I see many people misunderstand the events of Desh'elika, arguing that the Emperor acts out of character in being so hostile to Angron, and that he could or should have helped Angron win the battle and, by extension, his favour. This is wrong, built on a fundamental misunderstanding of both characters.

If the Emperor saved the Eaters of Cites and asked Angron join him in exchange, Angron would have refused. If the Emperor insisted, Angron would fight and die if he had to; I mean hell, that was his plan at Desh'elika anyway. Once he is at the point of preferring death in an unwinnable battle to a return to servitude, it doesn’t really matter how unwinnable the battle is or who he'd be in servitude to.

The Khan joins the Emperor because he realises the choice is between death and service, a choice which he had forced upon others in the past, and accordingly he chose service. Angron was never going to choose service; All Angron wants is for him and his siblings to retire free. He wants to live on a nice little farm with them in a little anarchist commune in the middle of nowhere, and he wants to grow old happy, undisturbed and free with the people he cares about. And if he can’t have that, his background as a slave means he finds dying in pursuit of that goal to be the next most preferable outcome.

He doesn't care about the fate of the galaxy or of the human race as a whole, he doesn't care about power (outside of winning his freedom), he doesn't yearn for conquest or glory or to spread an ideal, he doesn’t believe he is honour-bound or predestined to serve the Emperor; uniquely among the Primarchs, there are no carrots the Emperor can offer Angron which would entice him. Angron’s supreme ideal is freedom, which is anathema to the Emperor.

The Emperor, on the other hand, needs Angron as much as any other Primarch; partly to stabilise the Legion genetically and partly to lead them in accordance with his plan. The Primarchs are tools, and are treated as such. If someone steals your hammer, you may try to recover it. If someone damages it, you may try to repair it. But ultimately the hammer is a tool and operates under your direction. The Emperor lets the Primarchs think of him as a father because, for some, it’s a motivator and/or method of control. But to the Emperor, they are still merely tools used to achieve the project.

He needs Angron and can’t just let him go. Not only because he is needed for various aspects of the plan, but because the project of the Imperium (divorcing mankind from the influence of the warp) cannot be opt-in; it has to be universal for it to work, and if a Primarch can just choose not to be a part of it the whole thing collapses.

So all we have left is stick, and nothing but stick; the Emperor needs to break Angron's spirit. He needs to show Angron that he is a tool created for a purpose which he will fulfil, irrespective of what he "wants", and that the Emperor can indeed force his will upon him. However, he needs to do it without offering Angron the opportunity to martyr himself, because if Angron can die free he will choose to do so. So he pulls Angron out of the final battle, denying him his martyrdom and divorcing him from the fate of his siblings. He does this to show Angron that he has no choice, that he is not free, that he will lead his legion in the Emperor's name whether he likes it or not, and most importantly that the Emperor can make him do this.

I will again refer back to the hammer metaphor; if your hammer is not working (i.e. it’s broken) then you would probably attempt to repair it before discarding it, especially if you had spent time searching for it because it could not be replaced. That the repair process may be uncomfortable for the hammer, or may not work, is a matter of no concern.

The Emperor is not kind or altruistic. His treatment of Angron is not unusual; had the Khan refused, the same fate would have befallen him. The only unique thing is that the Emperor has nothing to offer Angron. If he had something to offer he'd have been as magnanimous with Angron as with any other Primarch, and if he'd completely lacked leverage over any other Primarch he'd have been equally as callous and heavy-handed with them as he was with Angron.

Postscript

I think it worth touching upon censure, which we know happened to 2 and 11 and was considered for Curze and Angron; clearly the Emperor isn't above discarding tools which no longer work. But we also know that 2 and 11 were found and put in command of their legions sometime before their censure, so we can assume that at the very least a living primarch would be needed for a time to stabilise their Legion's geneseed. And again, from the Emperor's perspective, "repairing" Angron from a wilful former slave to a dutiful imperial general would be preferable to discarding him outright.

