So I'm starting to GM a RT campaign in the near future, having run Deathwatch, Dark Heresy and a little Only War. Looking through the various books, I'd noticed that the blast radius for a Nova Cannon (1VU from where the shell detonates) is considerably wider than most earth-sized planets (2VU across is about 20,000km - Terra's only 12,000km across). Obviously, this means that any shell detonating on, or near, a planet swathes it in fire. My question is, therefore, what happens on the ground?

How much damage should a Nova Cannon do to a planet hit by the shell? Should it really cover the whole surface of the planet in fire? If so, why aren't fleets armed with Nova Cannons all that's needed for Exterminatus? How do I prevent my players from simply wiping out any planets they feel are hostile once they, inevitably, get their paws on one of these **** things? Any suggestions would be most gratefully appreciated.

For simplicities sake I'd be tempted to rule that the presence of a significant atmostphere shields a planet from the worst of a nearby nova shell detonation and makes a direct hit from a nova cannon impossible as the shells are not designed to pass through an atmosphere.

So I'm starting to GM a RT campaign in the near future, having run Deathwatch, Dark Heresy and a little Only War. Looking through the various books, I'd noticed that the blast radius for a Nova Cannon (1VU from where the shell detonates) is considerably wider than most earth-sized planets (2VU across is about 20,000km - Terra's only 12,000km across). Obviously, this means that any shell detonating on, or near, a planet swathes it in fire. My question is, therefore, what happens on the ground?

How much damage should a Nova Cannon do to a planet hit by the shell? Should it really cover the whole surface of the planet in fire? If so, why aren't fleets armed with Nova Cannons all that's needed for Exterminatus? How do I prevent my players from simply wiping out any planets they feel are hostile once they, inevitably, get their paws on one of these **** things? Any suggestions would be most gratefully appreciated.

As to what they do on the hit the ground - espcially how big damage they cause - i have no answer... But while its a big explotion, i would think the force of the explotion would be hampered by the resistance of the atmosphere, and thus make the explotion much smaller.. (still likely to be enormus to people down on the planet, but not so big as in space).

Secondly Nova cannons are (from my point of view) made to deal damage over a LARGE area... i won't destroy a planet, it will detonate on the surface... To create exterminatus on a planet.. you need to destroy it utterly. Crack the tectonic plates systematicly, virus bomb it, destroy the atmosphere... nothing should be able to survive an exterminatus. Necrons care very little if there are oxygen or radiation... Besides Nova cannon shells are rare..no way you can use the nove shells en masse... (do they even still produce them?)

Secondly there could be the fact they are anti ship weapons not meant to be used that way... they could detonate as soon as they entered the stratosphere... making a very spetacular and intimidating light show... but not doing any real damage...

Yep, gravity and tidal forces screw with many weapons made to work in space. this has been brought up before, and we figured that, while some varieties of Nova Bomb ordnance could easily level a city, even crater a lot of the ground, the damage to a whole planet would be negligible.

I'm not a scientist, geologist, seismologist, or any of that, but when massive objects hit the earth, they do localized damage. Something the size of Rhode Island would hit hard, fast, and hurt, but the damage to Earth wouldn't be so bad. It's the extra crap that bothers. That impact will vaporize massive amounts of material, and hurl kilotons more into the atmosphere. This will blanket the earth, plunge it into darkness, and kill us with cold and hunger, or suffocation. Side effects were worse, globally, than the impact object. Nova Cannon shells won't do this. They are BIG, but not THAT big, and they detonate before impact, as to not damage themselves. They'd vaporize more, and less would get thrown up into the air. Atmosphere would also mitigate much of this. You could demolish my hive, maybe even crack the crust, but the planet will be fine, eventually.

This is why Exterminatus Ordnance are so ridiculous. REAL Cyclonic Torpedoes will rip warp holes in your planet, and over massive scales. Virus Bombs will infect the life cycles of your world, and bring them to a halt. Magna Meltas drill to the core of the planet, and detonate there, causing the planet to blow itself to bits. Of course, a fleet of navy vessels can also do this with conventional firepower. "Most "regular" weapons lack a scale to hurt a planet. Also, most people can't declare Exterminatus, so it would be in bad taste to then hand out Nova Cannons.

(do they even still produce them?

Yes they do but only at a few (very few) Forge worlds.

On a Side note Nova Cannons are COOL. And I thought Cyclonic Torpedos Messed up Tectonic activity.

