Voyage of the Devilfish

FISSION A nuclear reaction during which a uranium or plutonium nucleus is split apart after the absorption of a neutron. Releases two to three neutrons, two nuclear fragments, and 200 megaelectron volts of energy.

FIX A ship’s position. Determined by visual triangulation or radar when close to land on the surface, or by NAVSAT or BE sonar when at sea.

FIX ERROR CIRCLE The circle that the ship could be in as a result of time since the last fix, steering errors, speed errors, etc.

FLAG PLOT A chart room used by flag officers (admirals) to plot strategy or determine the distribution of forces.

FLANK SPEED Maximum speed of a U.S. submarine. Requires fast speed reactor main coolant pumps and running at 100 % reactor power.

FLASH The highest priority of a radio message. Receipt required within minutes or seconds.

FLOATING WIRE ANTENNA A buoyant wire trailed from a submarine’s sail used to stay in passive radio communication when the ship is deep. Tends to snag fishing boats. Seagulls love to ride on them. Not generally used by SSN’s.

FLOODABLE VOLUME The amount of a compartment that can flood before it causes the ship to sink.

FORWARD GROUP The main ballast tanks forward of the operations compartment. During an emergency blow, all six of these ballast tanks are blown dry simultaneously.

FRAME Hoops of steel or titanium that serve as the skeleton for the pressure hull.

FRAME 57 The frame between the operations compartment and the reactor compartment on a Piranha class submarine. The start of the engineering spaces. Anything beyond Frame 57 is called “back aft.”

FREQUENCY GATE A narrow range of frequency that the sonar is tuned to listen to.

FUEL ELEMENT An assembly of uranium with zirconium cladding in a nuclear core. The uranium heats the water, making steam in the steam generators, allowing power production in the turbines.

FULL POWER LINEUP Electric plant lineup when the reactor is critical and self-sustaining. Both turbine generators are at 3600 RPM and are supplying power to the ship’s loads. The battery is not discharging.

FULL RUDDER When the rudder is turned 30 degrees.

FULL SCRAM When all control rods (not just the controlling group) are pushed to the bottom of the core. It takes much longer to recover from a full scram than a group scram.

FULL SPEED Maximum speed of a U.S. submarine with slow speed reactor main coolant pumps running the reactor at 50 % power. A Piranha class does about 25 knots at full.

FUSION A nuclear reaction in which several light nuclei come together and release tremendous quantities of energy. Usually requires initial temperatures of several thousand degrees.

G A measure of acceleration. The acceleration due to gravity is one g. Two g’s is twice, etc.

GAMMA RADIATION Electromagnetic radiation released in a nuclear reaction. Generally similar to X-rays.

GEOGRAPHIC PLOT (1) A manual plot saved from World War II submarine days using the plot table to deduce a firecontrol solution. Works well on unsuspecting targets. Target zigs cause confusion on this plot. Useless in a melee situation. (2) A mode of display of the Mark I firecontro) system showing a God’s eye view of the sea with own ship at the center and the other contacts and their solutions surrounding it.

GEOSYNCHRONOUS SATELLITE A satellite orbiting at an altitude of about 33,000 miles. The orbital velocity matches the earth’s rotational speed, making the satellite stationary with respect to the earth’s surface. Ideal for communication satellites.

GI-UK GAP (GREENLAND-ICELAND-UNITED KINGDOM GAP) The northern entrance to the Atlantic, choked by Greenland and Iceland to the northwest and Great Britain to the east. Any sortie of Russian Northern Fleet units would need to pass north of Norway, then south through the GI-UK gapGMT (GREENWICH MEAN TIME) A worldwide time standard using the time at longitude zero at Greenwich, England. Also called Zulu time.

GO CODE Slang for a nuclear release message to units ordered to fire nuclear weapons.

GPS (GLOBAL POSITIONING SYSTEM) A series of satellites and shipbome receivers enabling extremely precise navigation fixes. Also called the NAVSAT.

GRASS/RADAR GRASS A region within about 50 to 100 feet of the ground that surface search and air search radars are unable to penetrate due to ground clutter. An aircraft or missile flying in the grass can sneak up to its target without radar detection.

GREEN BAND Normal limits for T-AVE during critical reactor operation. Between 480 and 500 degrees IF.

GROUP ONE One of three control rod groups in a Naval S5W/S3G Core 3 core. During about half of core life these control rods control reactor temperature and power level.

GROUP SCRAM A reactor scram using only the few control rods in the controlling rod group. Enough negative reactivity to shut down the reactor for several hours, but not so much that recovery is difficult.