Tractor envelope

"Look, this whole junkball's held together by a tractor envelope. Stops it from breaking apart."

- Chelli Aphra

A tractor envelope was a form of gravity field. The wrecked ships that made up the body of the Galactic Empire prison Accresker Jail were held together with a tractor envelope.

Appearances

 * Doctor Aphra 23: The Catastrophe Con, Part IV