Jump Drive

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The Jump Drive (also known as a J-Drive) is an Interstellar Drive which allows for Faster-than-light (FTL) travel, making space travel, exploration, and colonization vastly quicker and more efficient.

Description (Specifications)

The central theory of the jump drive operation is the idea of jump space, a method of quickly traversing the long distances between stars. The basic concept of jump space is that of an alternate space. Theoretically, jump spaces are alternate universes, each only dimly understood from the standpoint of our own universe. Within jump space, different physical laws apply, making energy costs for reactions and activity different and imposing a different scale on size and distance. [1]

Jump is defined as the movement of matter and energy from one point in space (called real space', normal space or N-Space) to another point in normal space by traveling through an alternate space (called jump space or J-Space). The benefit of jump is the time required to execute a jump is relatively invariant — about one week. [1]

Jump distances are calculated in parsecs (3.27 light-years). Jump-1, for example, indicates the ability to jump one 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.[2]

Jump takes 168 hours (± 10%) to complete. The time is related to the nature of the alternate space being traveled in, and to the energy applied. Where time is a variable in travel in normal space, energy is a variable in jump space; time is a constant. Consequently, distance depends on the energy applied. [1] The duration of a jump is fixed at the instant jump begins, and depends on the specific jump space entered, the energy input into the system, and on other factors.[3]. The exact time of emergence is usually predicted by the ship's computers.

Jump drives require fuel, displacement mass, and coolant, all of which are collectively called jump fuel (liquid hydrogen being used for all three functions). [4] Fuel used for ships is hydrogen, which is available in the atmospheres of gas giants (similar to Saturn or Jupiter) or from oceans of water. [2] The amount of fuel required for a successful jump is equal to 10% of the displacement of the ship per parsec of jump distance attempted. [5]

Jump drive machinery requirements are tied to the volume of the hull and the maximum distance the drive is capable of jumping the ship. There are upper limits on how many parsecs a ship may jump based on the Technology Level of the drive. [4]

Gravity has extraordinary effects on the function of the jump drive. Jump transitions to jump space are severely scrambled within the stresses of a gravity well; the transition cannot usually take place within the stresses of a gravity well. When it does, the turbulence created by the gravity well makes the results unpredictable.[6] Entering jump space is possible anywhere but the pertubing effects of gravity make it impractical to begin a jump within a gravity field of more than certain specific limits based on size, density, and distance. The general rule of thumb is a distance of at least 100 diameters out from a world or star (including a safety margin).[1] This limit is referred to as the 100 diameter (abbreviated as 100D) limit and referred to as an absolute requirement rather than a safety guideline.

One of the benefits of the Jump Drive is controlability; jump is predictable. When known levels of energy are expended, and certain other parameters are known with precision, jump drive is accurate to less than one part per ten billion. Over a jump distance of one parsec the arrival point of a ship can be predicted within perhaps 3,000 kilometers.[1]

The laws of conservation of mass and energy continue to operate on ships which have jumped; when a ship exits jump it retains the speed and direction it had when it entered jump. Commercial ships, for safety reasons, generally reduce their velocity to zero before jumping. Military and Courier ships often enter jump at a high speed and aim for an end point of a jump which directs their vector toward their destination in the new system. Such a maneuver allows constant acceleration in the originating system, followed by constant deceleration in the destination system. [6]

Jump Drive Components

An operating jump drive requires several basic components:

Power Source
Jump uses large amounts of energy to open the barriers between normal space and jump space.
Energy Storage
Once power is generated it must be stored until the instant of Jump.
Strong Hull
The hull of a starship must be constructed to withstand normal space and the rigors of Jump Space.
Jump drives have precise power requirements which can only be met if the power is fed under computer control. The calculations needed for a jump require a high level of accuracy.

Types of Jump Drive design

Jump Bubble
A Jump Bubble creates a spherical, or egg-shaped oblate spheroid, field around the ship and centered on the jump drive. Jump Bubble is the standard for generating a Jump Field; it does not interfere with armor and produces a standard jump flash. Jump Bubble allows a ship to vary its effective tonnage from mission to mission (which makes Drop Tanks and Variable Jump Container Ships possible). [7]
Jump Grid
A closely-conforming Jump Grid channels jump energy through a mesh of conduits and cables embedded in the hull. Jump Grid allows a reduced safe jump distance, making it possible for a ship to jump closer to a gravity source. On the other hand, the Jump Grid reduces the strength of armor and increases telltale jump flash. [7]

Alternate Energy Sources

There are two other sources of energy sufficient to power the jump drive:

  • Collectors, a TL–14 technology, which can power the jump drive but not the rest of a ship's systems. Collectors are charged by opening their canopies to space for about one week.
  • Antimatter Plant, a TL–19 technology. Antimatter power plants use antimatter as a fuel source and capable of supplying the power required for jump drives without the huge volumes of Hydrogen fuel required for the fusion power plants.

