Onyx

***Onyx*** (BB-1702) was an *Iapetus*-class fast battleship in service with the Terran Alliance's star fleet. The next logical step in the ever-increasing upward trends of firepower and speed, the *Iapetus* type were incredibly resilient warships that could easily match several lesser ships by themselves: however, they were overall too costly to ever replace the ships they outclassed.

 Design

### Dimensions and Role

At 1.65 kilometres in length, the *Iapetus*-class star battleships were the largest of the new-generation battleships produced for the Terran Alliance Navy: they outsized their *Mars*-class predecessors by a significant degree, and the concurrent *Neptune* class by a smaller margin. This enhanced size made them perfect for situations where a dreadnought would be suitable, but for whatever reason was unavailable: the *Iapetus* class were often also used as command ships, thanks to their enhanced tactical displays based on the work done to the Alliance's flagship *Furious*.

These ships were conceptualized with one specific role in mind: aggressive fleet combat. This was especially due to the galactic invasion conducted by the Rin Empire in the early 2500s; the Rin had brought multi-kilometre-long battleships to every fight, requiring several dreadnoughts to counter. Firepower upgrades among Council forces during the conflict had made a *Terra* dreadnought equal in all respects to a Rin battleship—despite the size difference—but the Alliance did not have the stardocks to produce dreadnoughts in the numbers necessary. Therefore, the *Iapetus* was designed, with the goal of fighting a Rin battleship and its support units to a standstill: fighters were omitted, as it was never to operate without a fleet, and heavy point defenses were sacrificed for more anti-ship weapons.

### Hull

The *Iapetus* class was somewhat different than preceding warships: they took some minor cues from a variety of alien sources, including Consortium, Lucaelian, and even Vespiran starship designs. The overall hull shape was that of a long box, similar to other Alliance ships, but in contrast to most Terran designs the *Iapetus* only had one hull and sported aggressive geometry. This centralized all functions of the ship and improved resistance to damage: however, Alliance officers did not like the new configuration, preferring the *Neptune* class with its more traditional double hull. A relatively unique feature of the *Iapetus* was the placement of the main observation bridge on the *underside* of the hull, as opposed to the dorsal section. The combat bridge was, as in all Alliance warships, located in the heart of the ship and surrounded by thick armour protection and shielding.

Most ships were painted in the standard gunmetal grey of Alliance starships, but at least three ships (among them the experimental ships *Minerva* and *Euryale*) received ablative coatings which also changed their paint scheme to black.

### Power

The *Iapetus* class, thanks to its advanced design and efficient energy systems, produced the most power of any Terran battleship: 1E50 watts at peak output. Normal output was lower than this for safety purposes, but the high power output coupled with minimal energy loss in the system led to more powerful subsystems—such as shields and weapons—than any equivalent Terran-designed warship in the Alliance arsenal.

### Propulsion

For engines, the *Iapetus* class was equipped with three Class 1 ion-impulse nacelles located in the rear section of the craft: two smaller—but still quite large—Class 3 drives were on the sides of this, forming an asterisk arrangement to increase survivability. Though they had fewer engines than the preceding *Mars* or the contemporary *Luna*, they could make a respectable 300 km/sec in acceleration at full power: however, this speed was unsuitable for combat, and much lower speeds were almost always employed.

Manoeuvres were handled by a number of drive vents and directional ion thrusters located on various surfaces in the ship: they could be shuttered with armoured panels when not in use.

### Weapons

The defining factor in a battleship is the firepower it can bring to bear on a target: the *Iapetus* type was no exception in this regard. Much like its *Luna*-class battlecruiser counterpart, the *Iapetus*'s primary weapon was a massive spinal-mounted burnthrough laser: a superweapon capable of annihilating almost any target in one hit, it was even more powerful than the *Luna*'s own superlaser and second only to the more powerful variants carried by the experimental battleships *Minerva* and *Euryale*, and the Alliance's newest *Atlas*-class Star Dreadnoughts. Thanks to the power generation capabilities of the battleship, an *Iapetus* could continue to go 'weapons free' with all of its guns while the superlaser was in operation, something the *Luna* was incapable of.

