# A Question of Scale

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I don't know if I'm the only one (though I doubt it), but while looking at the Rogue Trader (and, later, Battlefleet Gothic) art of space battles and starships dramatically facing off in fleets or side by side and firing at each other like sea ships of old, I realized something...

Those never happen within the actual game. If you (as I) want these kinds of space battles to occur, you really, REALLY, need to nerf the scale of space combat. And while doing so, you may also fix a couple physics issues with the game, too.

The problem is, the Rogue Trader starship rules (which are actually based on Battlefleet Gothic rules and scale) state that 1 VU is equal to 10,000 km, and most weapons have ranges averaging 6 VUs (which means they fire up to 12, so thats 120,000 km) If that is so, space combat would almost never (probably 99% of the time) occur at the ranges shown in the art. Indeed, even at point blank range (1 VU away) your art should depict one ship only, and its opponent, even a 6km long ship, would only be a speck in the distance, even less visible than the stars in the background. Furthermore, the 1% of the time ship would actually fire at each other at those ranges would really be just a snapshot frame of the battle, and thats because of the ship's speed.

Have you noticed that if a ship has a speed of 10 (not even the fastest a ship can go), it goes at 200,000 kph (10 VU per 30 minutes). That's over 55 km PER SECOND, so unless the two ships have exactly the same speed and exactly the same course, even the slightest derivation would mean they would be out of sight in a matter of seconds, not to mention if they were going in opposite directions! The question of speed also brings a couple problems.

If your target is at range 6 (60,000 km away) and is going at speed 10 (200,000 kph), do you realise just how fast your macrobatteries ordnance need to be shot at in order to have even the slightest chance to hit your target? A bullet shot by a gun goes a couple thousand kph, but I know that's really not the same scale, and thats against atmosphere. But lets say the ordnance is shot at FIVE MILLION kph. By comparison, a moreton wave, essentially the shockwave on the surface of the sun resulting from solar flares, which are deflagrations that would easily vaporise the entire Earth, travels at around 3.6 million kph (so that's insanely fast, and probably unachievable by any sort of solid projectile battery, even in the 41st millenium, but lets say they can) At that speed, the ordnance travels at nearly 1,400 km per second. Our target is moving 55km per second, so the batteries would anticipate and fire ahead of course, but even at that ordnance speed, it would take more that 43 seconds for a shot to reach the target! So the thing is, if a ship is making any kind of evasive manoeuvres (by that, I mean adjusting either speed or heading by even 1% or 1 degree in any direction, and although I agree the ships aren't manoeuvrable at all, they still can go from 200,000 kph to a full stop or any speed in between within 30 minutes, and/or make at least one full 90 degrees turn within that timeframe, so it clearly is possible), they would evade the shots by several kilometers! Even if you shoot a lot, and with ships that aren't that manoeuvrable, with these kinds of scales, it really becomes nearly impossible for solid projectile batteries to hit.

Even worse though is the idea of ships ramming! At those speeds, that clearly becomes next to impossible, and if it should happen, the results would be cataclysmic! Lets take a small raider with a mass of 5 megatons (that's 5,000,000,000 kg) and moving at speed 10 (that's 200,000 kph) who rams a stationary ship (so its actually possible to hit it). The frigate would probably get slightly damaged by that action as well, seeing as the collision would generate kinetic energy of over 6 GIGATONS of TNT (so yeah, more than 300 20 megaton nukes all in one go), probably more than enough utterly destroy both ships in the process. Clearly, you can forget about the subsequent boarding actions...

Anyways, while I know starships have to be able to go at these kinds of speeds, and faster, to travel between planets in a solar system, it is clear that combat should occur at much slower speeds, and on a smaller scale, and I feel it will not only make more sense, but will also allow the kinds of battles you see in the art to take place. To accomplish this, here are some houserules I'd use (see, I didn't only come here to complain! )

1- Reduce VUs to 10 km, not 10,000. This will make probably reflect more accurately the ranges depicted in the space combat art.