Jump Tapes

Jump navigation requires some very advanced mathematics and a great deal of computer "number crunching". Every jump is different and a great deal of careful planning and computation has to be done before the jump drive can be turned on. [8]

During the First Imperium the Vilani developed and widely used a computational short-cut. A jump tape is designed for one origin-destination pair of star system. It contains some pre-computed parameters that apply to any jump from the origin system to the destination system. Even with a jump tape some computational work must still be done, but the work is much easier for the navigator. [8]

A jump tape is a specialized version of the Jump Program tuned for one specific pair of systems. The use of jump tapes has declined to almost nothing by the end of Third Imperium and vanishes thereafter.

Jump Drive Operation

The typical jump begins on a world surface or orbit when the ship prepares to leave. The ship leaves the world and proceeds to a point more than 100 diameters out. Along the way the astrogator has been preparing for jump using the computer. A jump destination has been selected. The computer is fed the coordinates and controlling data. [3]

Once the astrogrator knows which star system, they select a specific destination based on one of several different principles: central star, mainworld, some other world (or body), an orbit within a system, a range band from a world, or an arbitrary Point Alpha. [9]

The starting and ending points (in Real Space) are connected by a Courseline (specifically for Jump Drives called a Jumpline): a straight line course traced in Real Space. A Course cannot be changed once begun. A straight line course cannot pass through a bubble surrounding a mass of any appreciable size (within Safe Jump Distance of a gravity source larger than the ship; gravity sources smaller than the ship have no effect). [10]

When the jump drive is activated a large store of fuel is fed through the ship's power plant to create the energy necessary. In a few minutes the jump drive capacitors have been charged to capacity. Under computer control the energy is then fed into the appropriate sections of the jump drive and jump begins. [3]

A ship entering Jump Space emits an active flash of broad spectrum energy. The ship’s gravitational signature vanishes from any sensors. Entry Flash is subject to lightspeed and lasts about a minute at peak strength. [11]. With good analysis of the sensor information, the burst reveals the approximate size of the ship, and the time it left the system, and the direction of the jump (but not its distance). [12]

During the week in jump the responsiblities of the crew are directed toward maintaining life support within the ship, repair and maintenance of some ship systems, and care of the passengers.

At the end of the week in jump the ship naturally preciptated out of jump space and into normal space. Exit (also called Breakout, or Precipitation, or Transition) is the transition from Jump Space back to real space. The field sustaining the Jump effect collapses and the ship transitions to Real Space. [13]

Exit from Jump occurs without any specific input or control activity from the ship. Just before Exit, the jump drive shows signs of the jump ending (through decreased energy levels, increased vibration levels, and other readings). Rumblings occur about one hour before Exit; their absence is a sign that Breakout will be delayed; their early occurrence is a sign that Breakout will be premature.[13]

A ship leaving Jump Space emits an active flash of broad spectrum energy which is slightly less intense than an Entry Flash. The ship’s gravitational signature appears on any sensors. Exit Flash is subject to lightspeed and lasts about a minute at peak strength. [13] The energy pulse can reveal the approximate size of the ship and the time it entered the system.[12]

Because of the delicacy of jump drives, most ships perform maintenance operations on their drives after every jump. It is possible for a ship to make another jump almost immediately (within an hour) after returning to normal space, but standard procedures call for at least a 16 hour wait to allow cursory drive checks and some recharging.[2]


Any jump of less than one parsec is considered a microjump. Usually these are used to travel to distant parts within a system. For example between the two stars in a distant binary. The Terrans used the practice of microjumps within their own system after inventing the jump drive. A microjump has the same power and fuel requirements as a normal 1 parsec jump.

Synchronized Jumps

A military fleet maneuver the synchronized jump overcomes the problem of having a fleet jump into a system and ships exit jump over the span of several hours to a day or more. The process requires all the ships in the fleet calculate their jump simultaneously, and jump at the same time. When done correctly the ships in the fleet all arrive within two or three hours of each other.

