New Technologies To Aid Submarine Stealth?

During the last week, there have been announcements of a couple of new technologies that could make submaries even harder to detect. The first one, which has actually been built, is a system to send encrypted communications to submarines from expendable bouys that can transmit a digital signal underwater as far as 175 nm. Excerpt:

To communicate with a submerged submarine safely, a gateway mechanism is required to deliver messages deeper than periscope depth. The Deep Siren Tactical Paging system is comprised of a disposable gateway buoy with an antenna that gathers radio-frequency signals and converts them to Deep Siren acoustic signals that penetrate the water and are received by the submarine's sonar system. These acoustic signals are then converted on board the submarine to text messages with the Deep Siren receiver. The Deep Siren system also includes a portable transmit station which can be located on shore or carried on board a ship or airplane. "You want to have this be a global capability, where the buoy can be called from anywhere in the world," Matzelevich says.
Working with RRK Technologies, Ltd., in Glasgow, Scotland, and Ultra Electronics Maritime Systems in Dartmouth, Nova Scotia, Raytheon is developing a Deep Siren system that includes expendable buoys that are five inches (12.7 centimeters) in diameter and about 3.5 feet (one meter) long with antennas that receive signals from a constellation of Iridium Satellite, LLC, communication satellites. The buoys—designed to stay afloat for up to three days—can be ejected out of the sub's trash disposal unit without major modifications to the vessel. In this way, subs can set up their own acoustic networks without the need to tow an antenna.

The story says the system is supposed to get an at-sea eval in June as part of the Communications At Speed And Depth initiative. The story made it seem that subs only communicate now by using the Floating Wire Antenna at periscope depth, but I'm assuming that the writer didn't understand what the retired submarine Captain was saying.

The other new breakthrough has to do with defeating active sonar by "bending" sound waves around a submarine. This one is a fascinating theoretical advance, but I really don't see it having any practical application. (The abstract is located here.) The problem is that is appears that this would require covering the submarine with honeycombs of a still-undiscovered "metamaterial" which, I'm guessing, wouldn't have much in the way of the strength needed to retain it's shape at depth while still allowing for hull compression. If they can eventually tech this one out, I wouldn't expect to see boats using it for at least several decades.