Itokawa Deep Space Mining Vessel
Itokawa Mining Vessel
Image from Tengu459
Itokawa Mining Vessel with Electric Sail furled

History of Deployment and Use

The Itokawa Class was named after a 1st Century Japanese engineer and rocketry pioneer from Earth. Due to their input on the design, the recently arrived Otaku colonists were given the privilege of naming the class of ships, and most Itokawa Class vessels were named after Japanese astronauts, such as the Hoshide's Pride. Other ships were named after pre-swarm fictional anime spacecraft, such as the Toy Box 2 and the Bebop. More on the Otaku culture and colonists here.

The Itokawa Class of asteroid mining and cargo freighters were first developed and deployed in the Epsilon Eridani system shortly after the colonisation of that system. The impoverished colonists needed both raw-material-gathering capabilities and rapid in-system transportation. Intended to serve as mobile habitats as well as performing commercial and industrial functions, these ships saw widespread use throughout the system, both among the inner orbits of the planets and 3 asteroid belts, and as far out as the system's Oort cloud.
After receiving transmissions from SolSys detailing the chaos caused by the Technocalypse and Great Expulsion, a general distrust of fully automated systems spread amongst the colonists. The design of the Itokawa reflects this, in which a biont crew oversaw operations being carried out by tel-operated bots and turing-grade vecs. In particular, the colonists from the Macoss were instrumental in developing the Itokawa Class's on-board A.I., and the Otaku clade made widespread use of the design in terraforming Planet Two.

After the formation of the Eridanus League, multiple Itokawa Class ships were used as short-distance cycler ships, making use of Genetekker biotech and newer cryogenic pod designs to ensure the health of the crew on long, multi-decade trips. Several of these ships were notable for using copies of the virtual colonists from the Bismilla as crew (which arrived in-system at 675A.T.), and did away with the habitat ring completely. After allying themselves with the First Federation in 1000 A.T., several of these ships made sojourns into old SolSys, where their template was spread amongst Haloist and Belter communities. While the design was outdated and never saw widespread use, it's robustness and ease of manufacture ensured it saw limited use for several hundred years in multiple star systems.

Cultural Significance

The Itokawa Class ships saw use in over a dozen systems as a cheap, easy to produce mining and freight vessel. They were particularly noted for their use in the Epsilon Eridani system, and delivering materials used in the construction of the planet Aphrodite's sunshade, although their overall contribution was minor. The sight of an Itokawa Class craft on one's sensor readouts was relatively common in the system's multiple asteroid belts, and the Independent Accretion-Belt Mining Colonies were famous both for using the design and modifying it. By 2300 A.T. the design was no longer used outside of several enthusiasts, resource-poor fringe colonies, or low-tech Haloist clades, but the design periodically makes reappearances during fads embracing retro-tech engineering.

A single first-generation Itokawa Class craft is maintained as a mobile museum in the Ran system, where its 12 year flight path makes regular fly-bys of each planet. Tourist can even try their hands at harvesting small asteroids with authentic tel-operated bots (under hyperturing guidance of course). Useful metals mined are frequently sculpted into small "awards" handed out at the conclusion of team-based competitions, with titles such as "Best Mission," "Best Pilots," and "Highest Efficiency."
Nano-factured e-ink sheet print-outs of the original design schematics are also available to tourists, and it is a point of pride for the museum that the original sketches from the lead designer are housed on-board and kept on display.

Itokawa Mining Vessel extended
Image from Steve Bowers and Selden Ball
Itokawa ship with external systems extended

Ship Design

The Itokawa Class spacecraft were over a kilometer in length, mostly empty mining and freight-oriented craft that also serve as mobile habitats and possibly as interstellar transports, although most of their operations wee restricted to in-system jobs. Their design made use of modular cargo "cells" that were themselves sometimes used as refined material for trade or colony/habitat construction. While over a kilometer in length, their 0.1g acceleration and focus on microgravity operation negated the need massive structural frame work. This combined with their modosophont-friendly design principles made them relatively easy to build and operate, as well as cheap to produce.

Navigational Shielding

A series of superconducting rings and support beams formed a funnel-shape structure near the forward end of the craft, utilized to control smart-matter clouds ahead of the craft, which bonded with particulate matter along the flight path of the craft. Once bonded with potentially hazardous material and particles, an artificial magnetosphere was used to "push" the material aside, preventing erosion of the vehicle or dangerous collisions at high speed. Once a change in trajectory was achieved, the smart-dust nanobots would detach from the particulate matter and be recaptured by the ship's magnetosphere. These rings are also used to generate an artificial magnetosphere to protect the ship from solar radiation. At the base of the funnel were collection troughs/deployment nozzles for the smart-dust. At low velocities the system was utilized to capture materials lost while mining asteroids. In the very center is a "navigation" laser, which was used to ionize particulate matter in the flight path of the ship, allowing it to be pushed aside or otherwise manipulated by the ships magnetosphere. While the arc of the laser was limited, it could still be used to ablate larger masses the smart-dust cannot re-direct. The laser was considered powerful for it's time period, but by modern standards it would be considered woefully under-powered and limited in its frequency range. In heavily populated systems, this laser was often de-rated so that it did not pose a threat to habitats and orbital structures.