Jump point masking

Jump point masking occurs when the 100D limit of another astronomical body blocks (masks) the jump point of the main world. If the jump line intercepts the 100D limit the ship would be precipitated out of jumpspace well short of the destination. Astrogators must plot a course which just skims the 100D limit of these other bodies and usually requires significant additional flight time in Normal space to get to a clear jump point.

Deep Space Jumps

The mathematics of jump navigation is much simpler when there is a large mass, a star or large planet, in normal space close to each end of the jump. A Deep space jump is one where one or both ends of the jump is in deep interstellar space, far away from from any such massive object. The Vilani during the First Imperium never managed to discover the process of safely plotting deep space jumps. It was only late in the Second Imperium era the safe navigational procedures were developed for deep space jumping.

Interstellar space is not completely empty. Astromomers may be able to find massive objects even in the empty spaces of interstellar space; rogue planets, large comets, or cool brown dwarf stars. When found and occupied, these object are known as jump points or calibration points.

Calibration points are located in deep interstellar space, light-years from the nearest significant body. At the simplest level they consist of a natural source of hydrogen, typically a comet nucleus or other icy body, but rogue planets are rarely found and used. These natural calibration points are discovered and exploited. [14]


The most interesting event which can occur is the misjump, in which the jump drive malfunctions. At the instant of jump, a jump drive which is: a) within 100 diameters of a world or star, b) operating on unrefined fuel, or c) operating without annual maintenance may malfunction, resulting in a jump of random length and direction. A misjump involves a considerable random jump.[15]

The most common case of a failed jump attempt results in a simple failure. The fuel required for the jump is expended but the transition to jump space does not occur, and the ship remains in normal space.

Failure of the Astrogator to correctly calculate their Jumpline may result in hitting a blockage, the gravity limit of a world short of their destination, or ending up in the destination system at a location much further away from their indented destination. This is known as a Misexit.

In rare cases of bad Jumpline calculations the ship exits near a solitary world, comet, or odd chunk of rock in deep space between major systems. This is known as a blocked jumpline, or blocking.

A misjump occurs when the drive fails during the initial jump process, or when a jump is failed because it is too close to another object. A misjump can take the form of no jump, a failed jump (the ship enters jumpspace, but emerges after about a week in the same place it started), or a misdirected jump, where the ship emerges from jumpspace in an unintended location, usually far in distance and location from the intended exit point (this result is different from a misexit). A failed jump and a misdirected jump are indistinguishable before the ship exits jumpspace. [12]

In the worst case the jump space entered is one that collapsed in the brief microseconds after the Big Bang — entering a jump space that is effectively a singularity destroys the ship immediately. [16]

History & Background (Dossier)

Jump-Field-Sign-T5-Fan-Andy-Bigwood 06-Oct-2019a.jpg

The Jump Drive was first discovered by the Ancients more than 300,000 years ago. With it they explored the greater part of Charted Space. At the conclusion of the Final War, the Ancients' jump technology was lost, although intact (damaged) artifacts were found later on, and reverse-engineered to create jump drives of a more primitive nature than their source technology.

Jump Drive Technology Timeline

These are some of the important dates recorded as to when certain sophont cultures have acquired the jump drive:

  • Please note that not all dates may be entirely accurate.
Jump Drive Technology Timeline
(Imperial Dates)
Date Culture Remarks
c. -350,000 * Droyne Droyne achieve TL–10 on their homeworld; although Jump drive is often available at that level, they have not yet discovered it. [17]
c. -320,000 * Ancients The Ancients inhabit the general region of the Spinward Marches and explore all of Charted Space. [18]
-9240 Geonee Geonee of Shiwonee (Massilia 1430) discover a derelict Ancient starship in a planetoid belt in the Shiwonee system. From this they reverse engineer a Jump drive and explore the Stenardee Cluster. [19]
-9235 Vilani The Vilani of Vland (Vland 1717) discovers the Jump-1 drive. [20]
c. -9000 Vilani, Geonee Vilani explorers contact the Geonee, and discover that they have Jump technology not of Vilani origin. [21]
c. -7000 Droyne Droyne first observed using Jump technology; new colonies established, including Vanejen (Spinward Marches 3119). [22]
-6150 S'mrii S'mrii of Mimu (Dagudashaag 0208) acquire jump technology from Vilani-influenced traders. [23]
-5723 Vegan Vegans of Muan Gwi (Solomani Rim 1717) acquire jump drive technology from the Geonee, a Vilani-influenced Human minor race. [24]
-5583 Ziadd A Ziadd (of Zeda (Dagudashaag 0721)) ship performs the first in-system jump, copying the recovered design from wrecked Vilani scouts. [25]
-5450 Luriani Luriani receive Jump technology from an unknown race. [26][27]
-5435 Luriani A Sharurshid fleet discovers that the Luriani have acquired Jump technology. The Vilani launch an investigation to discover who gave Jump technology to the Luriani. [28]
-5430 Vilani Vilani develop the first known Jump-2 drive, but keep the technology secret from non-Vilani trading partners; Vilani core worlds reach TL–11. [29]
-5415 Zhodani The Zhodani of Zhdant (Zhodane 2719) develop a Jump-1 drive while working on fusion power sources in their asteroid belt. [30]
-4698 Hiver The Hiver of Guaran (Ricenden 0827) develop inferior jump-1 drive, which would melt down to slag after a few uses (no more than ten). [31]
-4212 Hiver Hiver scientists develop the standard jump-1 drive. [32]
-4142 K'kree K'kree of Kirur (Ruupiin 1315) begin experimenting with jump-1 capable starships. [33]
-3810 Vargr Vargr of Lair (Provence 2402) discover jump-1 drive on during the Colonial Rebellion. [34]
c-2800 Zhodani, Vargr Zhodani encounter the Vargr in Gvurrdon sector, accidentally giving them more advanced jump technology. [35]
-2431 Solomani Terrans of Terra (Solomani Rim 1827) develop jump drive. They use jump-1 drive solely for in-system use, due to the nearest star (Alpha Centauri) being jump-2 distance. [36]
-2398 Solomani Terrans develop jump-2 drives; Terran Confederation overall at TL–11.[37]
c-2285 Solomani Terrans develop jump-3 drive and early meson weapons (early TL-12). [38]
-1999 Aslan Yerlyaruiwo and Khaukheairl clans cooperate to develop jump-1 drive for Aslan on Kusyu (Dark Nebula 1226); beginning of Aslan Era of Expansion.[39][40]
c-1400 Aslan Aslan at TL–11 (jump-2). [41]

See Also

Please refer to the following AAB Library Data for more information:

Jump Space Drives:

References & Contributors (Sources)

