The exterior of a TARDIS is made up of a Chronoplasmic Shell composed of atoms of rare TARDIS metals (including mercury and in some experimental capsules, Validium) and inorganic polymers. It exists as a Real World Complex Space-Time Event that is Time Mapped onto the interior using Real World Logic Gearing, made up of Complex Block-Transfer equations. The Time Sensor Control fine-tunes the exact space-time coordinates of the molecules that make up a TARDIS. The shell holds the dimensional threshold that connects to the Micro-Universe within.[/ttv]
The Chronoplasmic Shell is driven by the Chameleon Circuit. The default state for the shell of a Type 15-52 TARDIS is a silver-grey metallic cube 3 meters on each side. For a later Types, the exterior is a white domed topped cylinder 2 meters tall and 1.2 meters in diameter. When in its default state the outer surface of the shell will appear, on close examination, to be rippling and changing like something unreal or dreamlike. Similarly the Exo-Shell's mass is distributed over the first 5 dimensions. This means that, from a 3-dimensional point of view, the outer shell has variable mass that tends to fluctuate over time. Thus the density of the shell tends to be different every time it is measured. While disguised as a police box a TARDIS weighs significantly less then 1,200 pounds. But the shell can reach a density of up to 2,300 grams per cubic centimetre
It is possible to use the chameleon circuit to create a small cubbyhole compartment to store a spare TARDIS Key. The specific Type of a TARDIS can be determined by checking the molecular patina of its Shell. The exterior does emit low levels of Tachyons, which can be detected using the proper equipment. The internal energy of a TARDIS can be diverted to the outer shell, delivering a massive blast of energy to anything it comes in contact with. Under the right atmospheric conditions this energy discharge can be modulated to induce precipitation in the exterior environment using basic atmospheric excitation.
Since the shell's atoms are merely Block-Transfer constructs, the exterior of a TARDIS is immune to almost all attacks and the design specifications state that it is 'technically indestructible' (even without the Force Field). It is immune to diamond and borazon drills, thermic lances, sonic lances, laser cutters, and meteor collision. The heart of a star does produce enough heat to instantly vaporize the capsule. If the Operator desires it, the TARDIS's defences can be disabled so that its exo-shell is no stronger then the object it is disguised as. If the exoshell was to develop a crack, chronon radiation would be released. To a lesser species this would appear to be a white glow.
The exterior is also radar-absorptive, making it invisible on some tracking systems. However, microscopic elements (such as bacteria) from each destination will often become embedded in the Shell. The
External Decontamination Function (EDF) can be used to sterilize the Shell leaving it appearing pristine and clean. Unfortunately the EDF doesn't prevent molecular or atomic level spatial elements from being embedded. While this does not weaken the Shell, it does create a time thickening effect on the underlying cosmological foam-structures of space. This slight gravitational change can be measured and used to detect the location of the materialization point of a TARDIS. Exposure to Zero Time (not developed until the Time War) removes the spatial elements from a TARDIS's Shell.
While the entire Exo-Shell can be transmatted or transducted without difficulty, the Interior cannot be penetrated by transmat beams unless the beam's power has been increased by a factor of 50 million. Certain gravitic, thermal, telepathic, and radioactive forces will be transferred to the inside (if the force fields are deactivated). Most of these forces (including gravity) can be negated by isolating this exterior shell from the interior Micro-Universe.
Certain violations of the 3rd Law of Time can stress the TARDIS's defence mechanisms, weakening the exo-shell. Under such circumstances, the corporeal shell could be shattered by something a small as a sub-sonic cannon ball. Such damage won't threaten the interior micro-universe, but the TARDIS will have to abandon most of the broken shell and re-grow an new one from what's left. If possible the TARDIS will use the HADS to retreat into the Vortex while this is done. Re-growing the exo-shell can take several weeks to complete, and the new shell will remain white until the process is complete.
Some areas of space are dangerous to a TARDIS interior. The Zeg Zone is one such area of space. The Electromagnetic Pulse Signature interferes with electrical and exitonic circuitry. If exposed to this radiation for too long the console will explode. Shortly after that, the TARDIS will seal its doors until it has repaired the damage and TARDIS has been physically transported out of range of the radiation.
In an emergency the TARDIS's exo-shell can also be used to temporarily plug some types of holes in space-time. In the post-Time War era severe temporal paradox can attract Reapers, which often leads to a break the link between a TARDIS's interior and its exo-shell. Faced with attacking Reapers, a TARDIS will separate its Exo-Shell from the interior universe to protect itself. This is done disconnecting its Time Vector Generator - leaving its Exo-Shell abandoned. The TARDIS will still retain a link with its Key and its owner. If the paradox that attracted the Reapers is removed, then the TARDIS will reactivated by the Time Vector Generator.
The exo-shell can be displaced from the current time-cone making it disappear. The auto-systems will try to return to the original time zone but need a standing wave generated by a binary induction system to home in on. A massive exterior gravitational force can warp the inner dimensions against the outer shell until a catastrophic schism develops in the outer shell. If this were to occur the interior of a TARDIS would break out and be randomly mapped into the area. This situation can be rectified with a sufficiently complex and powerful gravitational field that can draw the interior segments together, allowing the Endo and Exo-Shells to reform.
The following color code is used:
- Black: For information from the TV Series, including Dimensions in Time, and 1996 TV Movie.
- Blue: For information from the Novels and Audios including Target, Virgin, BCC, and Big Finish.
- Green: For information from 'licensed' reference sources such as the Technical Manual, Doctor Who Magazine, and the Role Playing Games.
- Red: For information from unofficial sources -The Faction Paradox series, behind the scenes interviews, author's speculation, and popular fan belief.
The TARDIS Technical Index is copyright Will B Swift.