Sensors and Communications

Another noticeable feature was the large telescopic arms projecting from behind the smart-matter/magnetosphere ring. These mounted high-definition sensors and high-capacity/bandwidth communication systems inside of pods mounted on the armatures. While the exterior hull of most of these vessels was plated in smart materials that provided basic sensor input and low-bandwidth communications, the armature-mounted sub-systems were far more powerful and had higher-resolution capacity than the hull-mounted systems. Because the ship-based systems produced so much "noise", these sensor/communication systems were extended past the artificial magnetosphere loops to provide adequate system isolation and sensitivity.

Propulsion Systems and Power Generation

In addition to serving a variety of roles, this class of ship was well known for its robust and redundant propulsion systems. When first produced, the Itokawa Class's amat-catalyzed fusion rockets were expensive to operate, especially in newly colonized systems whose amat production was either low or non-existent. While expensive for its time, the amat-catalyzed fusion rockets had a high enough specific impulse to propel this class of ship up to a significant percentage of the speed of light; typically no more than 1%, but with enough propellant, ships of this class could achieve a cruising speed of 10% C.

Liquid volatiles were utilized to augment thrust when needed, operating like an "afterburner", increasing thrust by adding density to the exhaust. In this operation mode the rocket provided copious amounts of thrust, but had a relatively low amount of specific impulse, making this method mostly useful in maneuvering between asteroids or habitats. Scavenged propellant from frozen gasses mined in asteroids or Kupier belt objects, such as methane, hydrogen, ammonia, and water vapor, could be used interchangeably without modifying the rockets.

Primary power for the ship was generated using magnetohydrodynamic taps lining the reaction chamber of the rocket. Even when not under thrust, the fusion reaction was sustained at a low level, acting as a bi-modal fusion power plant. Auxiliary or backup power was provided using a series of fuel cells, battery storage, high-density capacitors, and steam turbines that scavenged heat from the radiators.

The secondary set of communication and sensor booms also mounted the primary maneuvering and station keeping thrusters. Used mainly for small course corrections or maintaining an orbit, these chemical rockets used scavenged volatiles refined into hypergolic fuels.

A notable backup propulsion system commonly utilized was the Electric Sail, a powered, low mass variant of the traditional solar sail that did away massive photon sails and replaced them with electrically charged tethers. Thin superconducting wires several kilometers in length were extended from the craft, and charged to a high positive potential by an electron gun, allowing them to interact with solar radiation. In addition to being low-mass, the E-sail had the ability to "steer" the ship by asymmetrically powering down different wires, changing the apparent direction of thrust.
Later in time, a common addition to these craft were modular, detachable magsail structures used to operate using Beamrider Network particle streams. When not in use, these magsails were often detached and left in orbits around the edge of a solar system, lowering the ship's mass. When the magsail was in use, amat-catalyzed fusion rocket operations were suspended, both to avoid interfering with the particle beam, and to avoid cataclysmic interactions between amat and the boostbeam.

Cargo and Manufacturing Capabilities

Aft of the sensor and communication arrays were the cargo "cell" pods, arranged in concentric circles around the spacecraft's spine. Each cargo cell was "grown" from resources mined from asteroids, usually a mixture of metallic and ceramic materials. While primarily intended to shield refined frozen gases and metals from solar radiation, they were also used to store nano-factured goods from on-board autofacs, and were also used when empty as a trade good of valuable refined materials. In addition to moving cargo from ship to ship or ship to habitat, independent cargo cells could be used to deliver volatiles, refined material, and nanofactured goods to a planetary surface with the addition of a retro-rocket and parachute system. Steerable balloon systems were often used to deliver cargo to bubblehabs on gaseous planets. This made the cargo cells invaluable for early colonization efforts, as the goods were unloaded and the cargo cells were used to build the colony's infrastructure and housing.

