WH40K - Execution Hour (SDN)

[Mr. Oragahn]

Analysis of the first "Execution Hour" duology. Shadow Point is its sequel. Both by Gordon Rennie.

40K analysis: Execution Hour

Page 16: - "hundreds" of crewer ratings are used to physically haul guns in and out of position (up to and away from the gun ports, in other words.) as well as open/close blast shields over hte viewports Presumably, the guns are "locked" into position before combat (and probably anchored via some sort of force field mechanism against the recoil.

In other words, absolutely primitive by space faring standards. One would question why such a civilization can come with pseudo über tough hulls and immense power generation abilities, and yet must rely on flesh and sweat instead of oiled mechanical arms to do the menial work.

Page 18:

At the magos's command, the truly stellar levels of energy contained within the ship's [speaking of an Imperial Navy] cruiser plasma reactors were released into the warp engines, ripping a hole in the fabric of space and pushing the cruiser forward into the immaterium. The Gellar field, a teardrop-shaped bubble of reailty which protected the ship and its crew from the maelstrom - crackled with power as waves of warp energy lashed against it, rocking the Macharius from prow to stern,"

The (ought to be) well known "stellar levels" figure for 40K ships. As noted in the prior "Grand 40K quantification thread", the implication is as high as e26 (or higher") watts for output, but the actual reference can vary highly depending on the kind of star (much higher or much lower.) Generally, observed performance (and comparisons to other craft such as the Planet Killer) imply power generation is probably less than e26 watts.

Note that another interpretation of this quote may be that the "stellar levels" of energy was not referring to a "sustained" output (ie not power), but how much energy in total was delivered from the plasma reactor over an unknown timeframe (although no less than an hour or so, given the aformeentioned "time to warp" given earlier.)

In general, ,the quote is best used as a rough, "order of magnitude" support proof of the sheer magnitude and capability of 40K power generation, ,rather than an explicit reference.

Additionally, make note of the reference to the Gellar fields (and their description) - they evidently do not just protect against "psychic" incursion, ,but also against physical damage from the Warp (or at least interaction with it.)

<sorry folks, I know I just scratched the surface, but I'll touch on more of it later. I want to get to bed :D )

Or, another interpretation, is that stellar simply means fantastic, which is just as vague as it can get.
Pretending strong support for e26 W, peak or not, or even higher figures, on the mere basis of such hyperbole which is de rigueur in WH40K literature, is quite some wishful thinking.

It could also refer the level of local energies you'd find in a given fraction of the volume of a star, that fraction corresponding to the size of the Wrap rift as a ship enters or exist the Immaterium.
A star may generate much energy, but the intensity over a limited area (of its photosphere) that would correspond to the dimensions of a rift, large enough to allow a ship to move through it, would be peanuts in regards of the entire power output, and yet, it would still fit with a more literal interpretation of "stellar" energy.

Really, assuming that the whole of a star's output can be the only exact meaning of this particular piece of text, is just reaching for big numbers without trying, even once, to see if there could be far more reasonable understandings.

Okay, continued:

Page 19:

Aft lay the engine section, comprising fully one third of the ship's three kilometre length, but below him was the main body of the Macharius, brisling with crenellated gun turrets, observation domes and spires, antenna arrays and other baroque features of the vessel's superstructure. On each side of the hull were the heavy weapon batteries and the tiered ramparts of the cruiser's launch bays, each bay capable of unleashing wave upon wave of fast attack fighters and bombers. Ahead of him was the fearsome armoured beak of the prow, its metres-thick solid atamantine armour designed to smash through the hulls of enemy vessels in a full head-on ramming attack. There, too, was the ship's main frontal armament: six missile tube tunnels, each firing a thirty-metre long plasma torpedo.

Description of the Macharius' design. The ship is three kilometers long, and has a "metres thick" prow made of adamantium. Also note the thirty-meter length for the torpedoes (and the suggestion they are the most powerful weapon on the ship - against armor, at least.)

Adamantium is tough, but not that tough, since it can be pierced by powerful weapons when it comes to infantry scale. It is still good enough to protect the starship Macharius, when it plows through its target.
Take the Terminator armour plating. Let's say it takes one gigajoule of energy to vaporize 1 cc of its formidable solid (but inert) defense. The ratio itself is completely over the top, but it serves as an example.
Therefore, it would take one million gigajoules to vaporize one cubic meter of the same material, and then, 10 petajoules to vaporize ten cubic meters of this material.
Basically, some megatons would be plain enough to get through the meters-thick plating of any Imperium warship, and there would be no point pretending that such hulls could survive gigatons or teratons direct hits. It would be downright silly.

The firepower of the Macharius was formidable, but Solon Cassander knew that it was insignificant in comparison to the power contained in the merest flicker of warp energy in the maelstrom raging around them.

Comparison of the Macharius' firepower relative to the Warp segment it is traveling through.

Energy of a merest Warp flicker > Macharius' firepower.

Since the ship isn't destroyed, two solutions:

1. Those flickers are rare. Doesn't seem to be the case, by the book.

2. Gellar fields cheat even the Warp's physics, and push the Warp away so that the ship's shields only have to deal with a fraction --or none-- of the Warp's raging energies. Otherwise, a starship would quickly succumb to the high frequency of those flickers that surpass the starship's own firepower, and therefore represent a high danger to her shields.

Option 2 seems about right.

Pages 20-21

On the fringes of the Dolorosa system, a miniature second sun suddenly blossomed in the vacuum of space, its light outshining that of the real star at the far distant centre of the planetary system. Waves of energy cascaded out of the extra-dimensional breach as a three-kilometre-long metal leviathan ripped its way back into the normal universe, its shields straining at near-overload point to withstand the terrible energies surging around it.

Vessels emerging from warp emit a rather substantial amount of energy - possibly implied to be stellar-scale or greater (Based on implied luminosity, at least.) This may make sense given the amount of energy expended in going into warp (it probably should be the same amount of energy coming out, especially due to conservation laws and all that.) Further note another mention of the 3 kilometre length, as well as the fact that the shields are required to withstand the energies present in emergence from (and presumably to) Warp, also implying the shields can wiststand off some fraction of a stellar-scale power output (although the percentage absorbed is probably no more than half, sincee the energy is probably radiated omnidirectionally. Which also accounts for the detectability of ships emerging from Warp)

Assuming a material medium, a mere kiloton nuke blowing up nearby within it would completely outshine even our dear sun.

Hell, why not apply maximalism here, and consider that distant star means really far. Well, no, but let's remember that Earth is washed by 1.4 kw/m² of sunlight.
In a way or another, you don't need much energy to outshine a star, especially a distant one.

Now, the fact that the shields were nearly overloading only reveals that the Gellar fields fail to repel all of the Warp's energies.
Clearly, shields do work, they are effective to some degree. They probably reflect energy, but the process is not perfect, and some residual energy may pile up.
All in all, we do not obtain any figure unless we go for an absolutely literal interepretation of the texts.

Pages 21-22

Several hundred thousand kilometres directly behind the Macharius, the Contagion closed in on its prey. Power flowed through the Chaos vessel as its energy levels were gradually brought up, and Hendrik Morrau fought to keep the growing excitement out of his voice as he stared at the bright target blip on the surveyor screen.

"Maintain course and increase speed to mark point two. Stay in his warp trail. Bring the prow batteries and dorsal lances up to half power. Void shields to remain down until I give the order."

Morrau watched the target blip grow brighter on the screen in front of him. It was an ambush tactic he had long ago honed to perfection - using the energy trail of a craft recently emerged from the warp to mask his own approach from directly behind it. before the time the enemy even knew he was there, the Contagion would already be in position to deliver a crippling strike to its power systems.

The Contagion is several hundred thousand kilometers distant and as yet undetectable (to passive sensors at least - unknown if active sensors are being used or are used in such situations.) from directly behind the ship. Interference due to "warp trail" is implied. Curiously, this would suggest that Chaos ships (which have superior weapons range to Imperium ships) hae effective weapons ranges less than 200,000 km, although this is in fact stated later on (for Imperium ships, though.) Rather, we can infer that a Chaos vessel (and thus an Imperial vessel) cannot effectively disable or cripple a ship at 200,000 kilometers - it becomes a matter of precision and not of raw accuracy.)

Also note the implication that lance turrets and forweard guns can draw "half power" - presumably half of maximum output.

Page 22

Hito Ulanti leaned over hte console, quickly interpreting the surveyor scan symbols which flashed across the screen. "Still alot of warp energy interference, but possible target blip fifteen to twenty thousand kilometres immediately behind us and closing... Could be another ship!"

Semper didn't hesitate. "Helm control - hard to port! Engineering - open port vent valves and engage plasma reactor emergency release systems!"
...

"Target veering to port. Energy surge in his power systems," croaked the Contagion's toad-bodied helmsman.
"He's detected us!" Morrau snarled with a curse. "Full power to forward weapons. Fire when ready!"

Effective range for "disabling" fire - 15,000-20,000 kilometers. "full power" implied to be divertable to at least forward weaposn (if not others.) Also note mention of "plasma reactor emergency release systems./"

Or "full power" can mean that the weapons are to be set on their highest power capacity, not that the entire reactor's output can be diverted to the guns.

Actually, let's revisit the sequence.

Contagion's Hendrik Morrau placed his ship on a pursuit course, approaching stern, to exploit the residual energies from the Warp, masking its presence to the 3 km long Macharius.
Morrau has the weapons powered to half, and shields kept down. Speed is increased. At this point, Morrau planned to deliver a crippling blow to the Macharius' power systems.
A rather interesting fact.

While the Contagion keeps getting closer, the crew of Macharius spots a possible signal on its trail, 15,000-20,000 kilometers away.

The question then is how fast Contagion was closing in. The time needed for Ulanti to read the data, and then speak it out, then Semper to react swiftly and pass orders, that would easily take ten seconds.
The Contagion's distance from the Macharius would therefore be smaller.

Notice that without the surprise advantage, despite Semper not having Void shields up, Morrau doesn't take any chance and, although he could have dealt a critical blow to the ship, prefers to wait for weapons to come to full power and then have them fired ASAP.

This could mean that as the Macharius changed course, the Contagion wasn't guaranteed to deal a critical blow by striking with enough accuracy, and thus had to prepare for a shorter range battle, with weapons at full power.

The implication about fire range, with certainly not much residual warp energy at all (the window closed a while ago after all, matter expands fast) and the Macharius last burst of expanding plasma as a smoke screen, ends putting the effective range in the thousands of kilometers.
It doesn't take much for warships to lose a considerable amount of accuracy. Any battlefield filled with drifting debris, erupting reactors, engine flares, hull impacts and missile explosions would confuse those targeting sensors even more.

