Teacher's Guide: Glossary




The portion of a hull number designating a vessel as an auxiliary sub designed for


The portion of a hull number designating a vessel as a transport  sub. LPSS designates a
vessel as an amphibious transport  sub.

Attack center

Into this critical  location flow data from the boat’s sensors and status reports for evaluation;
from it issue the commands that direct the submarine and its weapons.

Ballast tank

A compartment within a boat or ship that holds water. In subs ballast tanks are used to alter
the boat’s buoyancy and make it submerge (take in water) or surface (expel water). Types of ballast tanks include the main ballast tanks, which are the primary tanks used for diving and surfacing, and trim tanks, which are used to adjust the submarine’s “attitude,” or trim, keeping it on an even keel both on the surface and underwater.

Ballistic missile

A missile that follows a ballistic trajectory with the objective of delivering one or more
warheads  to a predetermined target. Shorter-range ballistic missiles stay within the Earth’s atmosphere, while longer-range  models are designed to spend some of their flight  time above the atmosphere. Whereas a guided missile can be controlled throughout its flight, ballistic missiles can only be controlled  in the initial  and final stages. During the middle portion they fall according  to the laws of gravity.

BESS (Basic Enlisted
Submarine School)

A six-week program  that teaches the special skills enlisted personnel  will need to live and
work  aboard  a sub. BESS includes training  in, among other things, fighting fires, patching leaks, escaping  from  a sunken sub, and diving and driving  the boat. After BESS, Sailors either go directly to a boat or move on to more-advanced training.


In naval tradition, a boat cannot  carry a ship, but a ship can carry a boat.  Subs are typically
referred to as boats, perhaps because they used to be small enough to be transported on ships.


The front, or forward, section of a ship or submarine.


A small exposed platform on the top of a sub’s sail. A watch is posted in this area when a sub
is on the surface.


The smashing  of a ceremonial bottle, usually containing champagne, across a ship’s bow
just before it is launched.


The act of placing a ship, usually a naval vessel, in active service.

Conning tower

A small watertight compartment within a sub’s sail. The space is equipped with instruments
and controls, including  periscopes, that are used to direct the boat and launch torpedo attacks. It should not be confused with a submarine’s sail, control room, or bridge. USS TRITON  (SSRN/SSN-586), commissioned in 1959, was the last American sub to have a conning tower.

Control room

This space is the “brain” of a sub, controlling  nearly all the boat’s vital operations. The
periscopes are typically located here, as is the equipment for driving the boat and for figuring  out where it is and where it’s going.


The act of terminating  a ship’s career in active service.

Diving planes

Control surfaces used for underwater stability  and steering. On some subs they are located
on the sides of the boat near the bow. On other boats they are located on the sides of the
sail. They “fly” the boat through  the water like an airplane flies through  air.

Engine room

The area where the main engine(s),  generators,  compressors,  pumps, fuel/lubrication oil
purifiers, and other major machinery are located.

Guided missile

A self-propelled  missile that can be guided while in flight.

Hull number

A serial identification  number given to a boat or ship. For military vessels, a lower  number
typically  implies an older vessel. This number is assigned in addition  to a vessel’s name. For example, the hull number of USS NAUTILUS  is SSN-571.


The main structural element of a vessel, stretching along the centerline of its bottom from
bow to stern. It sometimes extends farther downward into the water to provide extra stability.


The act or process of floating a ship after construction is completed.

Medal of Honor

The highest military  decoration awarded by the United States government. It is bestowed
on members of the armed forces who distinguish  themselves “conspicuously by gallantry and intrepidity at the risk of [their  lives] above and beyond the call of duty.”


A self-propelled  guided weapon system. An unguided self-propelled  weapon is referred to
as a rocket.

Navy Cross

The second-highest military decoration for valor. It is conferred upon members of the
armed forces who are serving—in a time  of war only—with the Marine Corps, Navy, or Coast Guard and who distinguish  themselves in action by extraordinary  heroism not justifying  a Medal of Honor, the highest-possible decoration.

Nuclear reactor

The space in which nuclear fission occurs. This reaction  creates energy, mostly in the form
of heat, which can then be used to do work. Aboard a nuclear-powered sub, this heat is used to produce  steam to drive the turbines  that provide the boat’s power.


An instrument for observation from a concealed position. In its simplest form it consists of
an outer  case with  mirrors at each end set parallel to each other  at a 45-degree angle.

Presidential Unit Citation

An award given in the name of the President to units of the U.S. armed forces and allied
nations for extraordinary heroism in action against an armed enemy. The unit must have accomplished its mission under such extremely difficult and hazardous conditions  that they are set apart from and above other units participating in the same campaign.  The degree of heroism required is the same as that which would be required  for an award of a Navy Cross to an individual.


A tower-like structure on the top of a sub. When a boat is on the surface,  the sail serves as
an observation platform.  It also provides an entrance and exit point that is far enough above the surface to prevent water from entering  the vessel. Underwater,  the sail acts as a vertical stabilizer and also, in some cases, supports diving planes.


In naval tradition, a ship is a vessel that can carry a boat; a boat cannot  carry a ship. Subs are
typically referred to as boats, perhaps because they used to be small enough to be transported on ships.

Ship’s sponsor

By tradition, a female civilian who bestows good luck and divine protection  over a seagoing
vessel and her crew. In the U.S. Navy the sponsor is considered a permanent member of the crew and is expected to impart her personality to the ship and advocate for its continued wellbeing.


The portion of a hull number designating a vessel as a nuclear-powered ballistic-missile


The portion of a hull number designating a vessel as a nuclear-powered guided-missile


The portion of a hull number designating a vessel as a nuclear-powered submarine. All
present-day American subs are nuclear powered.


The back, or aft, section of a ship or sub.


A vessel capable of operating completely underwater.


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