Next Blue book update. apologies if some of the calcable examples seem more fragmented or convoluted.. I've added thoughts/sources and revised it more than once (both the macro cannon and bombardment cannon bits especially.)
Page 16
The aft section of a warship is a mass of enormous drive tubes and vast engine compartments, filled with thundering machinery, that run for up to a third of the length of the ship.
Engines of a warship will consume up to a third of its length. If the length of a ship's engines are known, ,then its length can be derived - in an approximate fashion, at least. Since it says "up to a third" it doesnt neccesarily HAVE to be that much. On the other hand, a few ships can go as much as half. As a rule, I tend to figure it varies alot depending on warship design. Given the incredible variance in ship lengths nowdays for even a given class (cruisers can range anywhere from 3 km to 8+ km) differences in engine type used may acocunt for this. Some ships may use smaller engines, others may use bigger. Some may even stick engines of say, a battleship on (known to be done to create some kinds of battlecruisers.) This might also help account for different performances in acceleration too.
Page 16
Ships moving under engines retain enormous amounts of momentum. If a vessel slows down without the correct preparations, it is so big that there is a very real chance that its structure will be damaged because the whole of its vast length isn't moving at the same speed. Because of this, ships must always move at least half of their speed unless they use the Burn Retros special order, detailed below.
..
If the ship passes its Command checkit cna move at up to half its cruising speed, or even remain stationary (hold station).
Although I'd thought I shouldn't ever have to point this out, 40K starships as a rule have momentum and retain that momentum, and that conservation of momentum exists in 40K. This quote is also interesting as it would hint that structural integrity/tensor type fields technically do not exist, although it has been mentioned in Planetkill (Phobos worked in Adamant) and Legion (infantry scale weapons strenghtned by grav fields) An alternate interpretation is that too sudden a course change at a given momentum (an unknown velocity) exceeds the abilities of said fields to cope with it. Or, some ships may not just have the fields and others do.
The fact of the whole "burn retros" bit, and the speed angle tends to suggest that maybe is the deciding factor, and that in context it applies to sudden emergency changes (having to avoid a collision, for example)
Beyond saying "there are limits to the structure and whatever supporting fields may exist", however, we can't really say much about it (certainly not much about velocities or such.) We certianly can't calc anythign definite. One could infer that these changes are much greater than whatever the forces nova cannons generate, but that ignores a directional component (IIRC, compensating for recoil in one direction does not neccesarily guarantee it would in all directions.)
I would note this also tends to make the idea the Imperium makes rampant use of mass lightening rather a difficult to use or improbable technology - at least a certain KIND of mass lightening tech. In sci fi lots of differnet approaches ot that technology have been utilized, so one cannot definiteively claim it works one way just because the technology supposedly exists. (and this quote would put limits on such a tech in any case.)
Page 18
Direct fire attacks include weapons such as lasers, fusion beams, and plasma launchers which when fired hit almost immediately, even across tens of thousands of kilometers.
Description of the "direct fire" weaponry. note "weapons batteries", which include railguns and missiles as well as fusion beamers, graviton pulsars, lasers and plasma projectors.") minimum velocity is established as "tens of thousands of kilometers" (or nearly .1c) though its probably MUCH faster for most wepaons (lasers certainly, and probably plasma/particle beams, since plasma diffuses very quickly unless it moves at near-c. unless it is some sort of physical projectile.) Definite upper limit will be the nova cannon (by virtue its a single, massive fucking gun running along much of the ship) and possibly bombardment cannon (although those aren't IIRC, primarily designed for space combat and generally have shorter ranges.) but it is not IMPOSSIBLE for higher velocities in broadside weapons (a railgun possibly could be near c velocity but with a very low-mass projectile. I am not arguing it DOES, mind, merely that it could.)
Macro cannon almost certainly are included as well, by definition, since only two categories of "direct firing" attacks are mentioned (weapons batteries and lances.) If Macro cannon, railgun, etc. were not included, they should logically be a separate category. Moreover, we see a depiction of plasma weapon firing in the blue book, and it involves what appear to be detonations (rather than a beam strike), which would probably be the plasma launchers (which even sounds like a projectile weapon.)
There is plenty of reason to consider this valid. Warp storm mentions that weapons battery salvoes are timed to allow a fractional-second delay (they say micro-second, but there is no way this can be literal unless everything moves FTL, which only happened in the Eye of Terror) to allow for both weapons fire to cross the intervening distance, as well as to compensate for the distance starships have traveled. The recent novel "Savage Scars" mentions macro cannon fire covering an unspecified "long" weapons range in seconds, which makes sense, since unless the projectiles are guided, even a starship moving at mere kilometers a second should be able to easily dodge dumb projectiels that take minutes to reach the target. Really, it shouldn't take more than seconds for a dumb projectile to hit the target, at tens or hundreds of thousands of kilometers, especially with railguns.
