Modern starships travel in a hazardous environment were radiation and physical mediums can and often will come into contact with the hull and while Battle-steel and Ship steel are designed with built in material based shielding it has long been a well known fact that it is better to stop the impact before it reaches the hull. Despite what the Holovids and old novels say ‘deflector’ shields are not the answer, while almost every known race has reached some level of gravity manipulation the simple fact is that the strengths required to ‘shield’ a ship using gravity is dangerous not only for the ship in question but anything around it so much so that to date only the oldest of races appear to have mastered the fine degree of manipulation required to generate such fields and then only across localized areas.
Instead most races use a combination system based on point defense arrays, magnetic fields and plasma windows, the first of these should be rather obvious weapon arrays most often rapid fire are placed along strategic locations on ships allowing for a wide area to be covered and attempt to engage incoming items much like the Counter Missile systems back on pre-jump Terra once did. Next comes the first magnetic ‘field’ layer this layer is a fluctuating field designed to ‘shove’ ferrous objects to the side so long as their mass is within certain limitations specific to the actual field strength, this field is often termed the ‘navigational’ shielding as it typically is always running and has the ability to move ionized gasses away from the ships vector path. The third layer is a dual ‘system” containing two magnetic fields which form a sleeve around the ship into which plasma is feed by shield generators, at minimum levels this sleeve of plasma is basically transparent however under battle conditions the plasma density is increased along with field strength, the combination of all three have the effect of being able to stop most projectiles however constant barrage or large volume impacts can and often will degenerate the system rapidly given each impact on the magnetic fields requires the generators to offset eddies created by said impact while impacts on the plasma sleeve typically result in localized loss of full containment causing the plasma to bleed and overall shield strength to lessen.