Originally designed to assist in assembling large ships and orbital installations, the salvage rig's gantry and manipulators are used to assist in recovering derelict hulks and scavenging useful material from wreckage and debris fields. The rig itself has no cargo or fuel capacity and requires ample supply to maintain. Increases non-combat salvage gained, with more difficult operations being able to make use of more rigs.
As a Destroyer sized class the Salvage Rig receives a 25% salvage bonus from its Salvage Gantry, compared to the 10% salvage bonus on the Frigate sized Shepherd class.
To check how this bonus stacks mouse over the Salvage Gantry hullmod in the refit screen and hit F1.
The Salvage Rig practically demands other ships to provide for its logistical needs, with its zero capacity for cargo & unable to meet its own skeleton crew requirements.