China tests radical magnetic propulsion system that could make nuclear submarines almost silent

a reply to: mysterioustranger

They claimed they tracked Gracie the whale by satellite when she was swimming very deep by following her wake back in the 80's. Must be some other kind of submarine that isn't hollow?

Exactly. Im thinking the movement of anything underwater creates a static-movement trail. The sub may be invisible....but its movements may not be by exotic detection means already available.

a reply to: mysterioustranger

They use a magnetic anomaly detector to find them initially. Then they refine the position using sonobuoys and other methods.

a reply to: Zaphod58

I knew it was something like that! Thanks Z!

The USN is big on modal analysis. Everything that moves in air or water puts out subtle frequencies due to inherent modal properties of the vehicle. The shape of the vehicle itself even has a unique modal signature. Broadband analysis using Fourier and Gaussian filters can discover enough information to actually classify a submarine unique from any other. This tech was in it's infancy when I was in the service, but one can just imagine how the computing power of today has taken it to a whole new level.