That isn't all either. We know from the BFG novels that torpedoes can travel at tens of km per second, and "Iron Hands" mentions boarding torpedoes moving at hundreds of klicks per second. Since both are munitions that technically can penetrate shields, and weapons batteries (at least as defined here) do not normally do so, We also know weapons batteries included guided projectiles like missiles as well as unguided (like macro cannon and railgun.) The latter two ought to move considerably faster than missiles, and a railgun (a weapon relying on impact to do damage, rather than an explosive warhead) ought to be faster still. In that context, velocities of thousands or tens of thousands of kilometers is hardly improbable either. I will admit that some weapons (EG guided ones) moving slower than tens of thousands of km is not unreasonable, but it is equally true that dumb fired ones will need greater speed to compensate for their unguided nature - particularily when one considers how gunnery is often depicted in 40K.
There is also a bit in Execution hour where we know the Punisher-class Strike cruiser's bombardment cannon move at close to 1/4 the speed of light. It is also noted in that same novel by Ulanti that the Macharius would have better accuracy at range than the strike cruiser - unless the macro cannon were all guided (possible, but debatable) the Macharius macro cannon would need to be capable of roughly similar velociites to be true. Nova cannon also hint at "direct fire" propogation rates being short.
Page 19
The attacks that ships make are divided into two sorts: Direct firing and ordinance attacks. Direct firing uses a ship's weapons batteries, lances, and nova cannon. Ordnance attacks include torpedoes and fighters, which are launched during the shooting phase but are not resolved until they hit their target in the subsequent ordnance phase.
Direct fire weapons again are noted to be weapons such as "lances, nova cannon and weapons batteries." Worth noting as we probably can establish ranges and velocities through various means (for example, using game stats could establish "direct fire" ranges for guns. Although it would clearly not work for all weapons - eg laser batteries or laser lances.)
Note again that direct firing do not make subdivisions or distinctions between weapons batteries as some have hinted. Indeed, lances and nova cannon both fall in this definition - their shots strike within a very short period of time (less than a second at ranges of tens of thousands of kilometers, easily.)
Page 19
Some weapon systems can shoot in more than one fire arc. For example, many cruisers have weaponry in a dorsal mount (ie, along the top of the vessel) and dorsal mounts can fire left, front or right. Some weapons can even fire all around.
Weapons it seems can be turreted to a certain extent (At least some can.) going by some of the sketches and drawings even broadside weapons can be turreted, although turrets tend to be far larger, more mechanically complex (and therefore, less numerous) than gun port mounts.
Page 19
Enemies at close range pose a much greater threat than those thousands of kilometers away, so a shp will normally target the nearest enemy. However, a ship can always fire at whatver targets you like if it takes and passes a leadership test on 2d6 first.
Range seems to have an effect on the "danger" that a target represents. Presumably this has something to do with both accuracy and coherency of weapons fire (weapons battery broadsides are more accuate closer up, and some weapons like laser and plasma will lose effecitveness over range.) Perhaps shields are more likely to be breached at closer range (not only will more shots hit on target, but they may be more concentrated.) This makes sense, since many weapons (like macro cannons) depend on accurate placement for effective damage, so the furhter away one is, the less likely one is to make direct hits (or even very close hits.)
Then again, some weapons like nova cannons and lances are probably more effective at longer ranges (being big, bulky weapons like they are.)
Page 20
Lances are incredibly high-powered energy weapons that are capable of burning straight through an armoured huull or cutting an escort ship in two. On Imperial and Chaos ships lances are usually mounted in huge turrets with quad or triple energy projectors that focus into a concentrated beam of destruction.
Lances seem to represent the "big/heavy" guns on a ship, the ones with the longest range and the biggest individual punch. They also seem to be a bit more versatile than weapons batteries, having cutting/piercing effects as well. Each lance is also a multiple-projector mount that seems to have a death-star like "composite" beam effect, although preusmably they can fire them independently as well.
Although in BFG they are primarily used against large ships, they have been used against fighters as well (various codexes and epic sourcebooks and suhc pertaining to the third Armageddon war describe lances taking out Ork bombers, and the HH novels have lances used in a point defense role against torpedoes, for example.) Although 40k fighters can sometimes get big (up to a small starship.. eg 100+ meters long) others are presumably alot smaller so its hard to say.
Page 20
Weapons batteries form the main armament of most warships, ensuring that much of their hull is pock-marked by gun ports and weapon housings. Each battery consists of rank upon rank of weaposn: plasma projectors, laser cannons, missile launchers, rail guns, fusion beamers and graviton pulsers. Weapons batteries fire by salvos, using a co-ordinated pattern of shots to catch the target in the middle of a malestrom of destruction.