Page 23

The Macharius swung round in space, gargoyle-faced vents opening up along its port side to bleed gaseous clouds of broiling plasma out into space. The expelled energy cloud appeared as a hazy after-image on the Contagion's surveyor screens, confusing the Chaos ship's targeting systems and sending its opening weapons fire blazing harmlessly past the Imperial cruiser.

"Engage void shields!" Morrau bellowed, already knowing that the Macharius's manouvre would bring its port batteries into firing alignment before enough energy could be diverted to the Contagion's void shield generators. At this range, the damage would not be critical, but the Chaos cruiser sustained several hull-deep hits as it passed through the sights of the Macharius's weapons batteries, before its void shields finally powered up sufficiently to absorb the energy blasts and macro-shell impacts.

"venting" plasma eivdently is a valid countermeasure tactic, as it seems to disrupt the targeting of Chaos sensor systems (active or passive unknown, but possibly both.)

Void shields evidently take some non-neglible time to raise (at least to full power.)

Also note that range seems to have an effect on the damage inflicted by weapons fire (implying at least some weapons have a coherency or dissipation problem.)

Page 26 - Contagion's weapons fire "violently rocks" the Macharius.

Yes, Void shields do take some time to raise, but what is interesting is that a broadside salvo from the Macharius, and that range, would not be critical to the Contagion, and that with the ship not having shields up.
Surely, this can swing both ways: either the hull is tough, or the firepower for that salvo was not so stellar.

A broadside salvo is ought to allow more cannons to fire than any frontal assault could. Since the Contagion was still closing in, we understand that whatever the even shorter range would be, the accuracy wouldn't be so fantastic since with even more cannons firing at an unshielded ship, the 3 km long warship couldn't deal any critical damage.

Coherency or dissipation could be a problem, but the book doesn't make any difference between the damage caused by the energy weapons and the (macro) mass drivers, therefore implying that accuracy is the problem here.

Note that the Contagion's own speed would add to the kinetic energy of both types of projectiles fired by the Macharius as much as it would to its own projectiles.
Which easily explains why the Macharius was violently rocked.

Also, let's notice that the hits from the Macharius' broadside salvo --with added relative KE for the mass drivers' projectiles-- left hull deep scores only, and there's no indication that all hits landed on the adamnatium reinforced prow. The details of the Macharius' trajectory are not exactly clear either.

I'd also point out that despite having the hull cratered, there's no indication that the Contagion's trajectory was affected that much.
Several high gigatons or even teratons worth of sudden nuclear-like ejecta would surely affect said trajectory.

Based on the former extrapolation about hull vaporization, based on volumes, we may be looking at a firepower in the high kiloton/low megaton.

Combat in warp space was up-close and deadly, the range of scanners and weapons targeters so limited here that engagements took place at distances measured in hundreds rather than tens of thousands of kilometres/ The area between the two ships was saturated with energy as enough firepower to level a city was unleashed across it. Void shield strikes registered as bright blossoms on surveyor screens, and both ships shuddered under the impact of on-target hits.

Fighting in warp involves vastly shorter combat ranges, because of the sensor-distorting influences of the warp itself (hundreds of km in warp as opposed to tens of thousands of km in open space.) Also mention of weapons fire being capable of "leveling a city".

Indeed, a mention of weapons fire being capable of "leveling a city". Why no calculation here?
Well, perhaps because leveling your average city may not require that much energy after all, especially when it would be evenly distributed.
Picking a 50 km wide circular city, with the NWEC, a nuke yield of 25 megatons would provide a range of 25 km for widespread destruction by air blast, and 7700 megatons for a ground contact fireball that large, although that's totally overkill and well beyond merely leveling a city.

Also, a range of hundreds of meters would be the maximum range, like tens of thousands of kilometers is supposed to be maximum range under normal conditions, and we see that those maximum ranges are not effective ranges.

Page 50

'Vandire's teeth!" Milos Caparan cursed, triggering his starboard thrusters and jinking the two hundred tonne attack bomber out of the path of a kilometre-wide explosive staburst which filled the view out of the cockpit's main viewing port. All around the lead Starhawk, the hard vacuum of space was filled with similar explosions and energy bursts. At this range - still almost one thousand kilometres away from the target - a direct hit was almost impossible, but each energgy blast emitted a burst of widespread and high-intensity radiation lethal to both a bomber's crew and control systems, while each each exploding anti-ordnance missile warhead or mass-reactive shell threw out a hail of shrapnel that could cover a volume of space tens of kilometres across.

Several items:

1.) STarhawk bombers mass 200 tons. Do we have any exact dimensions for such fighters? might be possible to guesstimate density figures based on those. (might be useful for missile or shell masses.) The fighters are evidently also agile enough to evade a "kilometer-wide" explosive burst - implying acceleration of at least tens or hundreds of gees (change direction to go around a 1000-meter wide space, disregarding forward velocity.)

2.) Anti-ordnancec defenses acting at a range of approximately 1000 km in this instance, although whether this is a maximum range isn't exactly clear, but its unlikely to be muchy greater though, given that the accuracy implied at this range is very low (they rely on proximity effects to hit fighters.

3.) Missiles and shells seem to generate shrapnel of uknown type that travels at hypersonic speeds. more curious are the "energy bursts" of unidentified nature- they seem to "explode' and release radiation effects (like some sort of EMP or neutron bomb) It makes one wonder what kind of weapon it is (plasma perhaps.) It probably is "encased" in some physical medium, since energy weapons do ont, by definition, detonate.

Page 52

Thirty-five remaining Starhawks launched half their full payload at once from a distance of just over four hundred and eighty kilometers.

minimal effective range for bomber-launched warheads (it is implied this is "close" or "optimal" range for such weapons in preceding and following pages) is 480 kilometers. Max range unknown, although given their latter unpredictable nature, its probably not much more than two or three times that (otherwise too many missiles would be "lost" to make an effective salvo.)

Minimal effective range? That's a rather poor choice of words. 480 km? How is that supposed to make sense? We'd say maximum effective range. Not minimal, because over that distance, there would be no good hit to miss ratio. This is a maximum distance from target, not a minimum.

Now max range is probably not going to rank higher, since despite the size of the target, and its lack of defenses against such "ordnance" as you'll see, the Starhawks still had to come that close.

Also note that even at a distance of 480 km from their massive target, 35 ships remained, so this pretty much answers the question of accuracy against small crafts. Even at 480 km and closing in, a typical massive warship of this class, whatever it is, doesn't possess anything capable of taking those crafts down (from the initialy 40; 4 squadrons).

If it does possess sufficient amounts of defense systems against small targets, then the problem lies in accuracy.

It is rather interesting, because it implies that over distances ten times this (4800 km), weapons upscaled from those usually used against smaller crafts would have very hard times to hit 246 meters wide ships (based on the Marauder's wingspan, times ten).
And that's not counting sideway movement or even more complex trajectories.

The guns aboard the Bellerophon suddenly fell silent, the ship's surveyor systems requiring a scanning field free of the radioactive static of explosions and energy bursts as the information they gatheredf was fed back to the ship's logic engines. All over the ship, non-vital technical systems slowed to a crawl or temporarily blacked out entirely while the logic engines devoted the greater part of their processing capacity to calculating speeds, trajectories, and interception points as the oncoming wave of missiles rushed towards their target at a speed of tens of kilometers a second.

Indication of the processing capacilities of starship engines and the effectiveness of Imperium automated point-defense. Also mention of the velocity of fighter-launched missiles.

With the missile cluster now only a hundred kilometers and scant seconds away, the Bellerophon activated its final anti-ordnance defenses, the logic engines feeding targeting coordinates and firing solutions through to these last-ditch automated defenses. A gridwork of multilaser turrets, autocannon batteries, plasma throwers and flechette launchers studded the outer hull of the Bellerophon and these activated now, throwing out a short-lived but concentrated curtain of firepower between the vessel and the missile wave.

Description of the "last-ditch" automated defenses of the Bellerophon. Evidently they cannot be used at very long range and not in conjunction with the manned defenses due to interference. Due note though, despite only intercepting one-fifth of the missile barrage, the ship was damaged and may not be operating at full capcity.

Also note the "scant seconds" implying that the missiles may have been anywhere from 30-50 km/s in velocity (which also gives us a benchmark on the reaction time of the automated defenses at that range.)

The interception weapons started bursting at 1000 km from the Bellerophon. They were said to be either radiation weapon (akin to EM/P) and very dirty frag grenades (lots of shrapnel). The Bellerophon's cannons were still shooting, as the Starhawks fired half their missiles, without getting rid of the enemy small crafts, despite area effects between 0.5 and 5 km.

These weapons, which somehow were lethal to 200 tonnes bombers, were not good enough against much less armoured but smaller missiles. This implies an ever greater problem about accuracy, and that what doomed the bombers was that they were just too big to avoid the space bound shrapnel from the area bombs.

The ship's systems cannot compute interception trajectories and angles while all the systems are on. It literally has to nearly kill several of other systems to obtain enough computational power to read the trajectories of missiles headed straight on.

The missiles accelerated up to a speed of several tens of kilometers per second. It seems that they didn't reach any higher speed.
Their speed would obviously be greater than that of the bombers that fired them, since their speed was relative to their target.
The Bellerophon activates its defenses while the missiles are 100 km away, not before.
None of the interception weapons involve guided missiles.
The fastest weapons to reach the missiles wave would be the laser beams, but at those ranges, the speed of whatever is fired as part of that defense screen would make little difference, especially as the missiles moved towards the warship. All would be decided within less than ten seconds.

Besides, it seems Void shields weren't even up then. It seems it really takes a hell of a time to get them up, or the Bellerophon was damaged.
The gridwork reference implies more than enough guns to take down the missiles, so it's likely that the interception rate had more to do with high concentration of fire in a given limited area, than exceptional aim with fewer shots.

[Mr. Oragahn]

Page 52-53

Each Starhawk had launched half its full payload of ten plasma warhead missiles apiece. OF these, over thirty perceent had, even at such close range, malfunctioned or failed to acquire their targget. Another twenty percent would be destroyed by the Bellerophon's anti-ordnance systems. Of the hundred and sixty launched in the bomber wave, less than eighty would reach their taget- and only a fraction of these would penetrate the ancient vessel's metres-thick armoured hull and do any damage that really mattered.

Indications of the efficiencies of Imperium missile targeting, automated point defense at 100 kilometers, and hull-thickness (again.)

