Macrocannon Size

[Lord Revan]

"low velocity" in this context is relative, it might not actually be that low but it's signigantly lower the "high velocity". For example pistol rounds are low velocity rounds, yet it's impossible for you to see them in flight with naked eye without the shooter using tracers.

[WhiteLion]

I'm not sure I understood what you meant

[Eternal_Freedom]

"Low Velocity" might mean, say, 1,000 km/s compared to "high velocity" of, say, 3,000 km/s. It's a lower velocity sure, but I sure as hell wouldn't want to get hit by a "low velocity" round in this context.

It's a relative term. Something can be lower than something else but not actually "low" in an absolute term.

We refer to red stars as "cool" but they're still 2,000 degrees surface temperature - they're just low-temperature compared to blue/white supergiants that are 10,000+ degree surface temperature.

[WhiteLion]

ok thanks, now I understand what you meant, unfortunately I understand English, but only written in a simple way.

I agree that a 100 kms bullet is still devastating. But the argument was based on the fact that mass and speed are factors that influence the power of the weapon.

In this case we have quotations that confirm that the larger macrocannons fire projectiles at 0.25c, which is the speed of the smaller macrocannons.

This is why I said that larger cannons will have a much greater power, speed does not change, but mass changes. A projectile of 100 meters in diameter launched at 0.25c, will have a power much greater than one 30 meters wide.

A glorian class, visually has 1/3 - 1/4 wide guns of the height of a frigate. They will have a diameter of 150-200 meters (wanting to be conservative), and the bombing macrocons in each ship class are at least double or triple in size, just look at the Eternal Crusader's macrocannons in one of the online photos, they are huge, two occupy the space of more than 4 macrocannons in the side of the ship, and have enough power to be used to destroy planets (as we see in the video game).

An Abyss class or an Ark Speranza class are mentioned as large as a continent. Even if we wanted to hypothesize a length of 100-150km we will have macrocannons to say the least enormous. In this case the difference is abysmal, and the power of the weapons changes accordingly.

[LaCroix]

A glorian class, visually has 1/3 - 1/4 wide guns of the height of a frigate. They will have a diameter of 150-200 meters (wanting to be conservative), and the bombing macrocons in each ship class are at least double or triple in size, just look at the Eternal Crusader's macrocannons in one of the online photos, they are huge, two occupy the space of more than 4 macrocannons in the side of the ship, and have enough power to be used to destroy planets (as we see in the video game).

An Abyss class or an Ark Speranza class are mentioned as large as a continent. Even if we wanted to hypothesize a length of 100-150km we will have macrocannons to say the least enormous. In this case the difference is abysmal, and the power of the weapons changes accordingly.

While WH40k seems to be a fantastic setting with no rules of physics apart from the "rule of cool", we still must assume the laws of physics apply (outside of the warp, which has their own set of those).

While the materials used are capable to create these, say, 200m guns and mount them on a 20km sized ship, there is no proof that this infers that they are able to build 1000m guns on a 100km long ship. They might be able to put 5x as many of the 200m guns on it than on the other, but even high gravity compressed super alloys and adamantium have material properties, and limits.

You are ignoring these undeniable facts, and are assuming that you can supersize the same weapon with no regards to these limitations.

Yes. Facts.
A macrocannon projectile can damage the same ship it was fired from. It can even damage the physical hull of an Abyss class, but due to the mass/size/armor, it would take a prolonged bombardement to cause any significant damage. But this is irrelevant to the point - it proves that the material is not immune to damage, which also means that there is a maximum size for any weapon made from it, for at one point, it would collapse under its own weight. Let alone the stress of firing a !SHELLED! projectile at c-fractional speeds.

Simple math - doubling the bore diameter of a gun, and not allowing for relative bullet weight and mass to change, means you need (at least) 8x the energy to fire it. Which means 8 times the recoil, which means you have roughly 8 times the mass of a gun. Thus, a 150m cannon will weight approximately 125 times as much as a 30m cannon (5 cubed), and will have 125 times the recoil of the smaller one.

