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Chōuryū Subsurface Torpedo/Sensor Platform

A surface/subsurface munition and sensor platform manufactured by Yugumo Corporation, the Chōuryū Subsurface Torpedo/Sensor Platform was designed by Yugumo Fleetworks and released in late YE 44. Chōuryū (潮流) is Yamataigo (邪馬台語) for “Tidal Current.”

About the Chōuryū Subsurface Torpedo/Sensor Platform

The Chōuryū Subsurface Torpedo/Sensor Platform gives its host platform unparalleled surface and subsurface standoff, attack, and remote telemetry capabilities.

Chōuryū Subsurface Torpedo/Sensor Platform
Year Created YE 44
Designer Yugumo Fleetworks
Manufacturer Yugumo Corporation
Name Chōuryū Subsurface Torpedo/Sensor Platform
Nomenclature See Nomenclature Catalog
Type Surface-Subsurface Torpedo Platform
Role Semiautonomous munition and sensor platform
Production Mass Production


With the development of the Umikagami Subsurface Operations Suite, in YE 44, the subsurface operations it enabled required appropriate weapons and remote sensor capacity. As a modern guided munition is essentially a drone with a self destruct, it was natural to combine the two missions into a single platform capable of carrying out both. This system was first deployed by Yugumo Corporation aboard the Misha-Class Explorer, the ISS Shiori.


The Chōuryū launch platform itself is contained within the hull of the host ship and its appearance is highly dependent on the implementation, being a system of tubes, valves, tanks, and pumps.

A Chōuryū torpedo is a sleek, Durandium Alloy cylinder, tapered at both ends. The front is a rounded ogive that contains the warhead, sensors and supercavitating shield emitters. At the rear is the thrust vectoring engine and retractable, steerable guidance fins.

Discharge Information

Besides launching a Chōuryū torpedo, other aspects of the discharge depend on firing mode:

  • Muzzle Flash: A plume of fluid and bubbles in impulse mode, none in swim-out mode.
  • Retort: Displaced water in impulse mode, none in swim-out mode
  • Effective Range: Dependent on munition
  • Rate of Fire: By launch system implementation
  • Recoil: Significant in impulse mode, negligible in swim-out mode.


A system that can launch the larger torpedo is generally capable of launching both, though exceptions exist, particularly for surface or air deployed applications.

Chōuryū Torpedo Damage Quickchart
Type Purpose
Chōuryū Torpedo, Heavy (Yu-Z1-1A) Standoff Weapon (Tier 9, Heavy Anti-Mecha)
Chōuryū Torpedo, Light (Yu-Z1-2A) Close-Attack Weapon (Tier 6, Heavy Anti-Armor)

Weapon Mechanisms

Torpedoes, if not dropped from an airborne or surface weapons rack, may be launched in either impulse or swim-out mode. In impulse mode, the tube is flooded with pressurized water, driving the torpedo out at high speed so that it may safely engage its primary propulsion sooner, or in swim-out mode, where the torpedo exits the tube under low-power for a quieter, stealthier launch.

  • Firing Mechanism: Dependent on launch platform implementation
  • Loading: Dependent on launch platform implementation
  • Mode Selector: Realtime onboard intelligence or launch command
  • Firing Modes: Swim-out or impulse launch
  • Weapon Sight: Onboard and remote guidance


This weapon is launched from an appropriately sized torpedo tube (see Nomenclature Catalog) or weapons rack (such as dropped from an aircraft or surface ship). When fired, the Chōryū activates its primary drive system. At that point, the onboard KAIMON system carries out the orders given. Controlling this munition requires a platform equipped with the Umikagami Subsurface Operations Suite.

A typical subsurface vehicle launch platform operates as follows:

  1. The round is loaded.
  2. The tube is sealed.
  3. The tube is flooded with the surrounding water or other medium, venting atmosphere, until the pressure inside it is equalized with the surrounding medium.
  4. When the pressures are equal, the tube is opened.
  5. The torpedo may “swim out” using its MHD, or be forced out with a water ram (“impulse mode”).
  6. The tube is closed, drained, and dried for the next shot.


Pricing for this system is independent of implementation. Implementations large enough to launch the larger torpedo are capable of launching both.

  • Chōuryū Subsurface Torpedo/Sensor Platform (Yu-XX-4500): 12,500KS

Replaceable Parts and Components

Specific launcher systems components vary and are generally bespoke to the host platform's class. Components for Yugumo Fleetworks subsurface launch systems (see Launcher Nomenclature) are described below:

  • Breech/Tube/Muzzle Assembly, includes Vent, Blowoff, and Equalization Valves (Yu-XX-W4500-F1): 3200KS
  • Water Ram Pump/Slide Valve/Tank Assembly (Yu-XX-W4500-P1): 2250KS
  • Flood/Drain Pump/Valve/Tanks Assembly (Yu-XX-W4500-V1): 2000KS
  • Power, Pump, and Valve Control System Unit (Yu-XX-W4500-E1): 1200KS


Ammunition is listed per round, by size.

Chōuryū Torpedo Price Quickchart
Type Price (each)
Chōuryū Torpedo, Heavy (Yu-Z1-1A) 5000KS
Chōuryū Torpedo, Light (Yu-Z2-2A) 3000KS

Nomenclature Catalog

Catalog of Standard Product Nomenclature System implementations for this system, by platform:

Platform Nomenclature
Misha-Class Explorer (1C) Yu-Y1-W4500

OOC Notes

Yuuki created this article on 2022/12/18 11:17. Approved here by Wes.

Products & Items Database
Product Categoriessubsystems, weapons: torpedoes
Product NameChōuryū Subsurface Torpedo/Sensor Platform
NomenclatureSee Nomenclature Catalog
ManufacturerYugumo Corporation
Year ReleasedYE 45
Price (KS)12 ,500.00 KS
DR v3 maxTier 9

corp/yugumo_corporation/weapons/chouryuu_subsurface_torpedo_sensor_platform.txt · Last modified: 2023/06/28 11:01 by wes