A ship’s rotating propulsion is not inherently electrically common with the bulk structure of the hull. However, the shaft will carry electrical current either from corrosion or cathodic protection sources. Without a designed low-resistance ground, the current can ground through various ship structures (e.g., shaft seals, bearings and reduction gearing), causing damage at the ground points.
Obtaining a consistent, electrically common ground between the rotating propulsion shaft and the hull is technically challenging. Present systems are less effective, requiring frequent maintenance of the contact interface. Ideally, a new system would employ highly consistent, maintenance-free shaft contact technology. Also, the associated electronic control package for the system should be able to output data, which provides useful feedback to the control of the ship’s impressed current cathodic protection system.
Also under development is an associated capability to measure current grounding to the hull at various points along the shaft, either where there is intermittent hard contact or where the design of the structure provides for close contact under normal operating conditions.
The new, advanced ASGS will ensure a consistent, low-resistance ground for the propulsion shaft. This will allow for more efficient operation of the impressed current cathodic protection system and will prevent the damage inherent in improper grounding of shaft currents.
The advanced ASGS will be transitioned to the fleet on the VIRGINIA Class, Block IV ships under the sponsorship of Program Executive Office Submarines (PMS 450).