Some questions of 40K

[Falkenhayn]

- 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.)

Semper is mistaken about the size of an Imperial Guard regiment. There is no regular size for them, the number of men in a regiment can vary dramatically depending on what planet it is raised from and what purpose it will serve. Unlike regiments in the real Earth, which are components of armies, regiments in the Imperium are armies in their own right.

Consider the following from Eisenhorn: Xenos

"By order of the Lord Militant Commander, seven hundred and fifty thousand men are being inducted into the Imperial Guard to form the 50th Gudrunite Rifles."

So that's 750,000 men making up a regiment raised from a civilized planet. Gudrun's population is never mentioned, but based on the description of the planet I'd say 4-12 thousand millions.

We have to take into account the anything-but-uniform nature of the Imperium. IIRC Cadian regiments top out at 8,000 men, and the Tanith levied regiments of 4,000. Gudrun, again IIRC, is levying men, ostensibly, for the suppport, consolidation or reinforcement needs of the Sabbat Worlds Crusade. It may well be the case that a Gothic sector ordinance puts Guard regiments at 8-10,000 for ease of transport by the Navy, though that act itself is in violation of about a million post GC mandates.

[GeneralTacticus]

Minor nitpick: it was for the Ophelian subsector crusade. The Sabbat Worlds Crusade was another three or four centuries off and in a different part of the galaxy.

[Adrian Laguna]

We have to take into account the anything-but-uniform nature of the Imperium. IIRC Cadian regiments top out at 8,000 men, and the Tanith levied regiments of 4,000. Gudrun, again IIRC, is levying men, ostensibly, for the support, consolidation or reinforcement needs of the Sabbat Worlds Crusade. It may well be the case that a Gothic sector ordinance puts Guard regiments at 8-10,000 for ease of transport by the Navy, though that act itself is in violation of about a million post GC mandates.

It doesn't say what, specifically, the regiment is going to do, but they are apparently mostly a regiment of conscripted foot soldiers. This means either front-line cannon fodder, or functioning as rear-guards or garrisons.

I think it does make sense that in the Gothic sector regiments are of specific size. As for violating other mandates, the Imperium is highly decentralized by necessity and there must be an insane number of contradicting laws, regulations, and ordnances throughout it. Hell, they even have surprising degrees of religious freedom. Any belief that can be reasonably tied back to the God-Emperor has a good chance of being sanctioned by the Ecclesiarchy. In Hubris, for example, they worship the Sun, specifically, "the Sun as Emperor".

[Falkenhayn]

Minor nitpick: it was for the Ophelian subsector crusade. The Sabbat Worlds Crusade was another three or four centuries off and in a different part of the galaxy.

Thanks.

[Connor MacLeod]

Sorry for the delay, I took a break frfom all this.

Page 222:

The first missile hit the palace at tremendous speed, passing harmlessly through the defence shield as it was designed to, just as if the energy screen were the void shields of a target space vessel. By chance, it crashed through the roof dome of the governor-regent's throne room, completely obliterating the chamber. Designed to penetrate through adamantium hulls and thick bulkhead walls, the densely-armoured warhead cut through the comparatively light stonework structure of the palace, ploughing on down through the building, before finally exploding in the kitchens and stockrooms levels, some twelve storeys below.

- the palace shields evidently ARE quite similar to void shields, and torpedoes are "designed" to penetrate them "harmlessly" (implying little or no interaction, ie some sort of shield-penetrating countermeasure.) It is also implied that the torpedoes rely on the momentum of the high-density warhead to penetrate through hulls before detonating (Implying that torpedoes have a "kinetic impactor" element to the damage they inflict in addition to the warhead element.

Page 224:

A las-blast felled the armsman beside Semper. The captain grabbed the man as he fell, intending to drag him into the bay, but then found himself staring into the excavated crater of the man's skull, where the las-shot had blown half his head away.

Description of the effects of a las blast on the human head. "half his head" blown away implies that half the mass was removed. According to here the average mass of a human head is between 4-5 kg on average.
"half" this would imply 2-3 kg was affected.

