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Jump is a fictional technology used by spacecraft in science fiction author C. J. Cherryh's Alliance-Union universe to travel faster-than-light (FTL). Jump can also be a verb, and is the act of travelling FTL using jump technology.

Development of FTL travelEdit

In 2220, Estelle Bok, a physicist investigating FTL travel, arrived at Cyteen Station with a group of immigrants. She continued her research there and achieved a major breakthrough in 2230 when she found a loophole allowing the Einsteinian limit to be breached. This enabled her to derive the Bok Equation, the theoretical basis for FTL travel. Cyteen management immediately initiated a program to apply Bok's principle to ship drives, and in 2248 the first FTL probe, Aurora, set out from Cyteen Station to Mariner Station, 6.8 light years [1] away, and back.

As news of the FTL technology spread, ships began arriving at Cyteen Station requesting FTL conversions. However, it was not until 2261 that Earth learnt of these developments and attached top priority to acquiring the new technology. When the technology finally reached Pell Station in 2262, Earth began studying it, and launched its first FTL warship in 2266.

Mechanics of jumpEdit

In the Alliance-Union universe faster-than-light (FTL) ships have two major drive systems, slower-than-light (STL) thrusters and FTL jump engines. The jump engines comprise vanes that are attached to the outside of the ship. When the vanes are pulsed, they generate gravity waves which create a field, or "bubble", around the ship that pulls it (and anything else in the field) along the interface between realspace (Einsteinian space) and hyperspace (jumpspace).

Jump takes place between two massive objects, called jump-points, which are generally stars or dark matter sufficiently massive enough to make "pockmarks" in hyperspace. Prior to jumping, the ship's navigators calculate an outbound vector, targeting the destination jump-point with direction and speed. The ship accelerates along this vector with a long STL burn until it is clear of the present jump-point's gravity well and the requisite velocity is reached. The jump engines are then engaged and the ship enters the interface between realspace and hyperspace. In this quasi-state of being half-in and half-out of hyperspace the ship is drawn along the interface to the nearest gravity well on the outbound vector, the destination jump-point. Here it re-enters realspace, travelling at the same speed and direction it entered the interface. Back in normal space the ship dumps velocity by cycling its vanes to graze the interface before the STL thrusters take over. It is possible to pass through several jump-points without slowing down, but this is risky as it can cause the ship's velocity to become uncontrollable.

Calculating the correct outbound vector prior to jumping is crucial, and the mass of the ship and its load have to be factored in. The more momentum the ship has in jumpspace, the closer to the destination jump-point it will re-appear. Too much momentum could result in it dropping into realspace too close to, or even inside, the destination mass. The ship can also "overshoot" the jump-point with too much momentum and will then drift through hyperspace until a sufficiently massive object is encountered which could drop it "anywhere" in realspace. Not enough momentum, or targeting an object not massive enough to pull the ship out of hyperspace will also leave the ship drifting. A ship's power-to-mass is significant, allowing an unloaded ship to travel faster in jumpspace than a loaded ship of similar design, even enabling the former to "over-jump" the latter. Warships have high power-to-mass ratios, making them fast despite their size. If another ship happens to be at your ship's re-entry point, both ships will be destroyed.

In theory it is possible to jump "any" distance, but the practical limit is about ten light-years. Calculating trajectories beyond a certain distance become too unreliable because of the unpredictable nature of n-dimensional hyperspace. Over short distances the calculation discrepancies are negligible, but over longer distances, the errors multiply. In addition, there is the interference of nearby stars that are likely to alter the intended trajectory.

Contrary to other "jump technologies", jump in the Alliance-Union universe is not instantaneous. However, just how long a ship actually spends in jumpspace is difficult to gauge because jump-time (also called "no-time") is not real-time. But sufficient time does elapse for minor injuries on "tranked" (tranquilized) crew's bodies to heal and for "night-walkers" to move about the ship. Typically subjective time aboard a ship in jumpspace can vary from a few days to several weeks. In the novel Finity's End, during jump, that ship (and its crew) experience approximately two weeks of "no time" while just over 4 weeks pass for the rest of the universe.


If a ship fails to return to realspace, whether through pilot error, or some other failing, it remains in hyperspace, lost permanently. Only one of Cherryh's novels, Port Eternity (1982), deals with this, although it is unclear when in the Alliance-Union timeline it takes place, except that it is after the establishment of the Alliance and Union and occurs in Union-side space.

The KnnnEdit

The technologically advanced (and enigmatic) Knnn from Cherryh's Compact space are the only known species that can change a ship's vector during jump. Knnn ships also have the ability to jump together in synchronisation, sometimes up to a dozen at a time. A single jump-field is created around all the ships and they are pulled into hyperspace as a unit. The Knnn sometimes use this ability to transport ships of other species through jumpspace. They cluster around an unsuspecting vessel, create a single jump-field and haul the ship with them.

Effects of jumpEdit

Time dilationEdit

One of the relativistic effects of jump is time dilation, that is, time slows down for objects in motion relative to those at rest, and the faster the object moves, the more pronounced the effect. Crew that spend much of their time aboard spaceships that jump frequently age slower than space station personnel and this gives rise to the notion of "ship-time" and "station-time" (or "Universal time"). A navigator on a merchant ship may be 30-years old ship-time, but considerably older in terms of station-time. To resolve this dilemma, a person's "true age" is calculated with medical computers using parameters such as what ships he or she has been on, what routes these ships took, and what load they carried.


Jump is a disorientating experience for those using it, although the degree of discomfort varies depending on the species. Most humans experience extreme psychological distress, potentially resulting in madness, and need to "trank down" or tranquilize themselves prior to each jump. The oxygen-breathing species native to Cherryh's Compact space, with the exception of the Stsho, do not require drugs during jump as their bodies naturally enter a deep sleep. However, some species in the Alliance-Union universe can function normally during jump and require little to no assistance.

For humans, the jump from realspace to hyperspace is perceived as the ship (and themselves) coming apart, and it became necessary to develop "trank-packs" that administer tranquilizers to the crews of FTL ships prior to jumping. Tranking down puts the crew into a quasi-sleep state for the duration of the jump, leaving them only marginally aware of their surroundings. "Nutri-packs" were also developed to provide essential sustenance for the crew upon waking after system re-entry, as jumps can sometimes last up to a few weeks of "no-time", leaving them extremely hungry, thirsty and nauseated.

Ships with tranked crews are always at their most vulnerable when they drop back into realspace. The crew is groggy and slow reacting to the current status of their ship and the possible presence of other ships in the vicinity.


A "night-walker" is someone from a species that normally sleep during jump (naturally or via trank) who have learnt to function normally while in jump. They embrace this alternate reality, with all its unworldly shapes and sounds, and believe there are new "worlds" to be found out there. New jump-points and routes are often discovered by night-walkers. Notable night-walkers in Cherryh's Alliance-Union universe include Chur Anify (hani) in Chanur's Homecoming (1986), Hallan Meras (hani) in Chanur's Legacy (1992), and Capella (human) in Tripoint (1994).

Night-walkers who are also navigators, like Capella, are valued because they are awake on re-entry into realspace and can therefore react quicker than crew still recovering from trank. They can also sometimes "hear" potential problems while in hyperspace, for example the presence of an enemy ship. However, they can't navigate the ship, as their computers do not work in hyperspace. But aside from just listening, they sometimes amuse themselves by wandering around the ship and entering tranked crewmates' rooms.

See alsoEdit


  • Cherryh, C. J. The Pride of Chanur, DAW Books, 1981.
  • Cherryh, C. J. Tripoint, Warner Aspect, 1994.

External linksEdit

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