Weapons batteries seem to be the "medium/intermediate/secondary" guns on the ship. Smaller but more numerous than the massive dorsal turrets (like lances, but not always lances) they possess less range and power individually but possess alot of punch collectively. Its a bit like Age of Sail or the intermediary "ironclad" period between broadside guns and turrets, it would seem.
Another detail worth noticing is that weapons batteries are perhaps the most diverse weapons around. However, not all ships will carry all those weapons at once. Some ships seem to carry only a couple of those, or maybe only one type (all lasers, or maybe lasers and plasma, or plasma and railgun/macro cannon, or lasers and missiles, etc.) This is probably meant to enable a ship to deal with more than one kind of enemy (one that may be resistant to laser or plasma fire may not be so against missiles or projectiles, for example.)
Third: The velocity issue, which I already covered.
Lastly, the need to coordinate weapons of different types and velocities, especially in large numbers (and coupled with their "medium" calibre relative to the big turret weapons) also means that their destructive capability at longer ranges is also more limited (fewer direct hits, or fewer concentrated hits.) Hell, the reason range matters is quite likely due to accuracy. Coordinating so many guns on a moving target is not bound to be easy, hence the "pattern of shots catching the target in the middle of a firestorm" type description (EG and the blast markers.) projectiles probably either proximity detonate or stand-off detonate (depending on how they work), beam weapons rake or sweep space around or near the target, guided munitions adjust course to strike (in the case of Kinetic kill elements to such changing course may reduce forward velocity and therefore the effectivenss of impact), and so on.
That said, it is quite likely that (due to velocity, guidance ability, etc.) different weapons have different ranges. Unguided macro cannon and railguns probably have shorter ranges than lasers (which move at lightspeed) and missiles (whcih are definitely guided) for example.
Again, range is also likely influenced by defenses like void shields. Voids can easily deflect and (if needed) absorb a ton of abuse, and the rule of thumb (at least as pretensed in BFG sources) si that a single ship facing one of equal power at range won't do much damage unless they get lucky (or very accurate.) This probably is dictated though by power allocation (eg some to shields, some to engines, and not all to weapons) as it is to the toughness/nature of shields or range itself. At closer ranges, against a more slower moving (or stationary taget), with more power diverted frome ngines to weapons, the situation might be quite different. Variables, as always, matter.
Page 21
the forty men pulled harder at the traversing chains, heaving the massive barrel of the macro-cannon into position amidst the clank-clank-clank of rusty gears.
"Avats heaving! stand by for reloading" ordered Murman and the men dropped the chains and hurried to stand by the gun's huge breech. At the signal from the Gun Captain, ten of the men sprang into action, pushing the breech-block. When it was open, the others bent their backs to the loading winch, ,lowering the shell, which weighed several tons, into the heart of the cannon. With a deafening clang the breech was closed again.
Capital ship "macro cannon", with a shell that weighs "several tons." Going with the "lower limit" velocity I established before of 20,000 km/s for "direct fire" weapons. At that mass/velocity, the KE of the projectile would be 4e17 joules, or just under 100 megatons. Assuming the 40,000 km/s velocity I conjectured, it goes up to ~400 megatons. This is definitely a lower limit. The mass can probably be MUCH higher (and is, ,given other sources. In Nightbringer they're hurling building-sized projectiles out to 300,000 km, and in Iron Hands they hurl shells "three times the size of a man." Both would mass FAR more than "several tons." On top of that a number of novels like Wolf's Honour, Let the Galaxy Burn, and so on describe shells that are tank sized or bigger.. being many tens or hundrds of tons.)
If we assume "tens of thousands of km/s" refers to 100,000 km/s, and apply the same logic (railguns travelling faster than missiles.) and assume a 10 ton shell, the KE is 3e20, or around 70-80 gigatons of KE. Macro cannons, IIRC typically fire explosive warheadS (like bombardment cannons and nova cannon) so they may not rely on pure KE/momentum as the primary/only damage component. In this respect, lower KE/momentum probably would be a benefit, though it probably has a shorter range. Railguns probably are more "KE/momentum" weapons. We do know from the Cyrene Extrminatus short story (Thanks to Teleros for providing the info) that Mass driver/railgun rounds are ~10 tons in mass in that instance, which would mesh well with the above in an OoM manner.
Note that given the "mass" of the shell, unless "several" means alot more than 2-3 tonnes, the weapon in question is far lighter than many other anti ship weapons (described as being as large as tanks, or larger, with masses of tens or hundreds of tons) Hell, In "First and Only" and "Necropolis" the higher-end ground based macro cannons were flinging "multi ton" shells. I'd say it might be a point defense weapon, but the rate of fire would be slow, unless its designed to fire those proximity-detonation shells or something (I think Execution Hour describes such) Then again, this IS 40K, so it may be some ships DO use point defense weapons like that. On the other hand, it could just be a small ship (an escort for example) or a vessel that has a large number of smaller guns (as opposed to fewer, bigger guns.)
