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May 2001 Vol. 16, No. 5   RSS Feed for Undercurrent Issues
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Navy SEALS Strap on Cochran Computers nearly 20 years after sport divers

from the May, 2001 issue of Undercurrent   Subscribe Now

The U.S. Navy finally seems to be catching up with the recreational diving community in the use of wrist-mounted computers. At least, if the specially-designed Cochran computers currently used by one SEAL team live up to expectations.

SEALs began requesting computers more than two decades ago, but it took the Navy brass this long to develop its own custom decompression algorithm and to negotiate for a specially-designed unit that would allow that algorithm to be applied to air, Nitrox or the Navys Mark XVI rebreather without requiring divers to reprogram it underw ater. Then the Navy put out the project for competitive bids.

Dive computer pioneer, Cochran Undersea Technology, won the bid and filled the bill by adapting its Commander model to the Navys specs. The Commander is the most aggressive sport diving computer on the market even more aggressive than the PADI tables, allowing no-deco limits of 60 fsw for 54 minutes. The Commander also automatically adjusts for water temperature, salinity, actual rate of ascent and altitude (barometric pressure). Moreover, each user can program it from a selection of 50 degrees of conservatism. The computer has passed hyperbaric tests conducted by the Navy Experimental Diving Unit and Navy divers have begun testing it underwater.

There were several reasons why the Navy chose to go with its own algorithm, according to Dr. Dave Southerland, whos overseeing the reliability assessment of the Cochran computer for the NEDU. First, none of the existing sport diving algorithms had been sufficiently documented by Navy standards. They are, after all, closely guarded by the manufacturers as trade secrets and there is very little information available on their performance. The Navy felt more confident developing its own decompression profiles, which are based on the assumptions that users are all 25 years old and in tip-top shape, working harder than recreational divers, in more hazardous environments, and willing to accept more risk. For sport divers, the dive itself is the ultimate objective, as Dave Southerland points out. However, for SEALs, water is camouflage.

That said, the algorithm in the Cochran Navy model is more aggressive than sport computer formulas in some ways, but more conservative in others. For instance, it allows dives to 60 fsw for more than 60 minutes with no decompression. But once it kicks into deco mode, it typically calls for longer decompression times.

The SEALs have already made some suggestions for tweaking the Cochran computer (empirical modifications in Southerlands terminology). Too often the end user has not had input to the development of military technology, he points out. If the Navy model gets the final blessing, then the Naval Sea Systems Command (the approving authority for navy dive gear) may make it available to other military divers, as well.

But dont look for the Cochran Navy unit to show up in dive shops. Sport divers looking to push their no-deco limits must make do with the Cochran Commander, which retails for $495-$1,450 depending on such options as Nitrox compatibility and choice of backlighting color.

By the way, the developer of the computer, 59-year-old Michael Cochran, co-invented the microcomputer at Texas Instruments in the 1970s and then used this so-called miracle chip to build TIs first hand-held scientific calculator. Cochran got hooked on diving 17 years in the Bahamas. In 1993 he introduced the first wireless, wrist-worn dive computer at the DEMA show. Cochran says they have a return rate of less than 1 percent. Most returned units come back because the diver has opened the case to see how it works, he says. We call these curiosity failures.

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