(Updates with description of battery fault in third paragraph. For more on Flight 370, see EXT3.)
April 16 (Bloomberg) -- An unmanned submarine trolling for the missing Malaysian jet went on its third deep-sea dive to scan the Indian Ocean floor after technical issues cut short two fruitless sorties.
Data downloaded from the Bluefin-21’s second trip, which was interrupted by a “technical issue,” didn’t appear to show any significant objects, and the submarine was redeployed from the surface vessel Ocean Shield, Australia’s Joint Agency Coordination Centre said in a release.
A minor battery malfunction interrupted the mission, said Jim Gibson, general manager of Phoenix International Holdings Inc., the company performing the search under contract to the U.S. Navy. The issue, involving how the battery compensates for high pressures under water, was “not unusual at that depth.”
The Bluefin-21, named Artemis after the Greek goddess of the hunt, had spent 11 hours searching before coming to the surface, Gibson said by e-mail.
While the sub is rated to a depth of 4,500 meters (14,800 feet), it can plunge as far as 5,000 meters with a software upgrade, Gibson said. The torpedo-shaped vessel surfaced midway through its first attempt because a built-in safety feature sensed it was below the rated depth.
“Artemis is capable of reaching 5,000 meters of sea water with some inherent risk,” Gibson said. Largo, Maryland-based Phoenix also operated the towed pinger locator from the Ocean Shield that listened for signals from the cockpit-voice and flight-data recorders from Malaysian Air’s Flight 370. No audio pulses have been detected since April 8, suggesting the black boxes have run out of battery power.
The sub’s side-scan sonar captured images of the ocean bottom on a 4-by-1-mile swath on its initial dive, Gibson said. It “recorded great data of the bottom and confirmed there is no wreckage in the area we were searching,” he said.
The use of the submarine is the latest phase of an international search for Flight 370, which disappeared March 8 with 239 people on board. At 40 days, it’s now the longest search for a missing passenger jet in modern aviation history.
The crash-proof black-box recorders are pivotal to determining why the Malaysian Airline System Bhd. jet vanished en route to Beijing from Kuala Lumpur, reversing course and flying into some of the world’s most remote ocean waters.
The Bluefin-21, equipped with sonar that bounces sound waves off the bottom to create images of terrain, is supposed to be deployed for 24 hours at a time. It is intended to spend two hours descending, 16 hours on the ocean bottom, two hours returning to the surface, and four hours having its data downloaded, Angus Houston, who heads the JACC, said April 14.
The dives are meant to produce a high-resolution, three- dimensional sonar map of the seabed.
The submersible will stop a mission if the bottom drops away in a fashion that would cause it to exceed its rated depth, said David Kelly, president of Bluefin Robotics Corp., the device’s manufacturer, in an interview with Bloomberg Television yesterday. At depths of 4,500 meters, it’s “pitch black,” the water is slightly above freezing and objects will be subject to high pressure, he said.
Bluefin Robotics hadn’t received any call for an alternative vehicle at this stage, he said.
Gibson said the device is designed to withstand greater depths and the 4,500-meter limit is conservative. Adjusting the software protections would allow it to go beyond that threshold, he said.
After reaching its limit on the initial mission, the vehicle attempted to move to a backup area programmed into its computer, according to Gibson.
“It tried, but that area was too deep also,” he said. “So we let the AUV return to the surface.” High winds and swells delayed the ship’s attempts to scoop the vehicle from the ocean, he said.
All the systems functioned without issue, according to Gibson. “So I think it was a very good first dive,” he said.
A British survey ship is also in the area measuring depths because existing estimates have been inaccurate, he said.
The underwater sonar search could take as much as two months, the U.S. Navy’s Seventh Fleet said in an e-mailed statement April 14.
--With assistance from Manirajan Ramasamy in Kuala Lumpur.