Sea Mines: An Explosive Problem
Getting U.S. military personnel onto foreign soil during wartime maneuvers without having them blown to bits by sea mines is an ongoing concern for the Navy.
The Navy hopes to replace the divers with fast and efficient unmanned underwater vehicles. In this case, sending a robot to do a man’s job is a very good thing.
“There certainly have been diving accidents mainly due to the inherent risks of diving,” said John Petrik, corporate communications officer at the Office of Naval Research (ONR).
Many countries produce and sell mines, and why not? They can be made cheaply, produced in massive quantities, planted in near secrecy, destroy with lethal accuracy, and can be left completely unattended. These factors make sea mines an attractive part of a defense program.
They also tend to have a long life. On April 14, 1988, the USS Samuel B. Roberts (FFG-58) encountered a World War I Iranian contact mine in the Persian Gulf, causing $96 million worth of damage to the ship.
Sea mines located in shallow waters prove to be the trickiest to locate.
“They are harder to detect and more sophisticated,” Petrik said. “They are more disguised — they can be made to look like a ripple in the water.”
Contact mines, which haven’t changed much over the years, look pretty much as you’d imagine — as you’ve seen in the cartoons, Petrik said. They are big metal balls with spikes.
Despite the basic technology sea mines are very good at their job.
Currently there are two methods for detecting them. The first involves a ship equipped with sonar, the second a helicopter dragging sonar in the ocean.
Both methods are slow. In order fro the ship to avoid locating a mine by detonating it, it has to maneuver very carefully and slowly. Using a diver to identify suspicious objects is not only very dangerous but also slows the process.
“Divers have to come up every so often. They can only dive for so long and can only swim so fast and cover so much,” Captain Tim Schnoor, deputy program manager at ONR, said.
An added drawback with both methods is that in wartime operations it’s pretty tricky to be stealthy when doing either.
The need for a better solution led to the Navy’s research with underwater robots.
One of the Navy’s potential recruits is the Acoustic Radio Interactive Exploratory Sensor (ARIES), an underwater vehicle in development at the Naval Postgraduate School.
“It is a free-swimming, pre-programmed vehicle,” said Professor Anthony Healey, director of the Center For AUV Research at the Naval Postgraduate School. “We have what you could call an autopilot for speed, heading control, depth control and altitude. The vehicle follows a designed course.”
The vehicle can be equipped with a video camera used to identify mine-like objects. It’s a fixed-focus wide-angle camera located in ARIES’ nose.
But visibility can be a problem.
“We are experiencing storm runoffs at the moment, so the visibility can be less than two feet, meaning it is very hard to get quality images. It’s like groping in the dark,” Healey said.
There are other problems with the ARIES. The vehicle has to be brought to the surface in order to retrieve its data, which is time-consuming. The team is currently working on this.
Another possible new addition to the Navy’s countermeasure team is CETUS: An unmanned hover-capable vehicle designed for survey relocation and inspection.
“The vehicle uses pre-programmed code and artificial intelligence to respond to certain objects in certain ways. It has procedural reasoning. It can interact like a diver or a dolphin,” said Gary Trimble, principal investigator at Perry Technologies where CETUS is being developed.
And that’s not even its best feature. “What is really sexy about our vehicle is its acoustic camera. It’s an imaging sonar that can take pictures with sound. The quality is as good as a photograph,” Trimble said.
The CETUS sonar can detect objects in zero visibility, from 12 meters away, collecting photo-quality images. Data transfer is slow, though. “You can sit around for an hour waiting for one picture to get back,” Trimble said.
Another candidate for the Navy is the Battlespace Preparation Underwater Vehicle (BPAUV), developed and built by Bluefin Robotics. It has side-scan sonar that gives acoustic images of what’s on the seabed.
“It can show up all sorts of things — mines, shipwrecks, individual fish, even a strand of kelp,” said Scott Wilcox, technical manager at Bluefin.
BPAUV can cover a wide range when detecting mine-like objects. Once it has spotted a suspicious object, it will refer the identification to a vehicle with a video camera.
Once the vehicle returns to dry land, its data is downloaded. One gigabyte takes about one hour. Bluefin hopes to improve on the model.
Reaction from the divers has been very positive.
“They are awesome … they make my job more productive and safer,” said Karl Erikson, staff explosive ordnance disposal officer at Mine Warfare Command.
Schnoor believes that, once the kinks with the Navy’s newest recruits have been ironed out, they will be in operation in the next two to five years.