The Drifter was a spacecraft that collected scrap.
The ship was piloted by Flotsam and Jetsam and their windmill-powered robot Dutch. They picked up the TARDIS, which was floating in space while the Fourth Doctor meditated inside. After the Doctor accidentally reactivated a Cyberman, it kidnapped Jetsam and stole the TARDIS. It went to AS4 to reactivate a crashed Cyber-Fleet.