Speaking of inefficiencies would be more accurate, imho.
Now, if I get it right, each Starhawk (a piece) has 10 plasma missiles, and each craft fired 5 missiles. On the 35 ships surviving, that's 175 missiles. But apparently only 160 were launched. That's 15 less, implying that if we keep the ratio of five missiles per Starhawk, three Starhawks had issues to launch their own wave.

30% malfunctioned or failed to acquire the target.
On the 112 missiles that locked properly, the PDs shot 32 down. Less than 29%.
80 missiles reached their target. That's half of the initial overall wave.

Only a fraction of those could get through multi-meter thick hull plating and then deal damage. We could consider that "multi-meter" would correspond to an amount of more regular type of plating (variations of reinforced steel perhaps), different than the adamantium used on the thicker reinforced prows.

Interestingly, no Void shield intercepted them.

Now, why did not all of these 80 missiles fail to penetrate the armour?

A quote would have been better than this transcription. By penetration, should we understand that we're talking about the missiles actually ramming through the plating like bunker busters (penetrator function), or the missiles exploding on the surface and, depending on the local thickness and composition of the hull, managing to vaporize some metal, eventually reaching beyond the plating in some cases?

Let's see each option:

1. Explosive penetrator (cum warhead)
   
   Let's pick the long range Taurus ATS missile as an example. It weighs 1400 kg, with two charges of 499 kg each (nearly 1 tonne in total), for a range of +500 km.
   Pretty much all you have to care about when passing this to Warhammer 40,000's space warfare context is to consider that the charges are more powerful to a certain degree, and that the missile is now flying through space and can do so, and thus its range would also be greater, since there's no friction (it would just have to be capable of aim and trajectory correction).
   
   We were formerly told that the missiles fired by the Starhawks flew at tens of kilometers per second.
   If the missiles flew faster, the point defense cannons would have been totally useless by engaging their targets when they were only 100 km away.
   
   At 20 km/s, a Taurus ATS missile would have a KE of 2.8 e11 J and a momentum of 2.80 e7 kg.m/s.
   At 90 km/s, a Taurus ATS missile would have a KE of 5.67 e12 J and a momentum of 1.26 e8 kg.m/s.
   
   That if it were a dumb projectile and had lost no mass.
   So what we would be looking at is terajoules of kinetic energy and not that much momentum.
   You can always multiply the mass by ten or even a hundred (absurd), you'd still get terajoules, not petajoules.
   
   Also note that the Bellerophon was previously spotted on the Macharius' trail 840,000 km away. She may have had her own speed playing against herself.
2. Surface detonation warhead
   
   If all of such a missile was annihilated (ignoring loss of mass due to fuel burn), it would provide 125.83 e18 joules, or 30,073 megatons of TNT.
   In theory, if the missile was largely composed of antimatter, and designed as a shaped charge to have it react with the target's hull, you could probably increase the theoretical yield, assuming the missile's mass is largely composed of antimatter.
   If the missile's mass was about 70% of AM, then beyond the 30% needed to react with the 30% of the missile's solid casing, the remaining 40% would react with the hull (heavenly ideal case). Again, in pure theory, you could increase the yield by 1.5, more or less.
   That's of course with a perfect annihilation going on at all levels of the detonation.
   
   Now, considering the Imperium's "prowesses", it's hard to believe that if such a weapon existed, they could achieve such an efficient annihilation.
   Besides, antimatter is something the Eldar use, not the Imperium.
   
   With a fusion warhead, only the nuclear fuel would be of value, the rest of the missile's inert mass would serve no purpose in providing more energy, although it would help transform the energy into a shockwave and cloud of high velocity debris (kinetic energy).
   
   Now let's use data from this page

   Code: Select all

   Material                        Energy Density (MJ/kg)
   Wood                              10
   Ethanol                            26.8
   Coal                                32.5
   Crude oil                          41.9
   Diesel	                           45.8
   Natural Uranium                 5.7 e5
   Reactor Grade Uranium	     3.7 e6
   

   Table 1 Energy densities of various energy sources in MJ/kg and in length of time that 1 kg of each material could run a 100W load. Natural uranium has undergone no enrichment (0.7% U-235), reactor-grade uranium has 5% U-235. By the way, 1 kg of weapons grade uranium (95% U-235) could power the entire USA for 177 seconds. All numbers assume 100% thermal-to-electrical conversion.

   Based on the percentage of U-235 present in the last type of reactant, we get 3.7 e6 MJ/kg for a fuel that contains 5% of U-235. Therefore a fuel containing 95% of U-235 would theoretically provide 70.3 e6 MJ/kg. That's 70.3 terajoules per kilogram, and will translate as 70.3 petajoules per tonne (in absolutely perfect conversions).
   The highest figure would translate as 16.8 megatons.
   
   The question, then, is to know what kind of reactants are used for the missile's warheads, and we'll get a good idea of how much energy is needed to get through the multi-meter armour plating of a typical Imperium warship.
   I'll still point that a high speed missile is going to benefit from its own mass and momentum in gouging more matter out of a hull. For a same yield, a surface detonation of a nuclear warhead will gouge greater craters if the weapon's casing is thicker and heavier. Likewise, natural impactors prove better at making craters, regardless of the energy of the impact.
   Crater sizes increase the deeper the warhead is when it detonates. Even one mere meter makes a good difference.
   A missile moving at tens of kilometers per second would surely put enough stress on a single point of contact on the hull, as to enhance the fracturing energies of its warhead.

Here we go again... (sorry, I'm a bit exhausted, so I probably won't be posting as many quotes this time, at leas tnot now.)

Page 80:

Although it was not one of the front-line systems, Belatis was abundant with natural resources and supplies vital to the war effort. Adamantium ore for the diamond-hard armoured prows of the mighty warships of BAttlefleet Gothic. Unprocessed promethium fuel for the war machines of the Imperial guard,

Implies that Adamantium is a naturally occuring material, which I believe imposes limits on some of its properties (It may be an element as part of the overall composition of the ship, though, so they may simply use it with others in more exotic processes, something I may touch on later.)

It also implies the material is quite "hard", which probably makes it a good penetrator, but may also mean something about its tensile properties.

Although it is interesting that adamantium is a natural occurring ore, what is most interesting is that once it went through whatever process the Imperium relies on to turn this material into the alloy used for armoured prows, it's considered diamond-hard.

Promethium is totally natural as well, and it will be a good thing to look at Caves of Ice, since it features a harvesting station mining this element, and at some point promethium filling the tunnels of the station, around and below, and the whole place blowing up (which makes the fuel behave more like gasoline! *sigh*).

Page 96:

On cue, metres-thick blast hatches ground open along the beaks of their heavily-armored prows.

Torpedo launch hatches are "meters thick"

Simultaneous flame bursts erupted from each opening as powerful engines, assisted by the launch tubes' own gravitic motors, roared into life, firing the hundred metre-long missiles out of their silo tubes and into the vacuum of space.

Initial thrust to the torpedoes is provided by gravitic accelerators in the silos as well as the engines inside the silos as well (the silos themselves also have to be resistant to the plasma-exhaust of the motors, incidentally)

Depending on how they're shaped and how the hatches open up, they could be as thick, thicker or thinner than the prow's own plating.
Also, the missiles are now 100 meters long? Assuming no typo or missing word, we must be talking about the Bellerophon now, since the Macharius' missiles were 30 meters long, and were her most powerful weapons.

Page 99 - A Starhawk bomber has about 9 crew: a Tech-adept, 4 servitor assistants, a bombadier, a pilot, a co-pilot, and one gunner.

As a sidenote, Lexicanum (yes, that site) says that the Starhawks replaced the Marauders.
A Marauder typically carries 2 tons of ordnance, and the Starhawk is said to be better, but just as large.
The Marauder is listed as 41 tons heavy, when empty. The Starhawk's mass is around 200 tonnes (???).
Marauders are not capable of space flight. I'm a bit puzzled by the claim that the Starhawks replaced Marauders. Moving 200 tons aircrafts for assaults, especially if done through an atmosphere, sounds absurd.
An empty AWACS weighs less than 74 tonnes. Max take off weight is 147 tonnes, and that's not going to make it agile.
That 200 tonnes figure would begin to make sense if it included its maximum ordnance load and copious amounts of fuel to carry all that around.

1. - An explosion on a Chaos cruiser-carrier flagship sets off promethium fuel reserves and ammunition stockpiles inside the hangar bays, causing damage. It is curious to wonder what the Promethium is used to "fuel", and what sorts of ammunition might have been set off (it evidently is fairly volatile.)

2. Page 110 - plasma reactors are evidently quite volatile, as they will blow up when breached. This suggest they are not merely f usion in nature.

3. Page 112 - the hatch on a torpedo silo masses seventeen tons.

4. Page 115 - sustained lasfire from a Imperium interceptor vaporizes a Chaos Swiftdeath interceptor (assuming 200 tons and iron composition, this may require 1.2 TJ to accomplish. Implied duration of a "few seconds", suggesting fighter lascannon are hundreds of GW, possibly severa TJ, per shot.)

5. - The Macharius has five plasma reactors.

6. Page 125 - Boarding craft from the chaos cruiser Virulent cross the distancee between itself and the Macharius in "less than a minute". Range is probably at least a few thousand km (deefense turret range at least.) but less than 100,000 km ('tens of thosuands of kilometers.) Suggesting an upper limit of a few tens of thousands of Gees for shuttle acceleration. Lower limit would be 167 gees.)

1. What could the promethium fuel be, really? Go figure. But why use a secondary fuel at all, if something else is used for the plasma reactors?

2. Or perhaps the reactor blows up because the present plasma energy it harnesses tightly gets released all of sudden and destroys everything, including any part of the reactor that is not built to control and withstand the reaction, and that is not supposed to be exposed to such violent energies and overpressure due to quickly expanding material.
No need to crawl and beg for magical fusion.

3. Interesting, for a thickness that would logically be no greater than 9 meters tops. Lacking context as to which ship this corresponded to, we can get the width of the silo and thus its hatch.
17 tonnes is not a lot at all.
Diamond (mineral) is around 3500 kg/m³. You'd get 4.857 m³ of diamond out of those 17 tonnes.
With such a density, if the missile was 1 meter wide, the hatch, assuming it's a cylinder, would be 6.184 meters thick; or 2.749 meters thick if the missile was 1.5 meters wide.
The only way to get greater volumes would be if a prow's adamantium has a lesser density than diamond.

