Karoline said:

Well, I think part of the reasoning for the fluff, is that it's always been a sci-fi trope to say "The most powerful weapon of our age is dwarfed by the incalculable power of the most basic weapon in the setting!" and also remember that 40k fluff has always talked more swagger than it brings in fact. It's part of the holdover from the over-the-top tongue-in-cheek days which I actually kind of prefer to the modern fluff, because it helped to hide a lot of bad writing.

In fact, before reading the supplement for the nuke, I had always assumed that the standard, low-grade, macrocannon batteries used nukes as their munitions.

Now, for an explanation of why nukes are "weak" according to the rules as they stand... I dunno. The closest I can see would be a sort of compromise between strength and logistics. If the ship were loaded to the gills with nukes, there not only would be containment issues, but also it would increase the chances that a heretic on the ship would find a way to push the button before the munition was chambered. So you can only carry a few at a time, and that's just not practical in "modern" space warfare, where you could be away from a naval facility for a century, or at least decades. Also, I'm not sure if it is ever stated what fuel the starships run on. Maybe there is competition for a scarce resource. Remember, in our modern times, there's only enough fissionable materials on earth to run our power supply for about ten years, I know the Empire of Man has more than a few mining planets than we have mines, but they also have a lot of energy demands. Also, in the Empire quantity IS a quality. Macrobatteries deal with the vastness of space, and resultant difficulty of hitting something that's moving relative to you, by bracketing the target with massive quantities of munitions. I'd imagine a standard macrocannon battery to consist of at least a dozen cannons (maybe two) firing around once every three or so minutes (or maybe unleashing a salvo of 10 shots each within the first two minutes, then taking 30 minutes to reload). In that case, I'm not sure how a single nuclear warhead has a chance of connecting, under normal (non-PC) circumstances.

I know all those reasons don't really make them "weak", but they sure do make them "antiquated" and "not practical in standard void engagements". Possibly also, their rareness would still exist if they were "stronger" but the fact that they are rarely used magnifies their rarity.

One reason nukes aren't used as ship to ship weapons can be inspired by that infamous button line from Starship troopers.

Only instead of a button, you have a laundry list of rituals and paperwork to perform.

Example. First step is a thousand year old key which must be taken from its stasis crypt only after the proper rituals of rest are given to its crypt. Then they key must have the appropriate rites and oils applied to it to keep it happy as it awakens. Next they key has to be taken down to the vault of wonderous explosives, in a small parade of servitors chanting in binary and swinging censors filled with holy unguent smoke stuff. After that, the key is inserted into the lock while a prayer of opening is enacted upon the vault doors..............

Then someone puts a knife through the head of the guy before he can complete the ritual......and you have to start it all over again. But only after you resubmit the proper forms for setting up a ritual parade route through ship decks with the seneschal (who requires a bribe).

This is why Imperial ships prefer ramming things. Then they get to be the knife, and the other ship is the button.

George Labour said:

You mean the fictitious line inserted by an idiot screenwriter directed by an ******* who hated the very concept of Robert Heinlein's famous book? A Rogue Trader's ship is his castle, and if he wants something done it gets done without too much bureaucracy. Yes, the Imperium operates that way but it should never be inferred that a Rogue Trader would operate his ship the same way. Isn't that the very point of assigning a Warrant of Trade instead of dispatching an official expedition?

You want the schematic to a Teller-Ulam design nuclear weapon? Because it's not hard. to acquire. Not everything has to be made by a Mechanicus tech-priest. Lasguns on Cadia for example. Definitely not a Forge World, they assemble lasgun rifles that have become the standard pattern. Warhammer 40k is set in the grim dark future of lost technology but even mid-20th century concepts (such as a nuclear weapon!) should be doable for someone with the resources.

In the grim, dark future of a Rogue Trader's ship, idleness is grounds for *BLAM*

Thing is, the people who make your ship run, design the weapons, and replace the servitors are a power unto themselves. A notoriously self absorbed and intractable power that doesn't share knowledge easily. In a way they're actually harder to strong arm than navigators.

You can't really threaten the tech priests the same way you can your lower deck crews, pirates, planetary populations, etc. Since if they decide you're not tight with the omnissiah you're likely to end up a servitor, or at least have to resort to hiring hereteks just to keep your plumbing working. Any way you cut it, ticking them off is not a good business move.

