Kris Osborn, DefenseTech.org, Feb 11
A new study says emerging submarine detection technologies, computer processing power and platforms such as underwater drones could quickly erode the U.S. military’s global undersea dominance and ability to operate in high-threat areas such as locations near enemy coastlines.
The U.S. military relies upon submarines and undersea technological superiority for critical underwater intelligence, reconnaissance and surveillance missions, which place assets near the surface fleet or coastline of a potential adversary.
In coming years, the technological margin of difference separating the U.S from potential rivals is expected to get much smaller, requiring the U.S. the re-think the role of manned submarines and prioritize innovation in the realm of undersea warfare, according to a January report by the Center for Strategic and Budgetary Assessments titled “The Emerging Era in Undersea Warfare.”
“America’s superiority in undersea warfare results from decades of research and development, operations, and training. It is, however, far from assured. U.S. submarines are the world’s quietest, but new detection techniques are emerging that don’t rely on the noise a submarine makes, and may make traditional manned submarine operations far more risky in the future. America’s competitors are likely pursuing these technologies even while expanding their own undersea forces,” the report states.
Navy officials told Military.com the service was doing all that it could to retain its undersea technological advantage.
The U.S. has enjoyed an undersea technological advantage because it has quieter submarines that are more difficult to detect – combined with advanced sonar technology designed to find enemy submarines, the report’s author told Military.com
“At the end of WWII we did not have an undersea advantage. The Germans had developed submarines with snorkels and the U.S. was searching for how they would deal with them. The new subs could avoid radar detection and were quiet when using their batteries. Then, nuclear submarines came along. Passive sonar worked really well against them because they make noise continuously. Passive sonar works well against nuclear submarines and is less effective against diesels,” said Bryan Clark, the study’s author and senior fellow at CSBA.
Submarines are built to be quieter and less detectable through special engineering techniques which reduce the resonance of sound from the propeller and place insulation and sound-absorbing mounts in parts of the boat which radiate sound, Clark explained.
“This requires high-end manufacturing techniques. You engineer every component on the ship to be quiet and engineer them such that the noise does not reach the hull,” he said.
In the report, Clark details some increasingly available technologies expected to change the equation regarding U.S. undersea technological supremacy. They include increased use of lower frequency active sonar and non-acoustic methods of detecting submarine wakes at short ranges. In particular, Clark cites a technique of bouncing laser light or light-emitting-diodes off of a submarine hull to detect its presence.
“The physics behind most of these alternative techniques has been known for decades, but was not exploited because computer processors were too slow to run the detailed models needed to see small changes in the environment caused by a quiet submarine. Today, ‘big dat’” processing enables advanced navies to run sophisticated oceanographic models in real time to exploit these detection techniques,” Clark writes.
If U.S. attack submarines, SSNs, or nuclear-armed ballistic missile submarines, SSBNs, equipped with the latest in quieting technology are unable to elude detection by potential adversaries – then strategists and planners might need to re-examine their roles and missions, the report suggests.
“In the last 20 years there has been a dramatic increase in computer processing power and a miniaturization of computer processing. It used to be that some of these technologies could not be used in real-time. The ability to process and use information in real-time was not there. Processing power is now small enough and powerful enough to fit onto a platform,” Clark told Military.com
As a result, Clark foresees a much greater use of low-frequency active sonar detection, a technology which can successfully detect submarines at greater distances than most current systems.
“Most hull mounted sonars are medium band transmitting 1,000 to 10,000 hertz (Hz), whereas low frequency active sonar is less than 1,000 Hz. At lower frequencies you get longer ranges. At high frequency you get good resolution. At really high frequency you can get almost photographic like images,” Clark explained.
With longer range frequencies, sonar systems can have greater success searching multiple areas concurrently, he explained.
In addition, the report points out that unmanned underwater vehicles, or UUVs, will increasingly be used for “covert coastal surveillance and mining” previously reserved for manned submarines.
“Advances in battery and fuel cell technology are expected to enable non-nuclear submarines, UUVs and other undersea systems to operate for months submerged and power a growing number of sensors and other payloads. For example, the newest Japanese Soryu – class submarines will use lithium-ion batteries instead of air-independent engines for power when submerged,” Clark writes.
The same improvements that are making submarine detection easier will also likely enable a new generation of
sophisticated counter-detection technologies and techniques, the report says.
“Against passive sonar, a submarine or UUV could emit sound to overcome its own radiated noise using a technique similar to that used in noise cancelling headphones. Against active sonars, undersea platforms could – by themselves or in concert with UUVs and stationary or floating systems – conduct acoustic jamming similar to that done by electronic warfare systems against radar,” the report states.
Clark also sees a rapidly increasing ability for UUVs and manned submarines to work in tandem. For instance, he explains how the Navy’s now-in-development Compact Very Lightweight Torpedo, or CVLWT, could be fired from UUVs as an offensive weapon. The CVLWT is less than one-third of the size of the smallest torpedo currently operated by the Navy.
“Although the CVLWT has a short range, large UUVs could carry it as an offensive weapon and exploit their small size and signature to maneuver the torpedo close to a target,” Clark added. “Similarly, small UAVs such as the Navy’s Experimental Fuel Cell UAV have relatively short endurance but can be launched by submarines or UUVs close to adversary coasts. They can take advantage of continued miniaturization in electro-optical, infrared and radar sensors to conduct surveillance or electronic warfare missions.”
Undersea communication technology is rapidly changing as well, potentially allowing submarines to remain somewhat stealthy while communicating with other submarines and surface forces.
“Acoustic communications are increasingly able to operate over operationally relevant distances, while at shorter ranges LEDs and lasers could provide greater bandwidth. And new floating or towed radio transceivers enable submerged platforms to communicate with forces above the surface without risking detection,” Clark writes.
Clark recommends the Navy consider the prospect of thinking about manned submarines as an undersea equivalent to aircraft carriers – meaning they could project power, provide support and send forth smaller UUVs for sensing and attack missions.
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