A potential contradiction, as Imperial Overlords later says:
"Earlier fluff on admantium says that it has to be forged inside a plasma furnace. It's also very dense." And: "Only the temperatures at the heart of a plasma reactor are high enough to form and mold adamantium, which suggests it might be an alloy. Its also why its highly resistant to beam weapons as it takes an immense amount of energy to soften or melt, let alone vaporize."

Or the hatches are made of cardboard, sticking out as sore thumbs on the adamantine surface of the prow.
Mind you, all our metals have originated from stars. Yes, plasma furnaces. Iron, for example.
The hatch gets really thin with densities around 20~22 g/cc.

This alone is rather absurd since the missiles are at least 30 meters long, sometimes 60 meters long, and even 100 meters long on some occasions. That's not counting the drawings. According to WH40K fans, scales seem to be screwed up regularly, but still.

I can only conclude that those hatches cannot refer to those covering the large silos embedded in the prows of warships, instead covering the broadside smaller silos.
Equally, it also means that there is nothing stupefying about the density of the plating elsewhere than on the reinforced prows.


4. Oh, that's the typical "fighters have terajoules of firepower" syndrome, really. A trademark.
Connors assumes:

- 200 tonnes for an Interceptor craft. Why? Even the much bulkier Marauder is only 41 tonnes heavy, and the Interceptor is ought to weight much less, since it's not a bomber.
- a literal interpretation of vaporization.
- that the Imperium Interceptor's weapons are the sole source of energy. Gauging firepower on the destruction of structures or crafts that would be filled with fuel, and even masses of weapons, is not good to obtain a sure and conservative value for firepower. It's like gauging the firepower of a matchstick based on the explosion of the gallon of powder it ignited.
Is it really that hard to understand or what?

In reality, you could obtain a figure that would be between tens of thousand times smaller, it would not surprise me in the slightest.

5. Always good for thinking about power generation.

6. Boarding operations force ships to closer ranges, in the hundreds of kilometers. Not thousands of kilometers, and certainly not tens of thousands of them.

page 171

Tanker vessels had taken aboard hundreds of thousands of tonnes of processed promethium from the planet's many fuel refineries, all of it laboriously hauled up into oribt by a fleet of grimy haulage shuttles. Cargo transports filled their cavernous holds with similar quantities of mined adamantium, ferro-titanium, trikali crystal and other materials vital for the Imperium war effort.

- relative indication of the carrying capacities and scale of the transport fleets of a single battlefleet. The implication seems to be they carted off a good portion of the industrail wealth of the planet, which would require fairly large cargo-carrying capacity.

Interesting notice of "ferro-titanium', some sot of composite or combination of tittanium and iron, although the processes by which this occurs are not specified. Also mention of trikali crystals (use unspecified" and again 'mined adamantium", hinting that the material is a "naturally-occuring" mineral/element.

All natural resources.

A week ago, a massive and ancient transporter vessel belonging to the Adeptus Mechanicus had arrived in Belatis orbit, despatched by the tech-priests of Mars to rescue not only their brethren from the condemned world, but also the technology and arcane devices held sacred by the servants of the Machine God. For days now, their agile lifter shuttles had been flitting back and forth between the vessel and the planet's surface, carrying back not merely the products of Belatis's tech-priest-maintained industrial factories but also the some of those very factories themselves, disassembled by armies of servitor work-drones. These factories and assembly lines, churning out weapons and war machines for the Imperium armies, incorporated precious and irreplacable technological knowledge held sacred by the members of the Adeptus Mechanicus. The rescued knowledge inherent in these automated factories, ,once reassembled and transplanted to the soil of a Mechanicus forgeworld, would once again be used in the service of the Machine God.

- the AM evidently make extensive use of prefabricated/modular factories and buildings, for them to be able to rapidly tear down/set-up faciliites and transport them from one planet to another. In addition, many of the factories, especially the ones incorporating rare/irreplacable technology are evidently automated (which may or may not hint at how good their industrail capability might be.)

For an automated industry that can gather masses and masses of raw materials, it doesn't seem to produce many new ships a year.

page 172 -

It was the Inviolable Retribution, a Punisher class Arbites strike cruiser, constructed in much the same way as the Adeptus Astartes variant and intended for much the same purpose: rapid response planetary assault force deployment and orbital offensive supporrtt. Ultani studied its lean, brutal lines and fearsome armaments with an admiring eye, while the naval officer in him couldn't help assessing the lawkeeper ship's likely capabilities and comparing them to those of his own vessel. The Arbites cruiser was smaller and faster than the navy warship, more heavily armoured and packed more of an offensive punch, but the Macharius was a long-range patrol vessel, designed for extended, independent operation and had a wider variety of offensive and defensive capabilities.

Page 172-173

Its main bombardment cannon armament makes it dangerous to ships and planetary targets alike, while its unorthodox main engine array suggests it that it will always have the advantage of speed and manoeuverability.

Page 173

"But I believe that the Macharius would still be the victor in any one-to-one confrontation with it." Catching Semper's expectant look, he continued: "Although a fine vessel, it's still primarily a blockade runner and rock-pounder, designed for dealing with orbital defence platforms and putting the fear of the Emperor into planet-based ground forces, not going up against a cruiser-class warship. I doubt that we could manoeuevre it into a position for a close-range torpedo strike, but its comparative lack of anti-ordnance defenses for a vessel of its size would leave it highly vulnerable to attack from our bomber squadrons. Also, our greater reactor output, ability to absorb high crew casualties and superior weapon accuracy at longer ranges would be the telling factors in any extended battle."

- Again, a comparison between the Macharius and the Arbites Strike cruiser designs, emphasizing the trade offs in capabilities the two designs incorporate. Curiously, it is implied here that torpedoes are much shorter-ranged than the weaposn batteries, whereas in prior examples (HElia IV) imply otherwise. This may suggest that there are varying kinds of torpedoes, or that torpedoes can trade off range for increased firepower, or vice versa (A close-range torpedo strike is more powerful than a longer range one.) Which would be consistent with what we know of plasma warhead torpedoes from Battlefleet gothic. It would also explain the evident variance in torpedo size, and why some torpedoes ar emuch slower than others.

of particular interest is Ulanti's mention of "reactor output" - evidently the superior firepower of the Strike cruiser is due to its heavy use of bombardment cannons (physical impactors and warheads both), rather than "directed energy" weaponry. Interestingly, this implies that the explosive payload of the magma bombs of the Strike cruiser are close in power to, but not quite equal to, the Macharius' power output. Alternately, this may also imply that the macharius' own weapons batteries cannot quite handle the full output of the reactor.

Actually, considering the locking abilities of guided ordnance, as demonstrated by the Starhawks' missiles, I believe the close range torpedo strike would allow the Macharius to increase her hitting ratio against the faster and more maneuverable Punisher-class Arbites strike cruiser.

The Inviolable Retribution (*sigh*) is badly equipped for ship-to-ship engagements, being more of both a blunt blockade running vessel and siege weapon, and obviously counting on destroyers for protection. It's like a ballistic missile weapon platform, coupled with anything useful to spam a relatively immobile target such as an orbital defense platform. It is not so capable at dealing with mobile warships, especially if they remain distant.
The Macharius has a greater reactor output, which I agree, would suggest that the Macharius would rather use beam weapon. We learn later on that they need to be recharged.
She also has a greater accuracy. This means the IR's missiles are not long ranged, and not meant to engage mobile warships and their coutner-defense systems.

Page 182

Inside the titanium shell of the passenger capsule, through one of the capsule's small, armoured-glasteel windows, Semper looke back to see the familiar hull-shape of the Macharius as it slowly receded from view

Naval shuttles evidently carry their crew in self-contained and separate personnel capsules that presumably double as escape pods. Mention of construction materials titanium and "armoured-glasteel (whatever that is.)

Titanium for the structure, and glasteel for the windows. Nothing too fancy here.

At its front the familiar armoured beak common to most Imperial cruisers, many metres thick and composed of strengthened adamantium, the toughest material known to human science. At its rear were the massive array of plasma drive engines, which, together with the generarium reactors and arcane technology of the vessel's warp drive made up over a third of the Macharius's mass.

again the prow of an Imperial cruiser is "metres thick". Also of note is the idea that Adamantium in the prow is "strengthened" in some way, either via the construction technique or the addition of other materials. The prime benefit of adamantium in the hull is evidently to give it structural durability (which makes sense with the "hardness" mentioned before.) Adamantium clearly is implied to have very good physical/structural properties, possibly superior to other elements such as iron, steel, etc.)

- the plasma engines, reactors, and warp drive comprise 1/3 of the Macharius' mass. Curiously, this seems to imply the inclusion of the fuel supply, which suggests the Macharius carries very little fuel despite its prodigious power generation capabilities.

I wonder if the hatches of torpedo-silos are made of strengthened adamantium as well. Many meters thick would be 6~9 m.
Also, I don't see the fuel tanks being listed as part of the item list that represents 1/3 of the ship's mass.

[Mr. Oragahn]

No two Imperium vessels -even those of the same class - were identical. Centuries, sometimes even millenia, of modifications and repairs using whatever local construction methods and materials were available in any of the countless different orbital repair yards and forge-world dry-docks maintained throughout the Imperium saw to that

indication of the operational lifetimes of naval vessels, hinting at their durability. Also mention that "no two vessels are alike", hinting that while they may be broadly similar, individual vessels can differ in small or significant ways from one another in some cases (which may account for evident disparities in capabilities which may arise.)

This sucks for standardization.

More than ten thousand souls, from Semper himself to the lowliest convict rating or servitor drone, lived within the armoured hull. More than ten thousand, a figure greater than the fighting complement of the largest Imperial Guard regiment, and many of that ten thousand-plus doubled as fighting troops, trained to take part in the bloody close-quarters boarding assaults that were a frequent part of space warfare. Indeed, the captain of an Imperial Navy warship commanded destructive capabilities undreamed of by any mere Imperial Guard commander. Its hull-side batteries could raze whole cities with sustained orbital bombardments. Its attack craft - it carried more than a hundred of them - could reach across star systems to strike at enemy targets, while its warp engines carried it across the vast interstellar gulfs to wherever the Emperor's enemies might be. There was even space within its cargo holds and crew compartments to carry thousands of extra troops - as much as a full Imperial Guard infantry regiment, if need be- from one war zone to another, and with greater speed
and safety than any slow and vulnerable troop transport vessel.

- The Crew of the Macharius includes officers as well as srvitor drones.

- Semper implies that no Imperial Guard regiment possesses no more than 10,000 or so fighting troops. Note that Semper is referring only to the solider complement, it does not include support elements (which may make up an additional, substantial percentage of the regiment's size.)

