Some GMs might want to run Stars Without Number in a setting that doesn’t have faster-than-light drives, perhaps to run a campaign set within Earth’s own solar system or to emulate a different setting focused around a single star. Here’s one way of tweaking SWN’s spaceships and system generation techniques to fit them into such a world.
Take out a blank sheet of hex paper. You can find hex-paper generators online easily if you’d like to print out your own. Put the system’s star at the center of the paper. Then roll 1d6 to determine a hex facing, with 1 being the face at the top of the hex. Place the first planet in that direction, one or more hexes away from the star. Then shift one hex-face to the right and place the next planet out along that direction from the star, working clockwise until you have placed all the planets at a proportional distance from the system primary. If you’re emulating the Sol system, you’ll probably have to compress some distances to fit the inner and outer planets all on the same hex map.
Next, draw in major systems features, such as asteroid belts, deep-space stations, and other decorative bits. Don’t worry about moons or orbital stations for now.
Finally, take a 3×5 card for each planet, deep-space station, or other “place” of importance in the system. Note down any moons or orbital stations in close proximity to that location. You can also use this card to note down any special navigational features or conditions to watch out for. The players will be consulting these cards during the game, so don’t write down any Secret GM Info on them; you can save that for your own notes.
Hard sci-fi fans will at this point be scowling over the two-dimensionality of the map, plus the fact that the planets are in a fixed position rather than orbiting at different periods around the sun. Depending on your degree of dedication, you can make up period tables for each of the planets and progress their orbits as game time advances, but in a practical sense, this is unlikely to give you a lot of benefit at the game table. It’s easier to just treat the positions as generalized abstractions and assume that they average out to a median travel time for the PCs.
Once you’ve drawn up the system map, just use the existing starship writeups. Each level of “spike drive” lets a ship cross 1 hex of the map in a length of time appropriate for your campaign setting- two days is a good baseline. A single load of fuel allows two acceleration/deceleration cycles, which allows a ship to eventually reach any single point in the system and return to its origin. If it changes course mid-flight, however, it’s going to have to find fuel at its eventual destination. Traveling to moons, orbital stations, and other near-space areas is treated under the “regions” section of spaceship movement, and uses no appreciable fuel. For spaceship combat, ships with stronger drives have better maneuverability, so the Phase rules for spaceship combat are retained, but simply treated as differences in agility.