Early on in the history of spaceflight, humans learned that space debris and particles can pose a very grave threat to any spacecraft. When traveling at the extremely high velocities typical of the Habitat, even the smallest speck of dust has the potential to become a lethal missile. Thus, the Habitat is protected by a simple yet highly effective defense system, the hull plating.
The Habitat is protected by a series of ablative armour plates. These plates are laminated and spaced away from the Habitat, forming what is known as an "ablative spaced-laminate". It is a combination of several techniques used to protect tanks and other armoured fighting vehicles. It has three ways of stopping otherwise lethal projectiles.
Ablative plate consists of steel plate loosely bolted onto the exterior of a tank chassis. When an artillery round is fired at the plate, it breaks off and carries the kinetic energy from the shell along with it. Though the plating on the Habitat is much more advanced than common steel, it shares the same principle. When struck by a meteorite or space debris, the plating is designed to shear away and thus carry away the energy from the impact. Since the newly liberated plate will continue along the same path as the impacting projectile, the ablative armour works only against glancing impacts as a straight-on impact will drive the plate into the wall of the habitat behind it.
To repair an ablative plate after a glancing strike, the damaged section is replaced. Since the plate is attached in small sections, the task is easily performed with minimal resources.
The actual plating itself consists of two or more sheets of tungsten. These sheets are separated from each other by a 5" filling of foam. When impacted by a small, high velocity projectile, the exposed tungsten plate will fail, shattering the projectile on impact. These small fragments are then easily stopped by the foam underneath. For better protection, three, or sometimes four, layers of tungsten and foam may be used.
The damage done to the laminate plate is extremely easy to repair. Liquid foam and a small patch are all that is needed; foam is injected into the hole, and the patch is applied over it.
Behind the ablative plate is a Whipple shield. A Whipple shield consists of several spaced plates of thin metal. If a large meteorite manages to penetrate the ablative plate, the plate will cause the meteorite to shatter. The spacing allows the meteorite pieces and the ablative plate fragments to disperse somewhat before hitting the side of the Habitat, minimizing damage.
For further protection during meteorite storms, both the ablative plate and the Habitat can be electromagnetically charged by running a strong current through the plate. This will induce a positive charge in the ablative plating. When impacted by large metallic objects, the plating will induce a similar charge on the offending object. Since both the object and the habitat are now charged, they will repel each other; causing both objects to move away from each other and thus avoid, or at least minimize, impact force.
Since this polarization requires a lot of electricity, the ablative plating can only be charged for about 2 hours before it starts draining power from other systems. To recover power, the ablative plate is constructed so that it will generate an electric charge when bombarded with electrons. When the polarization is activated, the charge of the plate naturally attracts electrons, which impact the plate and provide some power. The cloud of charged particles also helps block radiation; thus, the plating may be polarized to ward off electromagnetic storms as well as space debris. This function of the plating is vital to the survival of the astronauts, as they would otherwise be killed by solar flares.
The plating is normally about 10 cm thick, though double and triple plating will serve to increase the width. It is held about 5 feet from the habitat and comes in plates of about 1.5 meters. The entire Habitat and AYSE Drive are covered with this plating though only plating on the front and sides of the Habitat is able to be polarized. This is to prevent the polarized plate from interfering with communications and sensors.