This article has metadata.
This list of sources was used by the Traveller Wiki Editorial Team and individual contributors to compose this article. Copyrighted material is used under license from Far Future Enterprises or by permission of the author. The page history lists all of the contributions.
  1. 1.0 1.1 1.2 1.3 1.4 Loren Wiseman. "Jumpspace." Journal of the Travellers' Aid Society 24 (1985): 34.
  2. 2.0 2.1 2.2 Marc MillerFrank ChadwickJohn Harshman. High Guard (Game Designers Workshop, 1980), 17.
  3. 3.0 3.1 3.2 Loren Wiseman. "Jumpspace." Journal of the Travellers' Aid Society 24 (1985): 36.
  4. 4.0 4.1 Frank ChadwickDave Nilsen. Fire, Fusion, & Steel (Game Designers Workshop, 1994), 42.
  5. David GoldenGuy Garnett. Fire, Fusion & Steel (Imperium Games, 1997), 12.
  6. 6.0 6.1 Loren Wiseman. "Jumpspace." Journal of the Travellers' Aid Society 24 (1985): 35.
  7. 7.0 7.1 Marc MillerRobert EaglestoneDon McKinney. Starships (Far Future Enterprises, 2019), 73.
  8. 8.0 8.1 Paul DryeLoren WisemanJon F. Zeigler. Interstellar Wars (Steve Jackson Games, 2006), 170.
  9. Marc MillerRobert EaglestoneDon McKinney. Starships (Far Future Enterprises, 2019), 117.
  10. Marc MillerRobert EaglestoneDon McKinney. Starships (Far Future Enterprises, 2019), 112.
  11. Marc MillerRobert EaglestoneDon McKinney. Starships (Far Future Enterprises, 2019), 118.
  12. 12.0 12.1 12.2 Loren Wiseman. GURPS Traveller Core Rules (Steve Jackson Games, 1998), 121.
  13. 13.0 13.1 13.2 Marc MillerRobert EaglestoneDon McKinney. Starships (Far Future Enterprises, 2019), 119.
  14. Dave Nilsen. The Regency Sourcebook (Game Designers Workshop, 1995), 76.
  15. Marc Miller. Starships (Game Designers Workshop, 1977), 4.
  16. Loren Wiseman. "Jumpspace." Journal of the Travellers' Aid Society 24 (1985): 37.
  17. Marc Miller. Secret of the Ancients (Game Designers Workshop, 1984), 42.
  18. Marc Miller. The Kinunir (Game Designers Workshop, 1979), 38.
  19. Loren WisemanJon F. Zeigler. Humaniti (Steve Jackson Games, 2003), 68.
  20. John HarshmanMarc MillerLoren Wiseman. Library Data (A-M) (Game Designers Workshop, 1981), 27.
  21. Gary L. Thomas. The Travellers' Digest 11 (Digest Group Publications, 1989), 8.
  22. Marc Miller. Research Station Gamma (Game Designers Workshop, 1980), 43.
  23. Jae CampbellLeighton Piper. Signal-GK 01 (Signal-GK, 1989), 58.
  24. David L. Pulver. Solomani Rim (Mongoose Publishing, 2012), 3.
  25. Jae Campbell. Signal-GK 09 (Signal-GK, 1994), 11.
  26. Martin DoughertyHunter Gordon. Gateway to Destiny (QuikLink Interactive, 2004), 9.
  27. Andrea Vallance. Luriani (Mongoose Publishing, 2012), 19.
  28. Martin DoughertyHunter Gordon. Gateway to Destiny (QuikLink Interactive, 2004), 9.
  29. Gary L. Thomas. The Travellers' Digest 05 (Digest Group Publications, 1986), 49.
  30. Marc Miller. Expedition to Zhodane (Game Designers Workshop, 1981), 41.
  31. J. Andrew KeithMarc W. MillerLoren Wiseman. Hivers (Game Designers Workshop, 1986), 17.
  32. J. Andrew KeithMarc W. MillerLoren Wiseman. Hivers (Game Designers Workshop, 1986), 17.
  33. John HarshmanMarc MillerLoren Wiseman. Library Data (N-Z) (Game Designers Workshop, 1982), 26.
  34. J. Andrew KeithMarc MillerJohn Harshman. Vargr (Game Designers Workshop, 1984), 4.
  35. Don McKinney. Zhodani (Mongoose Publishing, 2011), 67.
  36. John HarshmanMarc Miller. Solomani (Game Designers Workshop, 1986), 4,18.
  37. Marc Miller. Referee's Companion (Game Designers Workshop, 1988), 34.
  38. Jon F. Zeigler. Rim of Fire (Steve Jackson Games, 2000), 43.
  39. J. Andrew KeithMarc MillerJohn Harshman. Aslan (Game Designers Workshop, 1984), 3,35.
  40. Peter G. CelellaJames Holden. Solomani & Aslan (Digest Group Publications, 1991), 14,15.
  41. Gareth Hanrahan. Aslan (Mongoose Publishing, 2009), 58.

Jump Drive Travel Time Table

Jump Drive (FTL) Estimated Travel Times
Distance: Jump-1 Jump-2 Jump-3 Jump-4 Jump-5 Jump-6
54 parsecs

(1 sector)

54 weeks

1 year

27 weeks

½ year

18 weeks

4.5 months

14 weeks

3.5 months

11 weeks

2.75 months

9 weeks

2.25 months

108 parsecs

(2 sectors)

108 weeks

2 years

54 weeks

1 year

36 weeks

9 months

27 weeks

6.75 months

22 weeks

5.5 months

18 weeks

4.5 months

162 parsecs

(3 sectors)

162 weeks

3 years

81 weeks

1.5 years

54 weeks

1 year

41 weeks

10.25 months

33 weeks

8.25 months

27 weeks

6.75 months

216 parsecs

(4 sectors)

216 weeks

4 years

108 weeks

2 years

72 weeks

1.5 years

62 weeks

15.5 months

44 weeks

11 months

36 weeks

9 months

270 parsecs

(5 sectors)

270 weeks

5 years

135 weeks

2.5 years

90 weeks

22.5 months

68 weeks

17 months

54 weeks

1 year

45 weeks

11.25 months

Jump Drive Travel Time Constants
# Note Remarks
1. Jump Duration: 1 week (168 hours +/- 10% variance)
2. Jump Velocity: 170.0c (+/- 20.0c variance)
3. Month (Time): 4 weeks (28 days by Imperial calendar)
4. Assumptions: (Top efficiency, near-instantaneous refueling, no crew fatigue, etc.)
5. Sector (Area): (size of a sector in 2D parsecs x & y coordinates)
6. Galaxy (Area): Milky Way Galaxy (estimated 55 kiloparsecs in diameter) (…over 1,000 years at J-1)