- "sustained orbital bombardments" capable of razing whole cities (plural.) It is also implied no Imperial Guard regiment possesses even close to this level fo firepower (at least not typicallyu.) Suggesting that high kiloton/low megaton level weaponry is non-standard/forbidden to most regiments.

- again fighter craft are implied to have multi-AU/light-hour operational ranges.

- A dictator-class cruiser can carry up to another full Imperial Guard regiment in addition to its 10,000+ crew.

An Imperial cruiser's batteries can raze entire cities through sustained orbital bombardment. Plural or not, it doesn't matter. We're lightyears away from the high gigatons or teratons, and considering that there's dozens of decks full of gun batteries and arsenals on such a ship, there's more than enough cannons to hit an entire nation in just one salvo and spread the gigatons or teratons (or more) without any form of sustained bombardment whatsoever. If this second option was valid, firepower would not be measured in its capacity to raze cities, but to slag an entire continent in one salvo.

Fighters range:
Fighter crafts may be able to get that far, but they'll run short on oxygen and fuel, and will cut out all frivolous consumptions when returning to the mothership. Quotes are provided to prove this, but Connor didn't comment on this limitation.

The Macharius has a crew of +10,000. That's not a lot for a several kilometers long starship.

Page 191

The Fury suddenly pulled up, its pilot hitting his lifter jets as he seeded the ruins below with high-explosive incendiary death released from the dual bomb racks slung beneath its wings. The Fury surged back upwards, pursued by a column of phospherant fire that expanded rapidly to devour over two square kilometres of buildins and ruijns, scouring them clean of all human life.

The "high explosive incendiary" payload of a Fury interceptor evidently creates a fireball/firestorm that consumes roughly 2 million square meters. If we assume the "fire" is literally a fire, then it might be a mile-diameter fireball (roughly 1 megaton.) If we assume extreme thermal radiation it would be roughly 1-2 kilotons or so.

(we can double check this by assuming a "lethal" temperature heating the air.. say 500 K. It takes about 1000 J/kg*K for heating air. Assuming a 50 meter height (conservative, IMHO, the quote implies the height was much higher) and 2 million square meters (density of air is ~1.2 kg/m^3) - about 60 TJ worth of energy, roughly speaking. Which should work well as an "order of magnitude" estimate, since I am being conservative, but I am also using a fairly average temperature.) assuming roughly 6,000 kg payload for the interceptor (might be higher) 6 GJ/kg.. rather high for chemical explosives I believe (which might actually hint at the figure being somewhat excessive..) It may be somethign else (plasma, melta, etc.)

Two square kilometers represents 2 million square meters. It would correspond to a circle with a radius of 798 meters.
Even if you go for the higher showing, that is, fire instead of thermal radiation, 2 sqkm represents a fireball diameter of 1596 meters (radius: 798 m). Nearly 1.4 megatons (5.86 petajoules).

We don't know if the Fury dropped only two bombs (the books mentions dual-bomb racks), or carpet-bombed a whole trench, the later being more adequate to the "column of phospherant fire", instead of a rough big sphere, if it corresponded to a description of the whole's fire blanket's shape.

Also, if you divide the area by four, that's 500,000 m², or a circular area with a radius of 400 meters.
That would be above the 300 meters blast radius claimed by the Russians for their more than 7 tonnes heavy ATBIP.
(6 charges, properly spaced, would need to affect a radius of 326 m to cover the same sum of surface area.)
A Fury can be up to 70 meters long, so assuming a good compression of the nanoreactants, we can consider that the Fury could carry a couple of such bombs.
Add a special design in order to increase the range of incendiary effects, instead of focusing on the blast capacity, by actually using a portion of that blast to propel the incendiary reactants, perhaps like in a cluster bomb, and we could theoretically come close to the effects described in the book, without looking for absurd energy densities.

The ATBIP is supposed to deliver 184.096 GJ of energy for 7.8 tons of explosives. That's 23.6 MJ/kg.
The chemicals the Imperium would use for their bombs wouldn't require to be much more explosive.

Perhaps a detail of importance; according to this source (Biology: a functional approach, by M. B. V. Roberts), 42°C is a lethal temperature for the human body. That's slightly more than 315 K. Less than the figure used by Connor.

Page 196:

After the initial shock of the attack, the wrath of the orbiting Imperial warships would be swift and summary, and the reinforced rockcrete walls of these underground silos and the hundred meters of rock and soil above their heads would offer little protection from the sustained bombardment from the gun batteries of a Capital class warship.

A capital ship's batteries (at least on sustained bombardment) can easily penetrate 100+ meters of rock By itself this is not really calcable, but it may give hints in other cases (if the surface area of the bases is known, for example, or the depth to which the crust may be turned molten in an Exterminatus - after all, if they can bury defense installations that deep, they can surely bury other facilities equally deep.)

Torpedo speeds of 10s of km (perhaps less to survive reentry) and mass drivers, a very few megatons will be more than enough to get more than a hundred meters deep crater in rock.
Beams will be focused to deliver energy into a tight spot, proving very useful to reach that deep.

More importantly, considering the number of cannons warships sport, this could be completed with only a fraction of all cannons firing one at a time.
The book mentions a sustained bombardment, and reminds us that the protection given by those hundreds of meters of rock, plus the layer of reinforced rockcrete, would be little (but not totally nonexistent).
If anything, this would prove that the warship couldn't craterize that deep in a few shots only.
Thinking of Exterminatus and crust melting in a typical SDN fashion is, once again, wishful thinking.

I don't know why the silos were built at such a shallow depth, but someone really ignored the capacity of a Capital-class warship, or thought that there were more risks of being attacked by smaller ships. But we're speaking of silos though, so this would suggest that the presence of large warships was something more than expected, but weapons would keep them at bay.

Page 204:

the volley of defence laser fire impacted against the cruiser's void shields, burning through them in seconds but expending the greater part of its energy in the effort. What was left struck the Imperial ship's underbelly, scoring through the armoured hull and into the mechanical innards of its engines' power feeds. Had the void shields been at any lower level, the lance beams would have punched through into the ship's generarium core, ,erupting amongst its volatile plasma reactors and possibly destrtoying the entire vessel in a catastrophic chain reaction.

The previous page indicates that the Graf Orlok, the vessel in question, was maintaining its shields at fifty percent power. At this setting the lance strike of the battery pierced the void shields in a matter of "seconds", but "most" of the energy was absorbed in the procecss.

This gives us an approximate duration on lance firing (as well as how long it takes to collapse shields.) It also tells us that hull armor in most places seems to be at least several times weaker than the shielding

We also learn, again, that plasma reactors are "volatile", which clearly indicates we are not dealing with mere fusion reactors (despite the reference to "plasma.".) The "chain reaction" bit is curious, as it implies the vessel's mass would be consumed in the chain reaction, implying some sort of anniliation reaction (or something more exotic.)

Huh. Why?
"Volatile" can merely be a reference to the power harnessed in the reactor, and that the most minute breach will suddenly unleash the current hot plasma.
They are, after all, harnessing excessively hot plasma. You bet that's volative! Especially if you punch through it with one of those lance weapons.

Also, this is "defence" laser fire. Should we believe it's not as powerful as, say... "assault" laser fire?
Because those "defence" lasers still caused much harm to their target.

When the recharged defence batteries strruck again less than a minute later, their deadly beams exploded harmlessly against the Lunar class cruiser's now fully-restored void shields.

A lance battery can take no longer than a minute (less, actually) to fire.. and this is an upper limit, probably generous (recharrge time does not necceearily mean that the energy is discharged at the same rate It could be much shorter.)

We also learn that "full power" shields easily stop the strike, meaning that an upper limit on shield durability would be twice the "half power" settings.

It also takes a Lunar-class cruiser less than a minute to bring its void shields from half power to full power (and presumably an equal time from zero power/standby to half power.)

A pity we don't learn exactly why the ship had shields at 50% or so (it lost the greater part of its energy in the attack), or if it was hit by other weapons before.

"Less than a minute later" suggests some duration close around 40-50 seconds. Anything closer to 30 seconds would be described as more or less than half a minute.

Elsewhere amongst the orbiting fleet, vessels fired up main drives and manouvering thrusters, seeking to escape the batteries' high orbital reach.

"high orbital reach" implies beyond geosynchronous orbit, so the ground batteries are implied to be capable of hitting targets tens of thousands of kilometers away (alot greater than the ranges implied in Battlefleet gothic.) This also means the following bombardment occurs at ranges in excess of geosynchronous orbit (36,000 km or so roughly.)

It only means that ground weapons, fixed and of unspecified size, are capable of such ranges. The very fact that the vessels didn't attempt to fire at these guns means that, unless they were shielded, the vessels of the orbiting fleet had less chances of hitting them than the grounded guns could hit the fleeing ships.

That's without knowing why the fleet came so close to these guns to begin with.

Now, if you read this post on page 2 the misc numbers thread, you'll learn that ground defense lasers are made more powerful in order to compensate scattering through the atmosphere. I point out that warships' lances will be at a disadvantage against a planet then, and may require getting closer to diminish the scattering. The defense laser silo max range out of the atmosphere is 500 miles.

Page 207

But, before the craft could recharge its weapons batteries' depleted energy reserves, an answering blast from the Charybdis's enormous starboard plasma cannon batteries tore off the Achilles's prow and destroyed its internal power relay systems.

A Sword-class frigate's laser batteries evidently run of capacitors that require an extended recharge time, though the reasons why are unknown. (It could be limitations in the power relay system that prevent it from venting the full output of the reactors to the weapons, it could be power being drawn by other systems such as engines or shields, or it cold be that the laser batteries are meant to be several times more powerful than the reactor output. Or the ship may have a substandard/damaged/ineffeicient reactor compared to other vessels of its size. As previously noted, Imperium vessels can vary even inside of a given class.)

Well, adamantium better has to be unobtainium, since the Charybdis' enormous plasma cannons can't do any better than tore off the Achilles' prow and destroy internal power relays behind.
Remember, we're supposedly speaking of ships which can sling teratons of firepower or more, but still struggle to get through the meters-thick (strengthened) adamnantium prow.
When I mean struggle, it's that such firepower, or even 10% of this firepower, doesn't immediately vaporizes a whole chunk of the massive warship, despite being hit with shields down.
Of course, with such awesome material, you wonder why they even bother mixing it up with other piss poor elements such as titanium or iron for their ground mechs.

