For the record I got the idea for minicosms (see Space: 2099 post) from the game Diaspora and an article in White Dwarf (can't find the issue sorry) by Marcus Rowland. You should check out Diaspora and anything by Mr. Rowland. The Alderson Drive used in Jerry Pournelle's Co-Dominium series is somewhat similar.
The idea of minicosms is that a group of stars is very closed in jump space for various esoteric (handwaved) reasons that don't have much bearing on their real space locations. Alpha Centauri might be very close to a star in the galactic core for example but Earth might be nearly impossible to reach.
Minicosms take the form of polyhedra with their component stars scattered across their surface. The most common form is a dodecahedron (sphere really.) Other shapes exist and I'll work them out if this game has any legs (a tetrahedron or torus would be awesome!) Unlike Classic Traveller in which a jump drive was measured in parsecs of range a jump is referred to as a stage. Stars one hex away on a map may be thousands of light years apart (a few dozen commonly.) The stage refers to the number of hexes you move on the map, not your real space travels (a minor but important distinction.) A minicosm might be composed entirely of a giant blue star and the four or five stars that are its far companions. A speedy maneuver drive could get you to all of them in a few weeks or months but the gravitational and electromagnetic interactions could make jumps a higher stage than your drive can perform.
Minicosms have one or more gates to other minicosms. They can be one way. They are generally a stage 2 jump. Hit the right button in the right star system and bang you're someplace very different. Gates generally link stars of the same or similar type.
Jump drives use a lot of hydrogen (10% of ship's displacement per stage number.) During the jump you're venting the hydrogen continuously to keep a bubble of semi-normal space around your ship. Jump space energy wants to get at your ship and will break down any normal matter except hydrogen (which is as basic as you can get, one proton.) Using other elements as fuel will result in radiation that can harm your ship. So you try to keep your hydrogen pretty pure. Using tainted hydrogen can cause radiation damage or worse allow jump space into your ship. More on that later. At the very least radiation and energy surges could throw your jump off course.
A jump takes one week as in Classic Traveller. It takes that long for you to create a path in jump space and exit it carefully. There are no (publicly known) forms of ftl communications other than taking a letter onboard a ship.
Next Up: The Toys.