Fuel and Habitat Ring

At the center of the craft, adjacent to the autofacs/refineries, was a set of 4 storage tanks. These were exclusively used to store propellant for maneuvers and cruising. Immediately aft of these propellant tanks was the rotating habitat ring, which used the propellant tanks as radiation shielding. The habitat ring rotated at a leisurely pace of about 3-4 rpm, providing up to 1g of pseudo-gravity, provided the habitat ring had a radius of at least 56 meters. Since most of the habitat rings had a diameter of 60 meters, a rotation rate of 3.85 rpm was necessary for 1g of pseudo-gravity. Most micro-gravity and low-gravity tweak clades disregarded this and spun their habitat rings at a mere 1 rpm - enough to provide a "down force" for unsecured objects, but not enough to impair their movements. All of the pressurized living space and most of the on-board aero-ponics gardens were located on the habitat ring. While the available aeroponics space was sufficient to provide all the nutritional needs of the crew, it did provide a comforting touch of "real" food for a crew that would otherwise be dependent on culinary autofabs for food sources. The aeroponics were also utilized to grow recreational pharma, and designing new strains was a common hobby amongst crews. Recreational and public areas often resembled parkland of various biomes, with control interfaces and necessary hardware embedded inside natural-looking plant life and rocks. Genetekker influences on the ship design were most noticeable in these areas, as biobots resembling unprovolved species from Earth, or fantastical creatures from mythology and virch games, were used in maintaining the biological portions of the ship's interior.

In general personal living space was divided into staterooms that could be reconfigured at whim through the use of sliding partitions, synsect swarms, and modular furniture. Synsect swarms controlled by the shipmind were used to modify the interior, sometimes forming new furniture or surfaces, and at other times breaking down and rebuilding unwanted structures. Most synsect swarms incorporated large percentage of smartex in their construction, allowing them to stretch out or flatten to form part of the surrounding structure of the ships habitat. Most of the synsects were designed to resemble naturally-occurring creatures such as squirrels or butterflies. However many crews would often mod their designs to create forms that mimicked creatures from pop-culture, or even entirely novel forms. The crew of the Kamaitachi's Revenge gained a brief amount of fame for modding all their synsect bots to resemble the leaders of various habs or polities, which led to them being issued a cease-and-desist order from several politicians that did not share the crew's sense of humor.

While a crew of up to 120 bionts could be supported, in most cases these ships had a crew of only 12 bionts, who worked in 3 shifts of 4 individuals. This was primarily a reflection of low numbers of available populations, rather than a reflection of limited space or life support. The rest of the crew consisted of the ship-mind A.I. and several dozen copies of a trusted A.I. vec or Starhand. Aft of the habitat ring was a small torus that severed as a docking/refueling/recharging station for the Starhand vecs and teloperated bots. This section also included the computronium banks that housed the intelligence of the shipmind A.I. Attached to this torus was a set of tether housings that made up the electronic sail.

Heat Transfer, Antimatter, and Radiation Shielding

Past the habitat ring and computronium torus, radiator panels projected several dozen meters away from the hull, stretching all the way to the shadow-shield that protected the craft from its powerful amat-catalyzed fusion rocket and solid-core fission reactors. In earlier iterations of this craft, four solid-panel radiators were used, mounted at 90 degree intervals. To increase efficiency, these were later replaced with two liquid-metal coolant systems, separated by 180 degrees. Foremost among the advantages of the liquid metal radiators was their lower mass; they reduced the necessary support structure by 40%. The liquid-metal coolant radiators also operated at higher temperatures (around 1200 to 1500 kelvin), allowing a smaller number of radiators to be used. Collisions with the working fluid would not damage the craft, but instead only cost it a small amount of working fluid. Dynamic steering of the droplet nozzles allowed the system to compensate for maneuvering under thrust. The anti-matter and boron-11 storage tanks were mounted between the cargo cells and the propellant tanks, giving the habitat ring as much protection as possible from amat-containment failure. A composite shadow-shield provided protection from the dangerous by-products produced by the amat-catalyzed fusion rocket. Made of alternating layers of tungsten and aerofoam, these shields were both heavy and expensive for early colonists, but were quite necessary. Sometimes alternative materials were used in lieu of tungsten, which required more mass and a thicker shield, but the basic design always specified tungsten.

Mining and Refinery Operations

Mining asteroids and Oort cloud objects was accomplished using a combination of tel-operated bots and truing-grade Starhand style vecs. The vecs and bots would swarm an object, placing explosives at key points, and then surround the object with sheets of glass-reinforced Kevlar. Once the object was enveloped, the explosives were detonated, and the shattered fragments towed back to the ship for processing. After being stored on a cargo cell, electro-static pumping stations fed material to refineries and autofacs near the reactor housing. Useful volatiles were stored in massive tanks for propulsion, and excess amounts where sent back to the cargo cells and refrozen into bricks measuring several hundred kilos each, to be used in trade. Useful metallic elements were likewise refined, and available materials were often compared to "wish lists" from nearby habitats. If the materials were available, the on-board autofacs would produce the finished goods, which were then sorted by destination and moved to an available cargo cell.
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Development Notes
Text by Tengu459
Initially published on 25 January 2018.