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data/vehicle_descriptions/en/Xihe.md

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 Xihe (Chinese: 羲和) is the first generation of interplanetary exploration motherships, designed for crewed missions to planets and large moons within the Solar System. Intended to operate as a mobile base of operations, Xihe provides life support, long-duration habitation, scientific laboratories, power generation, and towing capability for planetary surface vehicles. The design emphasizes sustained crew survivability and mission flexibility through modular habitat segments, closed-loop life support with an integrated greenhouse, and a high delta-v propulsion system based on a mass-driver architecture powered by a large fusion Arc-reactor.
 
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 ## Lead
 
 The Xihe-class motherships were conceived for sustained, crewed exploration of Mars, Venus, and the moons of the outer planets. Each vessel integrates modular habitat sections arranged along a central spine, a rotating artificial-gravity habitat, redundant power systems, and a mass driver main propulsion system. Xihe is capable of carrying a 300-ton payload (including surface exploration vehicles and supplies) and has a stated delta-v capacity of 1700 km/s in that configuration. Crew support facilities are sized for a nominal complement of 15 for missions up to several years in duration, with short-term capacity for up to 30 personnel.
 
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 ## Design and layout
 
 The Xihe-class follows an elongated, multi-segmented cylindrical "spine" arrangement. Major modules are stacked along the central axis to concentrate structural loads during thrust and towing operations while keeping the overall cross-sectional area small to reduce collision risk with micrometeoroids.
 
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 ### Front docking hub
 
 The forward section houses a reinforced front docking hub with five docking ports intended for shuttles, landers, and towable surface vehicles. The primary forward docking port is a 2.5 m diameter port that is structurally reinforced for towing under thrust. Four additional telescopic side ports (two 1.875 m and two 1.25 m) are provided for boarding and cargo transfer while the ship is stationary.
 
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 ### Command center
 
 Directly aft of the forward hub is the command center. This 5-meter-diameter module accommodates navigation, communications, mission control, and core avionics. It contains two airlocks for EVA (crew and cargo) and is equipped with advanced sensors and redundant computing systems for trajectory, attitude, and systems management.
 
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 ### Artificial gravity habitat module
 
 The primary habitation for long-duration missions is a rotating ring habitat with a 25-meter diameter that spins at approximately 4 revolutions per minute to generate roughly 0.41 g of artificial gravity via centrifugal force. The ring contains crew sleeping quarters, dining and recreational spaces, and laboratory facilities oriented to support both nominal habitation and mission science tasks.
 
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 ### Stationary habitat module
 
 A non-rotating habitat module immediately aft of the rotating ring provides medical facilities, additional laboratories, storage, and mission-support spaces. With a 5-meter diameter, it is sized to help sustain up to 15 crew members comfortably over prolonged missions.
 
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 ### Center docking hub and extension modules
 
 A secondary, center-mounted docking hub follows the habitats. It includes four side-mounted telescopic 1.875 m ports (two directly on the hub and two on extension modules). Each extension module terminates in a 2.5 m observation cupola on its upper face and a communications dish on the lower face. All center-hub docking ports are reinforced for towing under acceleration and are typically used to interface with planetary surface vehicles such as the [Echo Shuttle](/home/Space_Shuttles/Echo_Shuttle) and the [Amalthea MPV](/home/Vehicles/Amalthea). Echo Shuttles are prioritized for atmospheric landings while Amalthea-class vehicles are used primarily for landings on airless bodies.
 
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 ### Greenhouse module
 
 A 5-meter-diameter automated greenhouse module supports hydroponic cultivation and contributes to closed-loop life support by recycling carbon dioxide into oxygen and producing fresh foodstuffs. The hydroponic systems include LED lighting, climate control, and automated nutrient delivery. The greenhouse is sized to support the dietary needs of up to 15 crew members for approximately five years given the onboard fertilizer supplies; water and air reclaim systems are effectively indefinite, but nutrient (fertilizer) reserves limit continuous autonomous operations without resupply or in-situ resource production.
 
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 ### Main storage and secondary storage
 
 Following the greenhouse is a main storage module (5 m diameter) providing accessible cargo stowage for mission equipment and emergency reserves. The design allows for up to 10.5 months of extra supplies for the full crew complement to permit direct aborts to Earth or rendezvous with the nearest support station in contingency scenarios. A secondary storage module located near the truss stores EVA gear, spare parts, and maintenance supplies.
 
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 ### Truss structure and small Arc-reactor
 
 A truss framework separates the habitation and storage modules from the propulsion module. This truss supports radiators, external systems and provides standoff distance to protect the crew from reactor and engine radiation during operation. Two additional docking ports (top and bottom of the truss) support towing operations. Mounted on the lower truss is a small Arc-reactor that provides emergency electrical power sufficient for life support and attitude control in the event of a main reactor failure.
 