So since the Ad.mech love their rituals (out of actual religious devotion and belief that that's what makes things work) and you need them more than they need you...you let them pray to the toilets, and the nuclear weapons, or else.

Also, my comment was more a bit of satire on the nature of the 40k universe, and the odd relationships between faith and technology therein. XD

The good news is though, if they 'like' you then it's unlikely the inquisition will come knocking to ask about the dozen atomics you had them build. Unless they like the inquisitor more.

Where in the world are you getting your number for fissionable material? Because I can tell you it is entirely wrong.

And I thought that starships ran on that promethium stuff.

Regardless, I'm sure there are good reasons out there for nukes to be rare, but I'm quite sure that it isn't 'because they are weak and no one wants to use them'.

Incidentally, I kind of thought the standard macrocannon ammo was small nukes too

I've been assuming that the plasma furnaces work off of Hydrogen or some other similar element. Plasma guns are noted as using specialized flasks of hydrogen, and it's pretty easy to find anywhere in the universe.

However, since promethium is basically the go to word to describe any petro-chemical equivalent I imagine that any thing not connected to the ship uses it for fuel. Cargo barges and shuttles for example.

Though there are likely to also be hydrogen fuel cell generators used for shipboard vehicles and generators (less fumes to foul the air), and I know I've seen the word plasma conduits used in the fiction before...so I dunno why the ship itself would need promethium.

Concerning the standard macro canons shells, they are not atomics. For the good reason that you don't need atomics to get the same impact in space, du to relativistic differences of speed. If i remember well, you can yield the same impact of a nuke with only a 1 kg shell if you have the right speed (the speed of the shell against the speed of your target...). In space, except if your nuke explode in the ship, it will damage targets through radiation, not with the shockwave.

Yeah, you're quite correct. While the muzzle velocity of a macrocannon is never listed, it has to be absurd to have any kind of a chance of not being dodged over such absurd distances (though this is likely part of why weapons are limited to a certain range). And since the force is the velocity squared, it is far far more important than mass. Hence why guns work. Low mass, high velocity.

Still, a nuclear explosion after impact never hurts It'd be like a bolt gun for ships.

I disagree with the high velocity of macrocannons. While they would certainly be higher than earth-bound counterparts, Macrocannons are described as autocannons "on a much MUCH bigger scale", and seem to have more in common with Naval Guns of the mid-20th century. Plus, we already know that hypervelocity rounds (read: railgun tech) is limited to Nova Cannons.

Depends what you mean by hyper-velocity. A Mars-pattern macro cannon has a range rating of 6 VUs. Meaning it can shoot out to 12 VUs (12,000km) in a single strategic turn (30 minutes). Trying to work around gamist conventions for the sake of a workable turn-based combat system, those shots need to be moving at least 24,000 kph. And that's just the very minimum speed you would need to actually cross the weapon's range in a single turn. It is very likely the shells are fired at velocities far in excess of that minimum speed (there's not much of an accuracy difference between a macrocannon and a laser battery for instance so macrocannons must not have too much of a timelag between firing and hitting/missing). It may even be reasonable to assume that the macrocannons are fired at 10-30 times the minimum (hit/miss within one to three minutes of firing) so maybe their actual speed is somewhere between 200,000 and 720,000 kph?

Eitherway, that sounds pretty high veolocity to me.

28,000 KPH isn't even 1% of light speed. By comparison the Apollo 11 Saturn V Rocket accelerated to about 40,000 KPH just to reach escape velocity. I agree that the velocities are probably much higher, but then again we're discussing their actions in a vacuum, not an atmosphere. You also wouldn't need a very powerful primer/launcher to reach those speeds.

And yes, velocities are high in space. But most Imperial ships are built more solid than rock, using Unobtainium™ such as Adamantine to survive ship-to-ship collisions or crash into planets mostly intact, so it's also not unreasonable to state that most of the power granted by increased velocities has been negated by magic sci-fi metallurgy.

However, in contrast, the U.S. Navy's current railgun project has only been able to accelerate projectiles to approximately 8,640 KPH (this is in an atmosphere of course). So if macrocannons are magnetically based, then they're highly primitive.

Cannonball said:

Actually, VU is an abstract that can mean anything, from 1000km as you said to 100km. The books says as much. You really can't in any way accurately figure out the speed of macrocannon shells using the rulebook.

