The term hull refers to the body or frame of a ship or starship. Warp-worthy vessels must have a hull able to withstand extreme accelerations. The hull of a Starfleet vessel was usually separated into two parts: The primary and secondary hulls.
- Polyduranide alloy
- Ablative generator
- Ablative hull armor
- Dispersive armor
- Monotanium armor plating
- Parametallic hull plating
- Polarized hull plating
- Reactive armor
Structural integrity was an engineering term used to refer to the strength of the hull.
While standard architecture uses supports and bulkheads to make constructs stronger or more durable, the fantastic stresses presented by warp fields and spatial phenomena have caused engineers in the Federation and other spacefaring cultures to use force fields to hold the shape of a construction together. This is referred to as a structural integrity field.
In 2063, Data informed Captain Jean-Luc Picard that the structural integrity of the Phoenix was intact, even after the attack by the Borg sphere. Later, Geordi La Forge informed Zefram Cochrane that the structural integrity of the Phoenix was holding as the ship prepared to go to warp speed. (Star Trek: First Contact)
In 2151, Malcolm Reed and Trip Tucker repolarised the gravity plating of Enterprise to absorb the plasma recoil, caused by the newly integrated phase cannons, and shunt the energy to structural integrity. (ENT: "Silent Enemy")
The stress of a Romulan tractor beam caused sub-microscopic deformations in the structural integrity, especially the nose section and aft thrusters of the type 15 shuttlepod Onizuka. (TNG: "The Mind's Eye")
In 2369, Geordi La Forge planned to run a structural integrity scan of a conduit located in cargo bay 4 aboard the USS Enterprise-D, but had to report to sickbay due to an issue with his VISOR. Data stated that he would run the scan instead, and had just started it when La Forge returned from sickbay, having been abducted without his knowledge by the solanagen-based lifeforms. (TNG: "Schisms")
In 2374, during an encounter with a group of Omega molecules, Captain Kathryn Janeway ordered Chakotay to increase the structural integrity of a shuttlecraft in order to properly dispose of the molecules. (VOY: "The Omega Directive")
Hull stress was a condition where, on a starship, space station or other installation, the hull encounters a form of stress. This could be caused from a form of pressure pulling against the ship, such as an object pulling against another. Hull stress, if critical enough, can lead to a hull breach.
When the USS Voyager was caught in a quantum singularity in 2371, they found what they thought to be another ship caught further in the singularity. When Voyager attempted to lock on the ship with a tractor beam, the singularity started to pull the ship in. The ship was put into full reverse impulse, but with the tractor beam still on, this caused hull stress. (VOY: "Parallax")
Microfractures were microscopic cracks in the hull of a starship that, while invisible in the naked eye, could widen over time if something aggravated it and cause more drastic problems. The term also has a medical context.
The structural integrity of a material was diminished when microfractures were present. This could have dangerous, even deadly, consequences when the deterioration occurred in a ship's hull or other structure which provided containment, shelter, or life support, or in a living tissue. However, under certain conditions, a limited amount of microfracturing could be tolerable. (VOY: "Extreme Risk")
Some microfractures could be sealed by an engineering team, yielding a temporary or permanent repair. Other microfractures required the rebuilding or replacement of the structure. (ENT: "Desert Crossing"; VOY: "Caretaker")
Duranium alloys could be vulnerable to certain silicon-based parasites, which consumed the material. The weakened duranium could microfracture under stresses that normally would be within tolerances. (VOY: "The Disease")
Gravimetric distortions created violent stresses that caused damage beginning with microfractures and ultimately yielding total structural failures, if not mitigated by escaping the distortion. (ENT: "Exile"; VOY: "The Fight")
In 2369, the shuttlecraft Fermi was destroyed when an energy anomaly caused molecular deterioration and microfractures in the bulkhead. A plasma conduit at the Tyrus VIIa Particle Fountain Project exploded, due to an undetected microfracture. (TNG: "Rascals", "The Quality of Life")
The term hull breach refers to the failure of structural integrity where the shell surrounding said pressurized environment breaks, stresses or develops a gap for any reason. In space-faring vessels, this is usually catastrophic. The pressure of a contained atmosphere forcing its way outward in an explosive decompression can cause further damage to the area, and also have the added effect of endangering or killing any lifeform present. Since the pressure is internally generated, Lieutenant Commander Data stated to Commander William T. Riker in 2364 that being "blown out" was probably a more accurate term than being "sucked out." (TNG: "The Naked Now"; VOY: "Deadlock")
Most hull breach dangers are from pressurized material contained within a vacuum, or lower pressure, environment. However, it is just as possible that the pressurized vessel could be surrounded by high pressure gases or even liquid, causing an implosion, forcing the surrounding environment into a vessel. The USS Defiant experienced such breaches in 2372 when trapped in the atmosphere of a gas giant. (DS9: "Starship Down")
Vessels of spacefaring civilizations and cultures, such as the Federation Starfleet, protect themselves against the extreme stresses of both pressure and vacuum, as well as the added dangers of impacts, warp drive stress, weapon damage, energy phenomena and anomalies, by implementing a structural integrity field. This force field is designed to occupy the same space as the ship's hull, effectively giving them hundreds of times the ability to hold its shape. Force fields are also used to automatically contain the atmosphere, and repel external forces, should the hull be breached. (TNG: "Disaster"; Star Trek Generations; Star Trek Nemesis) Prior to the development of these technologies, emergency bulkheads and polarized hull plating were used to contain and avoid breaches (ENT: "Damage")
Notable hull breaches
- Enterprise NX-01's C-deck, caused by two Vulcan fighters and a D'Kyr type ship. (ENT: "Awakening")
- Enterprise NX-01's G-deck, in the Battle of Andoria. (ENT: "Kir'Shara")
- USS Enterprise-A's Saucer section, which was hit by a torpedo from General Chang's Bird of Prey. (Star Trek VI: The Undiscovered Country)
- USS Enterprise-B's Engineering section, which was presumed to have killed James T. Kirk. (Star Trek Generations)
- In 2369 Deep Space 9 had several hull breaches and fractures in their bulkheads caused by the graviton pulses of the embryonic lifeform. (DS9: "Q-Less")
- One of Deep Space 9's upper pylons were destroyed by a Jem'Hadar strike team. (DS9: "To the Death")
- In an alternate timeline, USS Voyager's Deck 05, caused by damage from Krenim weapons fire. (VOY: "Year of Hell")
- USS Enterprise-E's bridge, caused by disruptor damage from the Scimitar; as well as several decks' worth when the Enterprise rammed the Scimitar. (Star Trek Nemesis)
The basics of these incidents have been referenced in several episodes. More detailed explanations given by the writing and technical staff when creating the show are contained in the Star Trek: The Next Generation Technical Manual and the Star Trek: Deep Space Nine Technical Manual.