|Source||Privateer 2: The Darkening|
As it is in Heaven
The Return to Sender, or RTS for short is activated in those desperate moments when a brute missile with your name on it is attempting to perform some radical modifications on your ship. Your ship computer activates it, and stands a good chance of sending a locked missile back from whence it came, much to your amusement and your assailant's surprise. Not available commercially just yet, you may get one in return for completing a mission, once fitted it will attempt to return every missile that is thrown at you.
ORIGIN's Official Guide to Privateer 2: The Darkening
The Alvis Return-To-Sender is a defensive system that has a 50% chance of returning any missile fired at you to the ship that launched it. Once this system is installed on your ship, it is permanently activated. There is no way to de-activate it manually.