Worth mentioning that macrocannons fire batteries of shots, not just a handful. Even non broadsides probably have a dozen, if not several dozen, cannons going off at once, and they're likely firing into what is empty space right then, but won't be later if the bridge crew (guys making the BS roll) got their math right.

So really it's not the size of the gun that matters, but the complexity of the calculator you've got to plot with.

MILLANDSON said:

Actually the book lists one VU as being about 10,000km, which makes the mars pattern macrocannon fire roughly 120,000km in 30 minutes, or 240,000kph, which is a bit under 77000 m/s which is 0.02% of light speed. I doubt however that they take a full 30 minutes to travel that distance or nothing would ever hit anything. I mean, the ship itself is moving that quickly. I would think to have even the most remote hope of hitting something you would have to have a fire to target time of a minute or less, which means a speed of .7% light speed, or about 2,000,000 m/s.

Now, the biggest nuke ever detonated by the US released 63,000 TJ. A 1 kg projectile fired at 2,000,000 m/s would strike with 4000 TJ of kinetic energy. If it was a 10kg projectile (Fairly easy for me to imagine, given the size of things) that'd be 40,000 TJ of energy, roughly 500 times more powerful than the bombs dropped on Hiroshima and Nagasaki, and 66% of the yield of the most powerful bomb detonated by the US. So, individual strikes from a macrocannon could easily match modern nukes. If that isn't the case, you have to assume that either nukes are stronger in the future, or that they use very small projectiles, or they actually by some mericale manage to hit with projectiles that take longer than a minute to reach their target over a distance of a hundred thousand kilometers, which I can't even remotely phathom, because at those distances and speeds and lengths of time, the target ship could adjust its heading by fractions of a degree and be thousands of kilometers away from the projected hit location.

What all this math gets us I'm not sure (I guess that making the warheads of macrocannon shells small nukes would be unlikely to change anything). I still stand by my original point. Any weapon that outdamages the standard ammo by a factor of 5 or so should not be rare because it is weak, it should be rare because it is powerful or because the materials are rare or something else, but not because it is weak and no one wants one, because everyone wants it.

Which brings up a thought. How hard will nova cannon shells be to get?

At the minimum I'd say Extremely rare, and likely no modifier for scale just like new ships and atomics. This makes them hard to get, but a determined trader could get one or two if his PF is in the high 40s, and he gets some lucky rolls.

Times like this I wish FFG would release PDFs of things earlier than the hardcopies. I'd honestly buy both if they were set a few weeks apart. PDF for at home GM plotting, and the book itself for in game reference and to loan out to the other players.

Karoline said:

Boy this thread is off-topic. Not saying the discussion isn't fun, just madly divergent.

Anyway, my data is from a Nova documentary about alternative fuels from ~8 years ago. The person who stated these facts was playing a kind of "voice of reason" role on the show, shooting down various ideas (his opinion of biofuel: fine, as long as you didn't mind the entire biomass of the earth to consist entirely of two species: humans and corn).

I studied documentaries for a semester, so I know how misleading/false their data can be. To tell the truth, I had assumed that would have been a hard figure to miss, but looking back on it, I remember now that data was a lead-in to the idea of mining the moon for Helium-3, which was not shot down at all on that show. It's pretty obvious how biased Nova is towards space travel, and I should have caught that, but I'm also biased towards space travel, and that's probably why I stayed willfully ignorant. However you've provoked me to go and investigate that claim. Interestingly enough, I found a site which appears to discuss the very same claim I'm quoting.

www.azimuthproject.org/asimuth/show/peak+uranium/

The part I'm referring to is quickly referenced in the top, then a couple of other estimates reputing it are discussed in the article. As this is even more off-topic for the forum, I'd be happy to discuss this further off-forum. My field isn't math or science, but I made sure to supplement my soft-science education with a very solid grounding in the hard sciences (how else am I going to write convincing sci-fi?) As it stands now I'm happy to cede that I was incorrect, although likely it's not absurd to consider the lifespan of nuclear fuel reserves as comparable to the history of fossil fuel reserves.

Oh, and about the accuracy of projectiles which take 3 or more minutes to reach their target: remember, batteries work by enormous salvos that bracket their targets, and these ships are pretty massive and have a lot of inertia behind them (and there is some lag between orders executed and orders carried out). Plus, my assumption that the warheads were atomics was actually because I had always pictured a kind of flak-gun (or depth charge) effect. The chance of achieving a direct hit was basically nil, but you might hit close enough to shake the ship up a bit. On the other hand, the weapons are targeted and fired manually too. The fluff has sometimes described the gunnery crews as hopped up on stimulants in order to have even the chance of firing in the incredibly small windows of opportunity that exist in combat at this scale.