2- Reduce combat round duration to 10 minutes. This still makes space combat last a lot longer than regular character firefights, and allows time for repairs and moving around the ship, and makes a ship going at speed 10 go at around 600 kph

3- Distinguish cruising speed from combat speed. Cruising speed would be equivalent to current rules speed and used mainly to get from plent to planet within a system, but require most of the ships power to accomplish. Combat speeds represents ships moving at minimal speeds and using mainly trusters to gain maximal mobility and use all weapons and systems to maximum efficiency, and to avoid probably fatal collisions with other ships or debris during battle.

4- Extend weapon ranges rules to use the same range systems as character combat (long and extreme ranges, allowing ships to fire at more than 3 times the stated range, instead of less than twice)

So, there you are. What do you think?

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>> The problem is, the Rogue Trader starship rules (which are actually based on Battlefleet Gothic rules and scale) state that 1 VU is equal to 10,000 km, and most weapons have ranges averaging 6 VUs (which means they fire up to 12, so thats 120,000 km) If that is so, space combat would almost never (probably 99% of the time) occur at the ranges shown in the art.

That is pretty common across most science fiction in a visual medium. Visual range encounters just look better.

>> Our target is moving 55km per second, so the batteries would anticipate and fire ahead of course, but even at that ordnance speed, it would take more that 43 seconds for a shot to reach the target!

Not really a problem with half hour turns.

>> So the thing is, if a ship is making any kind of evasive manoeuvres (by that, I mean adjusting either speed or heading by even 1% or 1 degree in any direction, and although I agree the ships aren't manoeuvrable at all, they still can go from 200,000 kph to a full stop or any speed in between within 30 minutes, and/or make at least one full 90 degrees turn within that timeframe, so it clearly is possible), they would evade the shots by several kilometers!

Which is why macrobatteries cover most of the volume that the enemy ship might be in.

>> seeing as the collision would generate kinetic energy of over 6 GIGATONS of TNT

One of the forums I visit does calculate how strong various sci-fi settings are. While it does vary a lot depending on the author, there are some authors who depict the power of ship weapons in the high teraton/ low petaton range. If the armour can take that, 6 gigatons won't do much beyond removing the paint.

Here is their main 40k analysis thread.

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>> That is pretty common across most science fiction in a visual medium. Visual range encounters just look better.

I know, but why not make the rules fit that picture, since I don't see why not.

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>>>> Our target is moving 55km per second, so the batteries would anticipate and fire ahead of course, but even at that ordnance speed, it would take more that 43 seconds for a shot to reach the target!

>>Not really a problem with half hour turns.

You miss my point, which is that in that time frame the target ship will have altered course and/or speed to avoid the shots, but I guess you addressed it in your next comment.

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>>>> So the thing is, if a ship is making any kind of evasive manoeuvres (by that, I mean adjusting either speed or heading by even 1% or 1 degree in any direction, and although I agree the ships aren't manoeuvrable at all, they still can go from 200,000 kph to a full stop or any speed in between within 30 minutes, and/or make at least one full 90 degrees turn within that timeframe, so it clearly is possible), they would evade the shots by several kilometers!

>>Which is why macrobatteries cover most of the volume that the enemy ship might be in.

Here is why "A Question of Scale" is an appropriate title. When you say "most of the volume", I don't think you realize what kind of volume you are talking about.

Assuming that a ship moving at 55km per second would only adjust speed and bearing by +/- 1% or 1 degree, in 43 seconds, that would mean the "volume that the ship might be in" would be over 135 MILLION CUBIC KILOMETERS! Even if your kiloton ordnance (as described in the rogue trader book) has a blast radius (which would be a lot different from a detonation in athmosphere anyways) of say 100 Cubic kilmeters, and say you only cover only half the area, you'd still need to fire over nearly a MILLION rounds EVERY MINUTE to have about 50% chance of hitting your target ONCE and only with the blast radius! The rules describe the ships hitting multiple times with the batteries, and I'm fairly certain they mean at least some of the shots to be direct hits. I'm also fairly certain that even when they talk about rapid firing weapons, they are nowhere near that kind of firing rate. At the rate you'd use up ammo, even a 5 km long ship jam packed with munitions would be out of ammo in a few game turns.

