Navy Hunts WWII Wreckage 20,000 Feet Deep With Cableless System
By Marcus Boone ·
Lost military assets and WWII warplanes lay hidden in the abyss until the Navy used an untethered system to scan the seafloor 20,000 feet deep.
The Advanced Unmanned Search System (AUSS) is a seventeen-foot cylinder of carbon-fiber reinforced plastic with titanium semi-spheres capping the ends. It weighs 2,800 pounds and is designed to operate at depths where the pressure would crush almost any other piece of equipment. According to a program description mirrored by the FAS Intelligence Resource Program, the AUSS was the result of twelve years of development by a team of designers and operators at SSC San Diego.
For decades, deep-ocean search meant the "classic long cable"—thousands of feet of tether that linked a submersible to its mother ship. The AUSS was designed to kill the cable. By removing the physical link, the Navy created a vehicle that was both unmanned and untethered, relying instead on an acoustic data link to communicate through the water. This shifted the role of the human from a pilot to a supervisor.
4800 Bits per Second
The communication between the surface ship and the AUSS was not a high-definition stream. It was a narrow pipe of compressed data. The acoustic link transmitted search data to the surface at rates up to 4800 bits per second, while high-level commands traveled down to the vehicle at 1200 bits per second. Because of this latency and bandwidth limitation, joystick control was unnecessary.
The program description notes that "all critical control loops are closed on the vehicle." The operator did not tell the machine how to move; they told it where to go and what to do. The AUSS used a gyrocompass and Doppler sonar to handle its own navigation, allowing it to hover in a specific location or execute large search patterns without assistance. It operated autonomously until the task was finished or an operator interrupted with a new command.
To get the vehicle to the bottom, the Navy used a weighted line. Once the mission was complete, the AUSS was commanded to drop an ascent weight and float back to the surface. At its maximum operating depth of 20,000 feet, the descent and ascent each took roughly an hour.
Document imagery from irp.fas.org From the files: irp.fas.org
The Douglas Dauntless
The eyes of the AUSS were a suite of sonar and optical sensors. The primary tool was a side-looking sonar (SLS) with a 4,000-foot swath. When the sonar picked up something of interest, the operators would mark the coordinates and suspend the search to investigate.
These investigations often turned up "false targets"—objects that looked like the intended prize on a sonar screen but were nothing of the sort. To filter these out, the AUSS used a charge-coupled device (CCD) electronic still camera. Images were compressed and sent acoustically to the surface computer, where an operator could determine if the target was genuine. The record notes that false targets could be dismissed in ten to fifteen minutes, while "hours can be spent inspecting an interesting object."
In the summer of 1992, the Navy put the system to the test off the coast of San Diego. During these trials, the AUSS searched several square miles of the seafloor and located a World War II Douglas Dauntless dive bomber in 4,000 feet of water. It also found a test target placed at 12,000 feet.
Beyond the planned targets, the AUSS stumbled upon other ghosts of military history. On a single dive at 4,000 feet, the vehicle discovered and inspected a Korean War-era Douglas Skyraider night fighter and a 55-foot private yacht. These finds served as proof of concept for a machine that could sustain search rates approaching one square nautical mile per hour.
Document imagery from irp.fas.org From the files: irp.fas.org
10 Hours of Endurance
The power for these missions came from silver-zinc batteries. At a maximum speed of five knots, the AUSS had an endurance of ten hours, though recharging those batteries required twenty hours of downtime. Typical missions lasted between ten and fifteen hours. The program description suggests that with three sets of batteries, the AUSS could operate indefinitely, with only three and a half hours between dives to the 20,000-foot mark.
While the documents emphasize the technical triumph of the untethered link, they leave the specific strategic goals of the AUSS largely implicit. The ability to precisely inspect the deep ocean floor is rarely about archaeology; it is about the recovery of lost assets and the monitoring of the abyss. The AUSS provided the Navy with a portable, compact system that could fit on an offshore supply boat, allowing for rapid deployment of deep-sea surveillance without the logistical footprint of a massive research vessel.
In 1994, the Advanced Unmanned Search System was transferred to the Navy's Supervisor of Salvage and Diving.