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Unmanned Sub With No Engine
01 Jan 2005
Spray , a novel unmanned glider-type submarine with no engine has recently completed extensive crossings of open seas measuring salinity, temperature and pressure in the Gulf stream between the surface and 1,000m depths every seven hours.
Developed by Scripps Institution of Oceanography in California, Spray has a range of 6,000km and can reportedly stay at sea for months at relatively low cost, says Russ Davis of the Institution. It will allow observations of large-scale changes under the ocean surface that might otherwise remain undetected, he adds.
With a mass of 50kg, Spray glides up and down through water on pre-programmed courses by changing its effective density.
For this, a battery-powered pump shifts a litre of mineral oil between two bladders, one inside the aluminium hull and the other outside. The submarine does not just drift. Instead, as it sinks or rises, 1.2m-span wings ensure forward momentum sufficient to average 20km per day.
Spray records its position at the beginning and end of each dive by rolling on its side to expose a GPS antenna in its right wing tip. Researchers in the meantime obtain data and relay new instructions via a satellite and an antenna in its left wing tip. On its next scheduled trip between Woods Hole, Massachusetts and Bermuda, the vehicle will carry an acoustic doppler current profiler to give vertical profiles of current speed and velocity.
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