Page 208

Those who had seen the terrifying spectacle of Titans in battle - and Ramas himself had - never forgot it, but Ramas laughed at the notion of such power being described as godlike. No, the power to traverse the warp and travel anywhere within the almost limitless bounds of the Imperium of Mankind; the power to rain fire down from the heavens on the heads of the Emperor's enemies; the power to enter battle in command of an Imperial warship, to feel blows that would crush the greatest Titan war-machine deflect harmlessly off your armoured flanks, to send back volleys of fire
that would destroy an entire Titan legion with one blast.

Ramas contemplates thre relative capabilities of an Imperial warship relative to a titan. It would follow he means a cruiser, but its also possible he means a smaller vessel like a frigate as well. In parrticular, we learn:

1. The firepower needed to destroy the most powerful Titan would deflect "harmlessly" off of warship armor. If anyone has anything that can attach a number to this, it might be useful.

2. Also take note that the context implies that Imperial armor is designed to "absorb and redirect" energy fire striking it, much like Dura-armor in Star Wars, or the Excalibur's hull in B5/Crusade.

3. A single volley from a warship can destroy an entire titan legion, however many that is.

1. Your average Titan is small in comparison to a warship, nothing surprising.
You may want to read this, from the codex that describes the Emperor-class Titans (the biggest):

Emperor class Titans tower some 25 to 40 metres tall. They mount veritable arsenals of weaponry
and are protected by up to twelve void shield generators and armour so thick it would not be out of
place on a planetary defence installation. Emperor Class Titans are amongst the largest mobile battle
units that can be deployed on a planetary surface and each one forms a vital part of the Imperium’s
strategy. Emperor class Titans employ the same technologies as Battle Titans but on a massive scale,
featuring huge plasma reactors to supply their colossal requirements.

In "Epic: Adeptus Titanicus" (EAT for short), Titans are described as "giants with skins of adamantium", powered by "old-fashioned plasma reactors", "crude and dangerous", and as they're often pushed to their limits, their own plasma reactors are managed within "tight operating margins", and the consequences is a "melt-down or runaway reaction."
This largely proves the use of a fission nuclear reactor used by a Titan. Which is confirmed in Codex Imperialis (see the thread about Last Chancers, 13th Legion).

EAT also identifies a "Burst Circle Template" (marked (B) in Weapons Table) for the tabletop game thusly: "Some weapons create a huge explosion which will affect any target within the burst radius. When such a weapon is used, a burst circle is placed with its centre at the point of aim. Any Titan whose base falls under the template (even if only partially) is affect by the attack."

As we understand, this is quite a powerful degree of devastation. It's a huge explosion by Titan standards. Still, the marker that represents the blast is a circle patch that's just as wide as the base of a Battle Titan model (at the very best, a Warlord Battle Titan), and their own base barely extends beyond their shoulder width. Even with a Titan being 40 meters high (the maximmum is 100 feet high, or 30 meters, in EAT), and assuming that the disc represents a fireball, not the greater ranged but weaker destructive effects of a high explosive, you wouldn't be looking at more than 3/4 of the Titan's height as being the fireball's width. There, at best, 75 meters.

19/20 KT nukes make fireballs with a radius between 170 and 228 meters, depending on their closeness to the ground (1, 2).
Even the overpressure values associated to a 1 KT nuke show that whatever the weapon used there, if we worked from the game rules, the yield would be definitely sub-kiloton.
It is supported by the data on this NTI page:

Fireball

The fireball from a 10-kiloton explosion at ground level would reach a radius of 200 meters, hence would have a diameter of 400 meters or about a quarter of a mile. Everything within this radius would be completely destroyed. In the case of a badly designed or badly implemented bomb that yielded only 1 kiloton, the fireball would have a diameter about 2.5 times smaller, hence about 150 meters. The surface explosion of a 100 kiloton weapon, as conceivably might be stolen from the arsenal of an advanced nuclear-weapon state, would produce a fireball 1 kilometer in diameter.

10 KT -> 400 meters wide fireball.
1 KT -> 150 meters wide fireball.

Here, even the immediate fireball size of a 1 KT nuke already is 60 meters wide. The immediate size is not the final size. For example, it gives a fireball diameter of 130 meters for a 10 KT nuke, while we know that the diameter is ought to be greater.

A plasma missile has six warheads, becoming sorts of furious blobs of plasma or some such, each represented by a blast template when it hits, so in total, a plasma missile may carry the equivalent of a few couple of kilotons, perhaps 4.5 to 6 KT tops.

All this, in the end, to point out that a warship would not need any absurd level of firepower to down a Titan, or even a group of them.
Their own reactors may very well finish them off in a spectacular way, and therefore affect nearby Titans as all ammo and fission fuel goes up (they're "vaporized" when they blow up -- a picture shows that the thick armour plates are not pulverized much though).


2. The book doesn't speak about redirecting energy, but just "sending back volleys of fire." Just like one guy would fire his shotgun at a tank, and the tank would retaliate, or two armies exchanging lead and replying to each other's volley. No need to seek a pseudo ability to soak up energy and dump that into guns in return.

Page 212

Armaments that could hurl energy hundreds of thousands of kilometers across space now turned their power on the planet's surface in an awesome display of destructive capability, gouging wounds hundreds of meters deep into the rock and soil of the hills in search of the silos, command bunkers and generator caverns buried there.

Imperial Warships (and Arbites Strike cruisers) have effective weapons ranges of "hundreds of thousands of kilometrs", although just how many is unspecified (at elast 200,000.) Note as well that The Macharius was implied to have a longer range than the Arbites Strike cruiser, and Chaos ships in general are supposed to have even greater range than that.

Also note that the bombardment is punching "hundreds of meters" into the crust of the planet, not including the volume of matter in the hills themselves. Again, this tells us the depth to which vital facilities can be buried (possibly useful in exterminatus calcs.)

That ships can hurl energy over 100,000s km doesn't tell anything about accuracy. We know that their accuracy, a passable one, is at least one order of magnitude below that, and a source puts ranges at even shorter distances. See the battle between the Macharius and the Contagion.
At best, it tells us how far whatever particles or plasma is fired can fly before it has lost coherency or heat.

As for the bombardment, how many ships are involved?
Earlier on, we knew that a sustained bombardment would get through a hundred meters of rock --without an s-- so obviously whatever is going on here is going on here is not pointing to an equally short or even shorter bombardment, but to a longer one, since now it reaches hundreds of meters deep.
Hell, a sustained kiloton bombardment would do the job fine!
Still, it's nowhere close to the über gigatons, teratons or fucktons generally presented as facts.

A gunnery officer aboard the Borodino unwittingly granted their wish, directing a mis-aimed salvo of energy blasts away from his intended target down the hillside and onto the heads of the cultists, wiping the township and all it contained of the face of the planet.

A single weapons salvo from the Borodino evidently dcimates an entire town in a single hit (implying substantial vaporization over a larrge volume in order to create a fireball/blast wave effect.)

Destroying something does certainly not require vaporization.
Besides, a mere blast effect is enough to wipe a town off the map, unless that township is made of hard materials, in which case you do need more firepower, but nothing fancier than a regular and moderate nuclear hit, eventually in the low megaton range if we're very generous.
Notice also that this was the result of a "salvo of energy blasts", which would imply less firepower per weapon.

Globally, knowing what class of ship the Borodino is would have been helpful.
A RPG supplement by a certain T. Driscole identifies the Borodino as a Lunar-class cruiser.

Page 213

Seconds later, the roof of the chamber caved in. A split-second after that, the entire bunker complex was obliterated, vaporised, in the all-consuming furnace of white-hot plasma .

A single plasma burst evidently "vaporized" the entire command bunker. This may imply that the bombardment created a hundred+ meter deep/wide hole.

If we assume the blast was 100 meters deep, and the complex hundreds of meters in diameter, then the blst would probably have been in the hundreds of megatons range (bearing in mind also that while we dont know the duration/number of shots, this was also clearly a reduced-firepower incident: They don't want to render the planet uninhabitable after all.

Even a consequent multi-gigaton shot wouldn't render the planet uninhabitable, for you need to spread that energy more or less evenly to start menacing the biosphere. So the dialed down claim is pretty much moot. Nice try, though.

Let's also remember that this is the "formidable" firepower.
By the way, why assume a single blast? Isn't it a sustained bombardment? Could have there been more ships?
A single main warship's broadside counts numerous cannons, stacked over several dozens of decks.
Why, in such conditions, should we believe that one single weapon, one single projectile, did all that damage?

PAge 215 - "seconds" woth of laser cannon fire from 3 Fury interceptors can shatter/melt the armor of a surface-launched torpedo.

Assuming 10 seconds, and that the torpedo's armor masses as much as a fury (and half the armor is melted off), each Fury is delivering 4 GW worth of sustained firepower. Tyhis can be considered an approximation, or conservative, of course.

Or completely over the top, of course, since we don't really have any information about the area that was hit, what the plating thickness was, or what the plating was made of.
This is also all going by a transcript instead of a direct quote. Of course.

[Jedi Master Spock]

Well, let's say, for the moment, that the missiles used are 1,000 kg, 14 km/s, and has a 0.5 m diameter. I'd call those a reasonable estimate from what I've read.

Then it has a KE of ~100 gigajoules, neatly, about 100 times as much as a BT gauss rifle, with 16 times the area of impact (remember, I estimated the BT gauss rifle to penetrate around 10m RHAe) - and therefore, off the back of the envelope, based on KE density, with adamantium running a bit over 5x as tough as steel, that 12m of adamantium would be enough to stop it.

The missile is probably not quite as efficient a kinetic penetrator as a solid projectile (and it's probably in the process of exploding as it squishes into the armor) and we're not going to have great impact angles, so I can believe several meters of adamantium armor giving this projectile a hard time.

Actually, as far as hull strength goes vs KE penetrators, that's pretty good - with those particular parameters, that would be ~5x10^11 J/m^2. That's an order of magnitude higher than the kinetic energy densities ISDs can resist/are vulnerable to. It's in the same range as the kinetic energy density you get for a Jem'Hadar bugship using either Wong or G2k's figures if you use a 28.6 m^2 nose. Can't remember where I came up with the estimate of a 28.6m^2 impactor nose (which I use on the main site article), but it sounds reasonable enough.

So we're really talking about missiles that would likely penetrate a GCS hull or an ISD hull, if the shields were down. Tritanium may be twice as strong as adamantium (~10x steel vs ~5x steel for physical impact), but WH40k hulls are likely more than twice as thick. Factor in the large amounts of wasted space, nonfunctional space, and inefficient construction, and you have a ship that can take quite large amounts of raw physical punishment compared to its typical rivals in other franchises.

