WH40K - Shadow point (SDN)

[Mr. Oragahn]

Shadow point - Technical discussion and Analysis thread

Page 13 - An Inquisition fortress has a buried facility 300 meters below the surface of the planet (indirectly, this may serve as indication of how deep Exterimnatus bombardments must go to inflict damage.)

A fortress is, by design, going to have one main role: offer a good defense. It is not about sitting silent as the enemy lands or places a fleet in orbit, and it's certainly not going to try to be as discrete as possible when a flotilla or fleet or warships full of trigger happy Space Marines and some twitchy Commissar or Inquisitor onboard, or fileld up the chin with frothing Chaos horrors.
The facility may be that deep, but the fortress is ought to be fairly visible. No need to try to argue that an Exterminatus would have to remove 300 meters of rock all over a planet's solid surface (Exterminatus), since the target is extremely obvious, and 300 meters is peanuts for most respectable soft SF universes, TV or not.

Page 16

Standing with the others, he stared into the deep, still smouldering wound which had been gouged into the earth. A glance at the map display on his data-slate confirmed the almost unbelievable. According to the information, this twelve kilometre-wide gaping abyss of burning gases and smouldering, still semi-molten rock had, until just a few short days ago, been the location of a heavily-defended Imperium planetary base home to thousands of Imperial Guard troopers, Adeptus Mechanicui adepts and servants of the myriad of other branches of Imperial Government.

All across the planet's surface, other settlements and Imperial outposts had been struck and obliterated during the lightning-fast raid, but this, Horst knew, was the main object and target of the attack. Here the fell touch of Abbadon the Despoiler could truly be seen on the surface of Purgatory, scarring the face of hte planet forever.

Horst looked down, and, through the haze of burning, sulphurous gases, saw the marks on the sheer sides of the crater, where, from high above in space, an orbiting warship had directed a coruscating beam of lance energy down onto the palnet's surface, blasting away the topsoil and all of the fortress built upon that topsoil, and probing deep into the underlying bedrock of the planet.

How many lance-armed warships would it take to accomplish suc a task, the inquisitor asked himself? He both marvelled and feared the thought of the massive outpouring of firepower that must have been required to carve such a wound through the planet's dense, rocky crust. And then a second, more troubling, thought suddenly struck him. What if it wasn't a fleet of warships? What if all this were the work of something else, some terrible new addition to the Despoiler's armoury which they had yet to encounter?

A 12 km wide hole is punched in the ground by an unknown Chaos ship, evidently melting and vaporizing it into the planet's crust. With data given below (calcs below) a figure can be derived.

Oddity of note: Horst speaks as if he KNOWs a single ship did it, but later wonders how many "lance armed warships" would it take? with the implication being the feat was beyond Imperium capabilities.

So an Inquisitor, Horst, perhaps the man in charge of 100 Imperial warships:

- Considered this feat "unbelievable", while it should be painstakingly and boringly unsurprising.
- "Wondered how many lance-armed warships" it would "take to accomplish such a task." Ergo: He can't even come with a rough estimate of the number of ships needed for this. This alone pretty much implying that it's above the capacity of a flotilla or fleet of Imperial vessels.
- "Both marvelled and feared the thought of the massive outpouring of firepower that must have been required to carve such a wound through the planet's dense, rocky crust." This kind of event is pretty much new to him.

So much for the teratons and "stellar" power output for a typical heavy Imperial warship!

Page 17

He looked again into the depths of the crater, rechecking the stream of info-runes now scrolling across the face of his data-slate. Despite the enormous energgy stream that had been unleashed on the surface here, it was plain to see that it had somehow been expertly contained and targeted to an almost uncanny degree of precision. The overlaying surface material had been simply blasted away, yes, but, after that, the energy stream had been tightly focussed as it drilled down into the planet's crust, obliterating dense rock and mineral deposits in micro-seconds as it pushed deeper down into the planet's core, almost as if it were probing in search of something/

Again, reference to a single energy stream (implying a single ship, as above.) Also note that the process occured in a very short time (implied "micro seconds") as well as being an unusually precise and controlled bombardment, which tells us that the attack was unlikely to be a "maximum power" feat.

Micro-seconds indicates a power inferior to that of a nuke. That would mean you'd need a greater input of energy to obtain the same blast you'd get with a greater power, but it has the effect of delivering more energy into the same amount of matter, making it easier to melt and eventually vapourize targeted matter, instead of blowing it away.

Also, the idea that the beam was a dialed down version of its maximum capacity is more than disputable. Without direct evidence, especially from the same novel, it's a speculation best left ignored.

Drones and servo-skull scouts have been despatched into the fissure. We estimate it to be at least eighteen thousand metres deep.'

The hole extends at least 18 km into the planet's surface. However, we also know that it evidently did not breach the mantle (lack of mention of volcanic/mantle ejecta reaching the surface.) Assuming a 12 km diameter (which it should be roughly, given the menas of bombardment) and a silicon composition, the mass is 4.74e15 kg. Melt energy would be 1.21e22 joules. Vaporization energy would be 6.22e22 joules.
Thus, the energy (depending on melt depth) is at least 1e22 joules but probably not more than 1e23 joules. in any case we know by the fact that Horst was able to stand on the planet mere days after the incident that it wasn't an extinction event (or probably anything closer.) The evident lack of mention of ejecta or dust loading obscuring the sunlight is problematic, but we could conclude that since this was largely a recollection of Horst's memories, that it was there or just not recalled (or considered imortant enough for recollection.)

