Here we see the Tardis from the Bottom of the ship and from a different side angle. The Side angle shows the Dimensional Transmitter, and the communications, sensory antenna.
The Bottom of the Tardis is an important component in how the ship works.
As the Energy is drawn from around the Tardis, and fed into the main reaction chamber, just above the Time Sceptre, it is then collided and turned into Artron Energy, the life's blood of the Tardis itself, as well as the Energy used by the Doctor to Regenerate his body. This is why the Doctor must be inside the Tardis as he regenerates, because the Time Lord DNA structure is modified to accept that energy and react by regenerating their form into a new body.
Below the Tardis are several sections that affect the Time Space travel of the Ship.. Below is an explanation of each Component:
Dynamorphic Generators: The Dynamoprhic Generators act like Warp engines in Star Trek.. they Bend "Normal" Space around the Tardis and Transport the Outer Box to any point in the known universe, as well as time. Time Travel is a cohesion of the Dynamorphic Generators working in concert with the Cloister Room and the Artificial Eye of Harmony to move the ship into the Time Vortex and move time and space around the Ship. These Generators can make the Tardis Fly in a precise manner, and are used to stabilize the Larger Ship within it's own reality.
Dimensional Transmitter: The Dimensional Transmitter is used to beam information and data or signals through the Time Vortex and resonates at a level faster then light in a subspace frequency.
Communications, and Sensory Antenna: This dish device is used to receive psychic thoughts, psychic distress calls, intergalactic and computer distress signals, and normal time space telephone cellular signals. (most links that are used in that frequency are consistently maintained by the antenna unless cut off by a removal from space and time)
Cloister Room: The Cloister Room is a section of the Ship which houses the Artificial Eye of Harmony. This object is an artificial Singularity with a sense of consciousness tied to the Tardis itself. the Artificial Eye of Harmony is charged like a battery when a Tardis is First Born, and is the principle object that allows the Artificial Reality to remain open to "Normal Space."
The Original Eye of Harmony on Gallifrey is used to punch the hole in space and Time to create the artificial universe through which the Tardis is then grown. Once Grown that Tardis then needs it's own Eye of Harmony to remain connected to this reality and provide a principle power source for the Tardis. Hence the Name "eye of Harmony" the harmony of two Universes kept in constant view of each other. The Artificial Eye of Harmony's Raw Graviton and Tachyon Power is then focused into the Time Sceptre and used to keep the dimensional gateway open and allows the Tardis to extract Graviton, Chronitron, and Tachyon Particles from the Time Vortex rift. Those particles when bombarded in the main reaction Chamber then become Artron Energy.
Time Sceptre: This is the main device that is used to keep the Time Vortex, and relative Space open to the Tardis. This is also the Link that allows the Tardis Main Dimensional Causeway (a Doorway to Real Space) open and active. The Time Sceptre focuses the energies of the Artificial Eye of Harmony into it's shaft, which then focuses itself on a temporal point in "Real Space" and maintains an active opening always replenishing itself and the cloudy particles that are then used to sustain it's own reality bubble.