12 July 2005

Artificial gill may revolutionise diving

An artificial gill that mimics the way fish breathe could allow divers to dispense with bulky oxygen tanks, it was claimed yesterday.

The device, which has been developed by an Israeli engineer, could also be used to supply air to submarines and underwater hotels.

Fish gills filter water to remove small quantities of dissolved air.

The device, which was designed by Alan Bodner, consists of a lightweight cylinder containing a centrifuge.

Water passing through the device is rapidly spun and thrown to the outside of the cylinder, leaving a vacuum in the middle. The drop in pressure releases dissolved air, which is collected.

Not only can the device help divers to breathe but it may also provide a form of jet propulsion, according to Mr Bodner.

"The diver will be able to adjust the directions of the intake and out-take vents to use the flow as a propulsion method in a similar way to a Harrier jet," he told the Engineer magazine.

The invention has already attracted interest from the Israeli navy, as well as from diving equipment manufacturers.

Oxygen tanks are the biggest limitation to the amount of time a diver can stay underwater.

As the tanks empty, they also change the diver's balance and this makes it harder for them to control their movements.

Recharging tanks with oxygen also takes time and is costly.

Nuclear submarines use electrolysis - a process of splitting water into its oxygen and hydrogen components using electricity - but this requires large amounts of energy.

Currently, Mr Bodner's device is powered by a one-kilo lithium battery providing a diving time of about an hour. He hopes to extend this to several hours, however.

The "gill" is best suited to closed-circuit diving, where exhaled air is continuously recycled by cleansing it of carbon dioxide and adding oxygen.

In conventional open- circuit diving, exhaled air is vented into the water. This process, however, consumes a much greater amount of air.

To operate in this way, Mr Bodner's device would have to extract air from large volumes of water.

Source: thescotsman.scotsman.com


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