Achernar-class light cruiser

The Achernar-class was the CMA's last class of cruisers.

Specifications
An intermediary ship in terms of tonnage, the Achernar-class blurred the line between cruiser and destroyer, resulting in many calling them pocket cruisers, cruiser-destroyers, and super-destroyers in lieu of their actual classification. Their construction was more destroyer-like in practice, adopting most of the standards that the CMA placed on their earlier heavy destroyers of the Hillsborough- and Scylla-classes, but their larger size and improved capabilities were considered the minimum needed to step in as capital ships when necessary.

The protection scheme of the Achernar-class was on paper ineffective but proved remarkably resilient in practice. Their titanium-A1 battleplate measured only 1.5 metres at its thickest portions, and there was also no reactor shrouding as was standard even for the period, and instead opted for very large frigate-style protective wings that ran up and down the cruiser's stern. However, many opponents failed to note that not only did this primary plating offered far greater coverage than was typical of even Human-Covenant War vessels, they also never mentioned that the Achernar-class also boasted electromagnetic reactive armor between its external hull and internal bulkheads to vaporise kinetic penetrators. That such a system also momentarily released a powerful magnetic field proved fortuitious when the ships saw combat against the Covenant.

In a departure from traditional CMA shipbuilding theory, which called for a ship to be overgunned as much as possible in order to defeat or inflict as much damage as possible, the Achernar-class only had the armament and protection needed to give it a definitive advantage over destroyers. However, the two fusion reactors were still cruiser-grade models, with forty percent of their output not being used by the ship's systems and resulting in a remarkably quick cruiser. More importantly, a reluctance to directly scale them down to destroyer sizes meant that its machinery, crew, and cargo spaces were rather large for a ship of this size. This resulted in a cruiser class that in normal operations could comfortably accept more spare parts, food, and fuel to extend its operational range, or could carry a larger embarked ground force for specific missions. An often overlooked fact was that it also made them extremely forgiving when it came to modifications and upgrades, and this showed through with the CMA's constant tinkering with new variants, and the UNSC Navy also used them as technological test vessels.

Armament
The primary weapon of the Achernar-class cruisers was a 54B2F7 light coil battery, a twin-linked system with a cruiser-scale 1,651mm/181 cal MAC and a 1,270mm/420 cal destroyer-scale device. This was not a full high-velocity setup: size and space considerations meant that the Achernar could not fit a full cruiser-scale MAC anyway, and the CMA felt that lengthening the smaller gun instead better extended the cruiser's effective range and also saved weight. Specialist rounds were carried for both MACs, with larger magazines for 1,270mm slugs as they were interchangeable between both weapons. Although effective during the Insurrection, the UNSC eventually discovered that this configuration performed worse against energy shielding, as the Achernar-class couldn't manage multiple simultaneous hits at long range and even at closer distances, the firerate was limited by the speed the 1,651mm gun took to charge up. As a result, these cruisers were the only ships that were completed with such a mixed spinal setup, with all later ships like the reverting back to a all-high-velocity MAC configuration instead.

Uniquely, while most of their ships either focused heavily on either naval coilguns or missiles, and were generally overgunned, these ships attempted to strike a delicate balance between the two. Twenty-four silos of M48 Ares were carried, each with a single reload. Although formidable weapons, the Achernar-class was outgunned in this regard by some CMA destroyers and were more carried for deterrence or massed bombardment operations. Instead, its stock-and-trade missile system was the M96 Howler, a counterpart to the M58 Archer that traded explosive power and the ability to target fighters for reduced size and maneouvrability. Their purpose was to act as a less-lethal part of the cruiser's armament, as well as suppress and destroy enemy point defence guns and jammers. To this end, the Achernar-class carried twenty-six pods, each with six silos each. Wrapping this up was a payload bay capable of carrying two Hyperion-class fusion missiles, massive, long-ranged nuclear missiles designed to breach well-protected orbital installations. Finally, sixteen single (later upgraded to twin) LNT-450 naval coilguns were equipped on these cruisers. A scaled-up version of the very successful LNT-350 model used on the, the LNT-450 was a medium-range anti-frigate weapon. Their placement was well thought-out; five were mounted per side but were staggered to allow the cruiser to bring the turrets on both sides to bare above and below, while three were each mounted on the dorsal and keel sides to allow them to fire on both broadsides.

The air defence armament of the Achernar-class was originally limited to six quad M870 Rampart 50mm/50 cal point defense guns, with an assortment of counter-munition missiles backing them up. However, this was an area that was routinely enhanced across the class, with dual-purpose naval coilguns, anti-fighter missiles, and additional countermeasure launchers often being added.

Procyon-subclass
Commissioned with hull codes CL-010 - CL-015, the Procyon-class were the most simply modified of the class. The major alterations were made to their computer systems, giving them powerful sensor systems and the ability to deploy early slipspace probes. This made them excellent hunter-killers, particularly against stealth vessels.

Arethusa-subclass
The Arethusa-class were an attempt to provide enhanced performance at combating light frigates, cutters, and fighters, as already there were a number of incidents where the basic Achernar-class cruisers lacked the speed and the hail of fire needed to effectively deal with swarms of lighter craft. To achieve this, the Arethusa-class replaced all but eight of its Ares silos with pods of M96 Howlers, supplemented their LNT-450 coilguns with 18 twin M66 Sentry 279mm/36 cal naval autocannons, and added a very large Streak-I antifighter missile payload. They also received an engine upgrade to up their acceleration and manoeuvrability.