And thats only if the ship alters by ONLY 1% or 1 degree!

Clearly, that just doesn't work.

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>>>> seeing as the collision would generate kinetic energy of over 6 GIGATONS of TNT

>>One of the forums I visit does calculate how strong various sci-fi settings are. While it does vary a lot depending on the author, there are some authors who depict the power of ship weapons in the high teraton/ low petaton range. If the armour can take that, 6 gigatons won't do much beyond removing the paint.

Here is their main 40k analysis thread.

I assure you, no matter what this thread says, that a 6 gigaton energy release, not to mention ships going from 200,000 kph to a dead stop will most definately do more than scrape off some paint...

While I have skimmed a similar forum, and will go check out that one, I know that some weapons, the nova cannon being the most striking, would have that kind of firepower, I'm curious to see how they can explain how starship armor is supposed to sustain those hits.

As I've said, it's a Question of Scale.

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This is one of those nonsense things that you have to just ignore about sci-fi in my opinion. Along with the Emperor creating neutered superwarriors instead of ones who can at least breed the next generation of fighters (and only male ones at that for no sensible reason). There's also the descent from technological society to practically medieval which you have to accept as being likely. Or that people would begin to worship machine spirits - after a war with AI's. Or that psychic powers can exist.

I'm not saying you're wrong that the ship combat doesn't really make sense but it shouldn't surprise you. I think having the combats conducted at shorter ranges does make more sense and lends a sense of drama.

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>> Assuming that a ship moving at 55km per second would only adjust speed and bearing by +/- 1% or 1 degree, in 43 seconds, that would mean the "volume that the ship might be in" would be over 135 MILLION CUBIC KILOMETERS!

Could I see the calculations and assumptions that gave you this volume ?

>> Even if your kiloton ordnance (as described in the rogue trader book)

When a piece of fiction says that something is capable of x, but they show it being capable of y, I go with it being capable of y (weather y>x or x>y).

For example, take the clip from Star Trek at the start of this video. Is that a rotted corpse (what it looks like) or a very well preserved body (what Data says) ?

>> I assure you, no matter what this thread says, that a 6 gigaton energy release, not to mention ships going from 200,000 kph to a dead stop will most definately do more than scrape off some paint...

Shake the ships around. Sure.

Damage more fragile components from the shock. Also fine, and it doesn't require any deformation of the hull.

Some damage to the area where the impact happened is also reasonable. But when the ships can survive (with some damage) hits with thousands of times more energy than this collision, I don't see why the ship would be destroyed.

Also, where did you get the idea that the ship would slow to a 'dead stop' ?

>> While I have skimmed a similar forum, and will go check out that one,

Just be aware that there are some authors who depict ship to ship weapons in the kiloton range and that GW doesn't seem to make much effort towards keeping the canon consistent.

>> I'm curious to see how they can explain how starship armor is supposed to sustain those hits.

Suspension of belief means that I don't care how the armour survives those hits, only that it can. This is especially important when someone notices that the ships have only half the density of styrofoam, Which FFG explained with:

In the 41st Millennium, spacefaring ships use extremely lightweight yet strong materials in their construction. For the most part, humans use an adamantium/ceramite alloy. In addition to the great reduction in mass, ceramite conducts very little heat, making it extremely well-suited to engines and well as helping to make the ship's armour highly resistant to heat- and energy-based weapons.

Expecting any explanation beyond "it does what we say it does" is asking for disappointment. Especially when you are talking about a sci-fi universe like 40k which doesn't care that much about realism (Da red wunz go fasta).

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>>This is one of those nonsense things that you have to just ignore about sci-fi in my opinion. Along with the Emperor creating neutered superwarriors instead of ones who can at least breed the next generation of fighters (and only male ones at that for no sensible reason). There's also the descent from technological society to practically medieval which you have to accept as being likely. Or that people would begin to worship machine spirits - after a war with AI's. Or that psychic powers can exist.

