As you all probably know comms with a submerged submarine are tricky: In order to establish two-way comms the sub has to almost surface and stick an antenna out of the water (not really stealthy), if it is submerged the communications are only one way via extreme low frequency waves (3-300 Hz) that require antennaes of hundreds of miles length: The lower the frequency, the longer the wave: For 3 Hz frequency the wave length would be 100.000 km, i.e. you would have to build antennaes of around 12.000 km length to communicate, and you need earths mass to create the power (this is why it is one way only):
where c= speed of light in m/s, lambda=wave length in m, and f the frequency in Hz.
This is, of cause, not really practical, and solutions to this problem have been searched for since long, now it finally seems light is to be seen at the horizon, Lockheed Martin has developed a new system in the
Comms at Speed and Depth (CSD) program, Within a few years, all U.S. Navy subs will be equipped with expendable high-tech communications buoys that will allow two-way real-time chat, data transfer and e-mail.
The system rotates around some expandable thethered buoys that are ejected from the subs and communicate with them through optic fibres, establishing comms with ground, space- naval- or airborne units. Three buoys are in development, two of them tethered to the sub and one freewheeling acoustic-to-RF buoy which can be dropped out of an aircraft or even launched out of a sub’s trash shoot.
Here some schemes how it is supposed to work:
Rattler