The other point of contention is whether it was one ship or a group of ships. In parts it seems he speaks as if a single ship fired a single lance to do this, whereas later comments imply he felt a fleet might have been involved (and quite possibly a large number with multiple lances.) The context is also not clear on what kind of ship or ships are involved, although it is heavily implied to be Abbadon's planet Killer. The duration is implied to be very short.. no more than a second or so, and probably alot less (milliseconds or microseconds.)

In terms of firepower relative to Imperial ships, the quote does not seem all that impressive on the surface, especially in contrast to other incidents (such as a flotilla of battlehsips rendering a planet lifeless in a couple of barrages.) but do recall that this may not be an incident where maximum firepower was used. On the other hand, a single lance strike (as explicitly mentioned) could quite easily deliever the level of damage described above, so it could be reconciled either way. The best explanation, howver, seems to be that the attack was carried out by the Planet Killer, and that the duration was so shot it only involved a fraction of its full power (thousands or millions of times greater.) And that Horst was comparing the potential offensive firepower of the Planet Killer to an entire fleet/squadron of Imperial warships (couple hundred to a couple dozen, ,probably)

If we assume as ingle ship, non palnetkiller, with a single lance.. the firepower per "lance" is in the e22-e23 range (a battleship coudl be an order of magnitude or higher or so if we assume the ship is a cruiser.) If we factor in the "duration" of less than a second, the figuer could be anwhere from 2, 3, 5 or 6 orders of magnitude higher.

If this is the Planet Killer we are talking about, then tis sustained firepower woudl be somewhere in the e27-e29 watt range - a bit on the high end given what I previously calculated, but perfectl valid.

It would also imply Imperial power genration averaging around e25-e27 watts (consistent with the "stellar power genration", at least for Battleship class vessels.

The initial stage blew a crater out of the surface, then focused for some kind of drilling procedure, to hit deeper. Obviously, the shape of the entire excavated, melted or vapourized volume would be similar to that of a funnel, not a cylinder: Horst saw a deep crater, which is bowl shaped, with semi-molten material down there. The diameter of the molten material would obviously be inferior to the diameter of the crater by a significant degree, otherwise there would have been no crater to observe. It's also all the more logical that the deeper the beam would go, the harder it would be to expel matter out of the carved rock.

For instance, a shallow underground nuclear detonation leaves a hole, actually a crater, much wider than the hole left by the same nuke, detonated deep down inside the crust.
Let's be clear: if the weapon in question could only remove matter over a radius of 6 km, and that largely sideways, it would be at great pain to move the same radius of matter down 18 kilometers.
The width of the hole would be condemned to shrink, more or less proportionally to the depth, rather quicly, so most of the damage would leave a narrow bore.

Now, the dimensions are 12 km wide (picking up Connor's assumed width) and 18 km deep.

A cylinder of such dimensions would have a volume of 2.0358 e12 m³. Picking up the silicon density from SDN, 2330 kg/m³, we get a mass of 4,743,414 e9 kg, or roughly 4.74e15 kg, which is the volumetric value of matter Connor used.
So Connor did assume that the hole was a neat cylinder, right down to the last meter.

The claim that the power was dialed down is most peculiar, for there would be no reason, really, for the Chaos ship, and Abaddon here, to dial down the power of his weapon.

It is hard at this point to imagine how the event exactly occurred. I can only guess that the beam delivered its energy fast enough so that it wouldn't be impeded by the matter gathering back into the hole.

That said, the energy level is not going to be particularly lower than the figure Connor obtained. Perhaps one OOM. But remember that it's also a very powerful and unique ship, perhaps akin to a planet destroyer or something (that's Connor's words, perhaps there's such a crystal clear reference in the book).

Page 27

Not even the lowliest rating or indentured slave-worker aboard any of the hundreds of Imperial Navy warships under his command would be in any doubt abou tthe figure's identity, even without the magnificent diamond-inlaid and gold-woven rank sash he wore across his tunic breast

According to this Battlefleet gothic is composed of "hundreds" of warships. Whether this is just capital ships or includes escorts is unknown (presumably it includes escorts, though.)

That's not exactly one of the largest figures out there. Although a portion of the entire Imperial fleet (perhaps, I don't know yet), it clearly contrasts with the "million(s) of warships" concept seen from time to time on Internet.

Page 42

The Eagles bore on, until the pitted and battle-scarred hull of their target must have filled their entire universe, and then, at the last possible moment and with only scant metres to spare, they broke formation and peeled away, their navigator-companions simultaneously giving the mind-thought order to their craft's infinity circuit systems. A brood of missile-slivers launched away from each craft, piercing the target vessel's hull in a space of time immeasurable by the crude animal-minds of he vessel's occupants. Another infinitesimal moment later, and the missiles' sonic charge warheads detonated deep within the target, unleashing a carefully orchestrated symphony of destruction. The human vessel did not so much explode as shatter, transformed in an instant into a rapidly expanding sphere of twisted metal and fragmented ruin.

Their manuverability is such they can pull a sharp 90 degree turn mere meters from the hull (analogous to the ANH proton torpedoe's ninety degree turn.) Assuming they were travling at several km/s (which is what Imperial fighters frequently do), we could easily infer tens of thousands of gees worth of acceleration (which would be consistent with Imperium warships pulling high thousands of gees accel rates - the Eldar are considerably faster.

