By Kris Osborn, President Warrior
(Washington DC) – For many years now the US Navy and its industry partners have been working to pioneer new innovations and technological methods capable of enabling a non-satellite or air-reliant GPS-like undersea communications technology. Historically, only some very low frequency radios have been able to very slowly transmit some information undersea, so boats have had to surface and use antennas to enable multi-domain networking and connectivity.
Much progress has been made in recent years, and there are now emerging manned-unmanned teaming technologies wherein fully “undersea” transport layer communications technologies can take place between manned and unmanned systems. Instead of needing an Unmanned Undersea vehicle to return to a host ship before downloading its sensor data, undersea drones can increasingly track and destroy mines, network to the surface and even send data in real time to undersea host ships. Drone are increasingly being launched from submarine missile tubes, and while there are still great challenges in the realm of enabling high-speed, real-time wireless undersea data transmission, the possibility is fast becoming a reality.
Acoustic transmission works undersea very much like radar works in the air, pings are sent forward and the return signal is analyzed and processed to generate a rendering of a threat object. Much like electromagnetic “pings” travel at the speed of light in the air, acoustic signals travel at the speed of sound and can deliver a return image or rendering of a given object. While still challenging, the question now relates to the speed and fidelity with which wireless undersea data can travel beneath the surface, and sending acoustic data is much more difficult than sending RF above the surface
UnderSea Challenges
However, the scientific challenges of bringing seamless connectivity undersea, similar to the way GPS functions on the surface, are substantial, Haas explained.
GPS signals work with algorithms able to compute the distance of an object by knowing the constant or “fixed” speed of light and the time of travel. If the length of travel is identified, along with the speed of a signal, then algorithms can quickly determine a precise distance, therefore identifying an object
For example, an electromagnetic signal used by a radar system — or laser from a weapon’s laser rangefinder — would use the known speed of light, and time of travel, to quickly identify the location, shape or speed of an object.
However, with acoustic signals undersea, determining distance is much more complex, Haas explained.
“For GPS the speed of light is constant. That is not the case for underwater speed of sound. Underwater signals are a function of many things, primarily temperature and salinity. We have developed models that account for all these acoustic signals underwater. Underwater signals don’t travel in a single line,” Lin Haas, program manager for the DARPA Strategic Technology Office, said in an agency podcast several years ago.
As a result, there is no linear transmission from transmitter to receiver with acoustic signals as there is with RF.
“Acoustic signals will take many paths; the signal is refracted through temperature and pressure profiles. Algorithms can improve current models and develop new modes,” Haas added.
Therefore, underwater drones can use acoustic waves to relay real-time info back to submarines.
The operative question then becomes … how much can existing Virginia class Blocks V and VI be upgraded before an entirely new platform architecture is necessary?
Years ago DARPA and BAE Systems launched a collaborative effort called Positioning System for Deep Ocean Navigation (POSYDON) designed to quickly relay location coordinates from undersea drones on patrol to command and control systems on board a ship or submarine.
Virginia-class Submarines
Each new Virginia-class submarine “Block” of boats has advanced undersea attack and detection technology to new levels, generating a circumstance wherein current Block III and Block V Virginia boats are entirely different from the earlier Blocks.
With a Virginia-class Block VI under development and continued exploration of a much discussed SSN(X) future generation attack submarine, some might be inclined to wonder just how far the Virginia-class boats can be upgraded before a new hull is necessary.
No Limits to Virginia boats
There appear to be few limitations regarding the extent to which Virginia-class submarines can be upgraded. Block III Virginia-class submarines and beyond are all engineered with a “fly-by-wire” automated computer navigational system which enabled humans to set depth and speed and allow computer automation to maintain the boat’s movements. This replaced the legacy hydraulic mechanical navigation systems. Block III Virginias also have a redesigned Large Aperture Bow sonar system which brings new levels of range and sensitivity to undersea acoustic detection. Block III boats also leverage fiber-optic communications technology to enable commanders to view periscope sensor input from numerous locations inside the boat.
In recent years, Block III boats have also received new antennas, coating materials and quieting technologies as well, something which greatly improves their ability to conduct clandestine undersea reconnaissance missions. Block III also makes use of a “lock-out-trunk” area where Special Operations Forces can exit a submarine for clandestine missions without having to surface.
Block V boats add massive firepower through the integration of Virginia Payload Modules, a roughly 80-ft missile-tube section added to the center of the boat to increase its Tomahawk missile firing capacity from 12 missiles up to 40. Alongside these innovations there continue to be new breakthroughs with undersea drones able to launch from missile tubes and conduct high-risk, forward-operating sensing and reconnaissance missions.
Wireless Undersea Connectivity
The largest area of progress in coming years may be in the realm of undersea communications, and these are the kinds of breakthroughs which can massively improve and change submarine operations without there being a need to build a new boat. The Navy and its industry partners have made great progress with wireless kinds of undersea data transmissions, such as in the case of Raytheon’s Barracuda mine-destroying undersea drone. Since RF does not transmit beneath the surface, except in some mostly ineffective low-frequency signals, the Navy and its industry partners such as BAE Systems and Raytheon have been working to pioneer undersea non-electromagnetic connectivity able to function like GPS can onland.
A key tactical advantage here relates to the use of undersea drones, as the Navy is still largely unable to transmit data quickly in real time between unmanned underwater vehicles and host ship submarines. Progress is being made, yet by and large forward operating undersea drones have had to gather, collect and organize sensor data and then “download” upon return. However, this is changing as innovators not only launch UUVs from missile tubes but also uncover technological methods of transmitting critical information in real-time.
One promising effort uses a series of transport layers integrated through gateways. Undersea drones can reach great depths yet remain “tethered” to a fiber optic cable able to send key threat data to the surface. Perhaps an undersea drone uses forward acoustic “pings” to analyze a return signal and detect the presence of an enemy submarine? In this instance the drone can instantly send threat details to the surface through a high-speed cable.
Once the information is on the surface of the ocean, gateway technologies can use advanced computer technology and IP protocol to essentially “translate” data from one transport layer to another. A surface gateway can attach to an antenna or above water sensing and transmission device in position to send an RF or GPS signal to air, land and surface nodes. Moving beyond this, emerging technologies can increasingly approach or come closer to an ability to transmit real-time data wirelessly undersea.
There would seem to be few limits to this kind of technological advancement, and it is something which could introduce new concepts of operation and support a new generation of undersea combat without needing to redesign the Virginia-class hull.
Kris Osborn is President of Warrior Maven – Center for Military Modernization. Osborn previously served at the Pentagon as a highly qualified expert in the Office of the Assistant Secretary of the Army—Acquisition, Logistics & Technology. Osborn has also worked as an anchor and on-air military specialist at national TV networks. He has appeared as a guest military expert on Fox News, MSNBC, The Military Channel, and The History Channel. He also has a Masters Degree in Comparative Literature from Columbia University
