We have very little afaik on planetary defences. However, a planet with a good industrial base should be able to make a generational investment in system defence.

Find a suitable asteroid. Fit it with basic essential components (not warp drive or geller field). It might have 2 broadside slots and a void shield - perhaps a modest drive to give it Move 1. A dozen of these orbiting a world and you with need a fleet to take it.

If a world could build one of these every 50 years, in the timescale of the Imperium the average industrial world should be very tough.

Fresnel said:

Funny enough, a colony can grow every 90 days per Stars of Inequity, meaning a small outpost could grow remarkably quickly. Absurdly so.

Cryhavok said:

WELL BEYOND WHAT A COLONY SHOULD HAVE!!

Seriously. No colonly should be able to even remotely threaten a Grand Cruiser. Do you not have any idea of how difficult industrial production is in this setting??

If there's a Grand Cruiser that can be seriously threatened by a colony when it moves into position to bombard it, the Grand Cruiser is Doing It Wrong . Seriously, you've got so much space to play with, there's virtually no reason not to take (for example) the extra flak turrets. Fit that to an Exorcist and wow, suddenly you have a turret rating of what? 4-5? Plus, of course, fighter support from the embarked squadrons.
Combine that with the fact that ground-launched small craft are going to be extra vulnerable (as they're stuck on a fairly predictable trajectory) as they climb out of the gravity well, and (per Battlefleet Gothic) a single macrobattery "hit" will result in a squadron (actually, the entire formed wing, so potentially many squadrons) being mission-killed at least, plus the fact that ground-launched small craft are going to be less capable in void combat than ship-launched (again, to do with the fact they have to claw their way up to orbit), and we see that it should take dozens of squadrons, at least, to pose a threat to a serious warship over their world.

That said, if the colony can produce orbit-capable shuttles, they can produce planetary defence bombers, fighters and assault boats (basic engine requirements are the same, but the fuselage and total mass is going to be smaller, giving some more manueverability). They may not be up to IN standards one-on-one, but when you potentially have the resources of a planet to draw on, and aren't as limited by storage space and consumables, then given time they can produce enough to threaten/deter even a squadron of capital ships from taking position in their orbitals. Of course, once the attackers have the orbitals, it becomes much harder to launch against them without having your bombers/launch sites destroyed, so there's a narrow window for launching and having a hope of your bombers doing something before being destroyed. But if the defenders hit that window, they can do serious damage.
Hell, if they have the technology to produce ICBMs, they can deter a ship from taking the orbitals without being careful and launching small craft from further away, as even a chemical rocket booster can loft a half-decent torpedo (ok, Poor Quality, but that can still do some nasty damage) into the guts of an unwary ship.

For that matter, what on Terra is a grand cruiser doing without escorts? Really, the largest ships that should be allowed out alone are (maybe) battlecruisers. What happens if they don't is they get picked on by lots of smaller, more maneuverable vessels until they get crippled/dead. Look at what happened to the Planet Killer (at least battleship sized, if not a dreadnought/superdreadnought)- taken out by 3-6 Cobra destroyers who just "parked" themselves behind it and pumping torpedoes up the aft.

Cryhavok said:

I can think of dozens of examples of planets that do not have starship tech but suitably tough ground and orbital defences that have cropped in my games over the years. We had one where the locals had a nuclear satellite defence grid and nothing else in orbit, but they had excellent ground and air defences when we finally tried to invade.
Remember that to profit from a world you have several routes:
A) Trade agreements - you discuss with the leading trade faction or rulers of the planet about what you want from them and what you can offer in exchange. This could be a like for like trade of goods, it could involve services (offering priests, doctors, techpriests etc in exchange for a rare local commodity, or even taking pilgrims from a world to a distant shrine they have ancient tales of but have never been able to visit).

B) Covert profiterring - this could be as simple as sneaking up on a valuable asteroid ring in a system you are considered hostile in, or as complex as sending undercover agents down to a planet to hijack operations and funnel profits or valuables back to your ship.