If the targeted human ship, likely very large (the larger the better for Connor's claim actually), perhaps a couple of km long at best, was all the bombers' pilots could actually see through the canopy, it's rather obvious that said small crafts were extremely close to their target, and didn't approach head on, on a normal course to the hull, at a speed measured in the km/s.
They had, after all, only scant meters to spare.
Human reflexes wouldn't allow for the tight pull to avoid the hull of the target. Enhanced reflexes, that would still be a huge stretch to argue a high speed with only a couple meters left to pull up before crash.
Now of course it was all about Eldar reflexes here, but what's the evidence that they're higher?

And what about the possibility that the ships were not approaching at a 90° angle?

Additionally, note the velocity of the missiles was sufficient they could cross "meters" in a time immeasurable by human reactions (what Eldar reactions are, is not known to me.. anyone know?) It also implies their "needle" like deisgn allows for very high penetration.

It's a figure of speech. Your regular bunker buster breaches reinforced concrete at speeds of 750 m/s with some rocket boost, and unless you can observe the thing frame by frame, any human will have hard times picturing just how fast the projectile was.
Hell, even if the missiles hit at 100 m/s, it would still be very fast, covering 10 meters in a tenth of a second. Hulls on Imperial and Chaos warships are meters thick, so if we assume that it could be about the same on this human ship, then there's nothing surprising here that the target's hull was breached that fast... aside from the fact that the hull was breached at all.

If mere small crafts can do that, one has to wonder how that target would have fared against the solid projectiles of warships.
Was the target a warship? If not, then it's not such a big deal.

Page 47

She had stood on this deck and watched in satisfaction as star-bright beams of pulsar lance energy effortlessly laid open the thickly-armoured hulls of the human vessels, as flights of eldar torpedoes, mind-fast and almost impossible to detect, ruthlessly and effectively hunted down and destroyed the slow and ponderous enemy ships

Eldar Pulsar lances can penetrate Imperium shields and armor effortlessly (implying nearly isntant penetration?) This suggests their "per lance" firepower is at least an order of magnitude greater than Imperium ships (whose hulls and shields can take many seconds worth of bombardment from their own weaponry, usually.) This might imply something on the closer o mid tof high TT/low PT firepower, dependiing on the calcs used.

Just for things to be clear again, Imperium firepower is considered to be around low to mid teraton, even petatons at several times, at SDN, and Eldar crafts then above that.
That despite what Connor had quoted from the book a couple of paragraphs ealier on. This is trying to force an inconsistency, or literally denying the existence of a fact sharply established in said book.

Page 49

The tiny mechanoid creatures were a marvel of technological achievement, nano-devices the secrets of which had taken the eldar thousands of years to attain, and far in advance of anything the galaxy's younger and less refined races could yet manufacture.

The quote implies nanotechnology, although the machines are evidently detectable to Eldar vision (which suggests they aren't nanoscopic.) Its possible this refers to nano-scale precision engineering, representing the scale of miniaturization of technology the Elder are capable of (and what the Imperium and other races lesser than the Eldar cannot do.)

They're called nano-devices. I don't think it can be any clearer.
If younger races could manufacture any device down to that size, it would be considered crude in comparison. The whole question then is what do these Eldar nano-devices do?

Page 64

Even when not in battle, there were at least a dozen deaths a week on the Macharius, an unremarkable statistic which passed as the normal hazards of duty aboard a navy vessel. Crewmen crushed by heavy machinery in the torpedo room or flight bays, crewmen vaporised by energy surges while working amongst the innards of the ship's power systems, or even, for those wretches unfortunate enough to be consigned to the lower decks where the ship's atmosphere processing systems were at their least dependable, poisoned, frozen, or killed by sudden air pressure changes.

1. Lif aboard ship is hazardous even in noncombat situations. Note tat at a rate of 12 deaths a week (minimum) and a 10,000 crew, the Macharius could still last for years (16 years) before needing a replacement crew. Although the decrease in muscle power would have to limit some tasks.

2. Also note that eviently the ineffiuciencies/residual energies of the Macharius's power transer systems can "vaporize" a human beingz. Given the many teratons or more of energy they are capable of generating, losing megawatt/Gigawatts of power in such a fashion speaks of great efficiency (Although I can't say it would do the interior of the ship much good if it happened ferqurently)

1. The death rate statistic is literally unremarkable! It comes down to a question of what do you take in excess while packing up? Food, or crews? I suspect some crews routinely make lethal bad jokes to their comrades so they may steal their ration of roast chicken. Hey, perhaps harsh language does kill.

2. So despite the source being abundantly clear that the death rate in non-combat situations is absurdly high, due to inadequate, cumbersome and hazardous design, we still must praise the same design for its "great efficiency" because it only unleashes gigawatts on its people when there's a breach of energy.
Of course, nothing is told about where the energy leak occurs. It could be anywhere down a mundane power conduit where gigawatts just happen to flow, not more.
It really takes a formidable dose of love for a franchise to both point out that power conduits routinely leak energy, and yet they're magnificent because they don't vapourize the ship (without establishing that such PCs have access to greater power outputs).

Page 76

Still, at least the energy release from their weapons fire gives our gunnery surveyors an easier target to lock onto.