Like many people have rightly said, stories about how bob drives his car for his 9 to 5 job aren’t exactly exciting, but I’ve always thought civilized worlds deserve more attention. Tbh, I didn’t know civilized worlds were a world type, and thought they were more just an umbrella term for “worlds that aren’t lawless/feral”

Maybe it’s because of how grim dark it can be, but picturing a world with suburbs, privately owned cars, non overly polluted, and cities that aren’t hellish hive cities is fascinating to think about. The setting is so massive that to think there are multiple worlds that could resemble 2nd millennium Terra is pretty fun to think about

I see memes about him but who is he? (I dont care about spoilers I have no desire to read the Horus Heresy)

In the last post, this series explored the fundamentals of ship production in the Imperium. Here, we’ll take a look at what the lore says about shipyard capacities, ship production timelines, mass production, address the last major constraint, and make the final calculations of the series. 

Individual Shipyards

Docking facilities are not described in much detail, but we do have some sources to work with. In some cases, they appear to be single-ship cradles, wrapping around a ship and providing all the services it could need. In other cases, we know that the docking limbs on large Imperial structures (like the arms of a Ramilies) are capable of repairing ships, and some shipyards might take the same shape. One interesting factor to consider is the idea that a shipyard/docking arm could service multiple smaller ships in the same space as a single cruiser, as that’s something we sometimes see:

>The tender simply vaporises the Ultramar Azimuth Graving Dock, shredding the superstructure of the giant berth cradle, and the cruiser Antipathy docked inside it. [...]
The Aegis of Occluda catches fire, all seven kilometres of it, in its ship cradle. [...]
The Ultramar Zenith Graving Dock suffers integral gravimetric failure and drops out, breaking and twisting towards the planet below. The grand cruiser Antrodamicus, supported by that dock, rips free of its moorings and begins to slide backwards out of the collapsing cradle, in some ghastly parody of a ship launch. 

>- Know No Fear

>The largest shipyard in the system, B/017 is a gigantic gothic-tiered scaffolding almost twelve kilometres long, designed to house all but the very largest Imperial warships and mass conveyors.

>- Rogue Trader Into the storm page 240

>The largest are capable of handling several large military capital ships at once, although most can only cope with a single cruiser or squadron of escorts at a time.

>- Battlefleet Gothic Rulebook page 144

>A single large craft, or multiple smaller vessels, can easily be accommodated at each of the four docking arms.

>- Only War: No Surrender page 8

>The actual location of the container is still to be determined, as 17 other craft were in the process of unloading and loading in the same cargo bay. Two were still docked when the breach was discovered. 

>- Dark Heresy Blood of Martyrs Page 109

Individual Production

Here’s a lot of general quotes. They’re pretty contradictory, but establish a general rule that shipbuilding takes a long time. One of the things I noticed is that they tend to operate in brackets (years, decades, centuries). In fact, if we’re willing to read into the very first quote a bit, the smallest ships take years while the largest ships take centuries. I want to keep that quote particularly in mind as we explore ship production times:

>Building a void-ship from scratch is a massive undertaking; it can take years to complete an escort-class vessel and centuries to build a capital ship. Such a vast effort requires countless numbers of workers and huge amounts of refined materials. A great work like this might not be completed for generations.

>- Battlefleet Koronus page 46 

>It is important to note that building a brand-new starship is an exacting task requiring many years (often decades) and much toil. Normally, building new starships is reserved to the Imperial Navy. Rogue Traders are far more likely to acquire a recommissioned Naval vessel or repair and refit a salvaged derelict.

>- Rogue Trader Core rulebook page 274

>In the Imperium, it is rare that ships are broken and scrapped. Each starship is a valuable prize representing decades of construction and filled with arcane and priceless technology. However, through battle, disaster, or hard use, some ships do become untenable.

>- Rogue Trader Edge of the Abyss Page 33

>The spaceships of the Imperium are vast constructions that take many decades to build. Each craft represents a huge investment in time and resources. But once completed, fitted out, armed, and commissioned, a spaceship continues in service for centuries, even millennia.

>- Rogue Trader Core Rules page 316

>Ships take decades, even centuries to build, if the builders have the required skills and knowledge base in the first place. It is rare to find a "new" starship—most are hundreds or thousands of years old, and some date back to the earliest days of the Imperium. Therefore, ships are never mass-produced, and even two ships of the same class are rarely alike. A Lunar-class cruiser produced in the shipyards of Mars will be vastly different from another Lunar hailing from the docks of Port Wrath.