Damage mechaism isn't precisely known, except that "blowing" half his head away implies an explosive effect (consistent with what is known regarding the damage mechanism of las weaponry.) Purely mechanical damage (shock wave from explosive vaporization of a tiny portion of the water content in the body) could cause such damage with very little energy input (several times the kinetic energy of a 7.62 rifle bullet) but would have little to no thermal effects (IE no cauterization.) and lasguns DO have a singificant thermal effect.

If we assume that enough energy was input to raise the temperature of the body to the boiling point (from a base temp of around 309 K to 373.15 K), which should suffice for inflicting severe (third degree) burns on human flesh, at least 536 kilojoules must be injected to boil the water content in the body (70%, or about 2 kg if we assume a 3 amount affected.) - 225 joules may be required to raise the temperature of the other kg to the boiling point.. thus hinting at firepower somwehre between 500-750 kilojoules minimum for a single las-blast of unknown type (probably a las-gun, but possibly a las pistol.)

If significant cauterization occurs (possible, due to other examples) or substantial vaporization of the water content occured, then the calc could be increased by a further 4.8-5 megajoules (for vaporization of the water content), and possibly by several more megajoules depending on the temperature for cauterization (at 1000K, for example, near-cremation temperature, the energy for 1 kg of flesh would be ~2.45 MJ).

He fired, seeing his target disappear from view in a burst of exploded flesh and shattered stonework.

Effect of a shotcannon on human body, evidently quite similar in effect to bolters.


Page 225-226: three other torpedoes detonate in the aforementioned palace. This is rather peculiar, because these are supposedly "anti-ship" torpedoes, yet the detonations are definitely sub-gigaton, and possibly sub-megaton in yield. Perhaps the warheads were faulty, or shaped charge, or they weren't "plasma" warheads per se?


Page 231

This far out-system, it would take many light-minutes for the energy of the object's unique and massive warp-burst signature to register on the surveyor screens of the Imperial vessels gathered further in-system, but already the strong but localized disturbances in the currents of the warp caused by the object's arrival would have been sensed by every psychically-sensitive being in the Belatis system.

It takes "light minutes" (minutes?) for the signature of the Planet Killer's presence to be detected by surveyors. This also confirms that warp emergences do appear to have a signfiicant radiation/electromangetic element to them.


Page 233

The Planet Killer had arrived in the Belatis system, and the time to the planet's imminent destruction could be measured not in weeks or days but now in mere hours.

According to this, it could take hours (less than a day) for the Planet Killer to reach belatis. As previously noted, the Belatis system is 1/3 the size of the Sol system, and we know the Planet Killer emerged on the fringes of the system. In other words, it takes the Planet killer at least 2 but no more than 23 hours to cross approximately 14 AU. If 23 hours, the average acceleration is at least 60 gees. If 2 hours, the average acceleration is aroun 8000 gees.



Page 238

All Imperial communications had been disrupted since the arrival of the Planet Killer in the Belatis system - just one of the Chaos weapon's many strange and unsettling technological properties which the Imperium's tech-priests had so far been unable to explain

The planet killer is capable of disrupting Imperium communications frfom light-hours out, although not enough to prevent close-range transmissions. (Although when it gets closer, it can block out planet-wide communications.)

Page 239

"They had less than a day to live, if the estimates of the astrogation lexmechanics were correct. For, moving through the outer system towards Belatis was the Planet Killer, closing slowly but inexorably on its target. Long-range surveyor scans showed that most of its escort fleet ere still with it, moving slowly in-system at the same ponderous speed a the gargantuan vessel itself, but other vessels were speeding ahead of the main fleet, rushing to secure the target world in advance of the Planet Killer's arrival.

- Again, confirming that it takes "less than a day" for the Planet Killer to reach Belatis. Also notes that this rate of approach is considered slow compared to other naval vessels, even battleships, other ships (presumably cruisers and escrots) approached the planet much more quickly.

At its present speed - agonisingly slow by the standards of a warship vessel, but as fast as many of the aged and barely spaceworthy transports could manage - the convoy should be safely out of reach b ythe time the Planet Killer arrived in-system, but Ultanti still knew that it would be a long and nerve-wracking run towards the new jump point at the system's far fringes.

Again, implies that other ships are considerably faster than the Planet Killer, although the aging transports are implied to be as fast/no faster.