I think you have to be careful when making that argument. I used to have a debate with D&D fans who found it quite silly that I commented on how stupid falling damage was handled in that system, since even first level characters were more than likely to survive falls of 50 feet or more. They couldn't understand why that bothered me, but accepted the idea of magic spells and monsters just fine.

Because, of course, that is a complete non sequitur argument.

The creators of a world like Eberron, for example, clearly intended for people in that setting to be able to learn and cast magic spells. However, they clearly assumed that gravity worked in essentially the same way for all people in the setting, unless they had special means by which to affect it (like spells, for instance). People don't simply fly around without spells or magic items, nor can they walk on water, and they fall when they walk over a precipice. The fact that magic spells exists, or beholders who float around exist, has no relation to the fact that falling 50 ft. HURTS a lot more than the mechanics described. The problem, therefore, lies with the mechanics, not with the setting.

Now, I'm not saying you're wrong about some weird ideas about the 40k setting, though I think you could justify many of the above examples you gave with the appropriate background, but clearly, there is a disconnect between the illustrations of space battles from 40k products and the mechanics of space combat.

I'd also point out that I can live with the fact that some sci-fi mechanics are most likely not realistic. However, since some facts also support my idea of bringing down the scale of space combat, I was merely exposing them to give more than one reason to do so.

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>>I'm not saying you're wrong that the ship combat doesn't really make sense but it shouldn't surprise you. I think having the combats conducted at shorter ranges does make more sense and lends a sense of drama.

That is also how I feel about it. I simply don't like the idea of these massive ships zipping past each other in the blink of an eye and firing at each other without ever actually seeing each other. I much prefer the idea of both ships slowly passing each other with each of their broadside turrets blasting at each other like the Star Wars batlle scene or old sailing ships... as they show in the art.

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Glimnir said:

I feel about it. I simply don't like the idea of these massive ships zipping past each other in the blink of an eye and firing at each other without ever actually seeing each other. I much prefer the idea of both ships slowly passing each other with each of their broadside turrets blasting at each other like the Star Wars batlle scene or old sailing ships... as they show in the art.

Actually, star wars happens at huge ranges (100-2000km typically, with a maximum effective range of over 5500). If you watch the movies again you might notice that you never see two ships duking it out on in the same frame even after they move into "point-blank" range (I can't find the source, but point-blank range was still several kilometers away). The fighters are the only ships you see get up close and personal.

The thing is, slowly cruising by each other guns blazing away doesn't make any sense either. Its cinematic, which is why the artwork does it, but doesn't make any sense for space combat, or even sea based combat. In WWI and the beggining of WWII ships preferred to engage from miles away. Line of battle style combat from mid range makes a lot more sense with the technology they are using (it is also the style of combat used in starwars for capital ships).

Now using combat speed does make sense. Like you point out, two ships going full speed would just pass eachother in a flash. If one ship does that and the other doesn't the first ship will quickly find itself exposed to rear fire if the other ship positions itself right. It is all about maneouvering, and to manouver properly you need to slow down. If you have ever played a newtonian physics based space combat sim this is exactly what happens. Both ships have to slow down to 'combat speed', otherwise the guy going too fast can't control himself and takes a hit to the rear. But the close up battles demonstrated in the artwork still don't happen.

All that said: It is a case of pick your poison. Realistic space based combat isn't actually all that fun, so we choose something cinematic and find ways to justify it in-game. I don't have a problem justifying it the way it is written. The ships have to slow to combat speed, their gunnery batteries use sophisticated targetting computers to attempt to predict where the enemy ship is most likely to be and do their best to saturate that area with fire. Shure the ships can try to evade, but the targetting computers are likely ancient archeotech that places shots so as to statistically maximize the chances of hitting. Over half an hour of combat dozens, or even hundreds of shells the size of houses are launched at near relativistic speeds, combat computers and gunnery crews engage in an intricate chess match, trying to force their opponents into a situation where they will be unable to avoid a shot. Likely only one or two shots will land, the immense kinetic energy temporarily bringing down the victims void-shields for just a moment, just long enough to unleash that critical lance shot into the suddenly vulnerable ship. As energy capable of cracking continents lances into the victim, boiling away armor plating and rending through decks, the victims crew work desperately to shunt the excess energy in the void shields and seal off the damage. Ancient ships, with weapons capable of laying waste to entire worlds and defenses capable of absorbing near limitless amounts of energy, engaged in a delicate fencing match of parries, feignts, and thrust, each looking for that one misstep, that tiny hole in their opponents otherwise impervious defenses, that will allow for the killing blow.

