I like the idea of using missiles as torpedo warheads. Give the mine a rating
to use for both detection and avoidance  to reflect both its own
stealthiness and ability to avoid detection and its ability to detect a target
which is of course reflected in its cost (or TL if you want to go down that
road).
Something Like:
Mine Quality
Ships Signature Low Normal High
Low N/A 6 5, 6
Normal 5, 6 4-6 3-6
High 4-6 3-6 2-6
Sensors Active ---- Automatic ----
If the mine picks up the ship it fires a salvo of missiles which are resolved
normally.
I was thinking along the same lines, but using a SML salvo as the mines. If we
say the SML missiles are small missiles that get their range from a large
drive, with a small drive and warhead used at the end to give them their 6MU
attack radius. All we would need would be the final drive and the warhead, so
we could have a mine as a cut down SML, deployed from a minelayer (same mass
as a SML launcher?, or slightly less, say mass=2?), with the mines as
ammo, just like SML`s, but lighter (say, mass=1 per 6 mines/1 mine
marker?). If we say, instead of using a quality of the mine, we just use the
1D6 SML`s on target, and any mines within 6MU of the ship at the end of it`s
movement attack said ship. To give the ship some chance, we can have all the
mines attack as just one salvo, to aviod the waste of PDS against light
salvo`s. The only problem with this, is a single ship will clear a 6MU radius
circle of mines, meaning a small ship can be sacrificed to clear mines. As a
secondary rule, when each mine is layed, it is given a number, and the number
is the order it will attack. Mines with a 1, will attack any ship within range
first, and mines with a 2 will attack after the first
wave/on
the second turn (if the ship survives). If the ship is destroyed with the
first salvo of mines, the second salvo (and later ones) will wait for another
target to come within range. A ship equipted with a mine sweaping system can
attempt to intercept the mines before they launch, and PDS or fighters can be
used to minesweap before the following wave attack, but only after dealing
with the first wave (if they survive). Fighters attempting to clear the mines
roll the same as if intercepting normal SML missles salvos, with the same
chance of being caught in the explosion.
Or, if you don`t like the idea mine waves, we can have instead that
different size ships have mines attacking at different radie, IE- upto
50 mass=3MU, 51 to 100 mass=4MU etc.
Just some of the ideas off the top of my head.
BIF
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Another idea for the mines is that each mine counter is actually 18 mines (at
2 mass), and each turn a target is within 6MU of a mine counter(s), 1D6 mines
attack until the 18 mines are gone. For the tech level, a simple ideaa would
be to alter the number of mines that attack each turn. For low tech,
have say 1D6-1, normal tech of 1D6, and high tech of 1D6+1.
BIF
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