Etheric said:

Hmm, yeah, I'd have to say that that opinion of biofuel is highly slanted. While it would take quite a bit of farmland to fully replace fossile fuels for automobiles and such, it wouldn't preclude the existence of other species. But that is an entirely different matter.

I'm surprised that the numbers on nuclear reactors are so poor, even given a 'best case senerio' for uranium deposits (though they do ignore other fissionable materials), though I'm simply trusting to their math.

Still, presuming that it isn't being used as a fuel for anything else, there is plenty of material to go around for making all the nukes you could ever really want (especially if you estimate that every planet has a similar amount on it, or at least comparable amount on it).

As for the accuracy, I want to look at this a bit closer. Lets continue with our example of a weapon that has a long range of 12 VU, and assume that a VU is roughly 10,000km as the book says. That puts the two ships at 120,000km apart. Lets assume a cruiser (biggest target) that you have a profile of, and so is traveling at a right angle from the direction you are firing from. A cruiser is 5km long by (round up) 1km high, so, assuming it makes a perfect rectangle (it doesn't, but whatever) there is a 5 square km target. Now, a cruiser will generally be traveling at a speed of 5, which is 50,000km in 30 minutes, or 5,000 km in 3 minutes (your proposed fire time).

Now, we know a ship is perfectly capable of making a 45 degree turn in 30 minutes, so it should be more than capable of making a 4.5 degree turn in 3 minutes, or to make math simple, lets assume a 1 degree turn instantly.

Okay, now for perhaps the biggest assumption of all. How many cannons there are. Lets assume for the sake of giving slow projectiles the best possible chance of success that there are 100 cannons being fired as part of your normal barrage. Lets also assume that they are coordinated perfectly so that each covers a different 5 square km area near the projected location of the ship, giving a total coverage of 500 square km of space centered on the original projected position of the ship (High accuracy would be assumed then to be multiple successes with this pattern as opposed to multiple shells striking at once).

Okay, so, that is alot of figures and quite a few assumptions in favor of slow projectiles. Lets see if a slight turn made whenever weapons are fired puts the ship well out of the kill zone or not.

Using fancy math I can calculate that the cruiser would be 87.265km away from its original location (Above, below, left, right, but always slightly behind), and since the original spread was only 500 square km (or a touch over 22 x 22 km) it means the ship only had to move 11 km off target., which it exceeds by nearly 8 times with a 1 degree turn. This means that it could avoid those shots with less than a 0.2 degree turn.

Now, there is a possibility of doing a left or right turn in this circumstance, which could leave the ship in the line of fire, just getting hit slightly sooner or later. However, the 1 degree turn puts the ship 61.165 km behind its trajected position, as well as 62.242 km off to the left, right, up, down, or whatever. So quite simply, the act of turning has 'slowed down' the ship enough that it wouldn't be hit. Once again, a turn of under about 0.3 degrees or so is all that is required to cause a miss under these circumstances.

At a travel time of one minute for the shells however, the target ship would only be 29 km off target from a 1 degree turn, and a 1 degree turn is going to be a bit harder to manage in 1 minute than it is in 3 minutes. And of course this is long range, which does have a penalty to it, so it seems understandable that it wouldn't be perfectly in that spread. If it was at standard range, then it would only have a 30 second travel time, and the target ship couldn't make more than a 0.75 degree turn (not even including reaction time, interita, or anything like that). Now, suddenly and very interestingly, the ship is slightly under 11 km off of its original position, which puts it just inside the spread pattern. This seems to indicate that my original calculated speed for macrocannon shells (with a range of 6) is roughly correct assuming a 100 cannon battery, or a battery which can fire 100 shots in rapid succession, and fires multiple times in a 30 minute turn. If fewer shots are fired per salvo, then the speed has to be even higher, and if the macrocannons don't fire multiple salvos in a turn, then the speed must be higher still.

I'm rather surprised at the numbers, because I just said 1 minute as a rough guess, but it actually seems to work out as actually being the correct assumption for basis of speed.

