December 19,
2008: The U.S. Navy has developed a system for nuclear subs to communicate with
the rest of the world that, normally, could not be done until the boat came
close to the surface and poked a radio antenna above the surface. The new
system is called Deep Siren (or "tactical paging system"), and
provides a practical solution to the problem of communicating with a submerged
sub. The system consists of a disposable buoy, that is dropped in the water, by
an aircraft or over the side of a ship, in the general area (within about 90
kilometers) where the sub is believed to be. The buoy sends out an acoustic
signal that U.S. subs are equipped to pick up. This coded message either orders
the sub to get a radio antenna above water and call home, or simply delivers a
brief message. The buoy also has a satellite telephone capability, so that additional
messages can be sent from anywhere, to the sub. The sub cannot send messages to
the buoy (because powerful sensors are required to pick up the signals). In the
past, the only way to "page" submerged subs was via a large, shore
based, low frequency, transmission system. This system was less reliable than
the new one, although it had a much longer range.
The navy
recently successfully tested the other end of the system. The sub releases a
similar buoy through its garbage chute. The buoy hovers for a while, then rises
to the surface and sends its messages. The buoy delays surfacing until the sub
is far enough away so the buoy signal will not give away the exact location of
the boat. The buoy then receives messages (short ones) and uses a sonar type
device to send the data acoustically, for up to 90 kilometers, to the sub.
Outgoing messages, which are sent via satellite, can be longer, and even
include outgoing email from the crew to family. But the acoustically
transmitted messages are much shorter, and include orders from the surface
ships, or anyone in the chain of command, to the sub commander.
Deep
Siren will also be useful for American
carrier task forces, which are usually accompanied by at least one SSN (nuclear
attack sub.) Because thermal layers make underwater transmissions vary a great deal in range, the buoy sends the
command messages several times to insure at least one gets through. The buoy
from the sub can stay active for several days, if the sub is remaining in the
area. But eventually, the buoy sinks itself. The navy has not bought Deep Siren
yet, but is apparently going to test it more frequently, to see how reliable it
would be.