And The Exterminatus Virus Doesn't mess up the life cycle of a planet it eats all organic matter at a rapid rate turning it into goo and Oxygen then the fleet in orbit fires one round to flash fire the oxygen and the surface reducing the planet too a lifeless rock. and only Space Marines have the Exterminatus Virus. (I think)

How much damage should a Nova Cannon do to a planet hit by the shell? Should it really cover the whole surface of the planet in fire? If so, why aren't fleets armed with Nova Cannons all that's needed for Exterminatus? How do I prevent my players from simply wiping out any planets they feel are hostile once they, inevitably, get their paws on one of these **** things? Any suggestions would be most gratefully appreciated.

Because one good critical hit on a vessel with a Nova Cannon can completely screw it over. Its inability to fire at close range (or anywhere but directly in front of you) means you need a fleet to support it, and ships armed with it are capital vessels actually incredibly vulnerable to escorts because of the massive critical hit weakness.

Also someone going around Exterminatusing planets is a great way of getting the other Rogue Traders in the area to go "Fun's fun everyone, but this jerk is destroying potential trade because of some sort of overcompensation issue. Let's put our differences aside and each commit like, ten ships to destroying them".

Destroying an entire planet likely means you're destroying one or two incredible valuable things that you might not have known about, and that means someone else might've gotten there first and is trying to claim it.

Given the stated velocity of a nova cannon shell, it will burn up in the upper atmosphere if it hits a planet. Use that plus atmospheric shielding to justify it not causing exterminatus. (This satisfies both fluff and game balance.) It'll certainly torch anything under the impact point, and probably do a lot of damage to the local area, but not do the whole planet.

By the way, the Chixculub meteor (aka the dinosaur killer) was, we think, about 10 km across. That was enough to mess up the biosphere. As for actually shattering a planet, that takes much more effort - who do you think you are, Abbadon?

Cheers,

- V.

Also someone going around Exterminatusing planets is a great way of getting the other Rogue Traders in the area to go "Fun's fun everyone, but this jerk is destroying potential trade because of some sort of overcompensation issue. Let's put our differences aside and each commit like, ten ships to destroying them".

Destroying an entire planet likely means you're destroying one or two incredible valuable things that you might not have known about, and that means someone else might've gotten there first and is trying to claim it.

Yes, Planets are very valueble, but if you player do get their hand on some that can and you like to let them do it, that is fine... But they will make enemies just because you destory a xeno planet, doesn't meant the imperium will thank you... especially if it was something the imperium could/had planed to take over - some qoute said "men are the one resource that the Imperium can afford squander, planets not so much" - condeming a planet to death require inqisitorial order or oversight at least... depending on the alligence of the planet they destroy they will get an enemy for life... destorying a Chaos aligned planet might bring the wrath of chaos lord in the area, imperial won't be forgiving either... even if its unaligned, other races might like the Tau might be gunning after them (especially if people turn to them for help)... or people other places might start worship chaos for hope of saving... Orks might find it good sport and attack because of the change to fight a good fight...

But who know what might have been on the planet? Eldar having their maiden worlds destroyed can make fearsome enemies... or if there is a Necron tomb on the planet that gets destroyed they are likely to make an dread enemy indeed... Sure a strong group could take down a group of necron warriors... but when the necron troops in the thousand (or millions) are launched in retaliation across their world, its another story... and don't even get me started on facing their ships as coherent fleet...

so if they really destroy carelessly, don't be affraid to have someone give a brutal retaliation... There are things out there a rogue trader -no matter how powerful, ruthless and brilliant- has no hope of defeating.

I think it should **** up the planet, decrease it's atmospheric density plunge it into an ice age etc. However I have to question how many adventure scenarios is that a valid answer to? Seems to me the thing with nova cannons is they're a solution looking for a problem. It's a long buildup to where you could ever front these things and when you get there what the hell are they for? A RT having the things is like a multinational corporation owning and operating a state of the art aircraft carrier, I mean yeah maybe they can theoretically afford it and mayber they even built it themselves before....giving it to their security division but....why?

The thing is nothing but a gigantic hammer in search of a gigantic nail but even if you find that nail where's the personal gain in it?

I think it should **** up the planet, decrease it's atmospheric density plunge it into an ice age etc. However I have to question how many adventure scenarios is that a valid answer to? Seems to me the thing with nova cannons is they're a solution looking for a problem. It's a long buildup to where you could ever front these things and when you get there what the hell are they for? A RT having the things is like a multinational corporation owning and operating a state of the art aircraft carrier, I mean yeah maybe they can theoretically afford it and mayber they even built it themselves before....giving it to their security division but....why?