>- Rogue Trader Core rulebook page 189

>A cruiser is a warship through and through. These are the ships of the line of Battlefleet Calixis, the heavy-hitters that fight major naval engagements. These ships are rare—building one takes centuries if not longer, and requires knowledge and technology from mankind's golden age now only known to the most powerful tech-magos. However, each vessel—often five or more kilometres long—carries the firepower to burn planets. They are designed to win wars, and the Imperial Navy guards them zealously.

>- Rogue Trader core rulebook page 191

>..a single ship is extremely valuable—representing decades (if not centuries) of construction, and centuries or millennia of service. There are planets worth less to the Adeptus Terra than a single transport. 

>- Rogue Trader into the Storm page 149 

We do have more specific quotes. Escorts typically take a few years, and depending on their quality, cruisers can be produced in as little as 10 years or over 30. Space stations take a weirdly short 17 years to make, and in times of crisis, the Imperium can design and push (mostly) new battlecruisers in just a few years:

>Although no ship could be said to be mass-produced in the Imperium, the Cobra is one of the simplest to build, with a well-equipped shipyard able to construct one in only several years.

>- Rogue Trader RPG: Into the Storm, pg.152

>Perhaps the most remarkable example of this is the Lord Daros, constructed at the feral world of Unloth. The primitive tribesmen dwelling there were influenced to mine and smelt metals which were then presented for "sacrifice" at sky temples established by the Planetary lord. The raw materials were then lifted into orbit on each vernal equinox. After a period of eleven years, the tribes were rewarded for their effort with the sight of a bright new star moving across the heavens as the Lord Daros boosted out-system to join Battlefleet Obscuras.

>- Battlefleet Gothic Core Rulebook page 110

>Manufactured in the vast orbital shipyards of Cypra Mundi (as well as at other shipyards in lesser numbers), the Overlord is a difficult vessel to construct, but faithful and fierce in its service to mankind. It does not waste space on massive attack craft hangers or the temperamental nova cannon. Instead, most designs use powerful long-range macrobatteries and lance turrets, backed by prow torpedo tubes. This simple, proven, and effective weaponry plays to the strengths of Imperial Navy tactics and Imperial technology. The design is an ancient but successful one, and new examples of the class are still commissioned every decade or so.

>- Battlefleet Koronus page 22

>‘In recognition of your services,’ Nuministon said – unlike Plosk’s natural voice, his was that of a machine – ‘the fleet yards at the forge world of Triplex Phall will undertake to construct and present the Chapters of the Blood Drinkers Adeptus Astartes of San Guisiga and the Novamarines Adeptus Astartes of Honourum one strike cruiser apiece in a period not exceeding thirty standard years after date of construction, of a class of your choosing.’

>- Death of Integrity 

>The Peregrinus' machine spirit remembers well the long decades of its construction in the crowded void-yards above Gryphonne IV.

>- Dominion Genesis

>Port Wander originated as a standard Xerxes Mark IV Naval station, made from prefabricated and pre-blessed sanctionals and transported into the system by mammoth Greatholds over many months. Assembly took only seventeen years; the station was consecrated, declared operational, and thruster-anchored into position orbiting Rubycon II far ahead of Thamos in a stable position a year later.

>- Rogue Trader: Into The Storm page 234

>In the waning years of Abaddon's Incursion, the Adeptus Mechanicus Artisans of Hydraphur and the officers of Battle Fleet Pacificus faced a dilemma. In supporting Battle Fleet Obscuras the problem with pirate bands had become acute and the lack of speed among the standard Imperial cruiser designs meant that the tactical initiative remained with the pirates. At the direction of Admiral Knightsbridge the Tech Mages of Hydraphur designed and built in record time, the Long Serpent class battle cruiser. [...]

>As the war winds down, limited numbers of Long Serpents are finding their way into the fleets of both the Obscuras and Pacificus Segmentums.

>- Battlefleet Gothic Magazine Issue 2 pages 18-19

As we see, cruisers take decades, not centuries, on average. Going back to the start of the post, we focused on that quote which refers to the end of one scale by single-digit years, and the end by triple-digit. While there is one quote in the general collection stating that cruisers can take centuries, this doesn’t match with the more average figures or the specific examples. I believe it would be appropriate, given the lack of examples for actual ships taking centuries, that we reserve the higher-end times for battleships. Not only does that make sense (as battleships are often stated to be rare and costly) and fill the missing gap, it also makes the times into a parallel, somewhat linear progression of ship production to ship type. Escorts taking single-digit years, cruisers taking double-digits, and battleships taking triple-digits just seems intuitively right. 

