TARDISes are grown, not made. They draw their power from several sources, but primarily from the singularity of an artificial black hole, known as the Eye of Harmony. In The Edge of Destruction, the power source of the TARDIS (referred to as the "heart of the TARDIS") is said to be beneath the central column of the console. They are also said to draw power from the entire universe as revealed in the episode "Rise of the Cybermen", in which the TARDIS is brought to a parallel universe and cannot function without the use of a crystal power source from within the TARDIS, charged by the Doctor's life force.
Other elements needed for the proper functioning of the TARDIS and requiring occasional replenishment include mercury (used in its fluid links), the rare ore Zeiton 7, a trachoid time crystal and "artron energy". The latter is a form of temporal energy, generated by Time Lord minds, which is also said to help power TARDISes. Another form of energy, "huon energy", is found in the heart of the TARDIS and (apart from the activities of the Torchwood Institute) nowhere else in the universe.
Before a TARDIS becomes fully functional, it must be primed with the biological imprint of a Time Lord, normally done by simply having a Time Lord operate the TARDIS for the first time. This imprint comes from the Rassilon Imprimatur, part of the biological makeup of Time Lords, which gives them both a symbiotic link to their TARDISes and the ability to withstand the physical stresses of time travel.
Without the Imprimatur, molecular disintegration would result; this serves as a safeguard against misuse of time travel even if the TARDIS technology were copied. Once a time machine is properly primed, however, with the imprint stored on a device called a "briode nebuliser", it can be used safely by any species. According to Time Lord law, unauthorised use of a TARDIS carries "only one penalty", implied to be death.
A TARDIS usually travels by dematerialising in one spot, traversing the time vortex, and then rematerialising at its destination, without physically travelling through the intervening space. However, the Doctor's TARDIS has been seen to be able to fly through physical space, first in Fury from the Deep and at repeated times throughout the revived series, most notably in "The Runaway Bride", in which the TARDIS is actually shown launching into space (most previous incidents show the TARDIS flying only after it has dematerialised from a location). As seen in "The Runaway Bride", extended flight of this nature puts a strain on the TARDIS's systems. While a TARDIS can materialise inside another, if both TARDISes occupy exactly the same space and time, a Time Ram will occur, resulting in their mutual annihilation. In Logopolis, the Master tricked the Doctor into materialising his TARDIS around the Master's, creating a dimensionally recursive loop, each TARDIS appearing inside the other's console room.
Apart from the ability to travel in space and time (and, on occasion, to other dimensions), the most remarkable characteristic of a TARDIS is that its interior is much larger than it appears from the outside. The explanation is that a TARDIS is "dimensionally transcendental", meaning that its exterior and interior exist in separate dimensions. In The Robots of Death, the Fourth Doctor tried to explain this to his companion Leela, using the analogy of how a larger cube can appear to be able to fit inside a smaller one if the larger cube is farther away, yet immediately accessible at the same time. According to the Doctor, transdimensional engineering was "a key Time Lord discovery". To those unfamiliar with this aspect of a TARDIS, stepping inside the ship for the first time usually results in a reaction of shocked disbelief as they see the interior dimensions.
Susan Foreman, the Doctor's granddaughter, claimed to have coined the name TARDIS: "I made [it] up from the initials". However, the word TARDIS is used to describe other Time Lords' travel capsules as well. The Discontinuity Guide by Paul Cornell, Keith Topping and Martin Day suggests that "[she] was a precocious young Time Lady, and her name for travel capsules caught on." The Virgin New Adventures novel Lungbarrow by Marc Platt records Susan telling the First Doctor that she gave him the idea when he was, implicitly, the "Other".
As seen in The Trial of a Time Lord, the experiences of the TARDIS and its crew can be recorded and played back from the Matrix, the Time Lord computer network that is the repository of all their knowledge. The Doctor implies in this serial, with his protestations of being "bugged", that the TARDIS is not normally connected to the Matrix in this manner.
The TARDIS has been shown to be incredibly rugged, withstanding gunfire, temperatures of 3000 degrees without even scorching, atmospheric reentry, and falls of several miles. In The Curse of Peladon, after the TARDIS falls down the side of a cliff, the Third Doctor remarks that it "may have its faults, but it is indestructible." This clearly doesn't apply when facing certain extremely-advanced weaponry, often created after the Doctor's Type 40 TARDIS, such as Dalek missiles, for which the TARDIS requires additional shielding. Another piece of advanced Dalek technology which comes near to destroying the TARDIS is the power source of the Crucible in "Journey's End". Furthermore, in Frontios, the Fifth Doctor believes the TARDIS to have been destroyed in a meteorite bombardment, apparently contradicting the earlier claim of indestructibility. In 2007's Christmas special "Voyage of the Damned", the TARDIS is hit in mid-flight, creating a large hole in the interior wall, although its shields are down at the time. The Doctor later activates some controls and the TARDIS again becomes able to withstand an atmospheric reentry.and now it is to re-do again as Type 21
The Doctor's TARDISEdit
In the programme, the Doctor's TARDIS is an obsolete Type 40 TT capsule (presumably TT stands for "time travel") that he unofficially "borrowed" when he departed his home planet of Gallifrey. According to the Eighth Doctor Adventures novel The Gallifrey Chronicles by Lance Parkin, it previously belonged to a Time Lord named Marnal, who was, like the Doctor, something of a renegade. By the time of The Pirate Planet, the Doctor had been travelling onboard in time and space for 523 years.There were originally 305 registered Type 40s, but all the others had been decommissioned and replaced by new, improved models. However, the changing appearance of the primary console room over the years and the Second Doctor's statement in 1972's The Three Doctors ("Ah! I can see you've been doing the TARDIS up a bit. I don't like it.") suggests that the Doctor does upgrade the TARDIS's systems on occasion, though it has been implied that the ship's ability to reconfigure its interior architecture applies to the console room too. In the 2007 Children in Need special "Time Crash" the Fifth Doctor complains to the Tenth Doctor that he had "changed the desktop theme!". This implies that the TARDIS interior can be changed at whim to various different appearances.
The TARDIS was already old when the Doctor first took it, but exactly how old is a matter of conjecture; the spin-off media have, on a number of occasions, had the TARDIS wait around for the Doctor for decades and even centuries in relative time. In "The Empty Child", the Ninth Doctor claimed that he has had "900 years of phone box travel". In the unfinished TV serial Shada, fellow Time Lord Professor Chronotis said that the Type 40 models came out when he was a boy, which showed how old he was considering that he was on his final incarnation. When the 10th Doctor's TARDIS crashed down to Earth after his regeneration, it repaired itself and the interior changed once again.