Although the UNSC lamented their split secondary armaments, and the Arethusas never quite reached their ambitious speeds in service, they were nonetheless considered successful ships. They were frequently deployed as flotilla leaders for destroyer groups, as they could provide the same defensive advantages as a frigate yet had the armor to survive in prolonged engagements. It was discovered during the Covenant War that their coilgun-heavy armament made them terrific anti-shield vessels. However, they generally lacked the firepower to meaningfully tangle with larger enemy ships, and the Arethusas also had early issues with their fusion drives that usually required replacement.

Commissioned Arethusa-class vessels were given the hull codes CL-020 - CL-030.

Meridiana-subclass
The Meridiana-class was an upgunned version of the Achernar-class that attempted to finally reach cruiser armaments. All Howlers were replaced with additional M48 Ares missile silos, each with two reloads, and their fusion missiles were increased to ten devices. Four LNT-580 700mm/40 cal railguns, the only such weapon developed for naval applications, with two single turrets on each side. The CMA also looked into an attempt to fit a second cruiser MAC onto the ship, however there was found to be insufficient capacity left in the reactor and it would've taken up space reserved for the Ares and Spitfire magazines.

These ships were not considered successful designs. Not only did their new heavy weapons max out all available space and exceeded reactor capacity, but the new weapons heavily loaded down the cruisers. More importantly, although the LNT-580 railguns proved exceptionally powerful for their size, the very short lifespan of the electromagnetic rails coupled with the turret's tendency to distribute itself across the cruiser's side made them unsuitable for continued use. In light of this, the three ships built, commissioned CL-031 - CL-033, became the only Achernar-class vessels to be mothballed after only a year of service.

Atlantis-subclass
The Atlantis-class were the final and most drastic evolution of the Achernar-class hull. Their development addressed the CMA's critical manpower and funding issues, which by now placed most of their cruiser fleet, so necessary for command, electronic support, and multipurpose response, into reserve. This desperation was obvious with the hull of the new ships, which were bulged out to accommodate more space for a flag deck fit for an admiral, and were absolutely coated with communications dishes and RADAR panels. Their protection was improved, as well as the numbers of countermeasure dispensers. They even had sophisticated AI-directed electronic warfare capabilities, capable of performing battlefield jamming, launching cyberattacks to impair enemy systems, and decrypting enemy communiques on the fly. All this did come with a cost, and not just with the 12 Ares silos they lost. The CMA never invested in upgrading the reactors nor engines of the Atlantis-class, and it was later discovered that they suffered from vastly increased wear as they routinely overloaded their powerplants in an effort to both maintain speed and run their systems.

The Atlantis-class were given the hull codes CL-033 - CL-050 in CMA service.

History
The Achernar-class heavy destroyers owed its very existence to the CMA's growing dissatisfaction with their capital ship fleet in light of counter-insurgency operations. The Colonial Navy had amassed a fleet of the finest and most powerful cruisers and battleships the Human Sphere had yet seen during the Cold War, but outside of a handful of successful operations against entrenched Secessionist Union armadas proved exceptionally useless. There weren't enough of them to patrol the colonies, they were too slow to chase down fast attack craft insurgents began to prefer, and far too costly to operate, especially as the UEG's cuts to the CMA's budget and resources grew in light of the VERITAS Scandal. In an ironic twist of fate, CMA was reliant on the screening forces they had neglected for so many years.

The clear answer to this was a heavy destroyer class, one that continued the traits first expressed in the Hillsborough-class at the turn of the century, and the Scylla-class that succeeded them. However, simply maintaining their rough tonnage was not going to work; the widespread adoption of MAC-armed frigates like SinoViet's standard frigates meant that older destroyers could be hurt, even destroyed by this new breed of warship. Indeed, it was because of this that these ships, once intended as flotilla leaders, were being increasingly used as regular destroyers. Some CMA admirals attempted to push for the adoption of a new light cruiser, others like Commodore-Admiral Rosario Ortega still felt larger numbers of destroyers could carry any battle. Knowing that the CMA lacked the funds to man and operate full light cruisers, but unwilling to lose the potential firepower such a ship had, Commander-in-Chief, Colonial Navy Torsten Hermansson ordered the development of a true intermediate ship design. A ship that on paper carried the weapons of a cruiser, but built as small and as cheaply as possible.

The contract for development was awarded to Great White Spaceworks, who during the design of these ships would be bought up and incorporated into the Reyes-McLees Corporation. The ship that became the Achernar-class was designed by a team led by Kulai Mustafin, with close consultation with the CMA. Although Ortega paid close attention to the project, rival officers who wanted to use the project to further increase their prestige attempted to intervene. For instance, officers on the Naval Procurement Board who had financial stakes in certain manufacturers attempted to replace critical systems with obsolete alternatives, while others pushed for overgunning the ships as much as possible. Indeed, the first designs were far more heavily armed and weakly protected than the final ship would be. In the end, Ortega herself pushed to reduce the weaponry, as doing so would result in a ship that was cheaper, easier to man, and more importantly had space and generous reactor capacity. In short, it was built as a platform for the future, not for the short-term.

Ships of the line

 * CMA Achernar (CL-991) - Lead ship of the class.
 * , ex-CMA Endeavour (CL-852) - One of two ships to survive both the Harvest Campaign and the Siege of Sol, and last remaining Achernar-class light cruiser.