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Advanced Frigate
Ajax-Class Heavy Frigate
Production information

Reyes-McLees Naval Shipyards


Heavy Patrol Frigate

Technical specifications

460 meters

Engine unit(s)

SSXD-21 Fusion Reactor

Slipspace Drive

Shaw-Fujikawa Translight Engine (2545/2554 Updated Models)

Slipspace velocity
  • 2.625 lightyears per day
  • 38 lightyears per hour (2553 upgrade)
  • CEMPT-7
  • MJLNR-7X Solid Light Barrier Generator
  • Ceramic-Titanium Composite Hull Plating
  • Ancile Metamaterial



4 x D77H-TCI Pelican Dropships



Year introduced


  • Battlegroup escort
  • Orbital fire support
  • Human-Covenant War
  • War of Vengeance



Traditionally, the UNSC Navy has shunned the use of Heavy Frigates in favour of full-fledged Destroyers. Though similar in armament and defense, there are major differences in terms of functionality and combat role. Frigates are designed for long-term long-range deployment, operating in tandem with small groups of corvettes or other frigates. Destroyers, on the other hand, are designed as escorts for fleets providing a screen of firepower behind which larger ships can operate with relative safety. At the beginning of the Human-Covenant War, Destroyers outnumbered Heavy Frigates nearly 15:1.

As the war raged through the Outer and Inner Colonies, however, the Admiralty began to realise that the Heavy Frigate was desperately needed. Reconnaissance and patrol battlegroups were woefully underpowered against Covenant invading forces, and while UNSC fleets had found tactics that worked and made use of their few strengths, Destroyers simply couldn't respond fast enough for the Navy's liking. In 2549, the Reyes-McLees Shipyards were commissioned constructing XFFG-217, the prototype for the design - another nine were constructed and entered service, with the hulls for another seventeen laid down. The fall of Reach saw these uncompleted frigates destroyed, but the models that had already entered service acquitted themselves at the Battle of Earth, and though certainly battered, were part of the remnant of the UNSC Navy left after the end of the war. They would continue to serve in the UNSC Navy until 2567, when they were retired.


The traditional role of a Frigate is defined as a warship designed to fill an escort role in a naval formation, differing from a Destroyer in armament, armour and function; in the early days of the Insurrection, this distinction between Frigate and Destroyer suited the UNSC Navy well. Against the Covenant, however, the Navy found that Frigates, while cheaper to field, repair and replace than their heavier tonnage equivalents, were extremely ineffective against Covenant warships. By 2548, Naval Special Warfare had commissioned Bellum Aerospace Industries to submit a new Frigate class, intended to bridge the gap between the two designes - the result was XFFG-217, then codenamed "Medusa." Developed over the next four years by BAI, the Medusa design would make effective use of technologies developed by Project EXCALIBUR, developed alongside the XFFG-118/ALPHA "Jaegar". By 2551, the Admiralty approved construction to begin on the first prototype, the UNSC Ajax, XFFG-217.

Deployed in early 2552, the Ajax quickly proved its effectiveness in combat. With its advanced LASER-reflective/refractive Ancile metamaterial layer, prototypical fusion reactor, and heavier weaponry, the Ajax's combat trials raised eyebrows among FLEETCOM - with its dual MAC's and larger missile pods, the Ajax was a significant improvement over its predecessors, while retaining the flexibility and interchangable nature that Destroyers lacked. Approval was given for full-scale production on July, 2552. Many among the Admiralty felt that the Ajax and other warships scheduled to enter service soon were equivalent to "wonder weapons", and that it could change the tide of the war if introduced in sufficient numbers quickly enough.

Advanced Frigate2

The Ajax-Class Heavy Frigate features dual light MAC's, each with a 5 minute recharge time, firing alternately or in unison - the higher output comes at the expense of kinetic force, and thus firepower.

The invasion of Reach, and subsequent devastation of the Solar System, put a halt to these plans, but the design was a popular one. In the Reconstruction Period that concluded the Human-Covenant War, the Navy was eager to levelt he playing field as rapidly as possible and commissioned the Alpha Centauri shipyards to construct seventeen Ajax-Class Heavy Frigates. Entering service in 2554 as part of the Navy's modernisation of the fleet, the Ajax-class ships would see extensive service during the War of Vengeance as humanity entered the conflict on the side of the Sangheili Armed Forces, cooperating with SAF Fleet warships, gaining a fearsome reputation among the Sangheili, who respected the combination of firepower and flexibility. Proving itself especially during the Blood Covenant attack on Alpha Centauri in 2557. By the end of the war, the Ajax class had almost completely replaced the earlier Great War-era frigates, often paired with the lighter but still capable Miranda-Class Light Frigates. By the conclusion of the War of Vengeance, the Ajax-class had become a mainstay of the Navy.


  • "The middle section looks kinda brittle, don't it? I heard one cracked in two over Earth, the G-forces of manoeuvring snapping it like a twig. That turned out to be a load of bunk, but it's easy to believe."
  • "In terms of firepower, it can compete with any Destroyer in the fleet. In terms of defence, all it has in it's favour is a layer of Ancile metamaterial and anti-laser ablative coating. But at least it can carry fighters - you wouldn't believe how much I missed having fighter protection aboard the Cole"
  • "The engines are HUGE! Seriously, look at them! There's almost as much mass there as the rest of the ship!"
  • "It may have two MAC's, but they're light ones. Higher rate of fire, but less kinetic penetration. I still say a Destroyer is more useful in a head-to-head fight - It's just that we don't get many of those, these days, do we?"

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