New wave of drones could track "boomers" wherever they go and make them vulnerable to a first strike.David Hambling, Popular Mechanics
28 March 2016
The U.S. and the U.K. are both readying their next-generation nuclear-powered ballistic missile submarines, the vessels that would launch nuclear weapons from the sea. While both navies are keen to go ahead with these project and replace their aging nuclear subs, British politician Emily Thornberry ruffled feathers recently by suggesting that maybe nuke subs won't have a place in the future.
If a new wave of underwater drones could track the "boomers" wherever they go, then that would make nuke-carrying subs vulnerable to a first strike and useless for deterrence. Some have hurried to dismiss the worry as "tired old science fiction," since Thornberry is far from the first person to suggest nuclear subs could be vulnerable to attack. But is science fiction becoming science fact?
During the Cold War, the Soviets found themselves on the wrong end of an underwater technology revolution. America and its allies laid a chain of ultra-sensitive microphones called SOSUS (SOund SUrveillance System) on the seabed between Britain and Iceland and between Iceland and Greenland. Unbeknowst to the Russians, every Soviet nuclear sub that passed over SOSUS into the Atlantic was detected and quietly shadowed by a NATO hunter-killer submarine, ready to unleash a spread of torpedoes if the order was given. "I felt very comfortable that we had the ability to do something quite serious to the Soviet SSBN force on very short notice in almost any set of circumstances," U.S. Admiral David Jeremiah told a symposium on Operational Intelligence in 1998.
The question today is this: Has underwater tech advanced so much since then that a new threat, nation-state or otherwise, could put our subs at risk? As Thornberry pointed out, there are two big challenges so such tracking: communications and battery life. Both are starting to look a lot less daunting.
Underwater communication has been improving rapidly over the last few decades, relying mostly on sound pulses with less bandwidth than radio frequency. Just as computer users have seen a shift from squawking, low-speed modems on analog lines to digital broadband, underwater communication speeds have lept forward. In the 1980's the standard was a mere 80 bits per second with no error correction. Now many kilobits per second are expected, and that's fast enough for underwater robots to be controlled wirelessly without the need for a tether. These improvements have come from new techniques for modulation and coding, aided by the ready availability of processing power. Speeds are still improving.
Underwater communications are typically limited to a few kilometres, but the other big development has been acoustic networking. Communications can now travel from one underwater vehicle in short hops via intermediaries, just like our own internet, so communication networks can spread over a wide area. A recent exercise by the U.S. Navy's Space and Naval Warfare Systems Command in
San Diego showed how multiple underwater and surface robots could be networked together to carry out a task cooperatively. Building a wireless version of the Cold War SOSUS starts to look like a viable prospect in the next few years.
The other great challenge is power—giving underwater drones the energy for long-duration missions. But there is one type of unmanned submarine which is uniquely well-suited to long-endurance missions. It's called the underwater glider. Developed by Teledyne Webb in 1991, these gliders are generally about six feet long and resemble a torpedo with wings. Instead of using a propeller, the glider increases its buoyancy and rises slowly, "gliding" forward underwater as it does so. When it reaches the surface, it reduces its buoyancy and glides on a shallow angle downwards. It's a slow but steady form of propulsion. In 2009, the Scarlet Knight glider from Rutgers University crossed the Atlantic in seven months.
With no engine noise to interfere, gliders can carry microphones so sensitive, as one researcher put it, that they can "hear a fish fart." In fact, one project used a glider to track shoals of fish off Florida by sound alone.
Naturally, the militaries of the of the world have been all over this technology. The U.S. Navy already has a number of projects using fleets of sea gliders. In 2010, an American counter-intelligence report noted that the Chinese were targeting this technology specifically. China's indigenous glider, the Sea Wing, was launched at the Shenyang Institute of Automation in 2011, and since then there have been a vast number of Chinese underwater glider projects. Most notable is the Haiyan or Petrel designed at Tianjin University. The Haiyan is a hybrid that has a propeller for rapid tactical maneuvering in addition to the buoyancy engine. Chinese state news reports indicated that the Haiyan may be used for mine-hunting and anti-submarine warfare, and analysts suspect the new Y-8GX-6 anti-submarine aircraft may act as a flying control station for a large number of Haiyan. The gliders would indicate the approximate location of a submarine, which the aircraft could pinpoint with its Magnetic Anomaly Detector (resembling a gigantic metal detector) before attacking.
The Haiyan can stay at sea for about a month, but China is working on ways of extending that. One solution is an underwater docking station where Haiyans plugs in and recharges. Another approach, one that Teledyne Webb considered with the original Thermal Glider, draws energy from the temperature difference at different depths. The "temperature difference engine," developed at Tianjin like the Haiyan was, would mean the glider would not require any external power for propulsion, only for its sensors and navigation. And in 2015, researchers at Northwestern Polytechnic University at Xi'an demonstrated a wave-power generator for gliders that taps the seas themselves to produce a trickle of power sufficient for the on-board electronics.
Other Chinese researchers are working on improving the dynamics of the glider design. Like U.S. Navy engineers before them, they are experimenting with flying-wing and blended-body concepts in which the glider resembles a manta ray with the wings and fuselage fusing into a single streamlined body. The U.S. developed this concept into the Liberdade series of gliders, which looked highly promising before being apparently canceled in 2011. This type of design gives more lift and less drag, making it faster and more energy-efficient, and may replace the traditional torpedo shape over the coming years.
Improvements in electronics, including the powerful, low-voltage processors produced by the smartphone industry, are making gliders and other underwater drones steadily smarter and cheaper with more effective sensors. While gliders are not capable of forming an all-seeing anti-submarine sensing network yet, the pieces are already falling into place.
The U.S. SSBN(X), America's next nuclear submarine that will cost $95 billion for 12 subs, will not come into service until 2031. The UK's Trident successor will be a year or two later, at a cost of about $44 billion for four subs. Both purchases are being made on the assumption that the new boomers will hide in the ocean depths and not, like the unfortunate Soviets, be spotted and tracked from day one. As such, defense strategists are counting on gliders and other drones not making much progress in the next 15 years…which would be surprising given their progress thus far.
Not long ago, a celebrity could walk down the street without seeing a camera. Now the mobile phone industry has produced billions of cameras, all with internet connections to make everything instantly sharable. If Thornberry is right, then the SSBN(X) will suffer the same fate as it leaves port, being mobbed by scores of small, cheap, digital sensors, unable to find seclusion and privacy anywhere.