C) Invasion - Assuming you can't work the first two options, then invasion is your final calling card. You have to rock up in system, take out hostile ships, knock out system ships and orbital defences, get air-superiority on the planet, land forces and start taking over territory and resources. You could be stopped at any time along this route, or if you are really lucky you could be going up against a primitive culture who while incredibly aggressive simply do not have advanced tech enough to oppose you.

A well run (and played) campaign will have a mixture of opportunites for profit and plunder, and there should never be a situation where you can 100% predict exactly what sort of defences a planet will have, or how trade negotiations are going - if this is the case then the GM needs to vary things more and stop letting the players get away with pulling the same tricks over and over.

I agree with everything kasatka and alasseo just said. In the case of the grand cruiser I was speaking about, it was kind of silly for them to run around without escorts, not even fighters of its own. Many of the bombers were destroyed, but they did take out the ship. I think about 16 sqadrons were lost if I remember correctly. It turned the game, temporarily in to a behind enemy lines thing as the group rallied the survivors on the ground. The eventually managed to take the planet from the ground after a hard fought war, and then they called in one of the dynasties other ships to come pick them up. Everyone had fun even though they lost thier grand cruiser.

The Nova Cannon is still going to be ideal for rapidly stripping away orbital defenses and it can do so from outside of the range that ground-launched torpedoes can threaten.

If a system can build 30 squadrons of bombers/fighters, it can probably build an orbital platforms to launch them from. Build the bays into asteroids and 'run silent', and you might get the drop on invaders.

I am sure people can think of other ways to make invasion challenging too. How about a Nova cannon in an asteroid?

Fresnel said:

Well, yes, they probably could build bays into asteroids/moons. Trouble is, you then start to run straight into the problems of space and consumables, just as you would with a starship. Life support, munitions, spare parts… all the stuff that's relatively easy to produce, store and transport on a planet (even assuming you need to provide life support to the launch site/bay/base, which on a planet with a habitable atmosphere, you don't) suddenly becomes an issue for a void-based facility. Admittedly, it's not necessarily a major issue, particularly as a colony matures, but it does mean that your "secret" orbital bases will need regular (if not necessarily frequent) resupply. It'd be a stroke of bad luck to have attackers arrive to spot that resupply run, but it could well happen, with fairly predictable consequences.

Other tricks? SDF bases in close orbit of a local gas giant, alerted by listening stations on the system's edge (admittedly, that's something that requires a mature colony). Orion drives on asteroids to disrupt/annoy attackers. Mass drivers on the moons (stuff like the Lathe Grav-Culverin, ideally). Hell, a SAPL system is not necessarily that tricky to build (although in 40k terms, keeping your collector and targeting mirrors aligned and on target would be an absolute *****). Minefields. Orbital tugs dropping mines. Deadfall torpedo salvoes in the L4 and L5 points of a colony's moon. One-shot bomb-pumped lances fitted to asteroids, or in an oversized torpedo bus.

Starting more or less in order as to how the posts line up here on the last page…

A Nova Cannon may not be explicitely "Exterminatus class weaponry"m but you said yourself that firing off a couple rounds at a planet would devastate the surface to an excessive degree. Which is -basically- the same **** thing. Destroying a planet that is capable of holding human habitation without special measures taking place (as in, an earth-like planet), is most certainly going to provoke some sort of response, even if its just turning your reputation to **** with most of the Expanse.

And you still neglect that some people willingly choose destruction over domination. The modern western notions, of each and every person fighting against everyone else, for their own personal success and livelihood, never giving a **** about who they have to step over to get ahead in their own life. Well, assuming that ideal still holds true in the entire Imperium, or far-flung colony worlds, is a mistake. Sometimes the people holed up and trapped will tell the Romans to go to hell and systematically execute themselves instead. Some people kinda like the idea of dieing before being enslaved. So don't be so confident that you can just threaten to blow people up with a Nova Cannon and expect them to roll over every time, even after you have to use it once.