- targeting sensors here are represented as passive systems, at least partly, and their accuracy is added by detecting the energy discharged of weapons fire (presumably not the weapons fire itself, but inefficiencies in the dischrager - electromagnetic radiation or charged particle radiation, for eaxmple.)

Where is it said they're passive? The ships, thousands of kilometers away, were out of range, so no EMR could be properly aimed at the incoming Ork crafts for a strong signal to bounce back: the intensity would never match that of the ships' own cannons firing away.

What is interesting is tha the Ork crafts included Roks. These "ships" are not known for being small.

Page 83

" The torpedo wave's target had been the two largest rok-fortresses in the enemy fron tline. The roks were massive, one of them easily over eight kilometres from tip to tip, and possibly as many as four kilometres across. Eight torpedoes s truck it, the remaining six finding the other one. Normally, it might have taken several dozen torpedo strikes to destroy targets this large. Not today, however. Today the Imperium warships were using new ordnance: so called "rock-buster torpedoes", specially designed for the task at hand.

- Ork Roks arre approximately 8 km long and 4 km in diameter. Also mentioned is that it takes "several dozen" regualr torpedoes to destrtoy the roks. Six to eight "rock busters" strike the torpedo. Note that it might be tempting to assume that 1 rock-buster is equal to 3-5 regular torpedoes, but this comparison isn't quite valid because the two weapons work on distinctly different pricniples (as will be explained later.)

I would invite people to toy with Wong's asteroid calculator, notably the portion about cratering.
Try a 8 km wide round asteroid and what it takes to supposedly gouge a crater that wide.

The idea that warships, capable of throwing out teratons or even petatons under the form of beams, warheads and perhaps mass drivers, is not meshing well with this. In another thread, there were references of torpedoes being 30 meters long, some other being 100 meters long.
Also note the 6 to 8 special rok-busters, instead of several dozens.

Are Roks coated with special plating or something? Otherwise, I don't see how you can argue for teratons of firepower here. Hell, the calculator above would even point to shots in the megaton range to do the job.

Even the highest figure, 2.4 gigatons for a 4000 km deep crater, divided by a dozen, leaves 200 megatons a piece, and 100 if you consider two dozens.
Let's make no mistake here. The ships firing these torpedoes are glorious Imperial warships, not third rate scrapejobs.

The claim I read in the other thread, that Roks have shields, really surprised me, because this event clearly features torpedoes directly hitting the asteroid.

Page 84

The torpedoes struck the pitted and cratered surface of the roks, their armoured nose-cones spinning like giant drill-bits and boring into the porous rock. The missiles burrowed deep into the bodies of the aseroids, drilling through hundreds of meters of rock in seconds. When the high-speed drill motor burned itself out at the end of its short lifespan, it triggered the warhead payload. The torpedoes exploded. Their payload was not the conventional plasma-fusion warheads used in normal ship-to-ship actions, designed to melt and destroy ship's hulls and set their internal compartments ablaze. Instead, the rock-busters warheads were packed with high-explosive seismic charges, designed to shatter and pulverize rock, setting off a chain-reaction of aftershocks within the structure of their asteroid targets far in excess of the payload's explosive yield.

1. - nose cones of the torpedoes allow the rock busters to penetrate and drill in before detonating, at a velocity of about 100 meters per second or so. If we knew the mass of the torpedoes, figures might be deriveD (lower limit, anyhow) - also note that the armored front of the torpedo appears to be unharmed by the sudden/hard penetration (which confirms the idea that said torpedoes also tend do double as kinetic impactors as well as explosive warheads.)

2. - normal torpedo warheads are said to be 'plasma fusion", although this does not mean conventional fusion, but probably more like a plasma or meltagun effect (it burns through the target via prolonged contact.) In this case they "melt" through metal hulls (Thus they likely also can melt through asteroids fairly easily as anything metallic.)

3. - rock buster payload is stated to rely more on shock waves/seismic effects pulverising the asteroids as opposed to metling/shatering, despite the evidently low yield.

4. - Given the aforementioend asteroid dimensions tha if we assume rocky (with some metallic elements in unknown quantities), the asteroid would take around 200-500 megatons to "fragment", and hundreds (170-200 GT to 500-600+ GT) to melt (we can assume melting because thats what the "plasma-fusion" warheads mentioned later are stated to do.) Shattering will probably apply to the Rock-buster specialist torps we see here. Given the yield, we can safely assume (conservatively?) that conventional torpedoes would be in the gigaton+ range (single or double digit GT, depending on figures.) This coudl also vary depending on range (although in this battle that seems to be fairly close range.) The fragmentation energy for the rock-busters is probably in the low MT range (tens of megatons)

1. It's only rock, and 100 m/s is below the speed of a bunker buster. Nothing spectacular here.

2. Whatever their mechanism is, if they were teratons level weapons capable of melting copious amounts of adamantium, toughsteel, hardium and what else, those asteroids would not require special torpedoes to drill towards the core to enhance destruction while normal torps may fail to do enough damage.

3. If those HE charges have much higher blasts than the melta-like fusion warheads, it works.

4. We can assume melting?? Melting comes with material expansion as well. Which means fractures. Considering the violence of the weapons, it's just silly to pretend that hundreds of gigatons would be necessary with surface impacts. It's even more silly to pretend that you'd need to melt the entirety of the asteroid!
As for the fragmentation? With 8000 m, that's 512 megatons, with 4000 meters, that's only 62 megatons, so it sits between both. At least on that Connor is right. That's high tens of megatons if you pick the highest figure and divide it by six warheads, not even eight.

