A ship's power distribution system is its lifeblood. With few exceptions every device on board a ship requires power from the ship's power distribution system. Most non-spacers take power distribution for granted. Power either comes from a planetary distribution system or sealed private fusion plant. Power flows through hidden wires often turned on and off by a voice activated computer controlled switching system. The whole system is out of sight and out of mind.
Spacers know that familiarization with the power distribution system of their ship can save their life. Systems can go from very simple to extremely complicated, but most systems have a similar design and use equivalent components. The power distribution system can usually be divided into just a few parts.
Power originates in the generators. On most TL10-12 ships this is a MHD (Magneto-Hydrodynamics) electric generator attached to the fusion plant. Larger ships and military vessels will often have multiple fusion plants, for redundancy, to allow individual plants to be taken down for maintenance. Other kinds of power generators are also possible, including solar power units, black globe generators (which act as energy absorbers) and power cells. Small RTG or NPU's are also sometimes hooked into the system as emergency backup units for sections of the system or for specific components.
Each generator will have a terminating switchboard. A switchboard allows the generator to be isolated from the distribution system. At TL 10 there are to two general classes of switching devices, active switches (often called breakers) and solid state switches. An active switch is a mechanical device that will break an electrical circuit through the action of physically separating a bus bar component from a set of contacts. This is a method that has been used for tens of thousands of years. The action can be manually induced or can be the result of activation of a superconducting motor, magnetic, gravitic, pneumatic or hydraulic device, or even synthetic muscle gel, anything that can operate a lever. A solid state switch has no moving parts. It is made of a material which can change its resistance as the result of a biasing signal. At one time only very small currents could controlled in this manner. Modern solid state switches can handle thousands of amps of current as easily as a microamp. With the bias voltage on the switch is closed and will allow the conduction of electricity. With the bias voltage off no current can flow. Switches can also be designed so that biasing the switch will prevent current from flowing, a design often used for switches used to isolated emergency power units. As long as the normal power supply is working no current will flow from the emergency device. If the normal source of power is lost the emergency source will automatically and immediately begin to provide power. More information on solid state switches is given in the Control Systems section.
High current superconducting wire with ultrahigh resistance microthin insulation provides the major conduit between switchboards. Most ships use a system called zoned distribution, which allows sections of the ship to be easily isolated in case of fire or battle damage. Systems are also segregated from each other, so that, for example, lighting or gravity units each have their own subswitchboard in each zone. Major loads, like a weapon turret, or a computer system will have their own subswitchboard (often called a power panel.) Each power panel may provide power to other power panels, so that individual components in a turret will each have their own switch.
Power distribution wire is typically run by several routes throughout the ship so that battle, collision, or meteor damage can not easily disrupt power to ship's systems. Major trunks are most commonly run on both starboard and port sides of a vessel, or along the dorsal and ventral sides of a ship.
At this tech level (TL10-12) most ships have centrally controlled distributions systems. Like the power system itself (and most ship systems) the control system is distributed throughout the ship. Each power panel and switchboard is controlled by a Local Control Processor (LCP) which communicates via a fiber optic network with the ship's computer. Each LCP has a local control panel. On many ships these panels are locked out and will respond only to a keycode, to prevent tampering. Many also have a port to allow a portable maintenance device to be plugged in. Standard encryption and password protection protocols protect access to the device.
Power from the ship's generators can be routed from a control station in engineering to the various ship's systems. Under normal conditions most of these decisions are made automatically by the ship's computer. Under combat or other emergency conditions the duty engineer can shift power from maneuvering engines to weapons or from the meson screen generator to gravity control.
Military vessels will typically have "jumper" cables to allow emergency power to be rigged from generation equipment to power loads when battle damage disrupts normal power distribution. Portable LCP's can be rigged using fiber emergency "wire" or even short range encrypted com to allow damaged systems to be brought back on line.
Emergency power systems can take many forms. Large vessels and military craft often have small backup fusion generators with an independent distribution system that operates in parallel to the standard distribution system. The purpose of this system is to provide power to vital lifesupport and damage control systems to increase the survivability of the vessel.
On a combat ship such systems are sometimes set up to power meson screens and nuclear dampers. Contragrav and maneuvering systems are generally too power hungry to be supplied by such systems. Communication systems, at least emergency communication equipment, is usually hooked into an emergency power system.
Often these same generators can be connected to the standard distribution system by locally or remotely controlled breakers to allow emergency generators to feed devices through the regular power lines. Solid state switches are almost never used for this purpose, because they can arc over under some conditions causing damage to the emergency generators.
Most small ships have very few Emergency Power Systems. Instead they use independent power systems. Independent power systems are most often rechargeable powercells which are connected to the normal power system through a double biased solid state switch. The double biased switch allows power to flow from the ship's distribution system to the powercell during normal ship's operation. The powercell cannot be overcharge, but will simply "float" at its full charge. If normal power is cut off the switch will bias in the opposite direction allowing energy to flow out of the powercell to the device.
Even large ships usually have independent power systems for gravity control, power operated doors and sometimes even lifts. Most ships have at minimum a short range communication device that has an emergency independent power system.