And need I point out, if you make a habit of sailing up to planets, and giving them the choice of bending a knee or being blown up… yeah, you're going to become real unpopular really fast, and you will inevitably see other shipmasters putting you in their sights, as you're little more than a jumped up brigand at that point.

Now, as for the industrial capacity of a colony world. No.

No building hundreds of bombers and sending them flying away to blow up the starship (and why do people always latch on to something extra dumb, like that they can JUST create a few hundred bombers and that's enough). Most Imperial colonies conform to a simple design scheme, and one that does not provide for that kind of infrastructure or level of technology.

Simply put, most Imperial colonies in the early stages have one main city, around the spaceport (if it has one), while the rest of the population is dispersed out in to the surrounding countryside, doing whatever it is that makes the planet valuable in the first place (farming, mining, etc.). And it isn't likely to be heavy industry at this stage. No, that doesn't happen until the planet reaches a much larger population, and isn't even a sure thing, should the planet be set aside for little more than resource exploitation (lots of Prometheum or metals to extract, or its a prime candidate for turning in to an agri-world).

The only way most little colonies (because by the time they have several million people, infrastructure, and ties to the rest of the Imperium, they're hardly a "colony" anymore) in the Expanse would have the kind of things needed to even attempt to fend off an enemy starship, would be if the world basically acted like a trading hub and/or popular dive with the other travellers floating around. Tatooine basically, where despite the world being a lousy little nowhere, lots of people with spaceships stop by while passing through the area. Then, and really only then would they have the chance to get the kind of attack craft needed to fend off attack by a starship.

It may seem strange, after all my talk of planetary defences and how you need to be careful, about me doing a virtual 180 with the previous commentary. But there are small colonies, and there are established colonies that are essentially regular civilized worlds in their own right (and if you want to get really technical, everything but Terra is a colony, but that aside..). Most of the Expanse conforms to the former, where the atmosphere could be likened to a frontier town. Having defences, and having defences that can even attempt to take on a starship, are two vastly different things, and as explained above they're not likely to have them. Most such colonies get by on having little worth taking. If someone with a starship really has to resort to raiding your little world for food or resources.. well, they must be holding things together with prayers and ducktape.

Worlds with valuable resources, and worlds that have had time to grow up from the simple colonies they start as, are the ones that will actually threaten the offending starship. The former because someone, somewhere, will want to protect said resources (the Mechanicus, for one implacable example). While the latter class of worlds will have the population and relative wealth to see to its defences better, because there's simply more to steal.

Also…

Asteroids aren't free, citizen!

You make an excellent point about people being willing to see their whole world burn rather than surrender.

As for most colonies not having a large industrial base, I am not so sure. The Imperium have been going 10,000 years. What qualifies as a young colony? 100 years, 500 years, or 1000 years?

Drop a 10,000 people onto an Earth-like planet, given them standard Imperial level STC tech and where will they be in 500 years? A population of 10 billion? What kind of industrial capacity might they have? Look at the size of the Real World USA navy… Translate that tonnage into spacecraft and what do you have?

Sorry. I missed the qualifier 'in the Expanse'. However, if the RT has encounter an pre-Imperium human civilisation in the system… Well they might have enough system defence to challenge a full Navy strike force.

Please clarify something for me, before I make any arguments. Is your position that little colonies would be defenseless against any starship that passes by? I cant see someone putting the reasources together to get a colony started, and then leaving it to naught but prayers to defend it against the reavers, pirates, rival rogue traders, and other badies filling the expanse. Especially since it is outside the imperium and not the easiest place to access, I dont envision too many people ploping down defensless colonists and calling it a day. But Ill also admit I havent gotten stars of iniquity to see what they say about it also.

I don't think he means defenceless full stop, even the smallest colony may well have some AAA and militia/ house troops. The thing is with taking on starships that even a single macrocannon is an huge expediture of worked metals, chemicals for the propellants and infrastructure to make the shells and gun itself. If you wanted to import these things, they may take up an entire cargo ship. Colonies hovering on the edge of profitability may simply not warrant the expense. larger colonies i.e. self sufficent worlds, may be much more heavily guarded in the expanse then they might be in normal imperial space because of the known level of threat.