Your way is great too, ancient behemoths with hundreds of guns blazing away against eachothers near impenitrable armor, gouts of flame, the fire of cannons. It's just a question of flavor. I like my imperiem to insanely advanced technology that simply appears to be archaic, others like it to be a little lower tech, wooden ships in space. Both are valid, though I don't think your idea is necissarily anymore 'realistic' than what is presented.

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I thought RT was Space Opera? I for one have no interest in playing a game that requires Steven Hawking to explain to me.

There is a perfectly good reason for ships to be close together= Capture of an enemy vessel is enormously poriftable.

Also, most combat will likely take place in orbit, which puts ships close to one another.

If your goal is to play a ship-to-ship combat simulator, then RT is not for you.

If your goal is to have cinematic ship-to-ship combat, then RT is for you.

Initiating Nerg Rage in 3, 2, 1......

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I don't think you read my whole post (presuming you were replying to me). My whole point was that it is not, and should not be a simulator. I specifically stated that "Realistic space combat isn't that fun, so we choose something cinematic and find ways to justify that in game. I then went on to describe a justification for the system being run as is, and then to give a different justification for a close combat.

However I will still defend that close up combat doesn't make a ton of sense, especialy if you have ever played an age of sail type game (the type of combat RT emulates). Yes, capturing is a viable tactic, but you usually wouldn't attempt it until you have weakened your enemy with ranged fire. Getting right next to another ship of comperable power and blazing away at point blank is just a stupid tactic, even in a cinematic system.

Sorry, I don't mean to be harsh, but your post seemed to imply that the only way a system can be cinematic and fun is if it encourages close combat broadsides, and that if that isn't the only way you want to play you are playing the wrong game. But look at movies like Red October, Master and Commander, and Wrath of Kahn. There is a LOT of cinematic excitement to be had in a battleship chessmatch, which the current system lends itself to.

Again there is also a lot of fun to be had in a close combat style firefight, and that was my point, both types of systems are very fun, and quite valid. Your nerd rage is unjustified.

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When you are getting down to brass tacks about RT ship combat, let me ask you about a different but very popular game.  Don't you also find it odd that if I go around the board once I collect \$200?  Where is the realism in that?  Who ever heard of a battleship sailing around Parkplace or Boardwalk?  Isn't that dry land?  How come the money is different colors and there are \$500 bills?  Isn't this an American game?  Everyone knows the US mint only makes up to \$100 bills anymore.  The answer to your question of scale is, yes, you win and are a fine physicist.  I like to play a silly game according to silly rules and have a lot of fun with my friends while doing so.  If you find this game so out of whack that you can't enjoy it, I reccommend a home science kit or practicing to be a magician where the laws of physics really do apply.  Alternatively, make your own hard, reality Sci-fi game and put it out.  You might find an untapped goldmine.  Whatever you decide, good luck and have fun.

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riplikash said:

Actually, star wars happens at huge ranges (100-2000km typically, with a maximum effective range of over 5500). If you watch the movies again you might notice that you never see two ships duking it out on in the same frame even after they move into "point-blank" range (I can't find the source, but point-blank range was still several kilometers away). The fighters are the only ships you see get up close and personal.

Actually, there are several times ships appear in the same shot shooting each other (Beginning of Episode 4, beginning of episode 2, any of the detail we see in the battle of episode 6)... in fact, in the films there are very few instances where they are not duking it out at relative stone's throw distance. The Death Star is an exception, and in the battle in Return of the Jedi we can presume there is some longer range shooting (some ships blow up when not right beside enemy vessels), but in Episode 2, 4, and most of what we see of 6  ships blast away at each other at a matter of a few hundred metres. The creators intended it that way, saying that as far as they are concerned SW space battles are meant to happen at really close ranges. Now, many of the books have very different takes on it (According to one source Star Derstroyers apparently being able to accurately shoot targets up to 10 light seconds away... which is 3 million kilometres... blech), but as represented in the films space battles, all of them, happen at daftly short ranges.

