Tribophysical waveform macro-kinetic extrapolator
The Tribophysical waveform macro-kinetic extrapolator (or Extrapolator to save time) was a long, flat device. It could be ridden like a surfboard. It would wrap the user in a protective bubble, enabling them to ride the energy from a vast explosion.
History
Blon Slitheen intended to use this to escape early 21st century Cardiff, blowing up Earth and riding away on the subsequent shockwave of energy. (DW: Boom Town)
It was later used by the Ninth Doctor and Jack Harkness to create a force field around the TARDIS to protect it from the Daleks' missiles. It was again used to shield the upper floors of the Game Station from the Daleks' transmats. (DW: The Parting of the Ways)
By the time the Tenth Doctor used it to move the TARDIS two hundred feet away from the Empress of the Racnoss, it appeared to have been integrated into the TARDIS systems. It was wrapped in TARDIS coral. (DW: The Runaway Bride) Later, the extrapolator's shielding was still in use by the Doctor, but it was no defence against a fully-formed Dalek empire capable of taking planets out of orbit. (DW: Journey's End)
It is unknown if when the Doctor's TARDIS regenerated itself, weather the ship took it upon itself to full integrate the extrapolator into it's circuits
