, those might pass off as "negligible scratches".
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Old 06-14-2018, 07:16 AM   #3
RyanW
 
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Default Re: Maximum possible DR...

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Originally Posted by malloyd View Post
Theoretical yield strengths probably top out around 150 GPa, which is 200 to 300 times the measured value for moderately strong steels, so perhaps something on the order of DR 15000-20000 per inch. For *real* materials, the usual rule of thumb is you can't expect more than 10% of the theoretical strength out of a macroscopic sample of anything, but magic nanotech is often assumed to be able to ignore that.
Would DR scale with the tensile strength, or the square root of tensile strength? If the latter, the upper bound would be closer to DR 1200. Since damage tends to square with the square root of energy, it seems like it might, but I'm literally still in bed and can't get myself to do the analysis right now...

I assume you're using the DR 70 number. That's based on RHA, which is not a "moderately strong steel." So that theoretical super material is going to have about 150 times the tensile strength, for DR 10500 (860 if it should scale with square root).

On the other hand, tensile strength is probably only one factor in a very complex equation.
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Old 06-14-2018, 07:46 AM   #4
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Default Re: Maximum possible DR...

I'm kind of curious what non-conventional matter (like degenerate matter aka "neutronium") looks like in GURPS terms, but in normal terms it's not really relevant per inch, because you have to have an entire stellar mass worth of the stuff to have it at all.
Where it gets used in science fiction as super-high-tech hull material, it's firmly TL 12^ and held together with handwavium and force fields, so it's not the same sort of beast as the center of "a neutron star" or "a white dwarf" and has whatever stats have big enough numbers to be impressive.

It does still tickle at the mind though.
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Old 06-14-2018, 10:57 AM   #5
malloyd
 
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Default Re: Maximum possible DR...

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Originally Posted by RyanW View Post
Would DR scale with the tensile strength, or the square root of tensile strength? If the latter, the upper bound would be closer to DR 1200. Since damage tends to square with the square root of energy, it seems like it might, but I'm literally still in bed and can't get myself to do the analysis right now...
The two models of damage in GURPS lead to different results. If you go with the square root of energy scheme that's normal for determining how much damage something *inflicts* (or in the ratio of hit points to ST generated forces) then it should be square root of tensile strength too. But if you accept that DR is linear in thickness (as that 70/inch implies) then it's also linear in energy to crack through it (and hence tensile strength).

It's way, way too late to reconcile those.
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