[mac5732]

ftrs, mines and sats all count against your maximum limit in space. Check what maximum setting for units for the game. If its set low, 500 or 1000, it doesn't leave much open especially if you are using a lot of mines. Remember, as long as they are not launched into space they don't count. Only those units actually launched count towards your totals. This way you can still build them on your planets to replace what you use up but again, only up to the maximum set per player.
I also always set this limit to its maximum when playing, when defending planets & WP 1000 mines alone don't go very far let alone ftrs and sats.

just some ideas mac