[Icelander]

Originally Posted by safisher

I think I'd just stick with David Pulver's figures for compatibility sake.

David Pulver gives figures for several different kinds of steel, from TL6 to TL8 (in 'Cutting-Edge Armor Design' in Pyramid #3/85) and from TL3 to TL7 (in 'Low-Tech Armor Design' in Pyramid #3/52).

AR500 steel seems quite obviously much more expensive and effective against bullets, at least, than what Pulver calls 'Hard Steel' at TL6 and 'Steel, hard' at TL4, which represents the best possible armour steel at TL4 and more-or-less a standard armour grade for fighting vehicles at TL6.

AR500 steel is closer to what Pulver calls 'Ultra-Strength Steel', a TL8 material, but high hardness abrasion resistant steel alloys in the real world are neither as exotic nor quite as expensive as the triple hardened or nano-crystalline steels that are referenced in the description of that material.

I hadn't looked at the 'Low-Tech Armor Design' article for a while and when I did, I discovered that there was a TL7 'Steel, very hard' material that matches the Cost of the TL8 AR500 and similar steels. I imagine that most grades of high hardness, abrasion resistant steel alloys with high wear-tolerances are 'Steel, very hard' in GURPS terms.

On the other hand, the allegedly tested ballistic protection of TL8 AR500 steel designed for use as armour or steel target is about 70-100% higher per weight than using the stats for TL4 to TL7 steel would give. It's even about a third more effective against bullets, by weight, than the 50% more expensive TL8 'Ultra-Strength Steel'.

I don't think that it would do great violence to internal consistency to insert yet another grade of steel into a line-up of materials already including six types of it. To avoid stepping on the toes of 'Ultra-Strength Steel', it should be inferior for some applications and it seems, as I noted, to only come in what the armour design system refers to as Solid forms, i.e. it can only be used in trauma plates and not in armour shaped to the human (or any kind of streamlined vehicular) form.

If we gave it WM 0.3; CM $20; DR/inch: 100; Max DR: 20*; Notes: ‡; and Constrution: Solid; it would be a viable alternative to other steels. It would perform as TL7 'Steel, very hard' against all other threats than piercing and cutting. I suppose I'd reduce the Cost of 'Steel, very hard' by half in a TL8 campaign, so that it's no longer equal in Cost to this new material, which we shall name 'Ultra-Hard Steel'.

Not useful for armour with any coverage beyond trauma plates, but a cheaper option than ceramic composites for that role, which also last longer, as they don't break up at the first hit. Which is what it does in the real world, being used to shoot at all day long at long-range firing ranges, for example.

This is game-mechanical elegance, however. I don't really know how the modern AR500 steel alloys sold as trauma plates compare to typical TL7 steel of a similar hardness or whether there is a neat price diffeence. And I certainly don't know if such high-hardness, abrasion resistant steel suffers some meaningful disadvantages compared to more typical vehicle armour alloys.

I strongly suspect that something prevents more widespread adoption of such high-hardness steels for general use in those APCs and tanks not using ceramic composites. And as high-hardness means more brittle armour, I'm proposing that these are best at stopping fast, light penetrators of much less hardness than the armour plate. Cr, cr ex and imp attacks, as with most anti-tank rounds, penetrate it much better than bullets.

Edit: Though I discover that modern APCs, IFVs and MBTs actually do use AR500 steel as part of their construction. It's also used in the manufacture of money haulers, personal armored vehicles, riot shields, vehicle door panels, safe rooms, guard booths, bank counters and similar applications. And that steels used for protective applications in military contexts, like MIL-A-46100, would be identical in game terms, with the differences being mostly relevant for IP law, not material properties.

Such steels are specifically stated to be designed primarily to stop high-velocity projectiles (HVPs), which lends credence to the idea that they have a higher DR against piercing attacks than others. For applications where resisting HEAT missiles is required, other alloys may work better, such as nano-crystalline steels.

*Can be double for armouring uses where it is essentially a single thick plate, with no meaningful shaping, i.e. trauma plate or parts of helmet.
‡The full DR only applies against piercing and cutting damage. Divide DR (and DR/in) against other damage types by 1.5, i.e. it has 2/3 DR.

Originally Posted by safisher

Where I'd think you could get some interesting results is direct metal laser-sintering or fused metal deposition, which can work with steel and titanium alloys in a powder form, basically forging them into a shape like 3d printing, and using gradient materials, that is, blending materials seamlessly from steel to titanium and aluminum. It's capable of making rocket nozzles and turbine blades, so I suspect body armor is not impossible.

https://www.youtube.com/watch?v=vgGenOdq9iY

https://www.youtube.com/watch?v=V7IsFQLjRNU

Basically, you can build a helmet that's made from say, steel alloy, titanium, and aluminum, blending materials and shapes to maximize protection in likely strike zones while minimizing weight and using the best material for each area. You could have aluminum reinforcing bands inside the helmet, for instance, providing flex, that just blends into a rigid hard outer surface to deflect blows with no seams or connectors whatsoever. The whole thing could have fluting and various construction (captive infills, like triangles or i-beams, for torsional stiffness) to make it lighter and tougher as a result. That's not something you ever could build by hand. And it'd be fairly simple. It's just using one of those expensive metal 3d printers and a 3d printing file. Print, test. Adjust. Print, test, etc. Once it's perfect you scale it to fit the wearer and print.

Ok, that's awesome.

Now, what kind of 3D printer do you need to do this with a cuirass? How expensive, how large?

And, what skill does this use in GURPS?

Armoury (Body Armour), sure, but what kind of defaults could you usefully expect for this specific task from skills like Machinist, Mechanic or various Engineering specialities? What about from Armoury (Vehicle Armour)?

What kind of real world professionals would be best at using this sort of technology to make a suit of armour that looks sort of medieval-esque?

Because most of the people who actually have Armoury (Body Armour) in the modern world will be used to working with other materials, mostly fabrics and various synthetic composites, if they have the TL8 skill, or using more traditional blacksmithing technology, if they make re-enactor armour.

Also, could you use these technologies to fuse, weld, sinter or otherwise attach the new materials you are making to already existing plates of very high hardness steel covering the parts of the upper torso that trauma plates can cover, ie. about a square foot of the front and back, each, and a smaller area of the sides?

Basically, can you use it to make steel plates that actually are proofed against rifle rounds be a part of a cuirass that nevertheless looks mostly like medieval armour, not unrelated pieces of metal? I realise that you'd have to cover all the parts of the upper torso that can't be covered with gently curving or straight plates with much lower DR materials, of course.

Originally Posted by safisher

I'd call some of this more advanced stuff early TL9, perhaps. Just use the figures from David Pulver's articles.

Like I said, many figures, not always clear which real world steel alloys fit which grade of steel he gives. Not to mention that there is clearly room for more than one TL8 steel alloy, with different properties than the other.