Halcyon-class light cruiser

Halcyon-class Cruiser The Halcyon-class Cruiser (Pronounced 'hal-see-on') (known as Human Attack Ship class C-II by the Covenant) was a United Nations Space Command cruiser starship classification designed by Dr. Robert McLees in 2510. Their service lives were short due to a unique hull design that was costly both to construct and to maintain, lack of speed, and concerns about their tactical viability. They were subsequently replaced by the. An example of a Halcyon-class cruiser would be the Pillar of Autumn.

Background
At 1.17 kilometers in length and one-third the tonnage of the succeeding Marathon-class, the Halcyons were the smallest vessels to be designated as cruisers. Compared to later ships, the original Halcyons were sorely underpowered and under gunned: their Mark II fusion engines provided but a tenth of the output of modern reactors and their armament consisted of a mere six Archer Missile pods and a single MAC gun.

As the ship was designed and manufactured well before the Human-Covenant War, it was probably meant to suppress possible rebellions on outer colonies which might have had reasonable ground militia but scarce planetary defenses, making the ship ideal to take out small defending frigates or fighters and capable of landing an able ground force to restore order on the planet. The most noteworthy design feature was a series of internal cross bracings and honeycombs that made the ships surprisingly resistant to battle damage; ships of the class were able to remain operational despite sustaining breaches to all compartments and losing 90% of their armor. As seen in Halo: Combat Evolved, this superstructure made the ship capable of crash-landing relatively safely on a planet, though it would probably never fly again.

When the Human-Covenant War erupted in 2525 a number of Halcyons were reactivated from storage and extensively refitted with additional Titanium-A armor and dozens more Archer Missile pods. One such ship, the Pillar of Autumn, demonstrated the ability to launch over 1000 missiles at once. Some were even outfitted with a prototypical powerplant using 3 engine cores. 2 auxiliary cores would "super charge" the main core when needed. One such example is the Pillar of Autumn, in which the engines were cooled with a "laser induced slurry of ions chilled to near absolute zero".

Layout
Halcyon-class cruisers are composed of five hexagonal and octagonal sections mounted onto each other. The bridge is slung underneath one of the forward sections and eight docking bays are distributed throughout the ship. There are also slots for twelve lifepods on the classes' undersides. Lastly, the MAC cannon is visible as a bump on the bow.

Dimensions
A Halcyon-class ship measures in with a length of 1170 metres, a width of 352 metres and a height of 414 metres. This makes them more than three times longer than the currently-used Nimitz-class aircraft carrier of the US Navy.

Propulsion
Sublight thrust is provided by nuclear fusion reactions which are channeled to six exhausts at the ship's stern. There are six exhausts visible, two large and four small. These engines are likely powered by deuterium-deuterium reactions. The main engine core consists of several underpowered Mark II reactors which provided 10% of modern engine output. The class was also equipped with a standard slipspace drive for translight speeds. In refits of the class, a more efficiant reactor was added with two smaller auxiliary cores.

Armament
Known elements of the Halcyon-classes' original armanent consisted of the following; In refits of the class, the weapons were among the upgraded systems.
 * 1 MAC Cannon which was apparently underpowered and ineffective in combat.
 * 6 Archer Pods which were also far below standards at the time. Each pod would have contained several individual missiles.
 * 40 50mm point defense guns were used as a last line of defense against missiles or starfighters.

Superstructure
As mentioned in the Halo: The Fall of Reach, the most notable design feature of the Halcyon-class was it's unique internal design. There were many cross-bracings and honeycombed internal areas which allowed ships of the class to function even after losing 90% of their armour.

Crew
Halcyon ships would embark with a crew hailing from the UNSC Navy and Marine Corps. There would be a significant portion of naval personnel in addition to a marine detachment. Some of the ships would also launch with a squad of ODSTs to complement the conventional marines.

Interior
Corridors on the Halcyon-class were segmented by several retractable containment bulkheads. In the event of an emergency, these bulkheads could be closed and affected sections sealed from the remainder of the ship. A potential application of this was during a hostile boarding action, whereas the atmosphere in the sealed sections could be vented via commands from the bridge, asphyxiating enemy troops.

Armories were located throughout the ship, holding a selection of small arms and their requisite ammunition. Eight docking bays allowed a number of Pelican dropships, Longsword Interceptors, Warthogs and Scorpion Tanks to be carried.

A number of service corridors ran the length of the ship. Although normally restricted to personnel, they could be accessed by lifts in main engineering or connecting passageways from the docking bays. If necessary, these expansive corridors could permit passage to Warthogs and some sections were large enough to accept Pelicans. The corridors served a secondary purpose of lessening the ship's considerable mass, thereby increasing acceleration.