Anyway, 5000k is nothing compared to 40k space battles as represented in BFG and RT. RT presumes each unit measurement is 10,000 km.

"Is that a rotted corpse (what it looks like) or a very well preserved body (what Data says) ?"

- A well preserved body for its age? Many mummies look quite hideous, yet they are "well preserved". Frankly that body does look partially mummified to me.

Anyway, do I actually have anything to add to the main point? Well, the art is art. 40k Artwork is not meant to give an accurate reflection of how things actually appear or work. It is deliberately often propagandistic in its style. Obviously if you want your version of RT to work like that art, then feel free to change the units used. I intend to to ignore the sizes (going for pretty much half the length for every type of ship) and crew numbers provided). However, there are some instances of battles happening at distances vaguely similar to those presented in the art work. some of the battles in the Horus Heresy series seem to take place at ranges of hundreds, and even occasionally tens, of kilometres. They largely rely on surprise though, either through duplicity or (more than slightly unrealistic) stealth tactics. They also tend to end very very quickly (battles being over in what would be less than one RT or BFG turn), as the firepower of the ships at those distances is just ludicrous.

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My tip is to not even bother applying any realism to WH40k. Even the most basic cause and effect queries will pull the fatal string that unravels the setting. Just enjoy it for what is. Fantasy in space.

Still, one does tire of 40k after a while. I just run a rock hard science fiction setting in GURPS when that time comes. Realism carries an appeal often understated.

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Why would you assume any weapons (besides a lance beam) are incapable of changing course?

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DarknessEternal said:

Why would you assume any weapons (besides a lance beam) are incapable of changing course?

Well, and fire from a laser battery...  But yeah, torpedoes and macrocannon shells are semi-guided, as I recall.  Capable of making slight corrections.  Also, in the case of macrocannon batteries, they are intended to saturate the target area with ordinance.

-=Brother Praetus=-

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Are the macrobattery warheads set to go off when near the target, or is a timer set when they are fired ?

This is important because:

- With set timer warheads, you need to get the enemy ship inside the sphere it makes when it explodes. So you have to fill a volume of space.

- With a proximity detonation you could have the warhead go off anywhere along its flight path. So you only need to make sure your warhead passes close to the enemy which means that with completely unguided munitions you have a cylindrical shaped volume of potential area of effect, with the radius the same as the radius of the other warheads sphere. So you only need to fill the cross section of all the target ships possible locations.

But you aren't going to be aiming for all the possible locations, just the highly probable ones. For example, if your telescopes are good enough to see how your enemies guns are moving and you know who they are planning to shoot, you can estimate how they are going to move. For example, if your ship is behind and to the left of theirs, you think they are going to shoot you, and you see their port guns rotating towards the front of their ship then your gunners should be preparing for them to turn left.

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My question is: how is anything exploding in space going to do any damage at all other then shrapnel?  Explosions in atmosphere do most of thier damage through concussion.  Since in space there is no medium for sound or any other pressure wave to travel, how would exploding macroshells have more then cosmetic effect on a target they don't hit?

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You partially answered your own question, with shrapnel.  The other part of the answer is, we're not sure. The thing about the weapons of the Imperium is they they typically hide advanced technology within simple and reliable mechanisms, and most of it is left up to interpretation.

So what happens when the shell explodes? It could certainly be a simple shrapnel charge, though seeing the kind of munitions the Imperium favors I have my doubts. A cluster bomb? Plasma heated shrapnel? Some kind of advanced exotic effect? Hard to say, and likely no one outside the upper echelons of the AdMech really understand the technology at work.

Again, the key to most Imperial technology is: reliable mechanisms, simple operation, advanced payload. Using massive hand loaded cannons to shot nano-clouds or mini-singularities would be par for course.

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