Castrum: XTRO: Republic, Volume 1
(http://www.sarna.net/wiki/images/c/c9/Castrum.JPG)
Well let me be the first to say my views on 100,000 ton assault DropShips are well known. Basically I don’t like them and consider them boring. The weapons that they use are designed for small craft resulting in huge bays with weapons by the dozen. Tactics come down to firing the 10 gauss rifle bay or the 15 PPC bay. But I will try not to let that colour things.
The Castrum came into existence because the Republic of the Sphere managed to lose the WarShips the Nova Cats so generously gifted them. As a result sometime around 3100 the Republic started building Dragaus, Interdictors, and Tiamats with Naval C3. Castrums rounded out the force as the heavy assault DropShip. The entire force would then go on to be used as enforcers for the Republic.
The Castrum serves several roles for the Republic navy. Firstly the Republic lacks a good indigenous fighter carrier. The 18 Small Craft bays go some way to covering that. Secondly the Republic’s assault DropShips are all short range specialists. With its big batteries of SCCs the Castrum is meant to be a ranged platform.
All in all the Castrum is a highly optimised design according to current standards. Note the careful separation of heavy auto canon and AMS to keep the fire control low. Separation of weapon bays into easily bracketable groups. Plenty of AMS as well. Small Craft bays offering more flexibility (at a cost). Downright stupid amounts of armour.
The ships we are comparing the Castrum to were designed under a very different ruleset and have to devote 50% of their mass to a jump core. For comparison the most recent comparable WarShip is the Leviathan II which predates Strategic Operations. Everything else has been designed with period play in mind. For comparison purposes I threw together an identically equipped WarShip. It turned out a bit tougher due to SI requirements, and had a bit more crew, but I even squeezed in a grav deck and docking collar under 190,000 tons. Simply put, when only looking at combat systems, WarShips are more tonnage efficient, though jump cores clearly affect things.
The Castrum’s broadside is impressive. But at 100,000 tons it would want to be. A fast ship with shorter ranged SCCs would be a better ship killer, but the Republic already has the Tiamat. On paper the Castrum has the firepower of a mid-range destroyer and the armour of a frigate or weaker cruiser.
The nature of its role has forced some compromises upon the Castrum. Firstly its guns make it huge. The Castrum is effectively a flying Bane. Light Sub Capital Cannons are more efficient than Sub Capital Lasers, but they do woeful damage for their mass compared to their shorter ranged brethren. The Castrum can only put 24 points of capital damage out to long range through these guns. Fortunately they are highly bracketable.
For comparison the Castrum’s 16 AR10s can put 32 points of capital damage out on either beam. However as missiles these are vulnerable to counter measures, while using Barracudas is the only practical option outside 25 hexes. Naval C3 does change the equation somewhat by offering a chance for spotters to reduce the numbers.
The AA throw weight of a Castrum is amongst the top twenty in the game while it has the armour to last out many attacks. As an AA platform the Castrum has to be respected. Thanks to its AR10s it can put out very heavy fire to long ranges. The SCCs are effective out to around 25 hexes. The ideal setup would see a pinning force hold the incoming ASF at around 20 hexes while the Castrum pours in support fire. An end run on the Castrum for a quick kill is unlikely to be effective given the amount of armour it carries.
Defeating a Castrum depends on faction. Remember, this is a big ship and will take a lot of killing. Talking DropShips it is easy to forget just how physically large the Republic’s ships of choice are. The Interdictor is the size of an Overlord after all. So generally the Republican force is going to find itself swarmed.
Ignoring the WarShip option, (and given the Clans generally operate cruiser fleets you would still need a lot of Castrums) the FWL, Clans and Capellans would be best off using ASF to take down a Castrum. The Republic lacks good carriers relying on its big capital armed DropShips for quick kills. Using the example of the Republic’s peace keepers and the Rasalhague Dominion, I would have amassed a pair of Aesir Stars, unleashed 60 ASF, and used my DropShips superior thrust to never become engaged. Actually, 60 ASF probably would not be enough and the Castrum would survive, but it would be stripped of its escorting Tiamats, Interdictors, and Dragaus. This does not include the nuclear option and with its small cargo bay and AMS magazines the Castrum would be vulnerable after a single engagement.
For the Dracs and Federated Suns I need only point to Taihous, Arondights, and Vengeances. Big fast, capital armed DropShips supported by massive air support. Pin the Republic’s ASF and swarm the DropShips. Tiamats and Castrums are not easy kills but they are hugely inefficient. The SCC Arondight and Taihou are much more tonnage and cost efficient and will be going in with 3:1 odds at least. (Working on BV with all its problems, a Castrum weighs 100,000 tons with approx. 95000 BV, a Tiamat weighs 36,000 tons with 57000 BV, while an Arondight and Taihou weigh 12,000 tons with 37000 and 36000 BV respectively. On a BV balanced game the DC and FS can afford to lose the resources game, while on a tonnage based game they can take three ships for every Tiamat. Your mileage with BV will vary.) A tidal wave of death with no drawn out stuffing around with hundreds of small bites like with an all ASF force. Those Light SCC will soon find themselves outgunned in a close range engagement.
For the Lyrans and Periphery? They lack the big killer DropShips of the Suns and Dracs so will have to rely on ASF. Unfortunately they also lack carriers so massing the required numbers of ASF will be problematic. Avoiding contact until sufficient force can be massed is probably the best option. It is worth noting the Lyrans do have access to some quality smaller DropShips like the Avenger and Isegrim. Small ships are remarkably tonnage efficient so a swarm would be profitable if you can manage your JumpShips right. Remember one Castrum weighs as much as 71 Avengers…
As a bonus I did some combat testing.
First I played a game pitting a Castrum against a Fredasa. I had to cancel it but the Fredasa was doing surprisingly well. That made me try again.
This time I put the Castrum up against a Naga. The Naga won.
Okay. I am the first to admit I didn't pay to either ship's strengths as well as I might have. Frankly it became a brawl. The reasons it became a brawl were the Naga's evasion and superior ECM made ranged combat a very hit and miss affair.
So under 25 hexes both sides started hitting and something unexpected became evident. The Naga could regularly get important crits on the Castrum but the Castrum couldn't return the favour.
The 80% bracketed NAC10s on the Naga were landing 16 point hits, well above a Castrum's armour thresholds. The Castrum's 40% SCC bays were doing 5 point hits which should have been equally damaging. I think the difference came down to the critical tables. For example where 55% of a WarShip's side critical table is, well, noncritical only 28% of a DropShip's side criticals are noncritical. So the Castrum was twice as likely to suffer a battle effecting critical hit. Heck in the end it had:
3 Avionics
2 Sensors
L Thrusters totally disabled
1 R Thruster
So blind and unable to move.
Put simply between ECM and crits the Naga was able to degrade the Castrum's ability to fight at range so much a brawl became a necessity and our little tin clad was able to outlast the DropShip.
Now it will be pointed out to me I am comparing a 500,000 ton ship to a 100,000 ton ship. Well the Naga does devote 250,000 tons to a KF drive and 150,000 tons to cargo.
Also I am not going to say that a Naga is a superior tactical platform to a Castrum. The Castrum has better AA, superior nuke proofing, more thrust, much more armour, basically it is better. But by the same token the Castrum is much more optimised than 90% of the WarShips in the game simply because the rules were mature when it was created.
On a Cbill to CBill comparison the Castrum should be able to put light WarShips out of business. OTOH you should be able to design a 500,000 ton WarShip able to handle three Castrums. That is food for thought.