This would be an example - the white lines are the 'stable' circular orbits, while the yellow are 'unstable' orbits meant for easy course adjestment of orbital bodies and rockets/ships.

Every red dot would mark an intersection of orbits, as well as distance markers for speed. All orbital objects and ships must follow an orbit, but have differing speeds. An object with a speed of '1' moves from one red dot to the next in it's orbital path.

Here I have five levels of orbits, there may be more put in, maybe less.

The blue sphere represents Earth, and the black lines sectioning it like a pie indicate what portion of Earth's surface is 'visible'. This is important as both objects orbit Earth,and Earth rotates. It also makes a note of where a players' ships/rockets would be launched from.

There is a separate map for earth proper - This is just a top-down flattened map to show the orbits.

Game concept is mine.