Description
A spelljamming mine is a one foot diameter brass sphere that weighs about fifty five pounds. It is just the right size to be fired from a heavy catapult.
Powers
A spelljamming mine is a sophisticated homing weapon enchanted to detect an active helm within 1,000 feet (305 meters) and then move towards the helm's magical "energy signature" at a speed of 3,000 yards (2,743 meters) per round (equivalent to a ship travelling at a SR of 6) with a maneuverability class (MC) of A. When the mine strikes the target ship, a large charge of smoke powder installed within the mine will explode, inflicting 3-18 points of damage on unprotected crew within 70 feet (21 meters) of the point of impact, and 2-5 hull points of damage on the ship itself, possibly setting all flammable materials in range on fire. A spelljamming mine that has been activated by a passing ship and is homing in on its target can only remain active for 4 rounds before detonating, even if it hasn't reached the target vessel by then.
Before a spelljamming helm can be used, it must be armed. To arm the mine, a series of tiny studs located on the mine's surface must be pressed in a specific sequence. To prevent tampering, the mine explodes if the arming sequence is entered incorrectly three times in a row. The arming sequence is specific to each mine, and is so complex that even someone who knows the correct sequence can sometimes press the wrong studs while entering the code.
Once the mine has been armed, it remains dormant for 2-16 rounds, hopefully long enough for the user's to catapult it off their vessel and to put more than a 1,000 feet between them and the mine. At the end of this dormancy period, the mine becomes fully active and will home in on any spelljamming ship that comes within range. Because of the variability in its dormancy period, and the chaotic nature of combat in wildspace, a spelljamming mine is exceedingly dangerous to use in the heat of a battle. Like all explosive devices, a spelljamming mine will explode with three times as much force if encountered in the phlogiston.
History
Nobody knows for sure who developed the spelljamming mine, though most suspect it was the Arcane. Some Arcane are quite happy to sell spelljamming mines to their customers, but not all of them, and there is no guarantee they have any in stock. Spelljamming mines have occasionally been offered on the open market by other sellers, but this carries the additional risk that the seller might not be aware of the correct arming code.
Rumors
It has been rumoured that the humanoids native to the Borka cluster have placed a number of mines around the asteroid called the Egg.