It could also be that the ship opted for a more numerous number of smaller guns. Such a ship need not have equivalent firepower to a ship mounting a smaller numbr of more powerful macrocannon - perhaps they traded off raw firepower for greater versatility (better able to take on smaller targets or point defense duties, for example. It may also be possible that the smaller shells have a much higher velocity to compensate for the lower mass. Other possibilities may exist yet, but the point is, it is not neccesarily a contradiction for macro cannons to be firing different masses of shell.
On top of the KE, we know macro cannons are often warheads of a type. Assuming they carry something equivlaent to a nuclear warhead, we can work out (approximately) the yeild. Modern nukes get somewhere between 1-2 kt per kg (
here - yes I know its Wikipedia, but they actually do source the articles so its valid), possibly up to 6 kt/kg. For a 2-3 ton shell, that is between a couple of megatons up to 12 or more megatons. If it were a plasma munition rather than just a nuke, it would be 1000x better (as per Space fleet), upping the yield to single or double digit gigaton range. This is conservative, since we have no reason to assume (due to Space hulk nukes and Denzark's hammer example, if nothing else) that 40K nukes can get to very high yields suggesting their nukes are more efficient than ours. ASsuming close to 100% efficienciy (say 100 kt per kg) you get several hundred MT per shell (consistent roughly with the KE output) and a plasma muniton woudl get several hundred gigatons, easily (although exceeding 100 MT/kg easily exceeds the energy yielded from a single kg of fuel, so the energy owuld be coming from another source at that point, possible since a warp-based connection has been hinted at plasma reactors and weapons multiple times. If we assume it was close to E=MC^2, say 20 MT per kg, we're talking 40 GT per macro cannon shell or so.)
Page 22
A Nova cannon is a huge weapon, normally mounted in the prow of a ship so that the recoil it generates can be compensated for by the vessel's engines. It fires a proejctile at incredible velocity, using graviometric impellers to accelerate it to close to light speed. The projectile implodes at a preset distance after firing, unleashing a force more potent than a dozen plasma bombs
(First off I apologize for the length and somewhat fragmented nature of this analysis as well, but over time Nova cannon calcs have been disputed and discussed a ton, so a much broader and lenghtier analysis must follow.)
I would generally assume "close to light-speed" to mean at least 80-90% of C, but like most things this has been disputed. AT the very least, it should mean "greater than 50% of lightspeed." The size of a Nova cannon shell is never given precisely, but the diameter of the shell is given in other sources (50 meters in Warriors of Ultramar, though a 30 meter diameter nova cannon is mentioned. Mass can be derived by assuming the length is at least equal to the diameter, or (more probably) a multiple of the diameter (2-3x longer than the diameter, for example. A 50 meter diameter shell would be 100-150 meters long.)
Example: Going by a 50x150 meter shell made of iron (assume 30% solid, its supposed to be packed with explosive o funknown type and density) fired at ~90%of c yields a shell mass of around 770,000 tons and and a KE of 9e25 joules, putting Nova cannons well into the petaton range (~21 petatons roughly here.) In the literature, Nova Cannons are implied to "charge up" for firing just after loading, implying that the gun is charged in a matter of seconds - but it could alst for many minutes to close to an hour, depending on your source and whether you figure they constantly charge the gun up whilst loading.
Of course, if the WoU gun is a different class of Nova cannon, then its possible/likely that the shell mass I estimate isn't valid. It may not be, since Dark Disciple mentions Retribution class ships carrying 40 meter wide torpedo tubes and torpedoes are roughly the diameter of nova cannon shells (As per the Hammer class Battlekroozers.) and we know from the BFG magazine that 30 meter diameter nova cannons exist (suggesting similar shells. and failing that, there's always torpedoes anyhow, so it shouldn't affect the "Back of the envelope" nature significantly. If it does.. well.. thats why I'm going for a range of values now
Something that has been pointed out before WRT nova cannon calcs is that the diameter of the breech/breech door for the nova cannon is not going to be the same as the projectile (because that is how it is with real life cannon.) That has a certain amount of merit, but there are a number of qualifiers to that assessment as well. First of them being that a Nova cannon is not a chem propelled slugthrower. It's closer in role to an EM gun or railgun, which does not have to contain the pressures of a propellant charge by mass, or risk rupturing (EM guns have different considerations entirely.) There is no casing, no rifling, nothing. That said, there are other reasons for the breech end being heavy (at least in a turreted weapon) and that is to balance the gun (Thanks to Sea Skimmer for pointing this out, as usual) since a non-propellant weapon is likely to have EM magnets or similar along the gun itself. (Of course, since Nova cannon are fixed mount, the balance issue isn't as big a deal as it would be if it were turreted.)