Page 242 - mention of uninhabited, unmapped sections of ships, where stoaways or illicit goings-on may occur, hinting at the scale of such vessels.

Page 243

The big Imperial commissar saw the corruption was eating away into the very stuff of the ship, opening up brittle, flaking wounds in plasma-forged alloys made to last for centuries.

Mention of the "plasma-forged" alloys discussed earlier, although not specifically attributed to adanantium, nor is the exact temperature of the plasmas implied. It does suggest extreme thermal resilience, though.

Also specifies that 40K ships are deliberately designed to last for centuries, giving us an indirect idea of their durability. (I was already aware that some ships HAVE lasted for hundreds of years, if not thousands, By the way..)

Page 244

Kyogen tore a shotcannon from the grasp of a terrified armsman, turning it on the creature and firing it on full auto-spread, mercifully blowing apart the screaming preacher. The creature staggered under the impact of the explosive shotcannon shells, its tattered flesh knitting and reforming almost as quickly as the shotcannon shells ripped it aparrt.

A shotcannon on "full auto-spread" (whatever that means) can blow apart an unarmored (and presumably fairly slender) human being. again, damage seems roughly consistent with bolter-type weaponry.

Shotcannon shells are "explosive", again hinting at a similarity to bolters.

Page 245 - mention of "explosive head shotcannon shells once again.

Page 246 - the Virulent is "tens of millions of kilometres" distant from the evacuation fleet.

Page 249-250 - a Cathedral vox-ark has a transmission range capable of reaching the edge of a "planetary system"

Page 250

Tech adept, could it be that our signals are being somehow jammed or blocked? There have been unconfirmed reports that worlds targeted by the Planet Killer experience planet-wide communications blackouts shortly before they are attacked.

- again mention of the "jamming ability" of the Planet Killer, although much closer (tens of millions of km, possibly, as mentioned above) the planet killer can now jam the transmissions of an entire planet.

"However, the powere and jamming systems required to effect a total, planet-wide communications blackout from that far out in space would be...

- Implication that the power generation and jamming capabilities of the Planet killer are supposedly much greater than comparable Imperium ships.

Page 278

And, behind them all, came the Planet Killer, ,its massive energy presence blossoming urgently across surveyor screens. Crackling bursts of seething energy flowed freely around the spires and turrets of the huge weapons platform as it drew power directly from the warp itself, powering up its terrifying armageddon gun weapon array in readiness for unleahsing that energy, magnitied many times over by the arcane technologies used in the vessels construction, on its chosen target

- the Planet Killer evidently draws its power from the Warp, making it some sort of "external-tap" type power generation system, rather than a more formal reactor. Evidently it also must "charge up" to some degree before firing, hence the reference to "magnitifcation" (unless its hinting at something like the amplification of laser light...)

[Connor MacLeod]

AH, the final stretch analysis-wise!

PAge 283 - the Inviolable Retribution is mistaken for a Dauntless--class light cruiser by the Chaos ships, giving us a rough idea of the vessel's probable size relative to a larger cruiser like Macharius.

Page 283 & 284

Four squadrons of Starhawks swarmed out of the Macharius's launch bays, forming up into attack formations and quickly speeding towards the line of enemy escorts.

Even before they got there, the line had disintegrated. The Arbites strike cruiser's formidable bombardment cannons opened fire, their linear accelerator systems hrutling a stream of lethal magma bomb warheads through the void at something approaching quarter light speed. The salvo of warheads exploded across the line of Chaos ships with terrifying accuracy. One of them disappeared in a white flash, a hundred thousand tonnes of metal and machinery simply vaporised out of existence. Another tumbled out of formation, already breaking apart into burning fragments. The last remaining raider manouvered away in panic, abandoning its attack as its captain frantically sought to disengage from the battle.

Bombardment cannon velocity seems to be nearly .25c. A "stream of lethal magma bomb warheads" implies they also may have fairly high rate of fire relative to other Imperium cannons weapons (although this may also imply that multiple barrels/cannon turrets firing at once.)

assuming a conservative 2-3 ton mass (about the mass of a gun battery macro-cannon shell) stated as weighing "several tons" in battlefleet gothic, page 21) Each warhead must possess at least 6e18 joules of kinetic energy and 1.55 e11 kg*m/s worrth of momentum at 2 tons. at 3 tones, the KE is 8.9e18 Joules and 2.3e11 kg*m/s worth of momentum. This is, of course, conservative.