[WhiteLion]

40k It follows the rules of physics, but it does so in its own way. It provides an almost coherent physical basis for the operation of technology on ships, and then in several episodes it completely ignores it for greater theatricality. I don't mind this, on the contrary.

We have evidence that the imperium is able to build macrocannons of that size, for example we look at a glorian class compared to a ship of almost 2 km:
https://warhammer40k.fandom.com/wiki/Ir ... agship.jpg
The Iron Blood macrocannons in the picture are normal macrocannons, they are not bombing macrocannons, and they are about one-third the height of the Cobra Class, the bombing macrocannons are still bigger.
We can observe the bombardment macrocannons compared to normal macrocannons in the Eternal Crusader and in the cruisers:
https://i.pinimg.com/originals/d9/ab/de ... 8358da.jpg
They are about 3 times compared to normal macrocannons.

I'm not ignoring real facts, macrocannons are of different sizes depending on the ships, just look at the photos of the ships or the scenes of Battlefleet Gothic. Also consider that the ships resist the recoil of a nova cannon, which accelerates a projectile of 50 meters in diameter at "almost the speed of light" in the low end and "at the speed of light" in the high end. At the speed of light it is expressly mentioned to have "almost infinite energy". If a cruiser resists without more cannon shots then I am inclined to believe that a 20-26 km Battleship can easily withstand the recoil of a macrocannone that shoots bullets at 0.25C. But anyway we keep in mind that very often 40k contradicts the laws of physics for greater spectacularity.

If the theme interests you, I can quote the precise canon quotations of the nova cannon.

[LaCroix]

We have evidence that the imperium is able to build macrocannons of that size, for example we look at a glorian class compared to a ship of almost 2 km:
https://warhammer40k.fandom.com/wiki/Ir ... agship.jpg

A quick comparison to the known lenght of the Cobra Class Destroyer shows that the bores of these cannon are in the 100-150m range.

The Iron Blood macrocannons in the picture are normal macrocannons, they are not bombing macrocannons...

You have already provided that there is no difference in normal and "Bombarding" macrocannons in projectile velocity. Ergo, there is no difference between them. Both can used in either role, depending you have the suitable ammo provided to them.

We can observe the bombardment macrocannons compared to normal macrocannons in the Eternal Crusader and in the cruisers:
https://i.pinimg.com/originals/d9/ab/de ... 8358da.jpg
They are about 3 times compared to normal macrocannons.

https://warhammer40k.fandom.com/wiki/Ba ... arison.jpg
The Eternal Crusader is a battle barge - a retrofitted warship . And according to this picture just 10km in size, thus, a lot smaller than a Gloriana or bigger ships. Older design with only a few bigger guns due to energy/size/stability issues. See the size comparion with the aircraft carrier - the bigger guns are probably 60m bore, with the others around 20m, You can also see that they only use those near the center, a design choice that indicates a stability issue when using them - the ship would spin if used further ahead - which seems not to be an issue with the other 5 smaller guns.

All this shows that this ship uses a certain size of macrocannon as broadside weapon, and a bigger size (that usually is only found on bigger ships) as dedicated bombardement weapon. But, (see your own evidence above above...) there is no functional difference between these cannon, apart from maybe the type of projectile they have in their storage which may or may not be useful in ship combat, so they could just as well be used in combat, too. But for some reason (probably the ship sharply veering off course when they fire those) they usually don't use them in combat.

It scales nicely - the Eternal crusader uses 20m guns, with only two 60m guns - which are 2 seperate batteries that are usually not used together.
Also, the 5 smaller guns add up to about the same recoil as the two big ones - which means this seems to be the maximum amount of recoil the internal structure is designed around.

The twice the size Gloriana uses 9 100-150m guns (twice the size of the EC's "bombardement" guns) per broadside- which means that even if the EC would (in desperation) fire all their guns together, the Gloriana would still have about 4-5 times as much firepower.

