By Michael Mikesh

Traveller players familiar with the High Guard ship generation tables are probably aware of the relationship between tech level and jump drive technology. Beginning at tech 11, the maximum permissible jump-number rises one for one until jump-6 at tech 15. By projection, some have assumed that jump-7 drives can be produced at tech 16.

However, the official Traveller rules say that this is not so. Drives superior to jump-6 probably will not become available until tech-20+, and even then the drive might not be dependent on the same principles as the jump drive. That is reaffirmed in the Grand Census book from Digest Group, page 37.

Despite this, Marc Miller hints in his article, Jumpspace" in JTAS #24, that higher jump numbers may be possible by a proper understanding of the misjump. This suggests that a jump-36 drive is possible. Since the misjump phenomenon was know since tech-9, how much more advanced must technology be before "a proper understanding" can be achieved? About five tech levels seems like a reasonable upper limit. Yet, it apparently evades scientists even at tech-15.

In the interest of adhering to the game designer's intent and to provide a reasonable advancement in star travel technology leading to Ancient science, I'd like to suggest the use of "jump gates". The jump gate is an enormous ring, similar to star gates described in science-fiction games and literature. I treat it as a means of inserting starships into jump spaces otherwise inaccessible to those using conventional drives alone (except by accident). This is not a starship drive in the sense that it is not internal to a ship. And it does depend upon improved understanding of the misjump phenomenon.


The theory of jump space I subscribe to is that there are alternate universes, each possessing a quantum energy level corresponding to a jump number. Each of the 36 jump levels are collected into groups of 6, each called a "tier". Levels 1-6 are the first tier and levels 7-12 make up the second, and so on. Each tier is tangent to the tier immediately above and below, but not to non-adjacent tiers (i.e. tier 1 is not adjacent to tier 3, and tier 4 is not adjacent to tier 6).

Normal space (effectively tier 0) is tangent to the first tier, making it accessible to starships. But a jump 7 drive cannot make contact with a level-7 jump space as that is on the second tier (and tier 2 is not adjacent to tier 0). An attempt to do so will always result in a misjump (i.e. insertion into an arbitrary jump space). In theory, a starship can make into the first tier, then transfer to the second. In practice, this multi-stage method makes navigation impossible, carrying the ship in any direction.

A jump gate, however, does not travel through jump space, but remains firmly attached to normal space. By applying the enormous power of its own mechanism to a focus, it can open a "hole" in normal space to allow the passage of other ships into jumpspace. At tech levels above 15, it can sequentially open holes through holes which penetrate upwards through the tiers. This method eliminates the inherent problems of using a conventional drive configuration, making predictable flight beyond jump-6 possible.


Research stations have long experimented with applying jump mechanisms in exotic ways. But the technology to build reasonably practical jump gates accessing the first tier does not even begin until techn-15. At this level, any starship can be inserted into a jump space as high as jump-6. Tech-16 gates can access the second tier (i.e. up to a jump 12), and a new tier may be reached with each higher tech level until jump 36 at tech-20.

Despite the greater ranges, star flight via a jump gates is much the same as a conventional jump. One of the main differences, however, is that the starship need only expend fuel and energy as if it were travelling at jump-1.

The jump gate itself takes care of the rest. It opens the breach between normal and jump space, probes the many tiers for the right path, and launches the ship at the right vector and at the correct energy levels. While it is true that the gate has taken over from the starship the labor of creating the beach, the starship must still go through the motions of opening a breach to assure safe and harmonious insertion.

As far as fuel expenditure is concerned, the greater share of the burden is on the jump gate. To determine what it requires, treat the quantity as the same as for the ship if it were possible to jump the distance on its own. To illustrate, let us use a 100 ton free trader going 5 parsecs. Ten percent of the ship jump number must be allocated to jump fuel. This means the equivalent of 50% of the 100 ton ship, or 50 tons of fuel. The gate must now expend 50 tons of fuel to safely send the free trader on a jump-5 path. The trader, however, must still expend 10 tons of fuel for basic jump drive operation (which is the jump-1 needed for the ship to enter jumpspace).

Jump gates can work in reverse just as well. A starship, parsecs away, may jump to the coordinates of the jump gate using only jump-1 energy. At the end of the week in flight, assuming advanced coordinates, he gate is then opened to the starship and it appears.

This defies institution since it seems the starship would be committed to a misjump the moment it entered into jumpspace. However, I assume that jump flight is described by principles similar to quantum mechanics rather than conventional physics. Since it is remotely possible for the starship to misjump to the physical location of the jump gate, proper activation of the gate makes it a certainty. In a sense, the ship exists on all possible flight paths until the instant it will break out of jump space. The gate will make the selection.

Arrival time is also oddly influenced. As explained in Miller's article, "Jumpspace" , flight time for a starship can vary by 10%. When a receiving gate is involved, arrival time is precisely when the gate opens. This must occur within 7% of the expected arrival time to assure capture. Between 7% and 10%, there's only a 50% chance of capture.