[Mr. Oragahn]

Adamantium is mainly used on those reinforced ramming prows as I get it. Other parts of the ship aren't that armoured, and considering that adamantium is specified for those "beaks", it seems logical that other parts use a more mundane mix of steel, ceramite and armaplast. Some areas are decorated with fancy ornaments, structures and gothic pieces, but not covered with simple thick plating.
Although plating would be present underneath those structural details, it's not present in lieu of those details.
So only the ramming prows appear considerably well armoured, the rest less.
In case of the missiles hitting the ship, they hit everywhere. It would be rather counter productive to have them aimed on the reinforced adamantium prows.

[Jedi Master Spock]

Adamantium is mainly used on those reinforced ramming prows as I get it. Other parts of the ship aren't that armoured, and considering that adamantium is specified for those "beaks", it seems logical that other parts use a more mundane mix of steel, ceramite and armaplast. Some areas are decorated with fancy ornaments, structures and gothic pieces, but not covered with simple thick plating.
Although plating would be present underneath those structural details, it's not present in lieu of those details.
So only the ramming prows appear considerably well armoured, the rest less.
In case of the missiles hitting the ship, they hit everywhere. It would be rather counter productive to have them aimed on the reinforced adamantium prows.

The wikia wiki has some fairly specific figures regarding hull thickness. It claims most hulls are armored with adamantium, and that the armored prow thickness runs up into the hundreds of meters, while "normal" thicknesses total in the dozens of meters for battleships between three different hull layers, to about a foot for escorts - which sounds like it actually comes from some fluff quotation. Note that even the "normal" armor plating is probably not evenly distributed and doesn't have 100% coverage - there are gun ports, air locks, etc. It's like a mid-20th century warship - all kinds of bits and pieces, most with armor either on them or underneath them.

If the thicknesses on the wiki are accurate - and I didn't find any quotations to back it up on a quick flip-through of the BFG rules, so they might not be - then while escorts won't have hull armor that exceeds that of a GCS, cruisers and battleships would, at least for the purpose of KE. Trek ships simply don't have that much raw material. The original million-ton, 60,000 m^2 surface CCS, if it was a third armor by mass, and tritanium massed 5 g/cc, would have an average of one meter of tritanium in its hull. Under the same assumptions, an Intrepid class would have ~45cm of hull armor.

In general, from what we see onscreen, it looks like Federation ships generally have 10-100 cm thicknesses on the outer hull, so my hand-waving probably isn't too far off. True, we don't know very much about Trek hull materials, but it's generally likely that if we split the unknowns (10-100x steel, 10-100 cm thickness) we're looking at Trek ships generally having roughly the equivalent of 10 meters of steel armor. That's our best guess, and I'm saying that won't measure up to what an Imperium cruiser or battleship carries on a "typical" armored hull section - that's equivalent to only 2m of adamantium, and would be unlikely to stop a >10 km/sec missile.

Sure, Imperium ships are terribly inaccurate compared to Trek ships, they have shorter effective range against Federation ships than vice versa, they don't actually seem to carry horribly overwhelming firepower when we look at the totality of the evidence, they wallow like stuck pigs, et cetera. However, they are large, have heavy armor, and take a lot of blowing up.

[Mr. Oragahn]

All I read thus far about plating thickness is countless "metres-thick" references, equally used for the reinforced prow, torpedo hatches and other hull sections.
Never "dozens" or even "hundreds of metres thick". I suppose you could say that metres-thick can be more than 9 meters, but then anything can be many meters thick, from the moment it's thicker than two meters.
Titans are said to have metres-thick plating, and they certainly don't have tens of meters of plating on them, not even on the shoulder pads and thick dorsal carapace.
Not even the 40 meters high ones (Imperator/Warmonger Emperor-class titans, although they can be 25 meters "small"). Yet, an Emperor-class Titan has, along its 12 Void shield generators, an amount of "armour so thick it would not be out of place on a planetary defence installation." Installations which are meant to fend off warships. If those ground systems don't get that much artificial plating, why would warships?

Obtaining clear proof of "dozens of meters" thicknesses would be rather interesting.
I'd also question the reality of the presence of so many heavily armoured regions, considering the number of illustrations I've seen depicting large hallways running down the ships' length, only separated from space by windows.

Now, I know there's a reference somewhere, probably in one of those threads I recently posted here, which mentions a particularly thick window of glassteel, hit by a weapon, and cracks, without breaking. It's in one of the threads I posted I think, I'll try to dig it up.

In my opinion, no designer would bother putting hundreds of meters of adamantium plating on the reinforced beaks, due to the important strain on the structure, if it wasn't used rather regularly. However, for this to be possible, targeted warships would need to have the agility of a fat beached whale. With high acceleration capacities, they'd easily evade any collision course, with linear thrust only, way too fast for any approaching warship to turn in time.

Also, using picture of a top-down view of various game models, including an Imperial warship, assuming it's 2 km long, its reinforced prow is aroud 184.5 meters wide. In which case, if we're still speaking of hull plating, and not just a big slab of adamantium, then the plating cannot be hundreds of meters thick.
Would the ship be 4 km long, the same ram-prow would be 369 meters wide: basically, not large enough yet to have +200 meters of adamantium on either side.

[Jedi Master Spock]

All I read thus far about plating thickness is countless "metres-thick" references, equally used for the reinforced prow, torpedo hatches and other hull sections.
Never "dozens" or even "hundreds of metres thick". I suppose you could say that metres-thick can be more than 9 meters, but then anything can be many meters thick, from the moment it's thicker than two meters.

And equivalent to 2m of adamantium is my best guess for where Federation hulls fall - and 2m is fairly thin to be stopping >10 km/s projectiles.

What may be the case is that there's an outer hull and an inner hull. The wiki claims battleships have three hull layers - and the equivalent of dozens of meters between those layers. Say, several layers, each around 10m with some then walls/bulkheads between each layer. Still, the variance cited by the wiki is a lot - on the order of 100x the thickness for a ship on the order of 10x as long - and I think it reflects different armor thicknesses on different parts of ships.

That would be for the big 5-8 km ships. The one in this novel is, I think, 2.5 km long. I don't think it's completely out of place to have "meters thick" mean quite possibly close to 10m total effective thickness of adamantium in some places for something that size.

[Mr. Oragahn]

Possible, but there's that calc I did about a 17 tonnes torpedo hatch which, if it were supposed to be as thick as the armour surrounding it, would make the armour much less than ten meters thick. Of course, it's just a hatch, and it's unclear how it is embedded into the hull when at rest. The vast bulk of the armour plating could still be much thicker.

Now, it goes without saying that from what I've read of weapon hits and their effects, I never get the impression that there are several space layers of armour, as space by rooms and corridors and other pipes and so on.
Descriptions of effects tell stories of impacts against ships, with weapons failing to penetrate the hull, then sometimes plowing through it, but not telling anything about getting through the first layer, then going through rooms and other weak stuff, then another layer, then again another pack of rooms and hallways and so on, and then again a third layer, and then hitting something sensible.
The impression it gives is that the authors, in general, didn't really think of the ship as having pancaked layers of armour with space and stuff in between, or even treated the possible several layers as independant ones. Globally, the impression is that all the layers are foud on the outermost strata.

I also notice that the wikia article speaks of an "armoured prow, which is massively reinforced and can be hundreds of metres thick on the largest ships as it is also used as a ram prow." Which may not necessarily mean the plating thickness, but this section's overall thickness, although I reckon that in this case, it would be a weird choice of words, when most people would just say it's x meters wide, y meters long or z meters high.

The wikia article absolutely fails to indicate its sources.
The Imperial Navy article on Lexicanum, nearly a copycat version of the one you linked to, but trimmed down and without chapters about weapons and defenses, sources this page. It doesn't mean the evidence of the special plate-layering is to be found there, but there's dozens upon dozens of pages of rules and background data.

[Jedi Master Spock]

Possible, but there's that calc I did about a 17 tonnes torpedo hatch which, if it were supposed to be as thick as the armour surrounding it, would make the armour much less than ten meters thick. Of course, it's just a hatch, and it's unclear how it is embedded into the hull when at rest. The vast bulk of the armour plating could still be much thicker.

Definitely true. I'm going to be a little more precise. If a torpedo is 60m, the hatch should be at least 3m wide. That would be 2.4 tons per square meter, and I'm pretty sure that would put the hatch about a half meter thick.

Now, it goes without saying that from what I've read of weapon hits and their effects, I never get the impression that there are several space layers of armour, as space by rooms and corridors and other pipes and so on.
Descriptions of effects tell stories of impacts against ships, with weapons failing to penetrate the hull, then sometimes plowing through it, but not telling anything about getting through the first layer, then going through rooms and other weak stuff, then another layer, then again another pack of rooms and hallways and so on, and then again a third layer, and then hitting something sensible.
The impression it gives is that the authors, in general, didn't really think of the ship as having pancaked layers of armour with space and stuff in between, or even treated the possible several layers as independant ones. Globally, the impression is that all the layers are foud on the outermost strata.

Well, if it's not a large spacing, it wouldn't really be worth talking about much. And it is very true that impact angle and projectile design have a big impact on penetration depth, but even so, something stopping >10 km/s bombs/missiles should be pretty tough.

When I think to myself about the thickness, I try to put it into perspective. If this were an 800 pixel long picture of a WH40k ship, such as you might have as part of a desktop background, a single pixel would translate to 3-4m on a cruiser, 6-10m on a battleship, 1-2m on an escort, and would be barely noticeable on the scale of a model.

But let me run some really rough figures here. Let's say... S = L^2 - wrapping the thing in a square sheet its own size, and that adamantium is 5 g/cc. The armor has some gaps, especially over "unimportant" areas. So for a 5 km battleship, you get 8 meters of average armor thickness for each billion tons you spend. The wiki - which, you're right, is copied word-for-word on or from other wikis - is at least internally consistent on that account, because it says battleships displace billions of tons. I wouldn't put it past the Imperium to spend a significant percentage of mass on hull armor.

I think we're going to find a bit of inconsistency there between the kinetic energy of the missiles and the way boarding torpedoes can work, but 10 km/sec is a pretty fast kinetic projectile, and these bombers do carry at least several tons of ordnance.

I also notice that the wikia article speaks of an "armoured prow, which is massively reinforced and can be hundreds of metres thick on the largest ships as it is also used as a ram prow." Which may not necessarily mean the plating thickness, but this section's overall thickness, although I reckon that in this case, it would be a weird choice of words, when most people would just say it's x meters wide, y meters long or z meters high.

