Jumping Blind

A Shot in the Dark

A subsector contains about 40 worlds or star systems. That means it also has about 40 empty hexes.

Or are they?

For many 2d6 referees the empty hexes are forbidden. You may only jump from star to star for… very good reasons. So never mind. Astronomy as it is currently practiced indicates that there are a lot of things between the stars. There may be as many rogue planets as stars or even several times the number. Many of them are gas giants and thus could enable wilderness refueling. This would make a hash of those mains, routes of adjacent worlds. There is an economic reason for them discouraging empty hex jumping. 

If empty hex jumping was common, pirates, spies and invaders could infiltrate, bypass your lovely defense in (not enough) depth and nuke your core worlds before you knew anything. So there are military reasons for discouraging empty hex jumping. 

This discouragement can take the form of simply not including rogue worlds in ephemera. Navigators are taught that an empty hex is dangerous, that they could wind up with empty tanks around a dry as bone rock. Without water, ice or hydrogen, well, time to climb into cryo and aim for the nearest star. Eventually should-not-be-done becomes cannot-be-done in many minds.

IIRC the first time I heard empty hex jumping was in Trillion Credit Squadron. A ship misjumped into a remote star cluster. It eventually returned to its home space. It was said that jump-6 was required to reach a friendly star system or jump-3 and auxiliary tanks. So obviously, you do not need a star to jump, or even a rogue planet. The auxiliary tanks indicate the ships making the trip were not stopping for wilderness refueling. 

If the military hates empty hex jumps it will take steps to restrict purchase of drop tanks. {Port Authorities will not provide tapes for such a course and if you have to file a flight plan and lie, well, naughty naughty. 

What if you still want to do an empty hex jump (also known as flying with your headlights off)? Maybe you want to step around Borsten’s Leap, where the local business models all involve skinning innocent free traders?

As I said you’d need some drop tanks which might raise suspicion. Without those you will need a convenient rogue planet with water or hydrogen. Getting that information is either a navigation roll at 10 or better, some fancy streetwise rolls or buying a lot of drinks.

If shooting for rogue planets is a thing, the military will not be caught with its pants down. Rogue planets and brown dwarfs will be tracked and patrolled. Some may even be mined or have more extensive stations or fortresses. The authorities will also take a keen interest in people seeking information on such bodies.

Apart from begging, buying or stealing some coordinates, assume a ship can find and plot a the co-ordinates of a brown dwarf a number of parsecs away equal to their computer mark. A rogue planet can have its position fixed a number of parsecs away equal to half the ship’s computer mark,  rounded down, minimum of one parsec. 

Once you decide on on your target plotting a course to it is 9+ for a brown dwarf, 10+ for a rogue planet. The throw is modified by navigation skill, +1 if EDU is 10+, -1 per parsec after the first. Optionally, old charts and hidden records or logs from previous jumps may add +1 or +2 to the throw. In more modern Terms it's Edu+Pilot and a 10+.

Luck of the Draw

The Emperor himself said (Jumpspace, JTAS #24, p.34) jumping is accurate to one part in ten billion. That comes out to an error margin of 30,000 kilometers per parsec. Ships regularly aim for rock planets with average jump shadows of 800,000  kilometers. A brown dwarf is a little larger than Jupiter (@ 125,000 km.) However, it’s much denser and can mass as much as 80 Jupiters. 

Respectfully, I don’t think the 100 diameter rule works in this case. 

If the brown dwarf was the density of Jupiter it would have 4.3 times the diameter. Its jump limit would then be 140,000 (1) x 4.3 x 100 = 60,000,000 km. So it’s going to be a trip to get fueled from this beast. The fun begins once you reach the brown dwarf. It requires high speed passes through a breezy 1400 degree centigrade atmosphere. This is the point where you regret skimping on armor. Skimming such a monster will take 2-3 times as long as you stick to the thinnest and relatively cooler upper atmosphere, then fly far away to cool the ship and hydrogen off. Life support and fuel refrigeration will be strained to their max and all manner of hell can break loose. If you’re using MgT then a heat shield is what you’re looking for (High Guard). Again, m-drive ships take re-entry nice and slow. Heat shields are usually not necessary for them and buying one may trigger some alarms. On the other hand… armor will too. If you try to get by with armor, then I’d go with Medium armor by Cepheus Deluxe or at least 10 points of Armor by MgT. 

If your players are white knuckling rolls for refueling from a brown dwarf, you’re doing it right. 

But hold on, the brown dwarf could have its own planets: gas giants or lovely icy worlds! After a brown dwarf, Jupiter begins to look like tropic island nest. In any case, if you want to introduce some randomness, roll on the following table for an empty hex if your navigator blew the roll.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            

Empty Hex Contents (2)



4-Rogue terrestrial-ice covered

5-Rogue super-terrestrial-hydrogen atmosphere 

6-Brown dwarf

7-Brown dwarf with gas giant

8-Rogue gas giant

9-Rogue gas giant with assorted moons 


11-Rogue terrestrial-ice covered

12-Rogue terrestrial-hydrogen atmosphere

Referees not interested in making their group go through a loooong passage in a cryogenic berth, can allow for a comet a few weeks of travel away. Figure the objects in the table represent objects within a a week or two of travel.

A Day Late and a Dollar Short

Finally, make stuff up. If the characters have hit on a new route (with all its dangers traps, and snares) there is no saying they’re the first to do it. Lost colonies, secret military bases, pirate ports, all these people are going to really be pissed off when your ship punches a hole in their sky. And they are likely to be between you and that lovely hydrogen.

Synopsis: Yes, you can do a jump into and from that empty hex, and… (bear in mind the yes… and response is referee jargon for you’re screwed.) 

(1) I was just skimming T5 and Brown Dwarfs are generated like Jovian planets, with their radius multiplied by 4. Never underestimate the Emperor. 

(2) Note I am not a planetologist and have never been to deep space, but if Traveller was really a simulation game, the galaxy wouldn’t be one parsec thick! 


  1. Nice synopsis. And I like the random empty hex table.

    As for the 1 parsec map, over the years I've just adopted that the map is a 2D representation, and a jump is not necessarily a parsec. There are just lanes in space, sort of what the original '77 rules I think implied.

    But as I really don't think about it too much, and just play the game. When I can.


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