I’m afraid something is wrong here (or I read something wrong).
Ermmm, you need to halve that to get the armour thickness for a cube, unless the armour is only on three faces
Yes, I missed a step (the divide by 2 to get 6 sides, not just 3).
However, the point still stands that the displacement tonnage devoted to armor will cause armor thickness to vary for different configurations of hull that have identical displacements (such as 10 vs 10 or 100k vs 100k). So trying to use the tonnage fraction as a way to determine outer hull thickness of the "armored shell" variety is something of a fool's errand. Using that methodology will arrive at the wrong conclusions with extreme accuracy and confidence (as demonstrated above).
After all, the point of the exercise was to find a consistent "hull thickness" that would be true for all craft of the same displacement which can then be scaled to all craft of any displacement ... and it doesn't work like that if you start with displacement volume. You aren't going to get a "one
size formula fits all" solution to the question of how thick an armored hull ought to be from the tonnage fraction devoted to it and then working backwards.
Instead what you need to do is look up the armor table in CT Striker, cross-check the Armor Rating on the table with the thickness of material equivalence that yields that armor rating and then work backwards from there using the armor Toughness rating for the different materials (as I've now said repeatedly by this point). THAT methodology will give you a consistent, hull size agnostic answer to the question of how thick the bulkheads (and thus the outer hull of a craft) ought to be.
For this to work, the exterior armour has to be the same thickness as the interior armour.
Yup.
Bulkheads, wherever they are placed, ought to be the same thickness in all locations.
If you look at any deckplans for starships and small craft in CT (pick a book, any book), they all use the same thickness of lines for the habitable compartment spaces as they do for the lines of the outer hull. Coincidence? I think not.
If a craft is armored, ALL of the bulkheads used in the construction get thicker, not just the ones on the outer skin.
Pretty simple, really.
it is not consistent with later versions of Traveller (TNE/FF&S, T4/FF&S2)
And ...?
Are later versions of Traveller written for different systems retroactively "binding" on earlier systems?
The fact that many of the same authors worked on both is "nice to know" (for historical reasons), but is not germane to what is written for how LBB5.80 works and why.
Kind of like how later versions of D&D have Feats ... but the first editions of D&D did not.
The first versions of D&D used the THAC0 system ... which was (fortunately) later revised into the DC system.
Yes, the later versions "grew out of the former" ... but you can't just backport everything 1:1 and expect nothing to go wrong when it comes to reconciling everything involved.
On the other hand, MegaTraveller perhaps does follow something like what you suggest
For what it's worth, on the "historical precent" scale, MegaTraveller is "closer" to CT (game mechanically speaking) than TNE/FF&S, T4/FF&S2 in terms of "lineage" when it comes to how many "generations apart" the game mechanics are, and the concepts that they are founded upon.
If it helps, think about it a bit like plate tectonics. Hundreds of millions of years ago (because of geologic time scales) the continents on the surface of the Solomani homeworld were in different locations than they are in the present day. Same continents, different arrangement, different topography ... so a map for one era is not necessarily a good guide in a different era, because the terrain doesn't match up 1:1.
GURPS Traveller assumed armour was a skin
To be fair, GURPS in general treats armor like a skin.
Even CT Striker treated armor like a skin (at vehicle scale), since it was something applied to all 6 sides (front/rear, left/right, top/bottom) of a box shape.
When you get to the scale of small craft/big craft, you're not really dealing with "vehicle scale" stuff anymore, it's more like "building architecture" (like skyscrapers that go into space!) and everything gets a lot more complicated (to gloss over a LOT of factors very quickly).
MgT2 is also back to plain percentage of displacement, but it has a specific option for armoured bulkheads that provide protection to specific system, implying that normally they do not get tougher armour as the ship's armour value increases.
I am not familiar with MgT2, but it sounds like a way to
selectively armor certain high value systems, rather than just doing a "one size fits all" blanket armor value for everything (like was done in CT).
If Interior armour is significant, meson gun explosions should be at least somewhat affected by it, but they utterly ignore physical armour.
Meson guns "ignore armor" because of how they work.
The analogy is imprecise and isn't how meson guns "do their thing" ... but for simplicity of illustration purposes (and to get the idea across adequately and concisely) ... meson guns are a combination of weaponizing a transporter accident of an anti-matter warhead.
The mesons "don't interact with normal matter" until they decay (the transporter effect) and the weapon firing the mesons can control "where and when" that decay point occurs ... with the idea being that it happens inside the hull of an opposing craft (because you don't want to get any mesons on YOU). So meson guns "bypass armor" because they "skip over all matter" until they decay, creating all kinds of weaponized nuclear nastiness. Not a "true" anti-matter weapon, but certainly up there in the "poor man's antimatter" in the way that some highly energetic explosives can be described as a "poor man's nuke" ... and when it hits, it's going to be INSIDE your craft and it bypasses EVERYTHING (except meson screens and black globes) to get there and "make a mess of the place" at the critical decay point.
It's basically a high tech Sphere Of Annihilation that gets teleported inside of stuff.
If your targeting is right and a meson screen doesn't muck up the decay point, things get UGLY inside the target.
That's why meson guns "ignore armor" the way they do.
They're something of a weaponization of a transporter accident and an anti-matter warhead ... kinda sorta, if you squint hard enough.
It's not ACTUALLY that, but for the purposes of conversation on the topic there are remarkably few differences.
A TRUE (anti)matter transporter sending an ACTUAL anti-matter warhead would be MUCH MORE DESTRUCTIVE, I'm thinking.
So perhaps calling meson guns "early disintegrators" of matter would be more accurate ... kind of like how plasma guns are the precursors to fusion guns ... except that meson guns are more like "teleport disintegrators" rather than any kind of "disintegrator beam weapon" akin to a laser (that erases matter).
LBB5.80, p18:
Meson Guns create high energy mesons and direct them at targets. Mesons have short lives, which can be prolonged to precise durations by accelerating them to relativistic speeds. If the point of decay is manipulated to occur inside the target ship, the result is high energy explosions and radiation damage. Because of the nature of the meson, it can pass through armor and matter without resistance.
