China conducts test flight of a giant coil array. Can it detect nuclear submarines?

At an undisclosed test site, a helicopter takes off, towing a kite-like array of massive coils. The system, called Airborne Transient Electromagnetic (Atem) detection, works by firing a powerful pulse of electricity through a giant transmitter coil. This creates a brief, strong electromagnetic field that penetrates the ground or water. When the pulse is turned off, the magnetic field induces tiny,