Economies of Scale

Each of these sources says something slightly different, so rather than a typical excerpt dump, I’ll be going through these point by point.
Starting with the 2010 compendium, we’re again told that the majority are centuries old at the very least. Smaller worlds might have a single shipyard produce a single cruiser over multiple decades, while a larger forge world might be able to produce 1-2 per year. 
One of the interesting details to me is the fact that forge world’s measure a cruiser’s production time as a decade. More importantly, to produce just 1 cruiser a year (and some produce more) their operations will include at least a dozen being worked on simultaneously. Basically, we’re confirming what makes sense, in that forge worlds have cyclical production schedules, first in, first out:

>Imperial cruisers are gigantic constructions, most of them centuries or even millennia old. Those few that are constructed anew are often the result of years of toil by the population of an entire world – enormous shipyards that might produce a single vessel every few decades. Even the mighty Forgeworlds with their unimaginably vast, serried ranks of orbital docks and laying yards may only complete one of these behemoths every year or so despite easily having a dozen or more of them in varying stages of construction at any one time.

>- BFG 2010 Compendium, pg.83

>While the prodigious output of a Mechanicus forgeworld can see a new cruiser put to space several times a year, this is only through economies of scale, as a single cruiser hull can take more than a decade to construct from the keel-up for even the best and most well-supplied shipyards, and many smaller shipyards take decades and the resources of an entire world to construct a single such vessel.

>- BFG 2010 Compendium, pg.39

We then get a few good looks at shipyards and ship productions by type. In the first quote, we see that a shipyard can produce about 18 destroyers in a “series”. We have reason to believe that a series is probably an order or other measure of output rather than class, since the same quote mentions separately that they’re the same design:

>It was a lucky ship, one upon which the fates smiled. Its hull had been laid down on the forge world Aphret in the one hundred and thirtieth year of the Crusade. Seventeen other destroyers had been completed in the same series, their superstructures filled out to the same template, each one also destined for Legion fleets.

>- Shattered legions

This next quote is a little more difficult. The way it’s structured, one could interpret it as one event after another. First the battlefleet gets scores of ships (40+) and only afterward does it destroy the pirates. But I think this might be a misinterpretation, mainly because a battlefleet getting almost a whole other battlefleet added to it in one sitting seems pretty extreme. That’s the kind of figures we’d expect for a small crusade, perhaps suggesting outside support, but to my understanding that’s not what is happening. The more reasonable interpretation is that the fleet is adding 40+ ships over the course of the 15 years, which comes about to 2-3 years per year (probably rounding up):

>Battlefleet Calixis enjoyed a brief but rapid expansion under the governor's patronage, particularly among its escort squadrons which added scores of vessels to their number.

>Over the next decade and a half, Battlefleet Calixis methodically hunted down and crushed the Meratech clans in space before pounding their worlds into lifeless rubble.

>- Rogue Trader: Battlefleet Koronus page 56

We then have a source describing Belis Corona (a segmentum capital and forge world rival) as having dozens of cruisers. A later excerpt describes him as attacking an entire sector, but seeing as its supposed to be a relatively small black crusade, I think this might be a misnomer:

>Leading a small band of his elite warriors, Abaddon breached the Imperial Navy base in Belis Corona. While his fleet launched a diversionary attack against the shipyards, Abaddon and his Bringers of Despair landed on one of the system's outermost moons.
[…]
Abaddon places a terrible curse upon the worlds of the Belis Corona sector, infusing them with the touch of the Warp. Meanwhile, his fleet attacks the sector's shipyards, destroying dozens of Imperial cruisers being constructed or repaired. 

>- Codex Chaos Black Legion 6e

We also have instances, for those worlds capable of constructing battleships, that they too have multiple. In one case, an asteroid base (probably not even a full forge) can produce 5 battleships in a series:

>Jupiter was Terra’s shipyard, and its sky was forever filled with vessels. Centred around Ganymede and a dozen other smaller moons, spacedocks and fabricatories worked ceaselessly to construct everything from single-crew Raven interceptors up to the gargantuan hulls of mighty Emperor-class command-carrier battleships. 

