The Floating Zombie — D.F. Jones

The Taking of AT1: Before AT1 had ground down the slipway unchristened - rightly, said seamen, for it would be a ship with no soul - it had been dubbed 'Zombie'. That sinister name would stick and prove its accuracy.

AT1 was a robot-ship, a ship with no crew, only a tiny security force of three men & a woman. 'Invulnerable,' said its inventors, 'foolproof'. But it was neither - not if one of the four security guards was an insane, ruthless killer. And if the greatest, most powerful self-contained nuclear reactor in the world fell into the hands of such a person, the whole world was in peril!