Notice, also, the lack of mention of lances used to attempt destroying Roks, either due to limited efficiency, range or lack of firepower.

From the safety of the bridge, Semper saw one jagged shard larger than a frigate strike another rok, piercing it like a dagger and sending it tumbling askew out of the ork formation.

Section of a rock is "larger than a frigate", but is small enough to serioussly damage another warship.

In other words, a drifting frigate-sized piece of a Rok can impale and seriously damage another Rok, literally putting it on some random uncontrolled course.

Page 86
- They were within range of the Ork batteries by then, suggesting Ork weaponry is significantly shorter-ranged than the Imperium counterparts (probably because their accuracy sucks ass.)

Actually that doesn't sound that much more different than the Chaos' warship attempt at intercepting enemy bombers over a range of 1000 km, by using area effect bombs.

Page 90

A powerful tractor beam was brought into use as a huge and primitive catapault weapon, sieizing and ripping away parts of the rok's own asteroid body and hurling them into space at the Imperium ships. The weapon was typically orkish, barbaric and makeshift, and typically highly effective. One of the Cobras, turning too late out of its torpedo run, was smashed in half by the impact of an asteroid missile fully two hundred meters across.

- ork tractor beam weapon. Note that its evidently flinging massive projectiles, a 200 meter asterid enough to smash apart a Cobra destroyer. 200 meter long asteroid, assuming granite composition (ignoring iron)is around 1e7 tons (the metallic complements could add greatly to this figure, though Assuming it moves as fast as a torpedo (tens of km/sec - call it 30 km/sec) resulting in the kinetic energy of just over a gigaton and some 3e14 kg*m/s worth of momentum. The destruction of the destroyer, given the description, is quite clearly mechanical due to the ship being torne apart at the impact ppoint.

If Imperial warhships typically fight at ranges of tens of thousands of kilometers, and since they were totally aware of the approaching Ork ships, why would they allow the Ork ships to get any closer?
Of course the book said that at thousands of km away, the Ork ships were out of range. Orks also fight at closer ranges. It's the way they fight.
Anyway, either both fleets were considerably closer, and then there's no proof that the 200 meters wide asteroid would even need to be flying at tens of km per second, or both fleets were fighting at greater ranges, at least a thousand kilometers, but then it would take, at 30 km/s, more than thirty seconds for the asteroid to reach its target. Considering the acceleration figures generally attributed to Imperium ships by Connor (thousands of gees), the idea that the Imperium ship couldn't get out of the way of the obvious rock is rather bizarre. Hell, if ships can accelerate by the thousands of gees (I can't help thinking how stupid this number is), it suppose that to slow down, same ships could equally decelerate nearly as fast, and thus move backwards at the same rate.








Now the Famous NOVA CANNON!!!

From its position in amongst the main cruiser formation, the Fearsome fufilled its supporting role to devastating effect. Its massive, jutting, prow-mounted nova cannon wreaked havoc amongst the ork roks, firing explosive projectiles into their midst at near-light speed.

- mention of the nova cnanon projectiles traveling at "near-c". Assuming a 200 ton projectile, the KE of the round must be around 1e23 joules, with 4.2e14 kg*m/s worth of momentum.

(Incidentally, using the 200 ton figure from above with the .quarter light speeD" bombardment cannon velocity from Execution Hour, a bombardmen cannon would possess around 6e20 Joules of KE and 1.55e13 kg*m/s worth of momentum.)

We can still note that a Starhawk is supposed to be as big as a Marauder, yet as pointed out in the rulebook editions thread, a Marauder is 41 tons heavy only.

200 tons at 1/4c gives 5.89 e20 joules of relativistic KE. Annihilation of half that quantity as antimatter, the other 100 tonnes being the containment and the shell, would provide 1.79 e22 joules.
Notice that's for antimatter. For the same mass, fusion will be two OoMs below that (or 1.5 if your fusion stuff is really that magic), and it will keep going down until you reach the explosive chemical range.
It is implied that the Eldar use antimatter, but I have not seen such reference for the Imperium. All I got, aside from exotic names, is clear indications of fission and fusion reactors.
The name Nova itself, if we were to channel Connor's spirit, would imply a star-like type of nuclear reaction.

Momentum being what it is, no matter how explosive the device is, its whole mass will still move forward, until it does explode.

Now, I could go on and on about how the projectile could use a variety of shaped arcs to either slow itself down first, as part of a multi-staged explosion, so the next explosion, and thus the rest of the reactant mass, would actually have chance to hit the nearby targets instead of missing them entirely, or how the projectile would principally focus its power into a rear arc, so the expelled matter, while losing the advantage of near luminal KE since it would have to negate the forward velocity, could at least count on the energy of photons to deal some heat damage (but that would be rather piss poor).
However, both would be tiresome and unnecessary long explanations, theories and speculations, which would define explosive matter ejection models which would be asymetrical.

First, the bad news here is that with fusion, the projectile could never even muster enough energy to counter its forward near luminal motion, even if it were to use its whole mass in a giant fusion reaction, assuming 100% efficiency.
Eldar manage similar if not better energy outputs in most of their systems, and they seem able to use antimatter. Not the Imperium.

