The mechanism used to move a starship into jumpspace and thereby take it to a predetermined destination. Jump drives are rated in terms of the distance they can carry a ship. Jump-1, for example, indicates the ability to travel 1 parsec. Jump numbers range from 1 to 6. Higher jump numbers are not possible in ordinary usage, although misjumps can carry ships over greater distances.
A standard Imperial jump drive consists of four components: a high-yield fusion power plant, an energy sink of zuchai crystals, a jump governor, and a lanthanum-doped hull grid. The jump drive pictured above is of a kind typically referred to as a "Combination Drive." Combination drives are used on relatively small ships, typically less than 1000 dtons. In this design the power plant, energy sink (jump capacitors), and jump governor are incorporated on a common skid. Units on larger ships are "dispersed units", with separate jump capacitor banks and jump governors.
The special high-yield fusion power plant within the jump drive provides the energy required to enter jumpspace. The jump drive power plant consumes huge amounts of fuel very quickly in order to charge the energy sinks with high-grade energy. Hull radiators disperse low-grade heat energy. Part of the "fuel" is used to cool the jump drive during this process. The energy produced by the jump drive's power plant is stored in an array of high-energy sinks (also termed jump capacitors).
Most Imperial ships use a network of zuchai crystals for this task. No other known sink construct can retain such high levels of energy without decomposing. However, the crystals will begin to decompose after 2 to 3 hours if not discharged. In extreme cases, they can explosively decompose and do significant damage to the ship. Zuchai crystals store a near-perfect "impression" of the energy fed into them. Very little energy is lost from leakage; however, fluctuations in energy input are mirrored in the output when the crystals are drained. Thus both quantity and quality of the charge are important.
Ships in jumpspace are completely out of communication with the normal universe, and with other ships in jumpspace. A ship can make a jump equal to or less than its jump number, but fuel requirements round up to the next even parsec. All jumps take about a week (168 hours +/- 10%). Time spent in jump has no relation to the distance traveled; a 6-parsec jump and a 3-AU micro-jump both take about a week.
Each jump requires a quantity of liquid hydrogen. A portion is converted to energy in the ship’s reactor to open the “hole” into jumpspace and to maintain the “bubble” around the ship once it enters jumpspace, a portion is used as jump-drive coolant, and a portion is vented into jumpspace as part of the process of creating the jump “bubble” which separates and insulates the ship from jumpspace. For convenience though technically inaccurate, all of this is referred to as “fuel.”
Jump fuel is consumed at the rate of 10% of the ship’s displacement tonnage per parsec jumped. In-system microjumps count as 1 parsec for consumption of fuel. Ships may attach cargo pods, other ships, and such, then use their jump drives for the volume of the entire “assembly” as long as a ship’s jump drives and fuel are sufficient for the increased volume.
The ship must be approximately 100 diameters from the nearest concentration of matter. This includes other craft, celestial bodies, and even figures in spacesuits. The attempt to eject any kind of solid matter from the jumpship at this time will almost certainly result in a misjump.
When the command is given to jump, energy from the zuchai crystals is directed into the jump governor. This device determines how the lanthanum hull grid is to be powered up. The jump governor incorporates its own computer system and is linked to the main computer for guidance and backup. With utmost precision, the governor applies initial bursts of energy in the proper sequence to the hull grid. About 20% of the power stored in the zuchai crystals is used in this way to "warm up" the grid. At this point it is still possible to abort the jump.
The next step is the transition phase, and commits the craft to the jump. The jump governor feeds the remaining 80% of the zuchai charge to the hull grid, opening the weave of jumpspace and controlling the vessel's "tumble" into the jumpspace tunnel.
By now the governor has vented just the right amount of hydrogen into the jump bubble around the vessel to isolate it from the effects of jumpspace. In normal space the hydrogen molecules would quickly disperse, or ionize due to ambient radiation. In jumpspace the hydrogen cocoon will remain around the ship, requiring very little replenishment during in the week "in the hole."
The lanthanum hull grid is built into the ship's hull. It is fairly coarse, spaced about 1 m between grid lines. During jump transition, power is routed to specific portions of the hull as directed by the jump governor. By controlling the surges to within microseconds, the vessel's tumble is controlled, which properly directs the craft through jumpspace. If an external load is attached to the hull, outside the jump grid, the computer will compensate for this, extending the bubble beyond the load. Due to the delicacy of jump drives, most ships perform routine maintenance operations on their drives after every jump.
Not all the fuel is used to produce energy to charge the jump capacitors. A large part of fuel is used to maintain the jump bubble while in J-space. Some of this is passed through the jump drive to act as a coolant prior to being vented into space.
It is possible to make another jump almost immediately (within an hour) after returning to normal space, but standard procedures require a 16 hour wait to allow for cursory drive checks and some recharging. Most commercial vessels spend a week between jumps, using the time to maneuver to a world, land, unload cargo and load new cargo, and maneuver away from the world for the next jump
Black Globes and Jump Drive
Black Globes are devices that have been reverse engineered from Ancient technology found on Knorbes (1807 SM/Regina). A black globe is an energy absorbing force field. The design of these devices is highly classified, and as far as is known, no entity other than the Imperial Navy possesses this technology. A Black Globe can absorb both kinetic and thermal energy, so as to provide a defense against hostile weapon fire. This energy must be stored somewhere. The Imperial Navy has made a practice of using jump capacitors to store this energy. If sufficient power is being absorbed by the black globe device to completely charge the capacitors, then a ship can jump without fuel. This is possible because a black globe can continue to function while in jumpspace, but without absorbing any energy. It therefore, provides the isolation from jumpspace that is typically provided by the hydrogen jump bubble. It might very well be that this was the original purpose of these devices, jump space isolation.
To use a black globe in this capacity power must be shunted from the jump capacitors by the jump governor. As might be expected a standard jump governor is incapable of providing this function. The Navy installs modified governors on ships outfitted with black globes. Excess power, which is generated by the jump drive is shunted into the black globe, alleviating the need for coolant. On Imperial Navy ships this energy is used to help maintain the black globe field. These special devices make use of a black globe by a ship using a standard jump drive system problematic. Damage to the jump drive or even a misjump are the likely results.
Some ships have excess jump capacity installed. This allows them to carry excess displacement tonnage in the form of jump tanks or externally coupled auxiliary craft. Such craft can also use external grappling units to act as tugs for vessels with damaged jump units. A ship of with any jump capacity can install excess capacity to increase jump loading. For example a 1000 dton J-2 ship with excess capacity will become a J-3 ship. But it will also be able to tow a 500 dton vessel which does not have an operational jump drive at J-2. If sufficient excess capacity is installed to "push" the vessel to a higher jump rating than J-6 no performance enhancement will occur. Modern jump drives have not yet been able to (purposely) push the J-6 barrier.