>- Nemesis

>It would be a simple enough task to set up a comm-link between the Avenger and the berth monitoring systems that policed the space traffic around five massive starship hulls being assembled above the asteroid-base of Kapel-5642A.

>Corax had ordered the strike just in time. One of the new battleships was almost operational, the others nearing completion within weeks. Not the Mechanicum's finest work, Corax assumed, but speedily built in relation to the decades-long construction normally required. The primarch knew firsthand the efficiencies of forced labour and interned workers, and Horus's allies in the Mechanicum had been replicating such methods across dozens of forge worlds and shipyards like Kapel.

>- Ravenlord, Corax anthology

Finally, while shipyards in general might have thousands of stations, dedicated ship manufacturers can indeed measure in dozens to hundreds. Such manufacturers include a Dark Mechanicum forge world, Port Luna even after the Horus Heresy, and a frontier world meant to catapult a kind of pseudo-crusade (probably a high end / they don’t actually mean hundreds of full-sized warp-capable warships):

>Any appraisal of Samech would immediately reveal its origin as a Forge world.

>- Deathwatch: The Achilus Assault page 91

>The shipyards lie outside the main forge. Here, the dark Tech Adepts construct the stealth vessel that will be used to slip past the Iron Collar to the warp gate. The facility consists of a wide atmospheric platform and two orbital docking towers that stretch into space. [...]

>Dozens of these colossal dock structures dot Samech’s blazing exterior. The most powerful and influential forge districts do not just manufacture warp engines and plasma drives; they construct entire warships for the Iron Pit’s armada and their debased allies.

>- Deathwatch: The Emperor Protects page 111-112

>As the ship rose up away from Luna, the orbital docks and shipyards of the moon spread out in all their industrial grandeur. Hundreds of ships, thousands of forges, weapons platforms, grav habs and docking spindles sprawled through the void above the moon's chalky white surface, while swathes of the moon itself were carpeted in macrohives and sprawling junk yards like the one the crusade had so recently fought amidst.

>- Gathering Storm: Rise of the Primarch

>Tuchulca was initially just a frontier staging area for a large-scale exploratory fleet destined for what lay beyond known space, one which involved a number of Rogue Trader houses.
[...]

>The Tuchulcha Orbital Shipyards are a less massive object, though they occupy a much larger volume of space. Once the shipyards worked around the clock to produce hundreds of ships and repair components for the exploratory fleet.

>- Dark Heresy: Enemies Beyond pages 99-100

Post-Guilliman

In the last post, we mentioned a third constraint to Imperium shipbuilding, and it starts to make more sense as we’ve gone throughout this two-parter, or even the greater series. We’ve seen, all the way back in Part 13, that the Imperium’s reserve fleets might be full of ships that can work fine, but the Navy is biased against them. We’ve read that Forge Worlds devote most of their production capacity to explorator fleets, even knowing from Part 12 that plenty of these fleets won’t survive or achieve anything. 
It seems reasonable to suggest, in the face of all of this evidence, that the Imperium is constrained by motivation. The Imperium seems to make as many ships as its navies need to meet the status, and as many as certain limited buyers could want. And in a galaxy where ships might not be destroyed for hundreds or thousands of years, it simply doesn’t feel pressured to ramp up production any more than what is needed to make their weekly patrols. We could also retroactively apply this back to explaining why Forge Worlds mostly contribute escorts to sector battlefleets. Besides being cheap, we might expect escorts to be lost more often, considering not only how weak they are in general, but also the rarity of fleet actions and the commonality of pirates. 
We can see in practice that, when actually threatened and properly motivated by a genuine crisis event, they can produce ships to a much greater degree than before. We can see above how the entire Long Serpent class of battlecruiser was made in only a few years, or how production facilities during the Horus Heresy were churning out entire battleships for a conflict that lasted less than a decade. 
Nowhere is this more apparent than in the resurgence of shipbuilding that is repeatedly mentioned as a staple of the Era Indomitus. Between Guilliman and the Great Rift, the Imperium has never been more motivated to make warships:

>The Sol System was blessed by Mars' presence. Production of armaments and new vessels was proceeding at a breakneck pace. Raw ores, gases and water were brought in from the asteroid belts, the gas giants and the Oort Cloud, for even after nearly forty thousand years as a space-faring species, mankind had barely scratched the immense resources contained by Sol.

