Structural integrity is a measure of how tough a hull is. How much damage it can take before it becomes compromised. This figure is passively determined by the configuration of a hull, and the materials it was made with. The properties of those materials are also important, as they will affect how the hull would react to energy being directed against it.

Structural Integrity is also used as a term, by ship officers especially engineers to refer to a series of systems designed to actively increase the Structural Integrity of a ship. These systems include things like emergency bulkheads, force fields, and structural fields. Emergency bulkheads are a very old concept that on Earth started with wet water navies and famous ships like the Titanic. The idea of these bulkheads is that in the event of a hull breach they would drop into place thereby sealing the breach. For wet water navies, these bulkheads greatly increased a ship’s ability to stay afloat during battle, especially when combined with pumps. In space however water is often not a concern, but these bulkheads are still important. A breach in the hull must be sealed quickly lest a ship’s atmosphere leaks out into space. Something that can happen very quickly. As such even though the concerns are not the same they achieve the same effect, increasing the amount of time a ship can remain in a fight.

Force Fields are a space-age technology that can be used for the same purposes as emergency bulkheads and often are, as they can snap into place far faster. However, they require power to be used, and can’t take as much punishment as a physical bulkhead. As such they are often used as a supplement to emergency bulkheads. They are also good for intruder control, as they can snap into place quickly and can be used to restrict the movement of intruders. Early forcefield technologies, however, do not stop weapons fire in the same way that a physical bulkhead can. Later development can solve this problem, however.

The bread and butter of space-age active structural integrity are structural fields. These energy fields are run through the hull of a ship and draw power from the ship’s reactors. The field being run through the hull greatly increases the resilience of the material said hull is made from. There are numerous factors that determine how effective this field is. The amount of power available to the field is one of the biggest and most obvious. The material though is also very important, as different materials will react differently to structural fields. Refuge Titan Alloy for example has an extremely high level of reaction with such fields, resulting in a hull far more resilient than would generally be expected. 

Because structural fields are the bread and butter of active structural integrity they are often the focus of improvement for starship designers. The best way to improve them is to increase the amount of power available to them. General miniaturization of components in a given time frame often leads designers to increase the load capacity of the power systems so that a stronger field could be generated. The stronger the field the greater the effect. Another way to strengthen the field is to increase the power efficiency of the system. 

Now naturally structural fields are not normally needed to enable a ship to survive the normal rigours of space travel. As such these expensive active systems are not often found on civilian ships, but some civilian vessels do include them. Emergency bulkheads are often found on civilian ships because while rare it is not unheard of for something to breach the hull of a passenger liner or freighter on a normal run. Be it a random pirate encounter, a system malfunction or a minor collision with drifting space debris. Structural fields though are often of great importance for combat vessels. They are especially important to the combat vessels of the Sol Refuge. The refuge uses two distinct and different types of structural field systems in their ships, the general SIF, and the more specific AIF. The AIF is a localized and condensed structural field that runs along the outer hull. It is used to greatly enhance the resilience of a ship’s hull armor and does a very good job of that. The other system the SIF creates a generalized field around the entire ship and increases its resilience as a whole. Both systems are intended to work together and keep the ship together. The AIF, however, is unusual compared to the structural fields used by other races, and in fact, behaves like an energy shield running through the hull in addition to the normal reinforcement effects of a structural field. The result is that Refuge plating is very difficult to breach.

That is naturally the goal of structural reinforcement and for most combat vessels the Structural field is the ship’s final line of defense between an enemy attack and death. The first line of defense is often the shields but in the case of the Refuge that would be the Armor.