As for throwing up a couple of hundred bombers, given that our modern tech level can't get substiantial numbers of craft into space, discounting ICBM's, why would a colony world a fraction of the size of China be able to do it?

For Inspiration, it may be best to think of the age of imperialism, circa 1700-1900. some ports were heavily defended trading hubs, with forts to guard their entrances and dedicated monitors to their defence. If the Pc's build up a successful world, than this might be the result, and is worth underlining in the narrative when they approach the world.

for instance "Freeport Gidjanik was founded only two centuries ago, but the discovery of rich ores and stable warp routes made it a natural stopping point for traders heading into the foundling worlds. with more and more of their wealth stemming for the worlds manufactoriums and tarrifs, House Cavelock commissioned the construction of the Burning Fort whose partially exposed plasma reactor acts as a lighthouse to all that would visit her"

and "Drycove had been founded on high hopes, but like many worlds in the expanse, floundered swiftly. when the initial returns were not as strong as expected, the founder house have been infrequent visitors, seeking profit elsewhere. Without a tech priest cadre capable of expanding the few manufactoriums on the world, the vast majority of the populace uses locally manufactred items of low quality steel. while the satraps personal guards have lasguns, the PDF makes do with bolt action rifles, and while numerous, lack any kind of MBT or artillery."

I think that Damaris from the Frozen Reaches is a good benchmark for a high-end well established colony of the Koronus Expanse. It has fortified its moon to act as a space station (not a terribly impressive one) and has a small (but not specified) number of system defence ships in its flotilla. I think that most colonies in the Expanse make do with much less.

While thier very well may be colonies that are so unprofitable that they are abandoned to fend for itself. It stands to reason that assaulting such a colony would not be worth the cost of ammunition or fuel. And attacking somewhere that is profitable will have defenses that can deter ships, as how else do you think the are beliving an attack will come? Having defenses that could not handle a raider or frigate would mean they might as well not have defenses, as almost anything that might attack them will be coming by ship. It could be something simple like minefields or small craft, or more complex like ground to space guns, ICBMs, orbital platforms or system ships.

Now a colony abandoned by its protectors might be easy pickings, or maybe one that got cut off, like grace. But I doubt a world like that would be worth threatening. In fact in grace's case threatening them would be entirely useless. I would guess that if you gather info and select a target you could find a colony that is defenseless to you, but that would take just as much work as assaulting a defended colony, just work of a different type. Just exploring the expanse, I dont think you would find too many defenseless colonies.

As to using a novacannon to strip away defenses, I would agree. Static defenses with less range than it would be fairly helpless. A system without mobile defenses would fall given enough time, no matter how many layers of static defenses they have.

Cryhavok said:

The biggest issue here is that the Koronus Expanse has been written in a manner that suggests the PCs can accomplish a great deal despite the fact that they only have one ship, often a raider or frigate. This flies in the face of the fact that almost everything in WH40K is done large.

The Frozen Reaches is one example, where the PCs and their ship are instrumental in the defence of Damaris. Realistically, one more frigate is unlikely to be the decisive factor in the invasion of a world in most of the WH40K universe, but in the KE, that's the way it is.

HappyDaze said:

To be fair, it's not the ship that the PCs really bring to the table in that adventure, it's the organization. There are enough assets to defend the planet already (although that might need to be rebalanced if the PCs are particularly powerful) but there is no cooperation between the people who command those assets. The PCs are the trusted outsiders that everyone will agree to let command (since they don't trust other parties for various reasons).

But yes, the KE did change 40k fluff a bit by making it so that one frigate could make a difference in a combat situation. I was pretty surprised by that decision when I first read the rule book; it seemed like they could have easily kept the previous standard in the fluff of Rogue Trader's being given a cruiser with their warrant and that being the standard RT ship.