Also, a chaos Raider masses "a hundred thousand tonnes", which seems rather light for a vessel which is probably about a kilometer or so long.


Page 284

Now the Charybdis entered battle, its void shields flaring angrily as it passed through the expanding clouds of debris and residual energy vapour which only minutes ago had been its squadron of escort ships. It struck out with its forward lance batteries, beams of brilliant energy cutting through the Macharius's void shields and striking its prow, scoring burn lines metres thick into the super-dense material of the cruiser's armoured beak.

Assuming 100,000 tones (1e8 kg ) and iron composition, it takes roughly 760 TJ to vaporize a single raider. (roughly 2400 TJ for all three, Very conservative, in all liklihood. Assuming the explosive payload of a magma warhead is equal to its KE, it detonates 250 meters from the raider, broadside-on, and 4 warhead per salvo (I dont know how many bombardment cannons a Strike cruiser carries, I'm just guessing) you're talking about 4e18 joules of energy absorbed, total (roughly) This is still probably conservative, it also ignores shields, but the implication could clearly suggest that the raiders hulls are orders of magnitude more powerful.

Note that it took "minutes" to defeat the three escrots, which gives us a rough idea of their endurancee.

The diameter of a lance beam seems to be at least several meters.

Outgunned, the Chaos ship was attempting to break off from battle, radically changing course and cutting off the flow of power to its main systems, rendering it invisible to the surveyor senses of other vessels. It was a stnadard manoeuvre, and, if successful, the Chaos cruiser would simply fade off the Macharius's target screens, ,drifting away unscathed and undetected.

Again, note that a common warship tactic is to cut power and "run silent". curiously, though, there is no mention of using active sensors to detect them, even though such sensors evidently do exist in 40K (cutting emissions would only hamper passive sensors.) Clearly some other measure must be employed to protect against active sensing.

Page 284 & 285

In a pre=-arranged manoeuvre between the two vessels, the Inviolable Retirbution fired its bombardment cannons at the same time, the combined salvo finding and striking its targget with devastating force, ripping open the Murder-class cruiser's underside and blowig apart its starboard flank.

Evidently a coordinated strike between the MAcharius and the bombardment cannons of the Retribution. Not known how long it took for the torpedoes to land, but if it was a range could be established.

Page 286 - STarhawk Bombers can be equipped with melta-missiles (Evi dently the standard armor-piercing anti-warship missiles. By contrast, fighter missiles seem to be primarily krak warheads.

It will take an arbites shuttle and its fighter escrots an hour to reach the planet's surface from the Macharius' position.

PAge 297 - capacitors are mentioned onboard the Planet killer, confirming the assumption that it evidently charges up prior to firing - less than a da y though, but longer than a n hour or two it would seem. (an hour to get to the planet, the hour to "survive" before the Planet killer arrives, etc.)

Page 298

He noticed too that the surrounding enemy ships kept a wary distance from the vessel they were supposed to be protecting; unfocused and uncontrolled, any one of these random energy discharges could rip through a capital ship's void shields or completely destroy a smaller escort-class vessel.

Evidnetly a fraction of the energy output from the Planet killer's weapon is sufficient to down a warship's shields (IIRC battleships and a battlebarge as well as cruisers made up the PK's escort here.) and smaller escorts are completely des troyed. Since the approximate output of the planet killer is known, the rough magnitude of energy it likely generates (sustained or otheriwse) also would be known.

It was a terrifying craft, its very existence a threat to the order of the Imperium, Ulanti thought. He could well believe the whispered rumours that the details of its construction and estimated power requirements could not be easily explained by any normal technical means; that the powers of the warp themselves must have had a hand in its creation and operation.

Again, the power generation and capabilities of the Planet Killer are considered far above what standard Imperium warships (and conventional chaos vessels) are capable of.