Secondly, and probably the most important point, according to the BFG rulebook, the weapon clearly is one of area effect, which is omnidirectional and comes with a fixed radius. It's, in other terms, spreading in an ideal spherical fashion, evenly.
There's no wiggling around here. This can only be done if the projectile's momentum is suddenly reduced to a value which, on a scale of hundreds or perhaps a couple thousand of kilometers, would be negligible.

It is "simpler" to argue that the projectile is filled with a physics-raping engine system. At this point, of course, knowing the size of said system and its hardware would be tricky: it could literally be possible that for the blast effect to work, the projectile would use a form of mass lightening tech.
So once the device would be ruptured, with kinetic energy level remaining the same, effective mass would increase as speed would decrease. This could mean the "artificial" mass of the projectile could be several times lighter than those several tonnes used for calculations, when it's accelerated.

The problem is that it would require a type of technology that is not mentioned either. But the Nova cannon technology would be rare enough, or complicated enough, to argue that it would be a near lost legacy of some Dark Age of Technology, with perhaps a single factory churning out those projectiles, with the Tech-Priests incapable of understanding the physics behind the special Nova explosive bullets.

Also, instead of trying to be consistent with external misinterpreted sources, why not try being consistent with the data present in the same given book?
1 e23 joules stands for 239 teratons.

Now let's remember, earlier on, how our Inquisitor Horst, after observing the crater left on the surface of Purgatory, couldn't think of any weapon of the Imperium that could achieve that level of destruction, when a Nova cannon can unleash teratons on a planet, with a mass driver?
An asteroid impact, although much more massive, still left a 180 km wide crater in America. That was estimated at being 100 teratons.

Hell, the Nova cannon fired several projectiles. If Roks can't even come with anything better than a couple of gigatons, by decimating their own mass to throw it at the enemy, how the hell, with inferior ranges, were they supposed to be a problem for the Imperium?
The Imperium would steamroll any Ork naval force, and wouldn't even need to use shots at full power with nova cannons.

Also, Imperium warships, mounting such cannons, compensate the sudden acceleration with their own engines. I wouldn't want to be on the planet behind such a cruiser when it fires, even if it were in high orbit. Caught in the wake of teratons of ejecta. Ouch.

Still, with such a speed, even firing a mere kilogram of stuff is going to correspond to very large energies (although far less cratering).

The reality is that this number sticks out so much, it's just as good as the bizarre high ends we get in Star Trek like Obsession and TDiC.

The number starts to make sense when you use a speed in the very low 0.x c range, that's I suppose close enough to light-speed in comparison to pretty much any other speed anyway --a quarter of c is 1 OoM down from the maximum, while the light speed number is a multiple of e8.

A number of e20 J would perhaps begin to make much more sense as well, and if you use the 41 tonnes of the Marauder, that is just as big as a Starhawk. At 1/4c, that's 27.53 GT. However, both Starhawks and Marauders are empty crafts.
Horst wouldn't be puzzled in his extrapolation about Despoiler's ability to dig holes in a crust if he knew of any ship in the Imperium capable of a similar feature.

and Fury fighters adapted to specialist reconnaissance duties were in close amongst the enemy target cluster, feeding back accurate and instantaneous telemetry data to the Fearsome's gunners

-The Imperium uses Fury fighters to relay target-cooridnate information to other Imperium ships in combat (presumably to aid in long-range weapons fire such as nova cannons, and possibly torpedo guidance.) Note that the "instantaneous telemetry" bit implies the range is alot less than one light second (IE virtually no lag.. probably more like half or a third of a light second, tops.)

Presumably they utilize fighter-relayed telemetry to assist in longer range bombardments as well. Tactically, if they carry telementry-guided torpedoes (one fo the canon torpedo variants, IIRC), they probably can use fighter-relayed telemetry to enahnce their performance as well.)

Why even suggest the possibility of combat ranges of 1/2 or 1/3 of a light second? That's around one or two hundred thousand kilometers, which means that the Cobra destroyer that got blasted by a 200 meters lage asteroid moving at 30 km/s would have had more than 3300 seconds to spot it and move out its way.
And this doesn't fit with Orkish typical ranges either.

Besides, fighters are close in amongst the target group that's being shot at by area effect teraton weapons?

Page 91

- Four nova cannon shots reduced two roks to "drifting and shattered asteroid debris. The last shot "striking its target dead-centre and breakign it apart like a giant sledgehammer, indicating that Nova cannon ARE capable fo direct as well as indirect fire (they can work as kinetic impactors, in other words.)

Huh. A nova cannon projectile hits a Rok squarely, and it only breaks it apart? We know a big Rok is 8 x 4 km.
Nevermind that the energy itself would have been so huge that the asteroid would have been flash vapourized with otherwordly huge excess of energy.

- given Orkish technology and Ork nature (ie the psychic aspect of it) and the fact they can get usuable acceleration from chemical propelled engines, it may be highly possible that the "Roks" are more durable than they might normally be (think ORk Structural integrity field) which may explain why they require multiple Nova cannon hits to take out.

Despite the fact that Connor cannot find a single reference about the Rok's enhanced toughness?

- Ork fighter-bombers run on "chemical reaction thrusters". Rather odd, and absurd, that, since chemical reactions are grossly inefficent for propelling ships, even small ones.

