A replacement for the Lysandra-class light cruiser at the start of the Hegemony era of the Third Imperium, the Lachesis-class light cruiser was built specifically for the light cruiser mission in the Imperial Navy. This mission includes convoy and task-group escort, exploration, survey, and anti-piracy missions, with the Lachesis-class making the most of the experience of the Lysandra-class.

Debates about the class-namely the relatively light beam cannon load-would result in the replacement of the class with the Lindworm-class in the Middle Hegemony period.

Design History

Like the Lysandra-class light cruiser, the Lachesis-class was built for interior missions, including exploration and line-of-communications operations between Imperial worlds. With the class being built after the end of the Alpha Wars, combat with Alpha warships wasn’t a major consideration. However, the Imperial Navy did maintain combat capability against Alpha or other “near peer” warships as a major portion of the ship concept.

The Lachesis-class can be seen as a revision of the Lysandra-class, and it is only in defensive systems and support systems that the class can be considered improved. The ship is built around a spinal Metaspace Cannon with a 120m accelerator tunnel and a 30cm discharge aperture. Secondary direct-fire weapons are built around twelve 5cm positron beam cannons in dual turret mounts, considered to be a far too light weapons load for the class (the later Lindworm-class would mount 6.5cm beam cannons in dual turret mounts).

Long-ranged engagements are based around ten 350mm missile launcher tubes with gravity drivers on the ship’s port and starboard. While the class could use all Imperial-standard missiles, the Lachesis-class would have its fire control optimized for the Mk-21-B missile and the later Mk-23 and Mk-27 missiles. Point defense would not only consist of standard 20mm and 40mm x-ray lasers, but four 150mm counter-missile launchers. Debates about the effectiveness of mounting counter-missiles on a light cruiser hull is continually discussed, but against most light combatants it gives a ranged engagement option against missiles.

Passive defenses would be built around shields rated to withstand 1.5 strikes of a Lachesis-class equivalent main beam cannon strike on the bow, dorsal and ventral aspects, with a single-strike resistance to the port and starboard, and 75% resistance aft. Like Hegemony-era warships, the Lachesis-class uses battle steel armor. The ship mounts six Q-space coils and three slipspace drive rings, giving the ship a 360 G acceleration and 6 LY/day travel time. 

Sensor capability would include a 320 m/640 m VLBI array system (with two backup deployable arrays), an extensive passive and active EM sensor system, and standard navigation and operational sensor packages. The ship also carries a planetary survey package as standard, twelve sensor decoys (split between Rodeo-type anti-missile decoys and Mirrorball-type anti-sensor decoys), stealth systems backed up by a mil-spec hypersink, and the AN/SL(G)-82 electronic warfare package. The Lachesis-class would also mount the AN/SG(N)-33 electronic warfare package, which included two high-powered “spike” jammers for anti-missile duties.

Retrofits of the Lachesis-class would continue through the early Hegemony period, but no major revisions beyond reactor improvements of the hull would result.

Service History

The Lachesis-class would be built in five major “flights,” and at a replacement rate of 1.5 times the number of Lysandra-class ships currently in deployment. The only major variation between flights is the replacement of the Type 34 rectors with the improved Type 35-A1 antimatter reactors starting in Flight IV and later hull retrofits. The class would remain in Imperial service until the Lindworm-class was deployed, later to be assigned to secondary service then materials reclamation.

A proposed version would have replaced all of the missile launchers and the Metaspace cannon with bow launch arrays for Mk 25 missiles, but the Imperial Navy saw no need for a small bombardment hull and the class couldn’t carry enough missiles to be worthwhile. An additional proposal for specific revision of the hull for Survey missions was considered, but this mission would be filled by a version of the Hotspur-class heavy cruiser, the Serendipity-class.

A number of hulls would be modified for the Ghost Fleet mission, namely the removal of the antimatter reactors and replacement with fusion reactors, and secondary modifications to improve long-duration mission operations with the class.

General Characteristics

Dimensions: 180 m x 22 m x 18 m

Mass: 15,000 tons (consistent across all flights)

Power Systems:

2x Yoyodine Type 34 Antimatter Reactors (Hegemony Era, Flight I-III)

2x Yoyodine Type 35-A1 Antimatter Reactors (Hegemony Era, Flight IV-V)

Propulsion Systems:

6x Q-Coils (360 G acceleration, all flights)

3x Slipspace rings (6 LY/day, all flights)

Endurance:

180 days of antihydrogen at 90% power, theoretically unlimited material endurance (Hegemony Era)

Crew:

One Class VI AI, three Class V AIs, mixture of uploads and biological crew equaling 400 crew members, 100 Marines, backup bioshells and cybershells (Hegemony Era)

Armament:

1xMetaspace Cannon, 120m spinal mount with a 30 cm bow discharge aperture.

12×5 cm positron beam cannons in six dual turrets, two ventral, two dorsal, one port, one starboard.

10x350mm missile tubes with gravity launchers, two arrays of five port and starboard.

Defenses:

Stealth Systems: Radar sheath, IR dampener w/military specification hypersink, hull form.

ECM: AN/SL(G)-82 Electronic Warfare Array, with “spike” and “strobe” jammer options.
AN/SG(N)-33 Electronic Warfare Array with one port and one starboard “spike” arrays.

6x Rodeo-class missile decoys, 6xMirrorball-class sensor decoys (dispensers ventral and dorsal).

Point Defense: 10 40mm xaser cannons with double-bounce gravity mirrors in independent casemate mounts.

16 20mm xaser cannons with double-bounce gravity mirrors in independent casemate mounts.

4x150mm counter-missile launchers, mounted in pairs port and starboard.

Shields: Standard Hegemony Navigational Shields

Combat Shield Generators-150% capacity bow, dorsal, and ventral, 100% capacity port and starboard, 75% capacity stern.

Armor: Battle steel, 5.5 cm maximum (Hegemony Era)

Secondary Craft:

2xPinnance, 2xCutter, 6xHarvesting Drones, 14xType 2 Recon Drones, 6xType 3 Recon Drones (Hegemony Era)