The thing is nothing but a gigantic hammer in search of a gigantic nail but even if you find that nail where's the personal gain in it?

In making threats. Having the power to actually lay waste to a planet in a relatively short timeframe gives you a completely different position at the negotiation table.

Against who though? Most populated worlds in the expanse are so technologically regressed that you can hold them hostage with no more than a raider's macro-cannons. Any world you'd need a Nova Cannon to hold hostage is in the Imperium or belongs to the Imperium/another RT and I guess you can threaten to blow one of those up exactly once before you get declared an Arch Traitor. I suppose you could threaten the Eldar that way with one of their Maiden Worlds, at which point they'll be attacking you everywhere you go and everything you own when you're not there to protect it forever afterward because they have the webway.

Honestly I look at Battlefleet Koronus and nova cannons don't seem very good to me, it seems to me by the time you have one installed on a ship you've spent way too much money overspecializing a single massively expensive ship to fight an enemy you'll never just happen to bump into. Unless the goal is to hunt down Da Worldbreaka or something it seems pointless and self defeating. If I'm going to get that invested in ships I'd rather have several smaller ones with more practical armament where if one gets hulked it's not the end of the world.

Sustained lance barrages are better at wiping out advanced civilisations (big cities, hives etc), while extensive macrocannon bombardment (or even better bombard cannons) will mop up less advance or more widespread civilisations. There's no need to fire torpedoes or novacannons at planets, unless you have specialized ammunition for them (atomics, vortex) and even then it'd be overkill but still not planet destroying. Exterminatus grade weapons are extreme even by Rogue Trader standards...

Against who though? Most populated worlds in the expanse are so technologically regressed that you can hold them hostage with no more than a raider's macro-cannons. Any world you'd need a Nova Cannon to hold hostage is in the Imperium or belongs to the Imperium/another RT and I guess you can threaten to blow one of those up exactly once before you get declared an Arch Traitor. I suppose you could threaten the Eldar that way with one of their Maiden Worlds, at which point they'll be attacking you everywhere you go and everything you own when you're not there to protect it forever afterward because they have the webway.

Honestly I look at Battlefleet Koronus and nova cannons don't seem very good to me, it seems to me by the time you have one installed on a ship you've spent way too much money overspecializing a single massively expensive ship to fight an enemy you'll never just happen to bump into. Unless the goal is to hunt down Da Worldbreaka or something it seems pointless and self defeating. If I'm going to get that invested in ships I'd rather have several smaller ones with more practical armament where if one gets hulked it's not the end of the world.

Would the imperium actually interfere in a fight between 2 Rogue Traders outside Imperial space? Somehow I doubt they'd bother to listen to all the 'He started it' 'No, he started it!' back and forth and let you sort things out on your own as long as you don't cause too much collateral damage in the process. Also, you don't always need to threaten. Sometimes it's enough for people to know you could do it and they'd treat you differently.

And yes, nova cannons aren't that great from a mechanical point of view. A Hecutor plasma battery in that slot is way more useful 9/10 times. Having the capacity to perform mini-Exterminatus is fun though.

Imperial reactions to Rogue trader crimes seems to vary a lot.

There are mentions that getting a court case settled against a RT might take decades or longer and that justice might eventually happen even generations later as there is no quarantee of the RT even returning to Imperial space. I guess sometimes it really is a case of a loyal RT returning home after a dangerous trip and being greeted by Navy warships and an angry Arbites or Inquisition official who notifies them that after 121 years the courts have agreed that his grandfather's crimes are so severe that the entire Dynasty is sentenced to death and their warrant revoked.

In fact those cases in the fluff where it is mentioned that a Rogue Trader receives punishment (usually death, either to the particular trader or their entire family.) it has been from dealings with Xenos or Chaos or other form of outright treason. (Although the RT has the right to deal with aliens there also seem to be some Ordo Xenos inquisitors who still don't approve of that.)

As for the original scenario of RT on RT war beyond the borders of Imperium... I am not sure how Imperial "Justice" would deal with that, particularly since those planets would not technically be part of the Imperium. On the other hand I am certain that both sides could try to bribe officials and have their lawyers try to get the other side to lose their warrant over the war.

(...) is fun though.

