Military robot subs seek out sunken treasure

• 16:18 27 May 2008 by Jeff Hecht
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Robot submarines designed to hunt for underwater mines showed potential as underwater archaeological treasure hunters last week, turning up several new artefacts off the coast of Rhode Island, US.

Several military AUVs (autonomous underwater vehicles) took part in the archaeological treasure hunt as part of a US Navy event called AUVfest. The contest suggests that robotic submersibles could find many non-military applications as they become cheaper.

The US National Oceanic and Atmospheric Administration (NOAA) sought to test the ability of navy subs to investigate shipwrecks and inspect undersea cables and pipelines.

During the event, the subs discovered eight previously unknown objects associated with the wreck of 18th century frigate, HMS Cerberus, which was scuttled by its British captain in August 1778 during the American Revolution.

Mine hunting

The small AUVs involved (0.5 to 5-metres-long) are mainly used by the US navy to search for mines planted in harbours. These submarines scan the seafloor using sonar and magnetic sensors.

Aboard each submarine, software processes the collected images, trying to differentiate mines from lobster pots and other "clutter" on the seafloor.

If something matches the profile for a mine, the AUV can go back for a closer look. The data can be downloaded when it returns to base or, if the need is urgent, the AUV can surface and send the information via satellite link.

Several such AUVs were tested at four known shipwreck sites in Narragansett Bay on the north side of Rhode Island.

They discovered buried objects around two wrecks from the Revolutionary War, and provided more detailed maps of two 20th-century wrecks.

Hidden treasure

Sonar reveals a larger field of debris around the Cerberus than previously thought. One buried object, examined close-up with sonar and magnetic scanners, appears to be a cannon.

Small AUVs could be particularly useful for exploring wooden wrecks, says Charlotte Taylor of the Rhode Island Marine Archaeology Project, as they do not disturb sediment from decaying timber making it difficult to see the wreck.

It may be treasure hunters rather than archaeologists who first buy military AUVs, says Bob Anderson, president of AUV manufacturer Ocean Server Technology, based in Massachusetts, US. Ship-mounted sonars can easily spot potential booty below, but a small AUV could explore a wreck site without tipping off rival bounty hunters, Anderson says.