by James C. Sherlock
Upon investigation of open source literature, I find that offshore wind turbines are less noisy than I imagined. But they present obstacles nonetheless, both physically and acoustically.
United States submarine and anti-submarine efforts, operationally, in Navy labs, and in industry are led by some of our best and brightest.
That is true also, unfortunately, of most navies, including those of China and Russia.
The primary vulnerability of submarines is the noise they make, however minuscule. Submarine and antisubmarine technical and operational efforts are a constant cat-and-mouse game to minimize noise on the one hand and exploit it on the other.
The frequencies of the noise in the water from sea life, from shipping, from submarines and now from enormous turbine blades and the vibrations they cause in their supports are relatively discrete. That can help, or hinder, both submarine and anti-submarine warfare.
Weapons use against submarines presents other challenges. Attacks require targeting quality solutions, often from brief active-sonar transmissions. Again, noise.
Offshore wind turbines have complicated both offensive and defensive submarine operations.
Turbines are typically grouped about 500 meters apart in wind farms and generate noise in the water from individual turbines and group effects. As a rule of thumb, the bigger the turbine blades, the higher the noise generated. Bad weather exacerbates noise conditions.
The waters off of Norfolk and the nation’s other major commercial and military ports are of primary concern here. We expect and hope that the Navy is at the table in the design and location of each turbine field.
Here is a story from Germany that illustrates the issue.
- The Deutsche Marine requires locating devices be installed on German offshore turbines. The transponders are designed to be activated by a sonar transmission from a German submarine;
- Those turbine blades are much smaller than those to be installed off of Norfolk;
- The signal allows the submarine to locate the turbine where the transponder is mounted. The signal has to be strong enough to assure a sufficient signal-to-noise ratio and allow the submarine to avoid collision even under bad ambient undersea noise conditions;
- The acoustic impact on marine mammals has to be taken into account both in the far and the near field;
- But they do it.
If friendly submarines need active sonar and transponders to locate turbines to avoid collision with their mounts, it tells us that it would be difficult to detect enemy submarines near and amongst them. Though those fields would be as dangerous for enemy submarines as for friendlies.
Each blade on each turbine in the Norfolk field will be longer than a football field. Much bigger and thus likely noisier than those off the coast of Germany. And perhaps at different acoustic frequencies.
Now, understand that Germany has a far closer and thus much more immediate enemy submarine problem than we do. American antisubmarine efforts are concentrated in keeping enemy submarines from getting anywhere near Norfolk or Bremerton.
But nothing is perfect.
The American submarine fleet. Submarine Force Pacific Fleet (SUBPAC) writes:
With the number of foreign diesel-electric/air-independent propulsion submarines increasing yearly, the United States Submarine Force relies on its technological superiority and the speed, endurance, mobility, stealth and payload afforded by nuclear power to retain its preeminence in the undersea battlespace.
The Navy has three classes of SSNs in service. Los Angeles (SSN 688)-class submarines are the backbone of the submarine force with 40 now in commission. Thirty Los Angeles-class SSNs are equipped with 12 Vertical Launch System tubes for firing Tomahawk cruise missiles.
The Navy also has three Seawolf-class submarines. Commissioned on July 19, 1997, USS Seawolf (SSN 21) is exceptionally quiet, fast, well-armed, and equipped with advanced sensors. Though lacking Vertical Launch Systems, the Seawolf class has eight torpedo tubes and can hold up to 50 weapons in its torpedo room. The third ship of the class, USS Jimmy Carter (SSN 23), has a 100-foot hull extension called the multi-mission platform. This hull section provides for additional payloads to accommodate advanced technology used to carry out classified research and development and for enhanced warfighting capabilities.
The Navy continues to build the next-generation attack submarine, the Virginia (SSN 774) class. Twelve VIRGINIA’s have been commissioned to date and they will replace Los Angeles Class submarines as they retire.
So, if I count that right, we have fifty-five-three fast attack boats, some always undergoing repair and upgrades, for protection of two very long coasts, for ocean operations worldwide and for near shore operations overseas.
Many are built, repaired and upgraded in Newport News.
SUBPAC lists twenty-one fast attack boats currently assigned to the Pacific Fleet for support of operational commanders across their vast areas of operations spanning half the globe.
SUBLANT lists twenty eight. The PCUs are pre-commissioning units. The priority of assignment of attack submarines to the Atlantic Fleet reflects longstanding concerns about Russian submarines. The fast-expanding Chinese undersea fleet will change that calculation soon enough.
We have other antisubmarine forces, both air and surface, but they deal with the same acoustic issues and themselves would admit that the most lethal of our antisubmarine capabilities lies in our fast attack boats.
Bottom line. So, what will be the impact on submarine and anti-submarine warfare off of Norfolk when the largest-ever wind turbines are installed there?
Or anywhere off of America’s coasts?
The Navy is certainly not going to tell us. And should not.
The costs of the military solutions to the antisubmarine problems caused by offshore turbines are buried in the Navy budget, not in cost estimates from Dominion Power and the like.
Americans have a right to insist the new turbines planned off of Norfolk and elsewhere not prove a major operational obstacle to our defense. And thus to insist the Navy have a seat at the table in the offshore wind turbine decision processes.
Virginia State Corporation Commission take note.
We are left to hope they already have.