>- Dawn of Fire: Avenging Son

>The Light of Reason was a new ship, less than a decade old in a navy in which the average age was measured in hundreds of years. It was a novel pattern, designed to convey the regent's servants as quickly as was possible in this benighted age of warp storms and war. Many of the same type had led the torchbearer fleets in the opening years of the Indomitus Crusade.

>Guilliman's return had prompted something of a renaissance in ship construction, led, of course, by the multitalented Belisarius Cawl.

>- Archmagos

>He had turned the Imperium over to a state of complete and total war. New fleets had been constructed and whole populations recruited into the armed forces. [...]

>Some changes had been made to Imperial salvaging policies within the fleet. Guilliman had ordered the wrecks of the traitor's ships to be utterly destroyed. It had been the habit of the Adeptus Mechanicus and the Navy to recover enemy ships. Chaos vessels were of Imperial make, and were often of older, superior patterns. The primarch stamped hard on the practice. Build new ships, he had said. Leave the past where it is. 

>- Dark Imperium

>With the Imperium reeling from the disastrous effects of the Great Rift, Mars commands all forge worlds to ramp up production to unprecedented levels. They churn through raw materials and servitors as never before, and vast armadas are launched to strip entire star systems of resources.

>- Codex: Adeptus Mechanicus (8th Edition)

Calculations

So, before getting into the numbers, the assumptions of this calculation are as follows:

1. We’ll be ignoring support, merchant, and system fleets. I’ll be focusing solely on warships and assuming that they’re accounted for by outside figures
2. We’ll be focusing on escorts (destroyers and frigates), mainline cruisers (not light, not grand, maybe battlecruiser) and battleships specifically
3. We’ll be using forge worlds as a neat unit of measurement, but keep in mind, there are many sources of production, many of which will be greater than or equal to a forge. It wouldn’t be unreasonable to double the figure, even though I myself will not
4. We will assume that a minimum of 100 forge worlds are capable of producing battleships at all
5. We brought up in the last post that we’re working with the idea that a forge world has 2,000 docking facilities total. Of these, maybe 10% are devoted to interstellar ships, and let’s say only 25% of that are consistent production shipyards. That leaves 50 shipyards, let’s say 25 cruiser and 25 escort. For those 100 worlds with battleship production, let’s just add an extra 5 docks just for those
6. I believe these posts have established the reasonable expectation that escorts take a few years, the most common cruisers take around one decade, and battleships might take multiple centuries. We’ll assume that escorts take 2 years, cruisers take 10, and battleships 200. 
7. Let’s assume that shipyards are all producing cyclically and with conglomerate scheduling. So rather than 100 battleships dropping all at once after 6,000 months, they follow a first in, first out method across the entire imperium and drop in a consistent sequence

For every forge world, with 25 slots for cruisers and 25 for escorts, their production timeline will look something like this (with every number being a countdown of years until completion): 

Cruiser Sequence 1	Cruiser Sequence 2	Escorts	Escorts	Escorts
1	1	1	1	1
2	2	2	2	2
3	3	1	1	1
4	4	2	2	2
5	5	1	1	1
6	6	2	2	x
7	7	1	1	x
8	8	2	2	x
9	9	1	1	x
10	10	2	2	x

So every forge world should regularly produce something like 2 cruisers and 12-13 escorts per year. Across the Imperium, that would result in 2,000 cruisers and at least 12,000 escort ships annually. 

For battleships, it’s a little easier. There are 100 worlds able to produce battleships, each with 5 docks for 500 docks producing in sequence on a 200 year product. We would expect 2-3 battleships to be produced per year in the entire Imperium. 

On paper, this seems to be fairly reasonable, but even in this calculation there are big issues. 
The first is that these rates don’t match up with the ratio of battlefleets as established in Part 9. Battleships there make up 5% of the total count, here they make up about 0.017% of the annual production. Escorts, meanwhile, are supposed to represent ½ of the battlefleets, here they make up a little over 6/7th of the production, and outnumber cruisers 6 to 1. 