That does not invalidate the theory that there may be 200-300m guns out there(used on the biggest ships), but it still does not prove that there are 500m guns out there, simply by one smaller ship has two batteries with one gun 3x as large as the other, when the big one is proven to be smaller than other existing macrocannon.

Furthermore, those "bombardment" cannons are nowhere found on a Gloriana, which uses only one size of macrocannon for all purposes, further cementing the point that there are no such type of cannon.

[WhiteLion]

the image you posted is a fandom, the dimensions and proportions do not coincide with the canon.
The Eternal Crusader is not a battle barge (even if it has the shape), it is a Glorian class of the Black Templars fleet (source: https://wh40k.lexicanum.com/wiki/Eternal_Crusader)
the Glorian classes are around 20 km long, the Macragge Honor is even 26 km , and from the photos we see they have macrocannons about 150-200 meters wide.

Moreover, the capacity to resist the riculo of the ships is at least 6 times higher than the one we are considering, because in the Official Rulebook it is written that every battery of weapons is able to accommodate dozens of guns
"In Rogue Trader, weapons on spaceships are additional components. Each component of the weapon is not necessarily made up of a weapon: a single macro battery, for example, can have dozens of single macrocannons set aside."
Rogue Core Trader Notebook, page 219


 It means that a Battleship (for example a Retribution class) will have 3 arms batteries on each side, and hundreds of macrocannons on each side.

In addition, the adamantine armor of the ships is thick from tens to hundreds of meters, and is made to withstand gigaton-teraton impacts (low end and high end of 40k weapons). The recoil of the macrocannons is not comparable to a gigaton-teraton explosion.

We have no photos showing the macrocannons of an Abyss or Speranza class, but as we have seen, the larger the size of the ships, the bigger the macrocannons become. So it is likely that even the Abyss class can follow the main progressive line that we see in the other classes of ships.

[LaCroix]

the image you posted is a fandom, the dimensions and proportions do not coincide with the canon.
The Eternal Crusader is not a battle barge (even if it has the shape), it is a Glorian class of the Black Templars fleet (source: https://wh40k.lexicanum.com/wiki/Eternal_Crusader)
the Glorian classes are around 20 km long, the Macragge Honor is even 26 km , and from the photos we see they have macrocannons about 150-200 meters wide.

source: https://wh40k.lexicanum.com/wiki/Eternal_Crusader)

This article is about the Black Templars Battle Barge;

You don't even read your own sources, don't you?

The Eternal Crusader holds most of the Chapter's relics, chapels, and reliquaries and has been refitted many times over its ten thousand years of service. The ship has extra docking facilities for Escorts, additional launch bays for shuttles and Thunderhawks, and accommodation for twice as many Space Marines as a normal battle barge.

If they refitted the hull for all this extra stuff, something else has got to go - a perfect explanation for the reduced calibre of the 5 smaller guns of the broadside.

On the gun size - you are arguing by fiat. Provide evidence.
which photos show that size of what cannon - post the picture, and mark the gun you talk about and how you derived the size estimate you are claiming. Also - what dimension are you claiming - I am talking of BORE - the diameter of the projectile, you are talking of "Wide" - what do you mean with that foggy term?

Also - if the cannon (since you did not tell which ones, I guess you are talking about the "Bombardement" ones, again) are 150-200 m wide, it means that they are the size of the main battery guns of the standard Glorianna class. Which would sclae pretty well with my measurements of about half the size, since the picture I used said it was 10km instead of the 20km you claim.

Moreover, the capacity to resist the riculo of the ships is at least 6 times higher than the one we are considering, because in the Official Rulebook it is written that every battery of weapons is able to accommodate dozens of guns
"In Rogue Trader, weapons on spaceships are additional components. Each component of the weapon is not necessarily made up of a weapon: a single macro battery, for example, can have dozens of single macrocannons set aside."
Rogue Core Trader Notebook, page 219

It means that a Battleship (for example a Retribution class) will have 3 arms batteries on each side, and hundreds of macrocannons on each side.

