Cluster Mines Creates a field of mines, that deal lower damage than normal mines, over an area
m: Number of Mines in field. d: radius the mine field is in.
Explosive / EMP Mines at their lowest (Razor / Smoldering) class will have the highest speed (maybe around 100) and a refire of 0.5 (mine every 2 seconds); While at the highest (Nova / Inferno) class will have the lowest speed (by the same example, 50) and a refire of 0.1 (mine every 10 seconds), while Cluster Mines will have about half the stats of normal mines (ex: lowest class speed at 50 refire 0.25 (mine every 4 seconds), highest class speed at 25 refire at 0.05 (mine every 20 seconds)
Spatial ships are the only ship that has two mine slots, by adding variety to the mines available it makes the second slot more useful as well. In addition, the Cluster Mines could be made usable only by Spatial Ships which would make them even more useful in battles, making the ship's role more as a mine layer to hinder enemy movement (given their current ship stats).
It kinda fits if you ask me, all that cargo space to (in RP) hold the mines, 2 mine launcher spots, and its still a combat ship.
Again this is only a roughly made list just to give a basic idea of what i think would give more variety as to what mine a player uses. Of course, to stop the player's mine / cluster mine from going to waste or damaging his/her own ship, an increase of mine HP to atleast 10,000 would be needed.