Magnified by the viewing bay opticon, he saw the launch bays of one of the chaos ships - one of the dreaded Styx-class heavy carrier cruisers - yawn open and spit out a stream of attack craft.

Viewport windows incorporate optical magnification.

PAge 299 - at the Macharius' current position, it will take 20 minutes to get back onboard. According to ulanti's estimates on page 297, it will take about at least an hour or so for the Planet killer to get within position. And the Chaos ships ahead of it will be in position within 20 minute or so ((roughly implying they are at least 2-3 times as fast as the Planet killer itself.)

Assuming two hours as implied elsewhere, it might grow to 4-6 times.

KAether banked steeply away, charging all available power through to his forward shields

fighters and bombers have their own defelcotr shields even though Battle Fleet gothic implies ordnance is not normally shielded.

Page 300

Several thousand kilometres away, a larrge grroup of Swiftdeaths were speeding towards the two Imperial warships. Kaether studied their changing surveyor patterns, suspecting that they were oscillating their energy outputs, attempting to disguise the presence of larger, more powerful Doomfire bombers within their formation.

The use of ship maskign tactics by varying outputs (to make a ship look bigger or smaller than it is.)

Page 301: "hours" not minutes, sincee Zealot Zane began fighting the Nurgle-creature that is attempting to sabotage Macharius in the reactors (which began earlier just before the bombers launched and just after the Macharius and I.R. fought their way past the chaos ships guarding the planet and launched the recovery shuttles.) Which gives us our benchmark timeframe-wise for the battle.

Page 303 - Zane adjusts his laer pistol to "full charge" - thus indicating that las weapons can be designed for variable outputs (a fact which will also be noted in the various Gaunt's ghosts novels.)

- EVidently the plasma reactors generate some "residue energy" or "gaseous waste" during their power generation. The former may be a power surge of some kind, or it may be some colloquial term for the plasma. The gaseous waste may be either coolant, or the plasma itself. either way it kind of suggests a "non-reactor" design for the reactor. (sometliing like Gou'uld reactors.)

PAge 304 - the Bombardment Cannons on the Inviolable Retribution are shorter-ranged than the standard batteries of Imperium or Chaos ships, as the two sides could exchange standard weapons fire (and lance fire), but the I.R. was unable to use its bombardment cannons. I'd assume they have a range of at least 75,000 km or so, maybe half a light second, but its pure supposition.


PAge 307-308

In a torrent of energy that overwhelmed ships' surveyor senses and transformed hundreds of tactical screens into blank-faced displays of howling static, the Planet Killer unleashed its power on the world below. A roaring storm of destruction descended upon Belatis, passing through the atmosphere and increasing the temperature there a huundredfold in seconds, partially igniting it in a fiery borealis that swept out across the circumference of the planet

The energy blast struck the planet's largest ocean on the eastern hemisphere some two thousand kilometres south-west of Madina, sending up a huge cloud of steam clearly visible from space as millions of tonnes of sea-water were instantly vaporised, boiling away into the burning, super-heated atmosphere. The blast struck and cracked open the ocean bed, unleashing a super-tsunami tidal wave over three kilometres in height which would drown the two nearest continents and island chains and compete with the fiery borealis overhead in its race round the globe.

The Planet Killer's gunnery priests had not chosen this spot on the surface at random. Surveryor scans of the planet's geologic structure and daemon-voiced augurs had guided their aim. The planetary crust was weak and unstable here and the all-consuming energy beam ripped it asunder, setting off a series of cataclysmic underwater earthquakes, igniting chains of long dormant volcanoes into fiery, explosive life and cuasing new ones ot thrust up through the splitnering, broken crust. The seismic shockwaves rippled through the core of the planet, setting off disasters on the far side of Belatis long before the tsunami or firestorm would reach the continents there.

And all the time, the planet killer kept firing into an open wound now almost a hundred kilometres across in the planet's crust, the coruscating lance of otherworldly energy burning a hole deep into the planetary core, bursting open the planet's molten heart.

The Planet killer firing on another planet:

- a "hunderedfold" increase in temp in a matter of seconds. this implies the temperature of the atsmophere reached tens of thousands of degrees easily. However, given the later descriptions, it only heated part of the planet (a fairly large portion) in short order, and this presumably triggered firestorms which raced around the planet during the bombardment. Also note this is a secondary effect, in addition to the primary bombardment.

