Underwater Gliders

'Spray' uses primary-lithium-battery power and a hydraulic pump to periodically change its volume to alternately glide upwards and downwards. This results in a see-saw path at descent/ascent angles of 18-25 degrees and forward speeds of 25-35 cm/s. Heading and ascent/descent rate are controlled without control surfaces by moving weight (battery packs) inside the hull to change roll and pitch, much as a hang glider is controlled. As shown below, at the surface Spray rolls 90o to raise one of its wings, each of which contains a combined GPS/Iridium antenna. Using the wings to house antennas eliminates the drag associated with separate antenna housings and allows redundant systems so that communication and navigation can continue even if one antenna is damaged, as happened when one Spray was run over by a surface vessel.

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