'Degaussing Cables': How the USS Abraham Lincoln erases its giant magnetic shadow

The USS Abraham Lincoln is a massive steel structure that naturally distorts the Earth’s magnetic field. This creates a "magnetic shadow" that underwater sensors can easily detect. Without protection, the carrier is a sitting duck for sophisticated magnetic mines.

Underwater magnetic mines trigger when they sense a shift in the local magnetic field. These mines can detect a 100,000-tonne ship from hundreds of metres away. Degaussing is the primary defence used to avoid this invisible and deadly threat.

Inside the carrier, engineers have installed roughly 50 kilometres of heavy-duty copper degaussing cables. These cables are wrapped in specific patterns throughout the ship’s internal structure. They carry electrical currents that generate an intentional, opposing magnetic field.

The system effectively cancels out the ship’s natural magnetism by creating a precise counter-field. This reduces the carrier’s magnetic footprint by up to 90 per cent in most conditions. It allows the vessel to pass over mines without triggering their detonators.

The degaussing system on a Nimitz-class carrier consists of approximately 12 independent coil groups. These groups are controlled by computers that adjust current levels in real-time. This ensures the protection remains constant regardless of the ship’s orientation or location.

During its mid-life Refuelling and Complex Overhaul, the Lincoln received significant upgrades to its electrical systems. These improvements included more efficient power distribution for the degaussing network. This ensures the system remains reliable for the next 25 years of service.

Crews on the USS Abraham Lincoln monitor the magnetic signature around the clock. Any change in the ship’s cargo or geographical position can affect the magnetic field. Constant calibration is required to maintain this high level of underwater stealth.