CAN HAVE.
IS ABLE.
Yes, a Glorianna would be able to put dozens or hundreds of tiny cannons on their side, or a dozen big ones. THIS DOES NOT PROVE ANYTHING.
Show a picture of a ship, and we count the guns and will measure them. Or show a quote that tells us the exact layout of the armament, or at least states a caliber of any of them. "It has hundreds of Macrocannons" is worthless information.

The USS IOWA used in WW2 had "HUNDREDS OF CANNON":
9 × 16 in (406 mm)/50 cal Mark 7 guns
20 × 5 in (127 mm)/38 cal Mark 12 guns
80 × 40 mm/56 cal anti-aircraft guns
49 × 20 mm/70 cal anti-aircraft cannons

Still, for ship-to ship combat purposes, we only consider it a 9 gun battleship.

We have no photos showing the macrocannons of an Abyss or Speranza class, but as we have seen, the larger the size of the ships, the bigger the macrocannons become. So it is likely that even the Abyss class can follow the main progressive line that we see in the other classes of ships.

And this is the part where you fail to understand my point (and physics) again. You can not assume infinite scalability just because you have seen it for a certain range of ship sizes.

[Lord Revan]

The thing is that official pictures of a Glorianna-class aren't that hard to find, Both Macragge's Honor (the Ultramarines flagship) and the Vengeful Spirit (Luna Wolf/Sons of Horus/Black Legion flagship) were Glorianna class ships and have featured in official artwork so it shouldn't be that hard to find a pic, show the cannons mentioned and show how big those cannons are.

[WhiteLion]

@Lord Revan I posted a few posts above a photo of a Gloriana Iron Blood class showing the Macrocannons compared to a frigate of about 2 km. From the size they seem to be between 100-150 meters in diameter (remaining conservative) and wanting to be more optimistic up to a margin of 250 meters in diameter (high tolerance range)
https://warhammer40k.fandom.com/wiki/Gl ... agship.jpg

@LaCroix of course I read my sources, and in the source I posted it is expressly said: "The Eternal Crusader is a Gloriana Class Battleship and the largest ship of the Black Templars fleet", it is not a normal battle barge, it is a class Gloriana, the Gloriana classes ARE battle barges, but of 20 km (except the MAcragge Honor which is 26 km), source: https://wh40k.lexicanum.com/wiki/Gloria ... Battleship
the link is quoted:
 "Officially classified as a type of command of a battle barge, the ships were about 20 kilometers long"

The size of the macrocannons increases with the size of the ship, as long as you see any photo of ships of different classes, even in gothic battlefleet you see the difference, it is not an isolated fact but a constant.

Why do you say "CAN 'HAVE"? It is not a hypothesis, it is a canon fact. The number of macrocannons is by Official Rules (I posted above the quote) for a battery up to 24 macrocannons, depending on the player how many choose to mount on the ship.
You say it is worthless information, instead it is in the official regulation, therefore it is canon and supported by the authors of 40k as true.

As for the Abyss class, you're right, I don't have photos that show its macrocannons and I don't pretend to prove anything, mine are only hypotheses, but you have to admit that a hypothesis about scalability of weapons is plausible, given that there is a constant increase in the size of macrocannons with the increase in vessel size, in all classes without exception. It would be strange that only the Abyss class was an exception, also because in the novels we see a fire power to say the least enormous.

[WhiteLion]

The eventual rebound damages will never occur, simply because even a small 3 km cruiser will launch a Nova Cannon, which shoots bullets at "almost the speed of light" in the low end, and in the high end literally "at the speed of light" with "almost infinite kinetic energy". We speak of enormous powers, but for the authors of 40k they are canon. So if a 3 km cruiser normally supports such a recoil, I don't think there are problems with the recoil of a macrocannon a little bigger, even considering that we're talking about Battleship and Gloriana Class ships from 20-26 km with hundreds of meters of adamantium thickness as a hull.

