“Compelling and visionary. DiMercurio’s characters run as deep as his submarines themselves!”
--Joe Buff, author of Crush Depth and Thunder in the Deep

"DiMercurio really knows his subs...his characters step right off the sub deck and onto his pages."
--Larry Bond

"A Master Rivaling Tom Clancy."
--Publishers Weekly

--San Francisco Examiner

--Associated Press

"Superb storytelling."
--Virginia-Pilot/Ledger Star


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MAD (Magnetic Anomaly Detector) -- -- A detector flown on an aircraft that measures changes in the earth’s magnetic field that could be caused by the hull of a submarine.

Main Ballast Tank -- -- Tank that is used solely to hold seawater ballast, weight that allows a ship to sink, or when blown, allows a ship to be light enough to surface.

Main Engines (Propulsion Turbines) -- -- The large turbines that extract themal energy from steam and convert it to mechanical energy to turn the screw.

Main Steam Valves One and Two (MS-1 and –2) -- -- Large gate valves on the port and starboard main steam headers, at the forward bulkhead of the aft compartment. These can isloate the main steam system in the event of a major steam leak.

Maneuvering -- -- The nuclear control room, located in the aft compartment upper level. Smaller than most walk-in closets. Contains the EPCP, RPCP, SPCP and temperature monitoring panels (1TM and 2TM).

Maneuvering Watch -- -- The watch stations manned when a ship gets underway in restricted waters.

Mark On Top -- -- Term used to note that a hostile aircraft is flying directly over the submarine. Generally means the submarine has been detected by the aircraft and will be under attack almost immediately. Usually followed by an expletive, such as, “P-3 mark on top, goddammit.” Muzzle door -- The outer door of a torpedo tube.

Master -- -- (1) The designation of a contact with a “master number” to coordinate multiple sources of information. Sonar contacts are numbered with a “sierra number” such as sierra one five, the fifteenth sonar contact of the day. Visual contacts are numbered with “victor numbers” such as victor seven, the seventh visual contact of the day. Radar contacts are similarly given “romeo numbers.” To avoid confusion, the OOD will “designate” a particular contact of interest as with a master number such as master one. If master one is being approached with the intent of shooting him, he may be given a target number. Some ships don’t elevate master numbers to target numbers but simply shoot at the master contact. (2) What you call a master chief petty officer. They love it, particularly when the XO gives them an order such as, “Master, assemble the crew on the pier.” Doesn’t sound like an order, but more like talking to a genie.

Melee -- -- A situation in submarine vs. submarine warfare in which both subs have detected each other and are trying to attack each other. In some cases, they are both maneuvering to try to perform passive sonar TMA on the other sub, which makes a mess because TMA assumes the target is on a constant course with a constant speed. In the case of a melee, one philosophy is to “go active” using active sonar – the other guy already knows you are there, so stealth is useless (this does not work if there are multiple hostile contacts, such as when you are in the other guy’s back yard, and your active sonar may tip off other hostile combatants). When you go active you get a quick firing solution so you can hit him with one shot. A second philosophy is to clear datum – run away – and then come back with stealth on your side. A third philosophy resembles the Western shootout, in which you execute a snapshot salvo to see if you can fill the water with weapons to either scare the opposition or kill him with a lucky shot.

Moderator -- -- A substance that slows fast neutrons to make them thermal neutrons which will enable them to cause another fission reaction. The means of slowing the fast neutrons is by making them experience collisions with other nuclei, just as a cue ball in a billiards game is slowed by collisions with other billiard balls. Best moderator is water, because it is rich in hydrogen, which is essentially a proton, and a proton has the same weight as a neutron. Other hydrocarbons work, such as paraffin or diesel oil, because the high concentration of hydrogen slows the neutrons. Graphite (carbon) is sometimes used, although the higher molecular weight of the carbon neutron makes it a less effective moderator and more neutrons will leak from the core.

MPA -- -- (1) Main Propulsion Assistant; usually the “bull” lieutenant on board, who is the most expert junior officer assigned to the ship, and who runs the machinery division; (2) maritime patrol aircraft such as the P-3 Orion that cruise at low altitude at low velocity looking for submarines with sonobuoys and magnetic anomaly detection, and drop torpedoes from the air to kill subs.

Michael DiMercurio
Princeton, New Jersey

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