EMP Proofing Navy Ships

Nuclear generated EMP (electromagnetic pulse) can enter ships via "front door" or "back door" paths of entry. Antennas, tuners, couplers, and transmission lines are examples of "front door", or intentional, paths of entry for electromagnetic energy, while pipes, doors, hatches, windows, vents, power, signal, and control lines, and waveguides are examples of "back door" paths. Direct penetration of the EMP wave might be expected through doors, hatches, windows, and vents. However, tests to date suggest that the amount of energy which enters through these openings is small enough so that no additional measures are needed to reduce the EMP penetration. Cable, waveguides, and pipes can all behave as antennas, collecting EMP energy. The energy collected is then transferred as transient electrical currents through weather decks to the interior where it can cross-couple to other cables, or can flow through connectors directly to electronic and electrical equipment. Because of the way ships are built, EMP protection should be considered at two levels: the platform level, involving ship construction and equipment installation, and the equipment level, involving the construction and operation of "black boxes". This paper discusses hardware and procedures recommended for use at the platform level for preventing entry of EMP-induced currents into ship systems. Efforts in this direction carry incidental benefits to maintaining shipboard EMC as well.