[LaCroix]

@Lord Revan I posted a few posts above a photo of a Gloriana Iron Blood class showing the Macrocannons compared to a frigate of about 2 km. From the size they seem to be between 100-150 meters in diameter (remaining conservative) and wanting to be more optimistic up to a margin of 250 meters in diameter (high tolerance range)
https://warhammer40k.fandom.com/wiki/Gl ... agship.jpg

Good, lets analyse that picture:

The ship is a Cobra class Destroyer (clearly labelled) - which is 1.5 km long - 25% smaller than your numbers of "about 2km".
It is a low -res picture, but the Cobra is 61 pixels long - a bit below 24.6m per pixel
The glorianna is 800 pixels long - 20 km means 25m per pixel.
So we know that the picture is drawn at 25m per pixel scale.
The bore (the hole the projectile comes out) of the cannons is between 3 and 4 pixels (due to the low res) - so the average size is 3.5 pixels.
This means the BORE of the cannon is between 75 and 100m, averaging about 88 m. a good bit below your estimation of 100-150, maybe 250.

The size of the macrocannons increases with the size of the ship, as long as you see any photo of ships of different classes, even in gothic battlefleet you see the difference, it is not an isolated fact but a constant.

Why do you say "CAN 'HAVE"? It is not a hypothesis, it is a canon fact. The number of macrocannons is by Official Rules (I posted above the quote) for a battery up to 24 macrocannons, depending on the player how many choose to mount on the ship.
You say it is worthless information, instead it is in the official regulation, therefore it is canon and supported by the authors of 40k as true.

It is a constant for ships a LOT SMALLER than the Abyss. Claiming that this must continue is a no limits fallacy.

Because the words 'CAN HAVE', 'UP TO' and other things used in the rulebooks to describe how you can design your own ships are irrelevant when discussing a factual canon ship - a Glorianna, in this case, or an Abyss.

That the Glorianna, according to the rule book on ship design 'CAN HAVE UP TO 24 cannon in a battery' is nice to know.
But it doesn't. It only has 9.
Therefore, knowing it could be up to 24 is irrelevant when discussing the firepower of that particular ship type.

As for the Abyss class, you're right, I don't have photos that show its macrocannons and I don't pretend to prove anything, mine are only hypotheses, but you have to admit that a hypothesis about scalability of weapons is plausible, given that there is a constant increase in the size of macrocannons with the increase in vessel size, in all classes without exception. It would be strange that only the Abyss class was an exception, also because in the novels we see a fire power to say the least enormous.

NO, it is not plausible.

I have no idea who you are, and what your background is, but you are constantly using a flawed argument.
It is called the "No limit fallacy".

There is a shown size increase for the given weapons we see in the canon line of ships ranging from a few hundred meters to 20 km.
You therefore assume that this scalability extends to ships "the size of a continent", or even to one 'only' 150km long.
But you have no proof, apart from knowing that the firepower of said huge ship is "enourmous".
The physical world tells us that there is a limit. There ALWAYS IS.

But you are saying that since we have yet not seen a limit, there must not be one.

You can't do this in a discussion - if you are making a claim e.g. "Their cannon must be 5 times bigger, since the ship is 5 times bigger",
that means that you have to prove it. You can't just throw out a so-called hypothesis, and demand that other people prove or disprove your allegation.

Especially since the claim that the Abyss has magnitudes more firepower than a Glorianna is easily explained by it simply having multiple batteries, with hundreds of pieces of Glorianna main battery sized macrocannon in total. It does not NEED its guns to be bigger, just many more of them.

Occams razor applies, and it cuts sharp.
Unless you can prove there are bigger cannon than the ones used in a Glorianna, (which I just proved to you to be only about 100m calibre), your hypothesis is dead on arrival. And even then, you can only prove that certain new size of cannon to exist, raising the known maximum size - any bigger one will have to be proven by evidence, again.

