[Aktungbby]

Originally Posted by aanker

I guess 450 yards : )

http://archive.hnsa.org/doc/torpedo/ '...and as a result the spring contact of the switch is forced down, making electrical contact with the fixed contact. As soon as electrical contact is made, the condenser is discharged through the electric detonator (Fig. 8A), s etting it off, thus detonating the booster and the main charge in the war head.
Note: The exploder mechanisms are issued to the service with a pick-up coil and thyratron tube installed on their base. These devices are applicable to the influence feature only and will not be described in this publication.
Booster Above the exploder mechanism, when installed in the war head, is a thin sheet-copper container holding a charge of tetryl. This is known as the booster. It is so shaped that it fits inside the pocket at the top of the exploder casing, and rests snugly upon the top of the safety chamber. The detonator, during the arming operation, is moved up out of the safety chamber into a recess in the bottom of the booster; thus, the detonation of the detonator can set off the booster. Before the exploder is fully armed, the detonator holder is within the safety chamber, where it can explode without detonating the booster. It is not until the detonator holder is well extended from its safety chamber that it can detonate the booster; thus any accident which might cause the detonator to explode while the torpedo is still aboard, or close to its firing vessel, cannot cause detonation of the war head, since the torpedo must travel about 350 yards through the water before the detonator can fire the booster. ?? In some other articles the distance for a Mk 13 is 200 yards. The arming distance of a MK-15 is 450 yards http://www.simhq.com/_naval/PDF/naval_009print.pdf