Strangely, gate theory says that the arrival of the starship is not governed by the time the gate opens. Instead, the time the gate opens is dictated by the arrival of the starship. This seemingly opens a door to paradox.

If some fault in the jump gate causes it to fail to capture an incoming starship, it is possible for the starship to have already precipitated out of jump space as a result of misjump before the fault occurred. If the misjumped ship happened to arrive at the gate, it could perhaps prevent the failure that caused the misjump.

However, the science of jump gates is the science of "controlled misjumps". The mathematics shows a negative probability of misjumping close enough to the gate for this to happen, so such a paradox can never occur.


Tech 15 jump gates are constructed under Book 5, "High Guard". Beyond tech 15, you should supplement those rules, either with your own or some other source. I prefer to use Joseph Italiano's article, "High Technology Starships (16 to 30)", augmented by the "Grand Census" tech tables. Italiano's article was run in Multiverse #2, Spring 1984 (Australian). If you correspond with the more serious Traveller fans, you might be able to acquire a copy through them.

The jump gate is usually a ring 30 kilometers in radius. Though narrow, it displaces several million tons. This radius will allow the gate to safely accommodate a vessel displacing one million tons. Increasing the radius raises the limited by the cube (i.e. a 60 kilometer radius allows an 8 million ton ship to pass through). The ring is treated as a dispersed structure, and is rotated to add rigidity.

The gate mechanism itself displaces 100,000 tons times the jump range of the gate. The cost is the same per ton as for jump drives.

A "maneuver" drive is required. As Miller also pointed out, ships retain the speed and direction they had before the jump. A disaster is possible is ships emerge from a gate with unchecked velocities. A device called a "Q-catch" is used to translate the incoming vessel's momentum to the mass of the ring. In effect, the ship will be at rest with respect to the gat when it emerges. The Q-catch is actually a special application of maneuver thruster technology. It's treated as a regular maneuver drive under High Guard rules. The Q-catch can also be applied to correct the position of the gate in space. However, 1G drives aren't needed for this purpose; a 0.1G drive should be adequate (treat as a zero in the USP).

At a minimum, the power plant must be able to generate energy points equal to the mass of the gate mechanism. The weekly shipping capacity of a jump gate is: 100 parsec tons / Energy Points, or no less than 60,000,000 parsec-tons for a jump- 6 gate. (To determine how much of this weekly capacity of the gate a particular ship will consume, multiply the ship's tonnage by the parsec distance to its destination.) The capacity can be increased correspondingly simply by adding to the power plant.

It is likely that a small fleet of fuel skimmers will constantly be taking liquid hydrogen (L-Hyd) to the gate. Technically, there might be little need for the gate to have fuel tanks. However, a large store of fuel has benefit (particularly if the ring is under long term siege of if it is used as a port for servicing ships). Tankage is equal to 10 times the mass of the gate mechanism is in keeping with High Guard. Of course, when anti-matter becomes available, tankage is substantially reduced.

It is possible for single-purpose jump-6 gates to use model 7 computers. If the gate ships are no more than 100 kilotons, a model 6 might even be used. However, a model 8 computer is the minimum for a general use gate with model 9 being the most commonly used. Every additional tier requires another computer to be added in parallel. Each computer is dedicated to finding jump paths through its particular tier. For purposes of the USP, however, the computer rating is simply that of the highest rated computer by itself.

Bridge, crew, weapons, etc. for the gate can probably be treated no differently than if it were a ship. Regarding major weapons, though, the gate could conceivably mount one of astounding size. Unlike most major weapons, which are based upon the linear accelerator (also called spinal mounts), this would be a ring accelerator. However, designs such as this are severely damaged by battle damage (see JTAS #13, "Charged Particle Accelerator Weapons".)


Jump gates are expensive. This explains why they are so rate in the Imperium (if they exist at all). Resources are actually better spent in building and maintaining fleets.

Theoretically, jump gates become more common at higher tech levels. Even though the commercial benefits of jump gates advance, their political and even military advantages increase even more. Improving communications is vitally important to an empire, so a gate would naturally be constructed in the capital system. During wartime, an advancing enemy fleet is restricted to jump-6. The defender, however, would have much better intelligence gathering abilities and would be able to juggle its fleets around freely. To an enemy, destroying the gate would be of paramount importance.

It is possible the Ancients used a form of jump gate technology although it has not yet been confirmed through analysis of artifacts. An interesting note brought out in a Traveller seminar is the presence of a "ringworld" inside the Hinterworlds sector (built by the Ancients). This ringworld is barren of any life and atmosphere, suggesting it was not completed. Could this in truth be a form of jump gate capable of gating the star and itself?

Levels Adjacent to
Tier 2
Tier 1 and 3
Tier 2 and 4
Tier 3 and 5
Tier 4 and 6
Tier 5