There is a common misconception in many space and science fiction genre pieces. The misconception is that the ship\'s engines also produce power. This works with internal combustion engines, henceforth refereed to as ICE, since the engine also turns an electric generator and has a battery system. Chemical combustion engines, IE rockets and missiles, do not have this electrical generation capability, and the more advanced engines generally consume power than create it.
In the age of Space Colonization, the most common type of engine is the ion engine, which consumes electricity produced by the power core to create a controlled weak nuclear reaction, producing thrust. While the material component required to power an ion engine is neglible, the power requirements are not. Thus the power core is considered the most important part of the ship, followed by the life containment and support systems, defensive systems, and the onboard computer.
Full Item Description
The Fissionable Engine contains a large core of radioactive material. The most common military power cores are fueled by rods of Actinoids like Uranium and Plutonium. While the civilian counterparts are fueled with less volatile and cheaper to produce and extract Lanthanides such as Cesium and Praseodymium.
The heart of the core is the reaction chamber where unshielded rods heat a liquid shell of mercury to high temperature. The thermodynamics of the liquid then force the hot expanding mercury through a generator coil producing electricity. Cooler mercury is drawn in through a coupling valve, and does double duty as coolant as well. Surrounding this core of fissionable material is a thick shell of layered lead, steel, and boron plating to protect the rest of the ship from the radiation produced by the core.
Most Fissionable cores are very heavy, often composing roughly 45% of the host ship\'s mass to provide power enough to run the required systems at safe levels. While these cores are very reliable, often operating for decades without incident, they are very heavy and changing out fissionable materials in the core can be dangerous, and a full core swap is a major undertaking. Plus the ship runs the danger of a core meltdown that while might not end in an atomic explosion, will at the very least irradiate the ship.
History
Following the end of the Pan-Solar war (2362 - 2364), travel between the planets of the Solar System entered a 175 year lull with only a scattered handful of prewar ships surviving with functional ion engines. The rest of the ships of that time were powered by solar panels, and banks of thick rockets. The push back into space following the Consolidation War on Earth (2531 - 2539) required the Terran Hegemony to reacquire power sources previously lost in the Pan-Solar War. The fissionable core was the first non-chemical core recovered, and within ten years the Terran Hegemon commanded a flotilla of seventy interplanetary capable warships outfitted with conventional, atomic, and chemical rockets as well as primitive beam and particle weapons.
Following the sweep up of the Terran Sol system, the Hegemony recovered many technological secrets from the ruins of advanced engineering labs and facilities abandoned at the Jovian/Galilean Research facilities as well as the Martian shipyards that had survived the previous wars largely undamaged by conventional weaponry. The labs contained information and mock ups of theoretical fusion, hybrid-fusion, and other power cores. It would take a number of decades of government backed and private research and development before this information would evolve into something usable. In that time, the Fissionable Core went through a number of modifications to enhance it\'s power output, reduce it\'s weight, and increase it\'s safety rating.
The End of the Fissionable Age
In 2592 the first Fusion Core was successfully tested at Mars, heralding the end of the 53 year reign of the Fissionable Engine. During that time, the Fissionable engine had decreased to 39% of a ship\'s total mass and power output had increased by nearly 400%. The final generation of Fissionable cores would stay in production for another sixty years during the slow proliferation of the Fusion Core, and many of the fusion core equipped ships carried a smaller back-up fissionable core in case of fusion core failure.
By 2652, the civilian sector and bulk cargo sectors had reliable and available Fusion Cores, rendering the Fissionable Cores obsolete. Despite this, many ships with said cores are still in service in secondary roles and in the private sector.
The Fate of Fission
The Fissionable Core has a unique position in the history of the Terran Hegemony, as it was on fission powered flames that the Solar System was consolidated and the first 13 colonies were founded. While Fusion and hybrid-fusion cores would eventually replace the Fissionable core, it is this more primitive power source seen in the space frontier sagas and epics, and thusly, a key component in romanticized space frontier dramas and sagas.