There's also the issue of vaccuum being created behind a shell moving at such velocity and it sucking the air out of the ship (unless the area is vaccuum, which in the case of nova cannon is unlikely) so sealing it strongly by other means is important. This catually points out another reason why the breech doesn't have to be large, since 40K has a ton of forcefield tech and means by which such sealing could be done, the gun needn't have a huge mass of metal at the end.
Even if this were a consideration though, it is unlikely that it would change things much for a variety of reasons. Examples of the breech end
here and
here show that the difference between diameter of shell and door isn't all that significant (EG not an OoM difference, but maybe 1/2 to 2/3 differece.) which is not going to dramatically impact the calcs in the least. And failing that, we cna always check up against torpedoes and bobmardment cannons (which depending on source can go with mass OR diameter. The fact that 40 meter diameter torpedoes exist alone can justify the earlier calcs.) which just goes to show you why I keep revising this stuff.. its important to looka t a calc from lots of ways if you can just to make sure it all works out.
This is one sort of calc (and perfectly valid) for the nova cannon, given what we know, but it has been disputed. We can looka t it other ways. Torpedo yields (which can get to thousands of tons by scaling and by direct inference from a Gav Thorpe short story in Let the Galaxy burn. We know from Warp Storm/Armada that Bombardment cannon and nova cannon have similar bore diameters to torpedoes, which can go up to 40m or so, as per dark disciple.) is significant. We will also assume .6c velocity (not quite as "near-c" as 90% perhaps, but still possible. And we know inc omparison to bombardment cannon, as well as direct fire weapon descriptions, that a velocity of .5c or so would be more sensible at least.) a 2000 ton nova cannon shell would be 4.5e22 J of KE.
It is also interesting to note that the recoil generated needs to be compensated for by the engines. This suggests that the recoil/output of the Nova cannon is of comparable magnitude to the output/thrust of the engines. And if you know the specifics of one, you can probably estimate the other (IE figure acceleration from ship mass and the recoil of a Nova cannon.) Taking the shell example above, the momentum would be 4.77e17 kg*m/s. If the ship in question has a 5000 gee acceleration rate the ship itself masses somethign like 9.5 billion tons. A mass far greater than implied by a number of other sources, but I tend to believe 40K ship masses are dramatically under-stated in the vast majority of cases. Given the estimated accelerations from other sources like Sabbat Martyr or Grey Knights, and estimate the mass from starship dimensions, the output of engines for a cruiser/battlecruiser grade would be high TT/low petaton range easily (consistent with the "stellar scale" outputs mentioned in Execution Hour for warp engines, which aren't as energy intensive as the realspace engines as per Ravenor which does confirm the estimates.
We can be more conservative than that, though. The recent Rogue Trader RPG released stats for many ships, including masses and accelerations. A Lunar class cruiser has a mass of 28 million tons and a "max sustainable acceleration" of 2.5 gravities. At those values the engines have a momentum of 7e11 kg*m/s, which (in theory) the nova cannon could be capable of matching. At this scale, assuming a .6c Nova cannon velocity, the shell would have 7.9e19 J of KE and the projectile would mass... 3.5 tons. Possible.. but not very likely, given what we know torpedoes and macro cannons (or hell, even fighters) can mass. To be honest, the cruiser mass figures, if not the accel figures, can be argued to be off by quite a bit (and ships can be argued to be more massive.. something I will deal with at a later date.. nevermind the accel) but for our purposes her it does serve to provide a "canonical" lower limit.
Another useful detail we can derive from this is that nova cannons are a prow weapon, and thus powered by the reactor. From what we know we can infer (in a broad sense) that the other weapons (broadside, dorsal, etc.) and other systems (engines, shields) would draw roughly comparable levels of energy, which gives us a good way to double check these figures as well as infer capability of those other weapons even further.
The destructive power of a Nova cannon shell is up in the air, since the destructive mechanism cannot easily be agreed on.
If explosive, it ought to be at least comparable in magnitude ot the energy expended in getting the projectile to the target(s), which suggests its petaton range, if not significantly higher. Note that if this is the case, the energy density of the explosive, like plasma reactors, must be many many times greater than conventional nuclear fusion or even antimatter, for it to be equal to or greater than what a near-c projectile provides. Then again, 40K is not a stranger to "power sources with insanely high energy densities." either. The depiction above assumes an explosive projectile, which does not match quite with "implosion. On top of that, novels like "Cadian blood" give a very exotic nature to how nova cannon shells inflict damage, which does not seem to rely on raw energy (i hesitate to say "black hole" or even "vortex warhead".. but something arguably along those lines.) This does not preclude an explosive shell existing, mind, but it doesnt seem to be the point. We do know different kinds of nova cannon exist (some more like beam weapons, some seem to have different velofcities or firing mechanisms, too) but the Cadian blood one matches up best with the BFG one (supported by Shadow point, Chapter's Due, and a number of other novels where nova cannon sometimes appear.)