So, the shell from a macrocannon that has a range of 6 seems to be traveling at a speed of roughly 2,000,000 m/s at a minimum, which makes their impacts quite devistating due to kinetic energy rivaling that of top end modern day thermonuclear bombs.

Sorry for the huge off topic rant, but I think this thread has already been taken over by armaments discussion.

Karoline:

I like your math. Good extrapolation. However, I think there's a few assumptions there that just may not be true.

The reason I had assumed macrocannon warheads were atomics or some other kind of explosive was that would increase the kill-radius of each projectile. Instead of having a 5km square silhouette to target, if each warhead did some damage in, say, a 1km radius, and was armed with some kind of proximity detonator, you would have a 21km square target to fire at. This would allow you to increase the spread of the volley and create a wider net.

Also, you're assuming a simple volley-dodge-volley-dodge scenario, where each volley is centered on the target, and the target has to course-correct in response to each one, but not in response to any previous ones. Should the battery be able to fire multiple times a strategic turn, you could play cat and mouse with your target. By slightly staggering the volley and firing subsequent volleys based on your target's movement, you could create a game of option reduction, that with each volley slowly closes the net. The first volley may be easily dodged, but the second volley has already seen the beginning of your turn and has lined up with your intended destination. As the target focuses on weaving between shells (much like a boss fight in a side-scroller like Ikaruga) the gunnery-captain thinks two steps ahead. Another comparison to this style of stellar warfare would be the endgame in chess. At the end of the series of volleys, if the gunnery-captain plotted his vectors correctly, the target is forced to make a choice that will result in it being struck by a projectile or two. A high DoS means the target has worse "best of bad options" to choose between. An evasive maneuvers roll by the target means they are also thinking a step or two ahead, at the cost of being able to present their own batteries in the most efficient manner.

Yes, I know, my concept of stellar warfare doesn't stand the rasor test compared to yours, but I like it.

Karoline said:

Can you tell me where it said that? I have been looking and seen many references of RT getting more than one ship and a whole section on how to outright buy more ships. But nothing on how they should not have more than one ship (other than a mention about starting with more than one IIRC).

Ah, you're right, I misread that. It says only one can be acquired at a time, which I remembered as only one can be had at a time. So yeah, nothing in the book about not having multiple ships after all. In that case I suggest adding together the bonuses from the different ships so long as you can use them. It would for example be hard to impress important guests with your trophy rooms on multiple ships, or to enjoy the luxury of multiple state rooms or anything like that.

As for the idea of starship combat, that isn't going to work unless you fire your later shots faster than your initial shots, because it is entirely possible that the ship would avoid a second volley by moving to wear a previous volley has already passed by. And of course you have to remember that you have full 3D movement. It isn't just left and right that you have to cut off, but up and down and any mixture of thereof. And as I said, corralling is impossible in this situation anyway unless you're firing so fast that you may as well consider it one volley of 1000 shots instead of 10 volleys of 100 shots. And you're right, proximity detection and detonation could improve your chances of a 'hit' by quite a bit, but, sadly, explosions are fairly ineffective in the void since the void has a distinct lack of air, and I have trouble imagining shrapanel doing much to armor several meters thick unless the rounds being fired are the size of battleships. And of course if you're relying on an explosion to do the damage, you're wasting a huge amount of kinetic energy that you could be getting from an impact.

Also consider that we are dealing with the largest target, slowest ship, and not taking into account accelerating or decelerating either, only turning. I admit that you could certainly get another ship to adjust its course slightly, or speed up or slow down a bit with rounds that go speeds you're talking about, but you'd never actually be able to hit anything unless the other ship maintained a dead steady course and speed. We're talking literal twitches in the steering would cause the shots to miss by miles.

Even my estimates are on the low side because we are talking about a best case scenario where the target is huge, slow, and not adjusting speed. If you're looking at a small, fast target like a raider or something, you'd likely need 4 times my estimates, perhaps more. This high speed would also explain why there aren't any sort of accuracy bonuses for using lasers or anything similar. If the rounds are being fired at... say for example 5% of light speed, there really isn't all that much difference between hitting in under a second and hitting in 10 seconds or so. You have to lead a bit, but the other pilot won't have much time to react, and the ship will have even less time to overcome its inertia and get on a new path, but it is perhaps just enough of a lead that if the pilot is turning like crazy, and you're only talking about a handful of shots all aimed more or less directly on target, you just might get it wrong (Hence, evasive maneuvers)