The heavy gun armament of an *Iapetus* consisted of thirty-six (36) super-heavy laser cannons in twelve (12) triple mountings: these were more powerful weapons than either the *Luna* or the *Neptune* could bring to bear, thanks to the *Iapetus*'s power plant. Just one shot from a single barrel expended more energy than the total broadside of a *Mercury*-class battlecruiser, or all three guns in the turret of a *Neptune*-class battleship; only the main batteries of Alliance star dreadnoughts were more powerful. Their firing arcs were such that all twelve turrets were capable of firing within a wide cone forward, with at least ten able to fire on the broadside. Each turret was given its own capacitor and three backup battery cells (one for each gun) in case of action damage to the power conduits from the ship's reactors: the latter could also be decoupled in case of overload danger or if the guns were out of action, so as to prevent power drainage.

The 'medium' anti-ship armament was considerably 'beefed up' compared to its contemporaries in the Alliance: while most Alliance battleships were armed with a split secondary battery—15-cm laser cannons for anti-ship work, and 10.5-cm batteries for dual-purpose work against light craft and starfighters—the *Iapetus* stripped away the 'handy' 15-cm in favour of the much more powerful 20-cm laser cannon: these were the exact same guns used aboard a modern *Deimos*-class heavy cruiser, in twenty-eight (28) triple mounts scattered across the surface of the vessel to provide complete coverage.

To the impressive main guns were added a formidable 105-mm 'medium' battery of long-range laser cannons, emplaced in twin rapid-firing turrets and studded through the hull. These were the standard dual-purpose guns of Alliance warships, being useful against both smaller vessels such as destroyers and as point defense against starfighters and ordnance like torpedoes. They had an extraordinarily high rate of fire and were completely subdivided from the hull once 'closed up' for action, meaning that even if one was destroyed the ship would not suffer depressurization. The redundancy was a feature of all Terran designs, and extended to the main and secondary armament as well.

Medium-range point defense was handled by a reliable battery of fifty (50) twin 65-mm laser batteries: upscaled 20-mm snappers, they could confidently engage targets outside the 'kill zone' of the 20-mm lasers, but within the optimum range of the 105-mm cannons: these weapons proved highly successful from their introduction, first seeing service on the *Pandora*-class maintenance carriers.

For close-in defenses, the *Iapetus* battleships were equipped with over two hundred 20-mm laser cannons in twin 'snapper ball' mounts - so-named because they could snap a crewman out of their seat from the G-forces if their harness was not secured. The guns could be controlled remotely in their default setting or operated on-site by a single gunner. With a sustained 'burst' mode of 10,000 shots every minute, they were capable of burning clean through an entire swarm of torpedoes launched at close range and were one of the most well-regarded point defense systems in the entire galaxy.

Additional armament was backed by large numbers of 50-mm laser blasters, swarm torpedoes, and missiles; the former were for close-range broadside combat, where their relatively slow firing rate for calibre (only about 3,000 shots every minute) was made up for with hitting power: they could burn cleanly through a metre of starship hull armour if given a continuous track on the same spot for less than seven seconds. However, these weapons were not particularly effective against shields.

### Defensive Systems

As a battleship—and *especially* as a battleship designed and constructed by the Terran Alliance—the *Iapetus* class was heavily shielded and armoured: its outer layer of defense was the Alliance-unique ***Prydwen*** sectored shield system, which could oscillate its frequencies, strengthen a specific area of the shields, or keep sections of the shields intact while idling others to conserve power.

To this formidable shielding system was added significant quantities of armour: 750-mm plates separated the outer skin of the hull from the pressure seal, which itself was backed by a second layer of 375-mm armour plates to stop leakages and provide a second barrier that a projectile or energy weapon would have to bull or burn through. The hull itself was also finely subdivided into thousands of airtight compartments, with numerous redundant sections and their own independent life support systems: each section housed one of the ship's reactors, allowing them to sustain not only themselves but also adjoining sections that might suffer damage as well as continuing to operate subsystems. The armoured bulkheads which separated each compartment were double-layered: not only were they thicknesses ranging from 375-mm to 750-mm thick, they were also charged plates (around the reactors) and/or could be reinforced by the sectored shielding system.

The most armour, however, was reserved for the critical subsystems: each reactor compartment, the bridge, the main power conduits, and the primary and secondary gun turrets were protected with anywhere from one to three metres of armour plating. The barbettes for each turret which extended into the ship before narrowing down to a simple tube to protect the conduits were also a full metre thick, and backed with a second layer 500-mm thick to provide an extra barrier for an enemy round or beam to get through.