Toclafane rocket

The Toclafane Rockets were giant rockets created by Human slaves under the control of the Toclafane in The Year That Never Was.

History
As the Master planned to wage war against the rest of the universe, every scrap of metal was taken and used in making the rockets. All together there were two hundred thousand rockets. A hundred thousand were built in Russia and the rest elsewhere, including Britain. Each rocket also had a black hole converter in it, so that if the Master wished, he could activate them and Earth would be destroyed.

When the Doctor reversed time to prevent the Toclafane invasion, the rockets faded out of existence. (DW: Last of the Time Lords)