Triplanetary

Set in the 21st century, the map depicts the inner Solar system out to Jupiter. Scenarios involve racing, pirating, invasions, and a few others.

Movement involves vector mechanics. Players plot courses using a grease pencil on the map and use fuel to accelerate a maximum of one each turn. Planets and moons are used to modify the trajectory.

There are a limited number of ships. Most are limited in fuel, so making efficient use of gravity is important to reaching a destination.

2nd edition came out in 1981.

It is fairly easy to extend the game to much more than 3 players, although the board can become cluttered with ship trails (the game is sorta like Crayon Rails in this respect).