And it's all that matters .

Imperial reactions to Rogue trader crimes seems to vary a lot.

There are mentions that getting a court case settled against a RT might take decades or longer and that justice might eventually happen even generations later as there is no quarantee of the RT even returning to Imperial space. I guess sometimes it really is a case of a loyal RT returning home after a dangerous trip and being greeted by Navy warships and an angry Arbites or Inquisition official who notifies them that after 121 years the courts have agreed that his grandfather's crimes are so severe that the entire Dynasty is sentenced to death and their warrant revoked.

In fact those cases in the fluff where it is mentioned that a Rogue Trader receives punishment (usually death, either to the particular trader or their entire family.) it has been from dealings with Xenos or Chaos or other form of outright treason. (Although the RT has the right to deal with aliens there also seem to be some Ordo Xenos inquisitors who still don't approve of that.)

As for the original scenario of RT on RT war beyond the borders of Imperium... I am not sure how Imperial "Justice" would deal with that, particularly since those planets would not technically be part of the Imperium. On the other hand I am certain that both sides could try to bribe officials and have their lawyers try to get the other side to lose their warrant over the war.

Well, depending on how much Imperial property and personnel you are sucking into your little war, the Imperium might take a direct hand. Wasting the supplies of a Forge world (none in the Expanse), gathering up troops they can pointlessly waste on other skirmishes, or whatever have you is a problem, and I don't care how much money you have, sometimes money isn't as useful for them, when it won't fight, or refurbish the ships. Do enough, and I think some aspects of the Imperium would take notice. Many have the clout and pull to harass ONE Rogue Trader. As for taking their Warrant away, I'm not sure who actually can. I sort of wish that they had done a better consistency job with the receiving of the Warrant. Back in the day, you were empowered by the Emperor, and that meant He could revoke it, no one else. A bit later, the High Lords have the job, and they are a pretty august body to go around. Now, the fiction talks about "average" Nobles buying one for second sons, high-ranking Officers getting one as a reward due to a lack of further promotion (there are only so many Lord Admirals, and such) or other Inquisitors getting one for their fellow, to get rid of him, as he loses the one power set to gain the other, most likely goes away. When mid-level bureaucrats, who will never speak to a HLoT can acquire these, potentially making the receiver more powerful than they themselves, it seems they could more easily be broken. Personally, I like to maintain, and will for any games I run, that only the most upper echelon individuals can acquire and revoke these powers, in much the same way I like to say that the physical Warrant is on Holy Terra, in some sort of stasis vault, and the Rogue Trader might have a device, something like an Inquisitor's rosette, that links them to their proof, but keeps the Warrant out of firing lines. It just seems so dumb that there's a piece of paper with ink on it, and if your ship is blown up, even while you have several, or your capital planet is lost (do you have one of those?), the thing that empowers you is gone, and so might be your power, if anyone actually cared to say "you're a Rogue Trader, whatever that means? Prove it!"

As for impractical Nova Cannons, if you try to blast worlds that don't belong to the Emperor, that sort of doesn't matter to them; from their perspective, it DOES belong to the Imperium, borders be damned, and even if it doesn't, much of their property might be on that world. Sometimes, it just doesn't pay to be a d**k.

If you try to blast worlds that don't belong to the Emperor

Actually since mankind is "divinely preordained" to rule all, Every planet belong to the emperor... And i know Sisters of battle that would put a bolt round in your chest and head for saying otherwise

If you try to blast worlds that don't belong to the Emperor

Actually since mankind is "divinely preordained" to rule all, Every planet belong to the emperor... And i know Sisters of battle that would put a bolt round in your chest and head for saying otherwise

But not all worlds are under Imperial rule and if the people of the planet B23 haven't accepted the Emperor as their saviour then why would the Sororitas care if some infedels get blown to smithereens?

It just seems so dumb that there's a piece of paper with ink on it, and if your ship is blown up, even while you have several, or your capital planet is lost (do you have one of those?), the thing that empowers you is gone, and so might be your power, if anyone actually cared to say "you're a Rogue Trader, whatever that means? Prove it!"

The core rulebook does point out that the Imperium is a very hierarchical society where people are accustomed to obey their betters without a second thought. Therefore if someone shows up on orbit with a heavily armed ship and says that he is a Rogue trader then the people take it for granted. If only because that person does have a ship that could kill them all, and as long as person X does what a Rogue trader is supposed to do, offers part of his bounty to Imperium and does not do anything severely heretical or treasonous the higher ups are unlikely care if his warrant is real or something he wrote on a napkin.