They're still good enough in space, especially if they're huge and if the Ork believe the ship can go that fast. :p

The ork fighter was two hundred meters away, a second later and it was one hundred and fifty meters away. The time to lower the thickly-armoured blast shields over the command deck's vulnerable viewing windows was minutes gone.

Ork fighter-bomber mentioned traveling at a velocity of 50 m/s prior to near-collison. It also takes "minutes" to lower the blast shields over the viewport.

- Ork cannon shells from a fighter-bomber can partly crack but not shatter glasteel of the Macharius's viewport.

We understand that this is a speed that doesn't mesh well with the accelerations and ranges that are being insisted on.
Also, the glassteel window was one meter thick. Somehow I doubt our Ork fighter-bomber threw a kiloton level weapon at the Macharius' window.

Page 93

The Drachenfel's lance batteries gored into the sides of another rok, blasting away or vaporising hundreds of tonnes of soft, porous rock.

Vaporising "hundreds" of tons of rock requires tens or hundreds of terajoules worth of energy - seems rather low for he firepower a single lance could dish out, even on a cruiser.

Yet fits with Horst's appreciation of the Chaos supershot at Purgatory.
It's also intriguing that Ork spacecrafts and Rosk use fossil fuel and enriched plutonium.

Page 94

Whatever the substance was, it was apparently highly fissionable. It ignited instantly when the star-hot power of the lance beams touched it, setting off an instantaneous chain reaction through the interior of the rock. The entire rok disappeared in a nuclear flash, lighting up the void like a second, short-lived miniature sun.

The sudden and massive energy burst overwhelmed the Drachenfels shields and temporarily blinded its scanner systems.

If we assume 1/1000th of the ship's volume (to account for empty space and other materials involved in the rok), the mass of plutonium would be around 2e12 kg. Plutonium evidently releases slightly less energgy than Uranium per kg (about 8.5e13 joules per KG is what I found) releasing a potential 1.7e26 joules max (Probably lower, given the "plutonium would not be concentrated in a single location and I'm doubful how rapidly/effectively a chain reaction could be sustained in such circumstances. On the other hand, the feasiability of what is described to begin with is up for grabs too, so...

- the Drachenfels lances evidently have some sort of neutron element to them sincee they set off a "chain reaction" in the material (I'm not even sure you could technically GET critical mass in a fissionalbe material like that, anyhow. ) Although we don't know hte precise composition of the asteroids, the energy (Briefly) overloaded the cruise's shields and sensors.

Who else, he laguhed to himself, but the greenskins would build a fortress base upon an asteorid streaked through with deposits of enriched plutonium?

- The fissionable elements of the hull are said to be plutronium, confirming the nature of the nucllear detonation (As we didn't know.)

So the Orks can somehow compete with the Imperium, despite powering their space fortresses with deposits of enriched plutonium?

Page 106

The tractor beam wasn't powerful enough to bodily drag or hurl the Macharius through space, as the orks had done with the aseroid missiles which had been directed at the Graf Orlok and which had smashed apart one of Vanguard squadron's Cobra destroyers, but it was still easily capable of destroying the ship. The powerful gravitic forces of a tractor beam, recklessly manipulated in teh right way, could be used to crush or tear apart a target, or at least a portion of a larger target

- Description of how tractor beam weaponry works. The gravitic weapons mentioned to be part of a weapons battery prorbably work on a similar fashion.

It's rather intriguing that tractor beams capable of ripping apart a ship cannot be used to move it.
Now, this is explained: it's said the tractor beam would only damage a part of a larger target, most likely because it couldn't apply enough force over most of the volume without tearing it apart or "punching" a zone of the ship's structure into itself.

It also explains then how those tractor beams could tear off some rock chunks and hurl them away at enemy ships.

page 148

"You could hide a Ramilies star-fortt or two in the electronic backwash from that damned pulsar and anyy recently-arrived vessel here would be none the wiser from the scrambled surveryor readings it woudl get back from the thing. Emperor only knows how many ships you could claok in amongst the asteroid belts."

Semper smiled. "Agreed, Mister Ulanti. By the time you get close enough in-system to see what might be hiding in the petticoats of that pulsar star, then whatevers waiting for you in those rock fields would have had peltny of opportunity to jump out and bite you on the arse.

- the limitations of detection systems - the electromagnetic interference of a binar star pulsar hampered the ability of sensors to detect things in-system. ( And also hampered the coms.)

Evidently, the implied reduction in effectiveness was such that enemies in the asteorid field would be in attack range (tens or hundreds of thousands of km) before anything hiding in or around the pulsar was detectable (If the Stabia system were like our own, the asteriod field would be 2-4 AU out form the sun. ASsuming they scan at the edges of the system, assume 20-40 AU, we might see between a 10 and 20x decrease in sensor quality from the effects of the Pulsar.)

Do note, this does have implications for enemies with any sort of EW capability (at least if they can manage similar interference intensities.)

Page 150

"We've conducted a full surveyor sweep of the system," Smemper told Horst, careful to keep any inrritation out of his voice. "If there's anything out there other than us, we've not found it yet.

- Again, implication of system-wide (multi-Light hour?) scanning capability from the edge of the system, with teh further implication (but no certainty) of the detection including FTL detection.