Also note that "plasma bombs" is another term used in earlier sources for torpedoes, so this might imply that a Nova cannon is equivalent to a dozen torpedoes (a double salvo, in other words.) I do find it odd they say "force", as this implies that a Nova bomb detonation has some sort of blast/pressure effects like a conventional explosive (nuclear/antimatter warheads would not have blast effects, ,becuase the blast is a result of atmospheric detonations.) which may hint at some sort of exotic mechanism, perhaps like a seismic charge (or maybe a multi-function warhead). anyhow, this would imply plasma torpedoes are in the teraton range or so (double or triple) assuming a multi-petaton nova cannon. Again this gets into semantics and the explosive/implosive bits about nova cannons, so a direct comparison between plasma bombs (however one chooses to define it) and a nova cannon shell is up in the air. I think arguing that nova cannon are worth 12 torpedoes in effect (however that effect results) is the best.
All in all, Its probably not best to obsessively ascribe one single value to nova cannon or hinge one's entire argument on the truth/falsehood of a particular vlaue. A range of values is quite acceptable and can even be reconciled - we've known quite awhile there are many kinds of nova cannon - the different calcs could simply account for differences in design, requirements, performance, etc. Even velocity (Eg the WoU nova cannon). Gigatons can fit just as comfortably as the petatons can, depending on how the overall fit of the universe requires.
page 23
The weapons carried by some ships are powerful enough to reduce whole cities to plains of radioactive glass. Ships are armored and shielded in order to resist their savage caress,, hulls are heavily reinforced so that they can survive the horrific pounding of gigawatts of energy. But within every ship is a crew all too vulnerable to the fires of battle and the deadly cold of the void. Ships are often crippled by crew casualties long beofre hull cracks or drives explode.
We actually hear about ships destroying cities in various forms (vaporizing, melting, ,etc.) quite often. Battleships, cruisers (or rather specific weapons on crusiers) and even frigates have been mentioned as capable of destroying cities with their weapons. We also have heard of cities simply being "levelled" or razed or otherwise demolished/wiped out.
Cities can be quite large too. Either fortress cities (like we see in 13th Legion and Ghostmaker) to Hive Cities (which span many tens or hundreds of kilometers in diameter minimum, and extend many kilometers both above and even under the ground). Hell, some planets have continent sized buildings (like Terra, but also some Hive Cities and Forge worlds do ).
Calculating it can be hard, given the variables involved, though"reducing cities to glasS" implies melting. Assuming a 10 km diameter city, composed of iron, 90% empty and with an average building height of 300 meters (with a fairly crowded density), it would take at least 5 gigatons or so to melt. Something larger (say 50 km in diameter, or about hive city size) that extends up ~ 5 km in height, as a cone, composed of iron and 90% empty) would take around 738 gigatons to melt. THat doesn't include anythign below ground - assuming a 200 meter depth into the rock, 90% empty, would be several times greater) would add around another 40-80 gigatons depending on composiition. Again this is not a precise, absolute figure.. but just an approximation. Melting the ground to several meters deep would simply require a few hundred megatons, for example.
For shits and giggles if we assume a 100 km diameter hive city (some of them get that big, since we know a number of "normal" non hives can be several tens of km in diameter easily) several km tall and conical, with iron composition and 90% empty space, it could take 1.8 TT of energy to melt. If we go "contientn" scale.. say 1000 km and 10 km tall, and a cylinder, it would take ~590 TT to melt. We know Battleships can destroy hive cities (been done before) so that suggests we can definitely say battleship scale vessels get into the GT/TT range of firepower, proably within one shot.
The Rogue Trader RPG mentions starships destroying cities in a single broadside, and an early epic source (which I alreay covered) has described titans needing "hours" to do so (and cruisers without a doubt are MANY orders of magnitude more powerful than Titans...) I think it is safe to say a "single shot"
Like with the "continent destroying" comment before for bAttleships, this quote is somewhat speculative and open to interpretation, so it doesn't really tell us much since you can go from "small town" to "hive city" in definition, nevermind the varaibles in duration or method of destruction. Some of course treat it as an inviolable upper limit, but that can't be helped.
The "gigawatts of energy" is interesting in comparison to the above calcs and what we now of other weapons. Strictly speaking there is nothing "wrong" with it.. a ship that can resist kilotons, megatons, or even gigatons could shrug off gigawatts, and if one is loose in interpretation "gigawatts" could mean gigatons (just alot of gigawatts...) It might also be an error (someone said 'gigawatts" instead of gigatons or terawatts or petawtts or whatever, for example) such errors have creeped in (the "kilotons of kinetic energy for a supposed ground weapon ona Stryker wannabee from Emperor's Mercy, for example.) Again, I'm not going to stress over having a "specific" value for this.
Page 24
The weapons used in space are so destructive that when a ship is hit there is a chance that a vital location will be critically damaged. Critical hits can temporarily knock out a ship's weapons and engines, start fires or even breach the hull.
