Cold Fusion technology was researched extensively by the Terran Space Research Corporation in the early 23rd and 24th centuries with limited success. Working prototypes were created by the Old Federation by the 25th century, but the technology was never made viable for mass-production until the 2500s. The basis for Cold Fusion as a power source in Aquarius is the Helical Barycentric Cold Fusion (HBCF) reactor design.
Such a reactor is named so due to the Helical Barycentric Radioelectric power convertor used to capture charged particles escaping from fusing hydrogen atoms within the fuel catalyst. Hydrogen Fuel Cells containing super-compressed semi-solid hydrogen pellets are injected into the reactor complex, releasing the fuel-mix into the fuel catalyst. The cell is contained as close as possible to the catalyst in order to shorten the response time of the fuel injection feedback time necessarily to regulate Cold Fusion.
Semi-solid (fluid state) pre super-compressed hydrogen atoms (Fuel mix) are then further compressed by extremely powerful electromagnetic compressors and then exposed to an ion laser, inducing Nuclear Fusion whereby nearby Hydrogen atoms are fused into a helium atom, releasing huge amounts of nuclear energy in the form of charged photons. In a "warm" Fusion system, the released energy is allowed to propagate through the catalyst medium into a fluid (or similar) reservoir, exciting the molecules in the medium and producing immense heat. HBCF utilises powerful electromagnetic fields to 'guide' escaping charged particles into a magnetic funnel linked to a room temperature superconductive conduit, creating usable electrical potential (charge) that is immediately stored by a superconductive capacitor (supercapacitor). HBCF designs are not possible without the use of superconductors at "high" (room) temperatures due to thermal build up caused by resistance and eventual cascade (thermal runaway) at the convertor level, wasting charge potential and lowering efficiency to the point when Cold Fusion is no longer maintained within the core.
Due to the fact that the magnetic field created by the Helical Barycentric Radioelectric power convertor absorbs the photons before they have a chance to interact with the catalyst fluid medium (or be absorbed by the reactor wall shielding), very little heat relative to the total power potential, is generated. HBCF reactors typically operate in the 120-150C range, with colder designs indicating higher energy conversion efficiency. By the 46th century, ATIS HBCF designs are standardised at ~98% efficiency and regulated by complex computer systems. In such a design, 98% of the energy potential of the reaction fusion process is converted into usable electrical potential charge and stored in the Supercapacitor.
HBCF reactor designs such as those in use by essentially all starships in Aquarius, require extensive electrical regulation by advanced computer systems in order to maintain performance and stability. Due to the way in which Cold Fusion is maintained (extremely high efficiency energy conversion) HBCF reactors must operate within a minimum efficiency threshold in order to prevent extreme heat build up and eventual failure. For example, the energy potential removed from the fuel catalyst by the power convertor, on ATIS designs, must always be maintained at 98% of the energy capacity of the reactant fuel mix going into the reactor. If the charge rate drops below the equilibrium, the reactor's temperature rises (I.e, is no longer Cold Fusion), eventually resulting in catastrophic failure of the reactor.
In order to regulate this, HBCF reactors incorporate sensitive monitoring systems that measure the discharge rate of the supercapacitor (itself acting as a 'buffer' to allow response time - since even immediate fuel injection reduction will still leave some previous volume in the fuel catalyst with enough reactive potential to cause a meltdown), which is closely tied to the power consumption of the connected power grid. Using that information, the regulator system dynamically adjusts the fuel mix injection rate into the catalyst in order to slow down or speed up the rate of Hydrogen-Helium fusion so that the supercapacitor discharge rate is always 98% of the reactant potential energy output (on average). This balance allows Cold Fusion to occur and provides extremely high efficiency of energy generation from a given amount of hydrogen fuel.
It is this mechanism that gives HBCF reactors the quirk of heating up as power consumption goes down, if such a regulator was not in place.
The name is derived from the helical shape of the radioelectric power convertor that rapidly rotates around the fuel catalyst rod (where fusion takes place), suspended in a powerful magnetic field in rotational equilibrium with the fuel rod itself (barycentric centre of mass). The space between the rod and the convertor is maintained at near perfect vacuum as contaminant gases or matter can cause extreme heat build up as charged particles released by the Fusion process excite the contaminants, which then transfer heat to the fluid medium (nano-polymer gel) and ultimately, are absorbed by the reactor shield wall - ultimately leading to thermal failure and catastrophic melt down.
Due to the extremely volatile nature of HBCF designs of operated outside of this balance, the regulator system incorporates myriad safeguard and failsafe systems designed to prevent catastrophic melt down. Such systems include catalyst vacuum medium matter detectors (if matter beyond a certain threshold is detected within the space between the rod and the convertor, it triggers a warning), thermal sensors and physical proximity / integrity sensors in the entire complex surrounding the reactor (Citadel). The emergency shut-down system as standard on Aquarian Terran HBCF designs incorporates extremely powerful reserve supercapacitors; two banks exist near to the fuel catalyst, one is always fully charged and one is fully discharged, the latter bank has an even higher energy capacity than the output buffer capacitor and is used to rapidly drain electromagnetic energy from the convertor in the event of an emergency shut down.
This is necessary because there is often sufficient fusionable material remaining in the catalyst even after the fuel mix injector has disconnected, to create a thermal overload of the reactor core, so it is necessary to allow the Cold Fusion process to continue (i.e, drain the output potential) until the fuel mix runs out and the reactor shuts down safely. This system relies on the first bank of super capacitors (fully charged) to reverse the polarity of the magnetic field generated by the convertor, repelling the flow of charged particles from the catalyst towards emergency superconductive rails injected into the catalyst medium as the primary output rails are extracted from the core.
The resultant discharge of energy from the reactor is then transmitted to emergency solid-state single-use batteries usually stored in pressurised containers towards the rear of the starship. In severe cases, these batteries can be forcefully ejected from the ship by kinetic energy released by gas expansion (the process itself requires no power) in order to remove the energy from the ship entirely. In non critical emergency shutdown cases, the overflow charge can be stored by the ship's power grid, and is often used to kick-start the auxiliary power grid and provide a burst of power to transfer reliance over from the primary grid.
The reaction process creates two output products; electrical potential used by the starship, and helium. The helium is not considered a waste product and almost all Aquarian Terran starships compress the resultant helium from the reactor exhaust, which is then pumped to the primary drive system. Starships using Helium Fusion reactive drives then induce nuclear fusion on the resultant material, using powerful electromagnetic fields generated by the drive nacelles to force the resultant material outwards, creating thrust and releasing carbon into space.
Additionally, modern drive systems using this design have Recyclers in the nacelle cone that can re-capture some of the resultant carbon released by the fusion process and re-compress it into usable fuel mix for the propulsion system by means of reverse-fission (creating helium). The re-usable ratio is fairly low due to the energy released during fusion (in order to move the ship) but can increase reactor fuel to ship thrust efficiency by a few percent, enough to make a difference.
Waste helium not able to be used by the drives (example the starship is stationary) is stored in an ultra compressed (semi-solid) state in reservoirs near the rear of the warship. An amount of this compressed helium is then converted into fluid (liquid helium) coolant which is used to provide thermal regulation for a variety of onboard systems such as the electromagnetic accelerators on IMPAC weaponry.