Let's see. They don't have FTL sensors, and most use astroshmucks to achieve any long range communication.
Their sensors are screwed by the pulsar over a radius of 2~4 AU, perhaps less, perhaps more, yet they can complete a full sensor sweep of the whole system, including what's beyond the pulsar, on the other side, that from their unique position at the edge of the system?
Uh-huh.

Why even bother sending ships for scouting operations across a system, or even close to an enemy battle group (as it happened with the battle against Ork forces) if your ship's sensors can even sniff the shadow zone of a pulsar?
Sorry, but that's absurd.

Semper looked down at the technical data scrolling across the slate's viewing plate, and frowned. "These frequencies are extremely low-level, and the prime fluctuation vector you're suggesting in these equations is extremely unorthodox. The Despoiler's vessels aren't too dissimilar to our own, with a broadly similar power output signature. Anything two or more ratio levels above these figures is enough to detect anything, friend and foe alike, within a radius of at lest three AUs.

- These are evidently frequencies (as we learn) that Eldar vessels are detectable out to, and it is implied that a slightly "higher" emission signature would normally be detectable otu to several AU (which also establishes a harder lowedr limit on Imperium sensor ranges, incidentally.)

The range of 3 AU indicates a lower end, but wouldn't be far from the higher end either. Anyone knows that when saying something can reach up to "at least X [units]", the maximum is not very far either. This maximum range being mitigated by several factors. Also, without the difference of signatures in power outputs alone, the sensors would actually be incapable of spotting any significant difference.

Page 204: Lunar-class cruisers have at least 3 plasma reactors.

- curiously, internal fires are stated to be able to "ignite" torpedo warheads or the missile's fuel propulsion mix. This may indicate that the "fuel" itself is chemically reactive, even though its evident they run on more exotic annihilation (or greater) energy generation capabilities (at least they must in order to match their observed capabilities.)

If they use promethium, it's not surprising. That stuff burns very easily. It's refined at "petrochemical production plants" (Caves of Ice).

Last part!

Page 210 - dark eldar weapons are fired at "supersonic" velocity.

Page 211 - single heavy bolter round blows apart a Dark Eldar's head.

One would have expected a heavy bolter to do more than that.

Page 214 - Eldar version of a flamer has longer range and more powerful
than human version - its "potent chemical mix" can immolate and incinerate two humans in a matter of seconds ("before they hit the ground")
That implies that it generates hundreds of megajoules in seconds.

i am, however, not completely sure I believe this is merely a flamer. though, instead of a melta-gun. If it is, however, then the 'chemical mix" must have a very very high energy density, something close to or as good as burning hydrogen fuel (I'm not even sure its possible to go much beyond hydrogen.)

Before they hit the ground? That's three to four seconds tops, assuming the corpse somehow retains some force as the subject falls to his dissolving knees.
To do that, the weapon would need to throw more energy than needed to take care of the full body in a controlled manner. Actually, two bodies.
500 MJ would be conservative.
Now the flamer is probably going to deliver the energy over a second tops, and the matter devour the target over the remainder of time.
0.5 GW for an infantry flame gun?

Heat wouldn't even work fast enough for that. You'd be looking at some kind of funky acid/melta weapon here, the kind of Starship Troopers' Tanker fire (movie), just faster.

Page 249 - The Drachenfels fires four torpedoes at a Dark Eldar vessel with its mime engines active (imitating the Drachenfels, ironically), only one of which hits (one misses, the others miss but detonate and hit with proximity detonations.)

The fact they are proximity detonations does hint that most torpedoes are not "directed" warheads but probably omni-directional (not much of a problem though when you consider they are normally designed to penetrate on impact and detonate inside, though.)

Considering the materials and technologies available to the Imperium, only a group unsure of the hitting probabilities of its guided torpedoes would go on with omniblasts.

Page 265 - Horst has a plasma pistol that fires a shot that "melts" a substantial but unquantified portion of a ravine wall behind a Dark Eldar assailant. Implies megajoule-range outputs (but again we knew that already.) Assuming between a .5x.5 meter, .2meter thick hole and a 1x1 meter, half meter thick area affected, we could infer hundreds, perhals thousands of megajoules per shot.

A volume of 2.3824 e-2 m³ then.
A plasma pistol that outpust 1 GJ?
Why not assume a more reasonnable half melon sized hole, with some of the plasma also splashing over a larger radius on the cliff's wall?
Because it's substantial?

Also, is that WH40K plasma and funky physics at play?

Page 274 Seventeen capital ships, including two battleships, and twenty escorts was considered by Ravensburg to possibly be the "largest single naval force" gathered together for battle since the Horus Heresy. This is probably greatly exaggerated, given the scale of battles in other section of the Imperium (MacCragge comes to mind)

+

Page 276 - the loss of Ravensburg's forces here would represent a loss of "the grreater partt of the battlefleet's strength", and would leave insufficient force to stop the Despoiler (his vicotry would be assured.)

That's what we call an inconsistency.

Page 275 - the imperium vessels here had been hounding the Chaos forces throughout the Gethsemene system for "days" Assuming a standard earthlike system and a diameter of around 12 light hours (ignoring the fact that striaght-line courses are impossbile, and no doubling back) and a 2 day timeframe implies an acceleration of about 100 gees easily.. quite liekly more (hundreds or thousands, as this is probably at least an order of magnitude higher due to various factors.)

How one can get such figures out of some piece of blurb that's so vague is literally beyond me.