To be honest, I'm not really sure how to translate this into "in universe" examples, aside from lucky or chance hits that get by defenses or such (hit weakened bits of shield, exposed sections, whatever. IIRC voids dont even completely protect against the possibilities of critical hits, so there's lots of ways to handle that.
Page 24
Blast markers represent all kinds of events - huge explosions, expanding shockwaves, intense radiation clouds, ,tumbling debris, unexploded warheads, plasma bursts, etc.
...
They show areas of tumultuous, strife-torn space
[/quote]
Game mechanics after a fashion, but its interesting to note what "blast markers" would represent on the 40K battlefield - "shockwaves" (implying some weapons generate them despite vaccuum, again like a seismic charrge), radiation (presumably like the dumping of absorbe denergy from void shields, but also starship explosions) debris, bombs, and plasma burts (either plasma cannon or plasma torpedoes, if not both - it suggests they are omnidirecitonal blast weapons either way.) Again it gives an idea of the kinds of firepower and abuse get thrown at 40K ships, although how I interpret blast markers is still a cautious one, since it is a game mechanic. Also, given how I've seen it portrayed in BFG and elswhere, those "areas of strife torn space" tend ot persist for quite some time, which is hard to reconcile if you have nukes or antimatter bombs releasing their energies in fractions of a second
On the other hand, taking this too literally has other odd implications, like weapons spreading out to fully encompass hundreds of kilometeres of space and being hazardous throughout that volume as well as remaining persistant. That would lead to.. interesting calcs
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If a ship moves through any blast markers, it reduces its speed that phase by 5cm regardless of the number of markers actually moved through.
As tempted as I am to try to make sense of it in an analytical sense, I am not going to do so. I'll just leave it as notice that blast markers (and what they represent, eg weapons damage) seem to be able to affect the mass/momentum of a ship in a noticable manner (which is consistent, for example, with impacts shaking the ship violently, etc.) Mind you, given that speeds for shisp range form 30 cm to 20 cm, a 1/4 to 1/6 degradation in speed, ven at a few km/s, is still alot of potential momentum. We just can't figure out how much, or the manner in which it is applied, or anything usable other than it happens, which only plays into the "blast markers lead to weird ideas" about 40K weapons if taken too literally.
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If a ship's base is in contact with any blast markers when it is fired upon, its shield Strength is reduced by -1 per Blast Marker.
Once more, not quite sure how to interpret this WRT in-universe, aside from it taking multiple "blast markers" to knock down shields and that it only happens when in "contact" with whatever the blast marker is representing. I suppose with above it could imply that multiple blast markers would imply multiple changes in momentum to the ship before shields get knocked down, even temporarily.
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Blast Markers interfere with gunnery, as mentioned earlier, disrupting firing and causing plenty of 'ghost' images on the firing ship's sensors.
The phenomenon represented by "blast markers" represent some sort of sensor-disrupting measure, suggesting a potential means of electronic warfare. (which we see after a fashion in various novels, and in certain kinds of torpedo or nova cannon shell.) Void shields themselves seem to have a "EW-like" function in this respect, since their dumping/dispersing of attacks generates blast markers. And again, I dont see regular nukes or AM detonations doing this since the energy doesnt last long enough to do it, and this effect suggests blast markers can be persistant. Though in this case, its hard to see some weapons doing it regardless (EG lasers and particle beams and railguns.)
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Ships are protected by powerful energy shields, so that they can survive travelling through space. The shields form a wavering band of energy around the vessel, a teardrop of invisible force that can absorb or deflect the worst excesses of stellar radiation and metor showers or a series of weapons hits. The amount of damage shields are able to absorb is limited and they will be overwhelmed by a sustained attack, forcing a temporary shutdown while the shield generators vent off the excess energy.
Shields must also shut down while they vent excess energy. The reason for this has never been stated. Either the shields block such emissions (creating a temporary but dangerous vulnerability) or its simply a consequence of the design (it seems odd, but perhaps its designed so to avoid destroying the generator or damaging it.) Given that ships mount many shield generators to provide multiple layers of redundant protection,, its probably unlikely that the void shields themselves block the radiation process (however it works.), or if they do, they vent in such a way that other shields minimize the vulnerability. Of course we know nothing about the radiating method anyhow, aside it has a visible component), although Path of the Warrior evidently mentions Imperial void shields (from the Eldar perspective) dumping energy into the warp.
Void shields on a starships are "teardrop shaped" Also, It is worth noting that void shields are not *just* energy-absorbing devices. They can also "deflect" attacks, ,which suggests they redirect or disperse the energy of attacks so that the generators need only absorb part of it. This may explain the "teardrop" shape in some way - angled shields would help deflection, and the angle would be optimal in a "forward" configuration (which is where Imperium ships stick those heavy armoured prows as well.) The "absorbed" energy probably represents what the shields handle in the process of deflecting attacks. Deflecting attacks before absorbing makes sense, since you want to absorb as little energy as possible and save strain on you rdefenses as much as possible.