The wikia article absolutely fails to indicate its sources.
The Imperial Navy article on Lexicanum, nearly a copycat version of the one you linked to, but trimmed down and without chapters about weapons and defenses, sources this page. It doesn't mean the evidence of the special plate-layering is to be found there, but there's dozens upon dozens of pages of rules and background data.

I have the BFG PDFs that you can download from there. I have not yet found anything to corroborate the wiki's figures in them.

[Mr. Oragahn]

Now, it goes without saying that from what I've read of weapon hits and their effects, I never get the impression that there are several space layers of armour, as space by rooms and corridors and other pipes and so on.
Descriptions of effects tell stories of impacts against ships, with weapons failing to penetrate the hull, then sometimes plowing through it, but not telling anything about getting through the first layer, then going through rooms and other weak stuff, then another layer, then again another pack of rooms and hallways and so on, and then again a third layer, and then hitting something sensible.
The impression it gives is that the authors, in general, didn't really think of the ship as having pancaked layers of armour with space and stuff in between, or even treated the possible several layers as independant ones. Globally, the impression is that all the layers are foud on the outermost strata.

Well, if it's not a large spacing, it wouldn't really be worth talking about much. And it is very true that impact angle and projectile design have a big impact on penetration depth, but even so, something stopping >10 km/s bombs/missiles should be pretty tough.

When I think to myself about the thickness, I try to put it into perspective. If this were an 800 pixel long picture of a WH40k ship, such as you might have as part of a desktop background, a single pixel would translate to 3-4m on a cruiser, 6-10m on a battleship, 1-2m on an escort, and would be barely noticeable on the scale of a model.

But let me run some really rough figures here. Let's say... S = L^2 - wrapping the thing in a square sheet its own size, and that adamantium is 5 g/cc. The armor has some gaps, especially over "unimportant" areas. So for a 5 km battleship, you get 8 meters of average armor thickness for each billion tons you spend. The wiki - which, you're right, is copied word-for-word on or from other wikis - is at least internally consistent on that account, because it says battleships displace billions of tons. I wouldn't put it past the Imperium to spend a significant percentage of mass on hull armor.

I think we're going to find a bit of inconsistency there between the kinetic energy of the missiles and the way boarding torpedoes can work, but 10 km/sec is a pretty fast kinetic projectile, and these bombers do carry at least several tons of ordnance.

I also notice that the wikia article speaks of an "armoured prow, which is massively reinforced and can be hundreds of metres thick on the largest ships as it is also used as a ram prow." Which may not necessarily mean the plating thickness, but this section's overall thickness, although I reckon that in this case, it would be a weird choice of words, when most people would just say it's x meters wide, y meters long or z meters high.

The wikia article absolutely fails to indicate its sources.
The Imperial Navy article on Lexicanum, nearly a copycat version of the one you linked to, but trimmed down and without chapters about weapons and defenses, sources this page. It doesn't mean the evidence of the special plate-layering is to be found there, but there's dozens upon dozens of pages of rules and background data.

I have the BFG PDFs that you can download from there. I have not yet found anything to corroborate the wiki's figures in them.

Well, here's a batch of excerpts I gathered from my Googlean Quest.

http://www.rand.org/pubs/monograph_reports/MR1209/ > http://www.rand.org/pubs/monograph_repo ... 9.appb.pdf

If the projectile has a similar length and diameter, like our tungsten
spheres, cavitation dominates the effects. The size of the crater resulting
from a short, squat projectile depends on the projectile’s total
kinetic energy and the target’s hardness. If the angle of impact produces
a component of the velocity vector into the target that is
greater than the speed of sound in the target material, the crater will
be hemispherical. For more glancing impacts, the crater will elongate,
becoming more elliptical. Either way, the damage proceeds
downward and outward from the point of impact. In contrast, the
damage for an ordinary explosive detonated at the same point would
proceed outward in all directions.

If the projectile is long and rodlike, on the other hand, the steadystate
phase dominates the effects. The crater is more cylindrical and
its depth is proportional to the square root of the ratio of projectile
density over target density. If the kinetic-energy weapon must penetrate
shielding, e.g., a ship’s hull or a bunker, the depth to be penetrated
determines the minimum projectile length, depending on the
density of the shielding material. For example, a 1-m-long tungsten
hypervelocity penetrator should be able to penetrate about 1.5 m of
steel, almost 3 m of clay or stone, and 1 m of uranium. What penetrates
through that depth (or less) of target will be a very hot mixture
of target and penetrator material and any remaining penetrator
length. The damage is done almost entirely in the direction of the
impact, as with a shaped charge explosive, except for damage caused
by secondary fires or explosions ignited by the impact.

Abstract
A parameter study was performed to examine the (shock) damage obtained with long-rod and spherical mono-material penetrators impacting two varieties of limestone. In all cases, the impacts were assumed to be normal to the plane of the rock and at zero angle of attack (in the case of the rods). Impact velocities ranged to 15 km/s but most calculations were performed at 4 and 6 km/s and the penetrator mass was fixed at 1000 kg. For unlined underground structures, incipient damage was defined to occur when the peak stress, σpk, exceeds 1 kb (100 MPa) and the applied impulse per unit area, Ipk, exceeds 1 ktap (1 kb μs). Severe damage was assumed to occur when σpk exceeds 1 kb and Ipk exceeds 1000 ktaps. Using the latter definition it was found that severe damage in hard, non-porous limestone with spherical impactors extended to a depth of 9 m on-axis for an impact velocity of 4 km/s and 12 m at 6 km/s. Cylinders with length-to-diameter (L/D) ratio of 8.75 achieved depth to severe damage of 23 and 40 m, respectively, under the same conditions. For a limestone medium with 2% initial gas porosity, the latter numbers were reduced to 12 and 18 m.

Source

Limestone, sendimentary rock, with varying porosities, primarily composed of calcium carbonate, with such densities as:

2.71 g/cm³ (calcite)
2.83 g/cm³ (aragonite)

[Jedi Master Spock]

Well! And here I'd been presuming that as you went up, the dominant model was KE density. I should remember to always present the full range of penetration models, since we really know next to nothing about the materials involved.

The thing here is that the tungsten impactors being modeled in that paper is that they're being modeled as having a lower velocity on target impact - about 3.7 km/s, if I don't miss my guess, based on the ballistic coefficient assigned to the "representative" impactor - than the missile we're talking about. In general, a 1m roughly cylindrical column of tungsten delivers 13.7 MJ/cm^2 at 3.7 km/s; my rough guess of what the missile might look like is delivering 50 MJ/cm^2. We'd expect that to generally penetrate 2-4 times as far, in general principle, and probably on the lower side of that - a mere meter of adamantium would stand a fair chance of stopping it.

I may have been overestimating the effective penetration of the really high velocity impactors by simply extrapolating on "soft" armor dynamics from tank rounds, when the dynamic is not extending linearly on kinetic energy density. I'll look a little more at that later - it may also be that the standards for "penetration" are not quite the same in that paper and in the tank armor literature, but regardless, it deserves a closer look. I suppose I've been a little sloppy.

EDIT: Hm, I see, yes, the models are talking about the penetration depth equal to length is a more or less limiting case as velocity becomes very high. Excess energy is presumed to go into vaporization, cratering, etc. Interesting. I should re-do some of my estimates. The kinetic energy density and momentum density are still what you should pay attention to, though, in comparing projectiles.

[Mr. Oragahn]

I'm not sure missiles, being the cavities filled with fuel and perhaps explosives that they are, would bring a lot to the table in the bulk density ratio.

In all logic, I'd make the tip of the missile very compact, with the chamber for the fuel and other stuff as far as possible as possible in the back.

I wish it was possible to obtain more data on the size of the rods used for the tests, reported in the "Simulation of hypervelocity penetration in limestone" document.

A similar document's excerpt offers the following snipet of information:

Inert dense metal penetrators having a mass and geometry capable of missile delivery offer significant potential for countering underground facilities at depths of tens of meters in hard rock. The proliferation of such facilities among countries whose support for terrorism and potential possession of Weapons of Mass Destruction (WMD) constitutes threats to world peace and U.S. Security. The Defense Threat Reduction Agency (DTRA), in cooperation with the U.S. Army Corps of Engineers, the Department of Energy National Laboratories and private sector R&D firms have pursued an aggressive research effort to explore the attributes of high velocity impact penetrators for countering such facilities. The penetration of crustal rocks with metal rods (such as tungsten or steel alloys) at high velocities involves complex wave propagation phenomena within the rod and inelastic response of both the penetrator and target material. In this paper we examine the sensitivity of penetration depth (for a fixed tungsten alloy mass impacting a limestone target) to impactor velocity, strength and geometry. Analyses are based upon a matrix of first principle finite difference calculations using the Sandia CTH (release 7.1) Shock Physics Code. Results indicate that impact velocity, penetrator yield strength and target yield strength strongly influence the penetration depth. Maximum penetration depth is achieved by a delicate trade off between penetrator kinetic energy and penetrator inelastic deformation (erosion). Numerical analyses for the parameter variations exercised in this study (impact velocities 1-3.5 km/s and penetrator yield strengths of 1-4 GPa) produced penetration depths of a tungsten alloy rod (length 200 cm, diameter 20 cm) which varied from 5.1 m to 28 m in a homogeneous limestone target.

[Jedi Master Spock]

I'm not sure missiles, being the cavities filled with fuel and perhaps explosives that they are, would bring a lot to the table in the bulk density ratio.

Density, not really, but length, yes. It's a fair trade-off, for the most part - actually, length is more valuable in the limiting-case model mentioned (root density ratios times length), but I've also read that the efficiency goes down some as the L/D ratio goes up.

I wasn't kidding when I said momentum and KE density are really our best indicators of penetration on the general scale. They don't scale strictly linearly across different impact speeds, but they are the main indicators.

The thing is, though, regardless of the missiles' density, they're providing a remarkable hit of kinetic energy if they're moving that speed. Incidentally, I was just checking the probable dimensions of the BT gauss rifle shell, and concluded that if it's mainly nickel and iron, and is ~10 cm in diameter like the references seem to say, then it should actually be a 1-2m long-rod type projectile with a L/D ratio greater than 10, rather than the "musket ball" described in the literature. Either it's some unusually dense metal, or it's a much more conventionally shaped KE penetrator than previously assumed.

[Mr. Oragahn]

The ratio diameter/length only seems relevant as long as we're talking about a cylindrical block of matter. You'd probably lose a small bit of length if you were to compress the missile along its length axis, as to get the equivalent of a solid lump of matter with absolutely no fancy gizmo required for sensors, guidance, the fuse, the structure allowing a proper detonation of the missiles and the fuel tank.