Underwater mines are lurking in critical waterways around the world. Low-tech but highly destructive, they can blow up ships, destroy oil and natural gas pipelines, and wipe out international telephone and Internet cables.
By U.S. Navy estimates, some 50 countries stock more than 250,000 maritime mines that could be dropped in the world’s oceans. Naval analysts believe China has the most extensive and sophisticated inventory of mines. If Iran had shut down the Strait of Hormuz earlier this year, as it threatened, its strategy likely would have involved deploying its stockpile of mines.
The Navy currently relies on a small fleet of ships and divers dispatched from submarines to find mines and defuse them. Trained dolphins, equipped with cameras and sensors, also sniff them out. With the Pentagon facing $1 trillion in budget cuts over the next decade, finding money for those missions “is going to be a huge challenge,” says Captain Duane Ashton.
Instead, the Navy plans to rely on the Knifefish, an underwater drone that Ashton’s Unmanned Maritime Systems Program Office is developing. The 19-foot-long Knifefish weighs 1,700 pounds and is powered by lithium-ion batteries. Shaped like a torpedo, it will roam the deep seas for 16 hours at a time—unpiloted. The Navy is spending $170 million over the next five years to design and buy eight of the robots from General Dynamics and Bluefin Robotics. It expects to get delivery of the first Knifefish in 2017, acquiring 30 by 2034.
The drones are an upgrade from a small fleet of remote-controlled underwater vehicles the Navy has used since the 1990s to comb shallow harbors and clear debris for ships. These vehicles can make out suspect objects, but the Navy must send in divers to investigate further. The more powerful Knifefish sweeps for mines by sending out low-frequency sound signals; when they bounce off a man-made object, the drone develops an image that it takes back to analysts aboard the mother ship. Ashton says it “can tell a mine from a refrigerator littering the bottom of the sea.”
The challenge for the Navy lies in programming the drones to operate without a pilot directing them via a cable, which would restrict their reach in deep water. “The ocean is so big that you can’t just joy-stick” drones, says Tom Curtin, a former scientist at the U.S. Office of Naval Research. Sea floors aren’t well mapped and change constantly due to shifting currents and weather. Unlike their aerial cousins, underwater drones can’t connect to satellites or GPS to navigate.
Eventually officials hope to build underwater drones 10 times as large as the Knifefish that could blow up mines, says Thomas Swean, team lead for ocean engineering and marine systems at the Office of Naval Research. First the military has to develop better power sources so the bigger drones “can last three months instead of two days” without needing a recharge, Swean says.
“As much as people have been taken with unmanned aerial vehicles,” says former Chief of Naval Operations Gary Roughead, “you haven’t seen anything yet.”