The second is that, assuming my infamously bad math skills have not failed me, these figures add up to an average of about 14,502.5 ships made per year. With only 500,000 ships in its battlefleets, that would mean that the Imperium makes enough ships to replace its entire military every 34 years. This is almost impossible to reconcile with an Imperium where the average lifespan of a ship is centuries to millenia. I mean, the last time the Imperium even considered    changing its naval doctrine was something like M36, these numbers suggest it does so every generation. There are, however, 4 methods to try and alleviate this issue:

1. The Imperium suffers so much damage, year in, year out, that it’s actual loss rate can be much higher. Between 7 rival factions, having to go through space hell for FTL, and it’s own propensity for self-destruction, the Imperium certainly seems like it’s getting torn apart. The issue is that we’re trying to make the setting fit our numbers, and in doing so, we’re ignoring that most ships just don’t die. Most sectors are relatively peaceful, and even escorts are need quadruple-digit lifespans to be considered average age. 
2. Since we’re measuring by forge world and forge worlds typically produce towards their own exploratory fleets, the majority of these numbers are essentially dead on arrival, with the explorator fleets acting as the statistical equivalent of a shell company and hiding the real loss rates behind a figure we don’t see. Two issues:
   1. Explorators also typically measure their timescales in centuries before the next one is shipped and launched. One could point out that these can be exclusive factors; a forge world might only launch a followup to a specific explorator fleet after 300 years, but is otherwise launching them all the time in random directions. 
   2. It seems genuinely silly to argue that ALL Forge Worlds are wasting a setting-changing amount of ships for no reason at all, but hey, it is the Imperium we’re talking about
3. We might’ve genuinely overshot production timescales and escort lifespans. If escorts take 5 years to produce, we’d expect only 5 per year. After that, if escorts die at rates 2-3x higher than cruisers (which I don’t think is a hard sell) we’d get closer to the ratios in Part 9. However, that would still mean that the average ship lifespan (even accounting for escorts in particular) is decades or less. Unless every example of an old ship is an outlier, which is silly when we have quotes saying otherwise.
   1. For what it’s worth, we do have examples of cruisers taking multiple decades to make, so treating the entire category like Lunars is an uncharacteristic high-end on my part
4. The only solution that I think works is to consider that, even after dropping 2000 dockyards to just 50, assuming only 100 worlds can make battleships at all, assuming ever dock can only make 1 ship at a time, and disregarding every other source of production besides forge worlds, the Imperium doesn’t meet these figures solely and only because it is actively trying not to. Seriously, if it wasn’t for battle barges, I don’t think we’d even have proof of battleships being made at all past M35 because they just don't die. And there’s one very good, very stupid reason for doing this, and that’s the Horus Heresy shattering the collective willpower of the Imperium, and making them all obey asinine laws around separation of powers from sheer paranoia of a Horus 2.0. We already know that they do this with space marine chapters:

‘How many times have we seen the Lex bind our hands, when the Enemy has no law at all? We have held back from creating thousands more Chapters because we are held in thrall by the Lord Commander’s ancient doctrine. 

• Watchers of the Throne: The Emperor’s Legion

All of this is to say, the above calculation is the Imperium’s minimum production for when it actually wants to put belt to ass. It would certainly hep explain how the Imperium is still holding out after Abaddon's rage-quit at Cadia; even just half of that kind of production over 12 years would see the Imperium surge with a hundred-thousand new ships. And these numbers could always go much, much higher. I did, after all, do my best to get the bare minimum.

But in all other cases, it makes only what is needed, and then stops.

My first guess would be that they’d specialize into burrowing underground to better attack the Necron’s tomb complexes, which need to be destroyed to stop the Necrons from constantly reanimating, either being permanently destroyed or forced to teleport to another tomb world/ship to be repaired. 

(Destroying anything capable of creating portals for other tomb worlds to send reinforcements also seems like a #1 priority.)

I'm currently reading through the Eisenhorn omnibus, almost done with the second full novel, and I've been thinking about the short story the whole omnibus begins with. Eisenhorn is on a planet having a look into some murders the local authority believe to be cult related (SPOILER COMING UP NEXT), but in fact its a couple of da boyz who are coming through some kind of warp portal, hunting a couple hoomanz and then heading home. Eisenhorn dispatches the orkz, closes the portal and everyone is happy. My questions is, is this world now doomed? Is a couple of orkz visiting every week or two for a few hours enough for the fungus to contaminate? And if yes, how long does it have?