Manu ad Bellum

The Manu ad Bellum (Hand of War) is the first of a new class of warship. It's based on the pattern for an STC-compliant Astartes battle-barge, but modified to use the hybrid Human-Tau technology of Credence. It's a truly herculean undertaking, but the design and the actual construction, but the Central Intelligence has prepared for this moment for millennia.

The basic spaceframe and key subsystems, such as power generation, propulsion, and shields, are STC, but the entire computer system and weapon arrays are Tau-derivates. Attempts to more fully integrate Tau gravitics technology have not been successful. The Bellum can generate a gravity wedge in front of the ship, but only by dropping void shields, so it's a questionable tactic at best. To gain the full benefits of Tau grav tech would require a full redesign of the class, something that could take decades - if it can be done at all.

The Bellums's massive forward castle contains the ship's main long-range weapons. Two clusters of gravitic launchers capable of hurling a mass of swarm missiles flank the spinal grav cannon. The grav cannon is essentially a modified Nova cannon that fire grav (implosion) warheads. It's a potent weapon, but its size and external mount mean it's vulnerable to enemy fire. 

The forward castle also contains the cavernous launch bays. There is enough space to launch 3 Astartes companies, with additional heavy-lift capacity for orbit-to-planet operations. Secondary launch bays are housed in the ship's main body. These bays aren't big enough for large scale assaults and are reserved for priority transports and the like.

The ship's dorsal ridge and flanks are crowned by massive ion cannon batteries. These are essentially Tau versions of Imperial lances. Each turret is smaller and each weapon lighter, but when slaved together they are at least as effective as their Empire counterparts, and far more reliable. An alternate design for the Bellum did away with the spinal cannon, in favor of a second set of ventrally mounted ion cannons.

The Bellum's massive broadsides are made up of two distinct weapon types: two-thirds are medium-range railguns that cause damage based on kinetic energy alone and the rest are short-range heavy railguns that can fire a variety of warheads, such as magma and implosion bombs. The former have a lot in common with Imperial broadside batteries, but their accuracy at range is somewhat better. The latter combines railgun tech with the design principles of bombardment cannons. The effect on the target is largely the same, but again the accuracy at range is somewhat better due to the higher velocity of the ordnance fired. The battery bays are modular, and several designs were evaluated before settling on the current loadout.

Point defense is excellent, based around Tau burst cannon and integrated tracking arrays. Battle barges are already tough nuts to crack with missiles and small craft, but the Bellum class ups the odds even more. If more ships can be built using this new hybrid tech, Bellum has the ability to integrate point defense to create a nearly impenetrable grid.

The Bellum class can launch and support 3 companies of Astartes in Thunderhawks. It does not, however, have provisions for standard boarding torpedoes. Trials were conducted, but the rail launch kills even Astartes, so it's not a viable option. Likewise, drop pods were removed to free up space for additional ventral ion batteries. There are provisions for a full teleportarium, but Credence lacks the ability to produce this technology, so currently, the Bellum has no teleport capacity. A total of 5 Astartes companies and their wargear and support can be housed on board, but a more typical complement is 3 companies.

Like all battle-barges, the Bellum is heavily armored and superbly shielded, and equipped with numerous redundancies. That said, the Bellum lacks a lot of the manual overrides and backups that are some common on Imperium warships, and is even more reliant on it's tech-priests (technomancers) to operate at peak efficiency. Unlike other Astartes craft, battle-barges are not fast and agile. It's a blunt instrument, meant to hammer the enemy into submission on its own, or acting as the anvil is an Astartes battles group.

Once the kinks have been ironed out, a properly handled Bellum-class battle-barge with a full complement of Astartes has the potential to be among the most powerful battleships in the galaxy.