- instantly vaporizing "millions" of tonnes of water. 2 million tonnes requires megaton level enerrgy. Close to a billion a few gigatons. Not alot, but again, its only a part of the overall effects.

- as usual, the beam burns a hole a hunderd kilometers or so across down to the core of the planet (~2800 km deep). Assuming vaporization of the crust and mantle ought to take roughly ~1.2e27 joules of energy total, for a sustained firepower of roughly 1e24 watts. cracking the crust (1e10-1e11 megatons) should imply a sustained rate of fire of around e22-e23 watts, minimum.

- despite the fact it "blows the planet up", the bit about targeting a weak and unstable point, as well as the subsqeuent descriptions, clearly point to this as being technobabble mass-scattering, possibly at less than escape velocity.


Page 308 - the planet exploded apart after twenty minutes of sustained firing from the Planet Killer. Again, note that this indicative of a non-brute force destruction. the previous planet at the beginning of the book took hours to destroy, while others (like Savaven) took only an hour.


Page 310-311: the passage of the Virulent through the shattered remains of the planet.. mention of "violent waves of gravitational flux" as well as the planet's gravity well "collapsing", the stress of which threatens to tear the Chaos ship apart. The presence of gravity in any significant form is curious if the planet is mass-scattered.. this implies enough of the planteary mass remains present currently for the gravity well to be mostly intact (if diminished.)

Or, its just a result of the funky dameonic chaos magic in the beam.

Page 313

The torpedoes blazed towards their target, passing between the Macharius and Retribution in a bravura show of markshamship. Aboard the Virulent, Sirl was still trying to absorb the surprise of the Imperial cruiser's sudden appearance when the command deck alarms scramed in warning as the torpedoes' lock-on signals bounced off of the hull of their target.

Here torpedoes demonstrate active sensing technology.. and active targeting sensors at that.

Dying and powerless, the Virulent blindly tumbled away through space, falling into the gravitational pull of the remains of Belatis. There, it would be either mercifully smashed apart in collision with any of the massive, continent-sized planetoid fragments or would drift together amongst the rest of the detritus of the planet's destruction.

- Again description implies a distinctly "non-brute force" mass-scattering event, as a substantial portion of the planetary mass and gravity well remains.


Page 315

Behind them was a fading red glow that marked where the world of Belatis had recently been. In time, the drifting remains of the planet would spread out to form an asteroid belt halo around the system's sun, and future generations of Imperial statisticians and map-makers would mark the planet as Mundus Perdita, a world now lost to the Imperium.

- in compledte contradiction to what I mentioned above, evidently the planetary debris will eventually scatter to surround the sun (which implies it was not fast enough to reach solar escape velocity, which IIRC is around 50-70 km/s.)

my working theory is that the planet killer's bombardment caused a "build up" of chaos magic technobabble stuff that eventaully reached critical mass and technobabbled the planet aparrt, accounting for all the funky weird effects we normally see with it (planet flipping off it saxis, persistnat gravity wells, etc.) once the magic "dissipates", the effects return to normal and the planet probably will behave like normal (IE scatter eventually to form the asteroid filed, no longer held together by demon technobabble magic.)

[Imperial Overlord]

Shielding on attack craft is also mentioned in Sabbat Martyr. It is suggest that a Chaos craft was able to penetrate a theatre shield covering a city by putting its forward screens to maximum. BFG doesn't address the question whether or not ordinance and strike craft have shields at all, although its existence might be implied by the the fact that most types of ordinance and small craft can penetrate void shields which do stop such phenomena as rail gun projectiles, macro cannon shells, short range missles, and asteroid impacts.

