Tribophysical waveform macro-kinetic extrapolator

The Tribophysical waveform macro-kinetic extrapolator was a long, flat device which, when ridden like a surfboard wraps the user in a protective bubble enabling them to ride the energy from a vast explosion.

History
Blon Slitheen intended to do this to escape early 21st century Cardiff, by blowing up Earth and riding away on the subsequent shockwave of energy. (DW: Boom Town)

It was subsequently utilised by the Doctor and Jack Harkness to create a force field around the TARDIS to protect it from the Daleks' missiles. It was again used to protect the upper floors of the Game Station from the Daleks' transmats. (DW: The Parting of the Ways)

When the Doctor used it to move the TARDIS 200 feet away from the Empress of the Racnoss, it appeared to have been integrated into the TARDIS systems, being wrapped around with 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)


 * What happened to the extrapolator after the TARDIS rebuilt itself into its sixth version is unknown, though it is no longer attached to the console.