Today’s submarines are link blimps in the ocean. They float high over the sea floor. Dr Robert Ballard proposes submarines that hide on the ocean floor.
Modern nuclear attack submarines like the American Seawolf class are estimated to have a test depth of 490 meters (1,600 ft), which would imply (see above) a collapse depth of 730 meters (2,400 ft). Each 10 metres (33 feet) of depth puts another atmosphere (1 bar, 14.7 psi, 100 kPa) of pressure on the hull, so at 300 metres (1,000 feet), the hull is withstanding thirty atmospheres (30 bar, 441 psi, 3,000 kPa) of water pressure. World War II German U-boats generally had collapse depths in the range of 200 to 280 metres (660 to 920 feet).
In 1984, Dr Robert Ballard demonstrated the ability to operate on the ocean floor during a two-week exploration near Iceland’s Reykjanes Ridge. He took the Navy’s deep-sea research submarine, the NR-1, down 3,000 feet and drove it around volcanic peaks; he even hid in the occasional lava tube. At the time, the NR-1 was the Navy’s largest deep-sea research submarine and its smallest nuclear sub. At a length of 150 feet and 400 tons, it could support a crew of 13 for up to a month. But most importantly, the NR-1 had retractable wheels and portals. The wheels allowed the NR-1 to roll along the seafloor. The portals allowed the sub drivers to see where the hell they were going.
In a complex, jumbled terrain with rocks, mountains, and canyons, the sound waves get so jumbled up that it’s impossible to make any sense of the sounds that come back.
Navies also use very sensitive magnetic detectors to locate the giant, metallic mass of the submarine as it moves underwater. But this method is less effective in some kinds of seafloor terrain. For example, near basaltic rocks, which interfere with even simple compasses and create downright havoc with sensitive magnetic sub-hunting gear.
Between the jumbled sonar and the magnetic interference of the ocean floor, it can be very hard to find something hiding in the seafloor terrain. Ballard illustrated this point clearly when he dared the Navy to find him while he was tooling around on the Reykjanes Ridge in the NR-1. Two weeks of searching later, the Navy had no clue where he was.
SOURCES – Vice, Wikipedia, Ocean Service NOAA