I'm honestly not quite sure how to reconcile this notion of shields with the newer ideas of shields being warp-based or shunting attacks into the warp (Path of the Warrior, Imperial armour 6) or the like. It could be different kinds of void shield operation by different mechanisms, or it could be multiple mechanisms for disposing of attacks employed (again redundancy.) Or perhaps even both, since they're not mutually exclusive mechanisms.
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A blast marker is palced touching the ship's base for each hit blocked by the shieldst to show how much energy has been absorbed
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Once they have been overloaded the shields may not be raised again until the ship escapes the storm of energy blasts and shock waves represented by the Blast markers. The shields remain down until the ship moves away from the Blast markrs in a subsequent movement phase.
More blast marker fun. In this context, it seems to suggest shields are under strain in the magical "blast marker" damage zones, but also to reprenset the absorption and dissipation functions as well. This does not seem to destroy or knock out the shields, but is purely a temporary weakening.
Maybe, in context with the "warp dispersion" above, we should attribute Blast Markers to funky warp disturbances in the context of shields?
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The Intolerance was surrounded by a seething sphere of plasma and missile detonations, held back by the bright coruscating arcs of its energy shields. With a blinding flash the shield generators collapsed under the onslaught, leaving the ship at the mercy of its enemies.
In universe depiction of the blast marker/shields interation in action. I'm not quite sure how it could maintain a perfect sphere to begin with (a teardrop would be semi-sheprical), but one possibility is that its describing the shields behaving as the containment and radiating medium for the energy - much like a Mote in the God's Eye or the Lensman universe "screens". Though in the former case without the nanoying tendency of the ship to destroy itself when the fields are overloaded. And you can scan through them. Anyhow, the "sphere" would simply represent the energy being absorbed, deflected and dissipated away by the shields (and the more surface area the better for this), which would aguably make a sort of "sphere" effect, I suppose.
This also tells us that void shields can be strained or overwhelmed, although they only gradually fail against the assaults (greater the strain presumably, the faste they fall.) I have heard such argued for SW shields before.
Also note that the plasma weapons seem to be some sort of physical munition, as they detonate omnidirectional rather than behaving like a beam weapon (recalling the "plasma launcher" bit I alluded to earlier.)
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A ship with no hits left is effectively out of action. There may be some crew left alive, trapped in compartments which have not been breached yet, there may even be power available in some sections of the ship, but the ship can no longer fight. When escort ships are reduced to zero damage remove them from play and replace them with a blast marker, to represent the expanding lcoud of debris left by their passing. With a mighty capital ship, there is a chance that the vessel will be destroyed by catastrophic damage as its plasma drive overloads or its warpdrive triggers.
Escorts are less durable than capital ships, so any destruction that hits them is likely goign to totally obliterate them. although some of the larger frigates probably could survive this. Cruisers and Battleships, however would be much more durable and resilent to catastorphic destruction, and might merely be "crippled", mission killed, or howver you want to define it - basically the'd be a throughouyl blasted but largely intact hulk.
Another possibility is that escorts simply aren't as engineered/protected as better as Cruisers/battleships. The latter tend to be more highly valued and harder to build, whereas escorts might be far faster to build and replacable (They may even favor a mor disposable model of such ships to enable them to be built faster, for all we konw.)
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Blazing or drifting hulks will block lines of fire that pass ove their base, due to the clouds of venting gases and debris they produce. Likewise torpedoes which strikea hulk will detonate...
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Blazing or drifting hulks have no shields or turrets value. Hulks can be targeted by shooting (usually in the hopes that they wille xplode and cause vast harm to your enemies!)
more on crippled hulks/capial ships
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Drifting hulk : The ship is reduced to a shattered hulk in space. [2-6]
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Blazing hulk. The ship is reduced to a burning wreck with uncontrolled fires blazing on very deck. In time the fires either burn out or trigger a cataclysmic explosion.[7-8]
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Plasma drive overload: The ship's plasma coils overload and explode i na blazing inferno of white hot plasma. Remove the ship from play, leaving behind a number of Blast markres equal to half its starting number of hits. Every ship within 3d6cm of the imploding wreck is struck by lance shots with a strength equal to half the ship's starting Damage capacity.
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Warp drive implosion. The ship's warp drive implodes, ripping a hole in real space that tears at nearby vessels with horrific force. Remove the ship from play, leaving behind a numbr of blast markers equal to its starting number of hits. Every ship within 3d6cm of the imploding wreck is struck by lance shots with a strength equal to the wreck's starting Damage capacity.
Game stats, but it shows the manner in which catastrophic detonation could occur, although not guaranteed the way with escorts (due to armor, redundancies, etc.)