[LaCroix]

The eventual rebound damages will never occur, simply because even a small 3 km cruiser will launch a Nova Cannon, which shoots bullets at "almost the speed of light" in the low end, and in the high end literally "at the speed of light" with "almost infinite kinetic energy". We speak of enormous powers, but for the authors of 40k they are canon. So if a 3 km cruiser normally supports such a recoil, I don't think there are problems with the recoil of a macrocannon a little bigger, even considering that we're talking about Battleship and Gloriana Class ships from 20-26 km with hundreds of meters of adamantium thickness as a hull.

No. This weapon is using a completely different method of accelerating the projectile.

a typical Nova Cannon consists of an array of potent gravimetric impellers

A macrocannon is an actual cannon, a ballistic weapon, using an explosion to eject the projectile.

This means that the recoil of these weapons is not comparable.

Being a gravimetric weapon, the recoil of the Nova cannon is most likely neglible compared to a macrocannon.
It is still enourmus compared to a mere macrocannon.

The 'smallest' ship (all other are BattleCruisers and Battleships) using it is a Dominator-class Cruiser, which is a bigger variant of a Lunar class Cruiser explicitly rebuilt to hold one of them as a long range artillery support. The Lunar class is 5 km long, the Dominator is even bigger, due to modifications to the bow, and the novacannon itself. All other ships using them are simplarily at least 5km long.

But - it is always used as a SINGLE SPINAL MOUNT. Even the huge Battleships only have one, firing forward. All the smaller ships using it were pretty much built around this one weapon. That's the amount of structural support this kind of weapon needs. It is safe to say that using this weapon in the same placement as a Macrocannon, the recoil would rip said ship apart.

[WhiteLion]

I do not agree with the number of macrocannons, the regulation is clear, your personal opinions are not as valid as canon material, each macrobattery can have up to 24 macrocannons.

Instead I find your calculation of the pixels objective, even if the cobra class has different dimensions depending on the canon novel to which we refer (like everything in 40k, even the battleships are mentioned as large 5 km in some novels and large 20 km in others).

For the Nova cannon you're wrong, its recoil is so strong that the ship needs to accelerate the engines to counteract the recoil, and it can only be mounted on the spinal axis of the ship precisely for this reason. If the hull supports these solicitations generated by a weapon that generates over 6 petaton of power (and in the high end it is mentioned that the Nova cannon has almost infinite kinetic energy, canon quote), then surely it will have no problem to manage the stresses produced by a macrocannon of 10-20 gigaton of power.

[LaCroix]

1. 9 cannon IS "up to 24" - do you even know the meaning of "UP TO" in the english language?

2. Pixel analysis has been the most qualified tool for these kinds of discussions for about 20 years. I even used the picture YOU sourced for evidence to do it.

3. the Cobra class is sized at 1.5km in the plethora of sources. You are not to handwave established sized away by fiat the moment you don't like them because they do contradict your pet ideas.

4. Yes - that is indeed the meaning of spinal mount - you mount it in the same axis a the drive, so you can use the whole ship's structure (designed to harness the force of said drive) and the drive itself to combat the recoil.

This is my final post on this - I am not going to discuss a wall of denial. You obviously lack scientific understanding, and either lack the grasp of the english language to comprehend, or are blatantly ignoring anything you do not like. This is a wast of my time.

As we traditionally say on this board - Your concession is accepted.

[WhiteLion]

maybe I do not understand, I said that I accepted your assessment on the pixels, for me it's good is valid, I also reasoned above. I said only that the dimensions of the ships vary according to the novel that describes them, I do not think I have said an inaccuracy.

I'm just saying that the Nova cannon has a huge recoil, and that it is mounted in the spinal direction not because they exploit the ship's armor, but because they use the ship's engines to stabilize it, otherwise the ship would be thrown during the shot. The ship's engines accelerate when it fires, and this keeps it in a stable position.

However I accept your constructive criticism, I will try to improve.