Hull
Hull is an old term, and currently refers to the body or frame (outside) of a starship. All warp-worthy vessels are designed to have a hull able to withstand extreme acceleration, and nearly all space vessels are designed to adhere to a general form that serves the needs of stability and efficient propulsion.
The hull of a Star Fleet vessel is usually separated into two parts: The Primary and Secondary hulls.
Primary Hull
The primary hull (also known as the saucer section or saucer module) is a major component of the overall structure of a starship. The primary hull is generally located above and to the front of the secondary hull.
The primary hull typically contains most vital systems on board a starship, including the main bridge, computer core, sickbay, science labs, crew quarters, and other crew support systems. It does not generally house the warp drive or any major engineering systems, although in many cases it does contain its own impulse drive.
Ships capable of saucer separation were designed for this purpose in order to have the primary hull serve as a lifeboat for the crew in the event of catastrophic damage to the warp core or a loss of antimatter containment. It is for this reason the majority of crew comforts are nestled into the primary hull.
Saucer sections on some starships are even equipped to make planetfall and landing, although not all are designed to return to space following a landing.
The Galaxy class saucer section was also intended to act as a temporary means of escape for nonessential and civilian crewmembers while the secondary hull dealt with a dangerous situation. It can operate independently of the secondary hull and reconnect with its drive section after the resolution of a crisis. For this reason, it contains duplicates of many systems in the stardrive section, including a large shuttlebay/cargo bay complex, a torpedo launcher in the docking cavity for rear defense, and deflector array.
Secondary Hull
On many Federation starships, the secondary hull (also known as the engineering hull, the engineering section, the stardrive section, or the battle section) is a major component of the overall structure. The secondary hull is generally located behind and below the Primary.
The secondary hull is usually dedicated to engineering and support functions, especially in starships built after the mid-23rd century. It is the home of the warp drive, Main Engineering, and other engineering support systems. Separating these potentially dangerous systems from the majority of the crew located in the primary hull, allows the secondary hull to be abandoned in the event of catastrophic damage to the warp core or a loss of antimatter containment.
The warp nacelles also make a direct connection to the secondary hull. Other areas typically found in the secondary hull include the shuttlebay, cargo bays, and brig. The main deflector dish is usually located at the very front of the secondary hull, as are torpedo launchers.
See also: Helm and Navigation