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 ### Propulsion module
 
 The aft-most section contains the propulsion module with the main mass driver engines, fuel tanks (reaction mass), the primary cold-fusion Arc-reactor rated to produce up to 8 terawatts (TW), radiators, attitude-control thrusters, and communication arrays. The mass driver system expels reaction mass at high exhaust velocities to produce thrust and offers two operating modes:
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 The engines are smoothly throttleable in both modes to allow precise delta-v budgeting and maneuvering. The propulsion module stores roughly 196.3 tonnes of reaction mass, supporting a stated delta-v capability of 1700 km/s with a 300-ton payload.
 
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 ## Systems and subsystems
 
 - Power: Primary power is provided by a large Arc-reactor (cold-fusion) with an 8 TW output; the small Arc-reactor on the truss is a secondary/backup unit for essential loads.
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 - Radiation shielding: Enhanced shielding around habitat volumes, with the truss providing separation from the main reactor and engine radiation sources.
 - Docking and EVA: Multiple docking ports with telescopic mechanisms and two airlocks in the command center.
 
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 ## Construction and assembly
 
 Initial Xihe-class vessels were assembled in low Earth orbit (LEO) using repeated launches of the [Vulture Shuttle](/home/Space_Shuttles/Vulture_Shuttle) to deliver discrete modules and components. Assembly procedures included deploying a center docking hub early in the build sequence, then progressively attaching habitats, storage, truss, and propulsion modules. Larger modules such as the artificial gravity habitat required delivery by heavier-lift launch vehicles.
 
 Later production shifted to [Star Port Station](/home/Stations/Star_Port_Station), an orbital shipyard in LEO that streamlines assembly and outfitting. Components for later motherships are delivered by larger cargo craft such as [Qingtian](/home/Cargo_Ships/Qingtian), reducing the number of shuttle-class launches required for assembly.
 
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 ## Operational history
 
 The first batch of three Xihe motherships was constructed between 2050 and 2055. [XH-01 — Xihe](/home/Exploration_Motherships/Xihe/XH-01) completed in early 2052 and entered service on crewed missions to Mars and the Jovian system. During XH-01 construction, engineering improvements were identified that informed later designs and led to the development of the [Stellaria-class motherships](/home/Exploration_Motherships/Stellaria/ST-01), which adopt a newer [Lightspeed Engine](/home/Engines/Lightspeed_Engine).
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 As missions progressed, Xihe-class ships were used extensively for crew rotation, logistics, and transport of large surface exploration vehicles and construction materials for off-world bases.
 
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 ## Missions and mission profiles
 
 Typical Xihe mission packages combine scientific research, surface exploration, base construction support, and technology demonstration. Two common transfer profiles are described:
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 Mission planners commonly target a practical one-way transit of roughly 30 days for Mars missions and about 70 days for missions to Jupiter's moons while using delta-v budgets that balance time and fuel consumption.
 
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 ## Specifications
 
 ### Performance
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 - Short-term capacity: up to 30 crew
 - Life support consumables (without greenhouse): ~315 days for 15 crew
 
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 ## Fleet
 
 | Name      | Serial number | Status           | Notes |
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 | Changxi   | [XH-03](/home/Exploration_Motherships/Xihe/XH-03) | Testing in LEO | Third of its class; intended to support Europa Research Outpost rotation and Venus exploration. |
 | Unnamed   | [XH-04](/home/Exploration_Motherships/Xihe/XH-04) | Under construction | Fourth of its class; expected completion in mid 2061. |
 
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 ## Naming and variant notes
 
 Several Xihe-series hulls were reconfigured during production to incorporate newer propulsion options. Notably, two hulls were redesignated as early [Stellaria](/home/Exploration_Motherships/Stellaria/ST-01) variants ([ST-01 — Stellaria](/home/Exploration_Motherships/Stellaria/ST-01) and [ST-02 — Kristen](/home/Exploration_Motherships/Stellaria/ST-02)) after installation of the [Lightspeed Engine](/home/Engines/Lightspeed_Engine); these transitional vessels bridge the Xihe and Stellaria classes in capability and role.
 
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 ## Gallery (image placeholders)
 
 ![Xihe profile diagram](./images/Xihe_profile.png)
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 Notes for image use: The images above are placeholders. When adding actual images to the repository, store them in `data/vehicle_descriptions/en/images/` (or a shared images folder) and ensure the filenames match the references used above. Each image should be accompanied by descriptive alt text and the caption/description block shown here.
 
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 ## See also
 - [Stellaria-class mothership](/home/Exploration_Motherships/Stellaria/ST-01)
 - [Echo Shuttle](/home/Space_Shuttles/Echo_Shuttle)