[Ghost Rider]

Split here

[Inquisitor Ryan]

I have found more technical material, Canon, freely availiable that puts a single turn of battlefleet gothic at a minimum of 30 minutes.

http://www.blacklibrary.co.uk/pdf/warri ... tramar.pdf]

Deep in the bowels of the Argus, the fifty-metre wide door of the
nova cannon’s breech groaned shut as thousands of sweating
naval ratings dragged the massive weapon’s recoil compensators
into position. Hot steam and noise filled the long chamber, its
cavernous structure fogged with the furnace heat of lifting mechanisms
that hauled the enormous projectiles from the armoured
magazines below.
The chamber ran almost the entire length of the ship and
stank of grease, sweat and blood. A booming hymnal echoed
from ancient brass speakers set into grilled alcoves in the wa l l
accompanied by the droning chant of thousands of men.
Senior gunner Mabon watched from his gantry above the firing
chamber as a series of bells chimed and a row of lights lit up
along a battered iron panel before him. He couldn’t hear the
bells, his long service as a gunner in the Imperial Navy having
deafened him decades ago.
The shell was loaded and he muttered the gunner’s prayer to
the warhead as he squinted through a bronze optical attachment
that lifted on groaning hinges from the panel. He clamped his
augmetic monocle to the optical, lining up the thin crosshairs on
the red triangle that represented his target. The target was closing
on them so he didn’t have to make any adjustments for crosswise
motion. It was a simple shot, one he could have easily made, even
in the earliest days following his press-ganging on Carpathia.
Satisfied that the shell would be on target, he lifted his head and ran his gaze across the chamber, checking that his gunnery
crew gangs were clear of the greased rails that ran the length of the
chamber and that each had their green flag raised to indicate that
all the blast dampers had been closed. He reached up and took
hold of the firing chain that hung above his station.
He grunted in satisfaction and pulled hard on the chain, shouting,
‘Spirits of war and fire, I invoke thee with the wrath of the
Machine God. Go forth and purify!’
Steam hissed from juddering pipes and a high-pitched screech
filled the weapon chamber as the gravometric impellers built up
power in the breech.
Mabon rushed to the edge of the gantry and gripped the iron
railings. Seeing a weapon of such power discharge was a potent
symbol of the might of the Imperial Navy and he never tired of
the sight.
The screeching rose to an incredible volume, though Mabon
was oblivious to it, until the nova cannon fired, and the enormous
pressure wave slammed through the chamber. The
weapon’s firing sent the three-hundred metre barrel hurtling back
with the ferocious recoil. The air blazed with sparks and burning
steam as the grease coating the rails vaporised in the heat of the
recoil, the stench of scorched metal and propellant filling the
chamber with choking fumes.
Mabon roared in triumph, gagging on the stinking clouds of
gas that boiled around him. Juddering vibrations attempted to
topple him from the gantry, but he had long since grown used to
them and easily kept his balance.
The smoke started to clear and his gunnery overseers began
whipping their gangs into dragging the massive weapon back into
its firing position once more. The armoured bays in the floor
groaned open and the looped chains descended to be attached to
a fresh shell.
Mabon had drilled his gunnery teams without mercy and he
prided himself that he could have the nova cannon ready to fire
again within thirty minutes. This time would be no different.

Note that this also puts the breech door on a Nova cannon at 50 metres. The Weapons barrel at 300 metres and that the Nove cannon alone is crewed by "thousands" of naval ratings. *Men*

So if someone can do the calcs on a Nova cannon shell using the conservative size of 20 metres diameter and 60 metres long. (Three times as long as wide, as I said conservative) To give us a rough weight of a Nova Cannon shell using a Boltgun shell as it's "type"

[Grand Admiral Ancaris]

It should be mentioned that Void Shields appear to intercept incoming weapons fire based on velocity, which is why things such as Ordnance can pass through shields with no ill effect. This is pretty much stated in the Battlefleet Gothic: Armada supplement.

Because it is a relatively slow moving attack, like that of a bomber squadron, bio-plasma ignores shields.

It should also be mentioned the very slow speed of bio-plasma also severely limits it's range. Bio-Plasma is the Tyranid lance equivalent in that it is a high-energy direct-fire weapon that ignores armor value. It's not the "Big beam weapon O' Doom", but it'll eat through a hull just as easily.

[Inquisitor Ryan]

Good point Ancaris.
The same as I am under the assumption that the sole reason bombers are effective against Capital class vessels is 1: They are too slow for the shields to stop and 2: They can target more sensitive targets than another capship 10'000+ Kilometres away.