On one hand I understand why you don't like how easily the RPG fluff seems to indicate someone could get a warrant, but you have to remember that RT's are also very likely to end up dead or penniless. One mistake can end their lives and they are facing, not only xenos and heretics but also other Rogue traders who are more than willing to crush others for personal gain. (Particularly if they are beyond the borders of Imperium and don't have a risk of retaliation.)

I think the important thing to try to keep in mind even harassing another RT in the expanse that economies are weblike. Seize some colony world with major mining industries on it and you've probably just rendered a stock on the market completely worthless. Any number of people might have held some of that stock, like Navigator Houses, Planetary Governors, Adeptis Arbites Retirement pension funds....

Lots of brilliant ideas and suggestions here - thank you for your responses. I only asked because my party, much as I love em, do have some murderhobo tendencies and I prefer to curb their desire for mass murder. In particular I like the idea of Imperial justice and/or other RTs coming after them if they start ******* up planets like that.

Easiest way to curb murder hobo tendencies is to offer players a vile xenos threat to focus on - this shifts their killing and looting away from Imperial citizens and colonies. Also if they persist you can have Throne Agents and eventually Inquisitors show up when they are in port and 'inform' the players that they are tagging along to observe... see how quickly your players change their murderhoboing or swiftly descend to be wanted by the Inquisition for slaying it's agents.

N.B. I totally didn't order my crew to open fire on rival rogue trader's ship that we knew contained an inquisitor!

In addition to the above mentioned option (which I totally agree with), having another powerful/renowned NPC Faction present on the planet/space station/location is another determent.

Example 1: On planet Zorn is an indigenous civilization that has come to "dislike" the PC's. In this civilization are various Ecc. member trying to convert them over. So, killing/blowing them up would only make the Ecc. "upset" with the PC's.

Example 2: At mining location Bravo, the Casiblaca has prisoners/workers extracting rare minerals. Also with the dig site is a Office containing representatives of the (insert powerful named) Dynasty who receive part of the profit returns. Conducting small Raiding operations, or political subterfuge to obtain some the rare minerals would be most advisable to a full scale ground assault.

It could also be that killing/slaughtering/blowing up/committing gleeful genocide (because went isn't it a merry prospect?), renders any gains zero.

Example 3: The local inhabitants of city ships of Zayth are the only ones able to operate and maintain their technology. Any attempts to forcefully capture a ship results in its inevitable demise by a catastrophic 100 megaton explosion (game terms: Plasma Reactor Overload).

If you try to blast worlds that don't belong to the Emperor

Actually since mankind is "divinely preordained" to rule all, Every planet belong to the emperor... And i know Sisters of battle that would put a bolt round in your chest and head for saying otherwise

But not all worlds are under Imperial rule and if the people of the planet B23 haven't accepted the Emperor as their saviour then why would the Sororitas care if some infedels get blown to smithereens?

Their acceptance, is not requiered THE GOD-EMPEROR RULES ALL! THE EMPERAH OWNS ALL!! (i kinda wish he would wake up to see how would react to the imperium turing in to the exact thing he did not want it to be XD)

If Emperor ever wakes up and gets his @$$ off the Golden Throne I predict new crusade like the first one. (Actually It would be unbeliveably awesome scenario to play, think of all the manure hitting rotary osscilator and ocassions to plunder... I mean profit, during all that fighting...)

I know how the Emperor felt, way back then, but I sometimes wonder, if His senses were watching His Imperium, for all these millennia, if He'd come out the same, or have seen the truth of what is said; people need SOMETHING to believe in. They wanted it to be Him; Lorgar wanted it to be Him, and He said no, but that was, at least to a certain degree, because He was never weak, and under the gaze of beings so much greater than He was, coupled with His erroneous "starve the Chaos Gods by denying/concealing their existence" plan. I like to think, at least in part, He's seen what has befallen His Imperirum, and that their belief in Him as a deity is much of what has kept them around, to say nothing of how much power He has absorbed, like the same Ruinous Powers, from millennia of "worship". If that's the case, He might come back ever so slightly more enlightened of what His people need(ed), or it will go like DuneMessiah/Children of Dune, and He'll waste time creating a myth about Himself, only to then do all He can to tear it down; not sure which, but this is grimdark, and not the first time they'd have borrowed from Frank Herbert's works.