Its not.
Press the Pause/break button on the keyboard to pause (if you dont have one you may need to reassign the key via the options menu).
If you turn on autosave, each player will periodically autosave at the exact same time, allowing you to easily access the last autosave and reload the game if someone gets disconnected. Also, anytime a player saves the game, it creates a save of the same name on all the other players machines.
You can adjust the speed of the games features individually when setting up the game to begin with, but not during the game. When you're setting up just go to the game options menu before you start and adjust the speed settings, tour options are slow/normal/fast and you can change this for ship speed, build speed, resource collection etc.
If none of these options are available you may need to update your game via impulse.