Jump Drives are the only known means of faster than light travel. They allow spacecraft to travel through a wormhole that follows a "jump chord" between two nearby stars. Jump-1 chords connect stars up to 1 parsec apart. the chord has a well defined start and end point, usually within the inner system of its star.

The spacecraft travels in normal space to the local chord endpoint. It then engages its jump drive, and disappears from normal space. [STRIKEOUT:Approximately 5 days later the ship] It instantly emerges from jump at the chord's other endpoint, near to the destination star.

[STRIKEOUT:Travelling to and from the jump point in normal space is often the longest part of a journey.] Even with the best commonly available space drive (antimatter-catalysed fusion direct drive, capable of 1G [STRIKEOUT:continuous] thrust) it can take several days to travel between the jump point and a world in the habitable zone. Travel to the outer system often takes weeks or months.

Note: I've removed the traditional Traveller "5 days in jump". Passing through the jump wormhole is now instantaneous, from the perspective of the traveller. Ad Astra jump drive is now identical to theAlderson drive. Getting to and from the jump point takes quite long enough - having another delay during jump just seems unnecessary.

Jump Sickness

The extra-dimensional wrenching of jump space can cause mental and physical problems. The more jumps you make, the more you are exposed to jump sickness. The symptoms start out as mild headaches and trembling, but can rapidly progress to serious mental problems, physical weakness, and even death. Travellers have to ensure that they spend sufficient time in normal space, to allow the effects of jump sickness to dissipate.

Earth is located in the "Core Worlds" - a large island cluster, isolated from the Main.


Light blue: J1 routes. Dark blue: J2 routes.

Jump drives are invented on the "Dimensional Engineering" tech level track.

Tech Level 9

Although the simplest jump drives are invented at TL=10, it's possible to construct them TL=9, as long as detailed schematics are available.

Tech Level 10 (Jump-1 drives)

Tech level 10 is the highest generally available to civilization on the Main. Jump-1 ships are required to have spherical hulls.

Jump-1 drives cannot utilise jump-chords longer than about 1 parsec, even though such chords are theorised to exist. This places many stars completely out of range - such inaccessible systems are called "islands". Travel even to accessible systems might require highly convoluted multi-jump journeys. The sequence of connected systems, accessible to Jump-1 equipped starships is called the "Main".

For example (see map), in order to travel from Earth to Epsilon Eridani, a jump-1 ship would need to go via Wolf-359, Procyon, and Sirius, even though the distance is only 2 parsecs.

Since all J1 ships must enter & leave each jump chord at the singular end point, these end points have become popular locations for refuelling stations, customs inspections, naval blockades, and pirate ambushes.

Tech Level 11 (Jump-1+ drives)

The Jump-1+ drive is a development of the Jump-1 drive, with two key advantages:

  1. Increasingly sophisticated manipulation of the jump field allows J1+ ships to introduce a "bias" which can open the jump portal, even when the ship is some distance away from the chord end point. A skilled astronavigator can also influence the destination point of the ship. Not only does this enable a ship to avoid the possible dangers & inconveniences of the jump point, it can also shave vital days off the normal space travel time to the destination world.

J1+ drives can enter & leave the jump chord anywhere up to [STRIKEOUT:1] half an AU from the jump point, although more refined jumps get increasingly difficult and use more fuel.

In order to introduce the critical "bias" into the jump field, J1+ ships must not have spherical hulls. Cones, oblate spheres and even wedge shaped designs are all used.

  1. J1+ drives can access higher level (J1) harmonics, in J2 chords. This enables them to travel along a 2-parsec long jump chord, in two [STRIKEOUT:five-day] jumps. The first jump gets the ship into deep space, half way between the two stars, and the second jump completes the journey.

In order to perform this feat, the J2 chord must be completely and accurately mapped. In practice, the J2 chord can only be used if both ends are accessible by ordinary J1. So, although J1+ allows for much more convenient routes, it does not allow ships to access island worlds.

Such jumps into deep space are highly dangerous, and must be attempted only from the precise location of the jump-2 point.

Both Earth and the Esperanzan Commonwealth routinely use J1+ drives. This innovation has given them a critical advantage over the civilizations of the Main. The Xa Imperium, which controlled humanity's access to the Main for centuries has been completely bypassed in the century since the invention of J1+.

Jump-1+ drives produce much stronger jump sicknesses than normal J1 drives.

Tech level 12 (Jump-2 drives)

Finally at TL=12 the jump-2 chords can be used directly. These drives can complete the 2 parsec journey in [STRIKEOUT:only a week] one jump, and can do so safely even without a detailed survey of both end points. Island systems are trivially accessible. This opens up whole new worlds to exploration.

Procyon's various megacorporations have been researching the J2 drive for decades. The recent arrival of many talented refugees from Earth, including some brilliant uploaded minds, has enabled them to finally unlock the secret...