U.S. company launches motor-less submarine

William Atkins
Monday, 11 February 2008 21:26

Science - Energy

Massachusetts-based Webb Research has successfully tested an unmanned mini-submarine that uses temperature differences in the ocean to power itself.       

Webb Research Corporation, based out of Falmouth, Massachusetts, has invented what it is calling a “Slocum glider.”

The name Slocum comes from Canadian-American seaman and adventurer Joshua Slocum (1844-1909), the first person to make a solo circumnavigation of the world—sail around the world alone (between 1895 and 1898).

The Webb vessel is also called a “thermal glider” because it uses thermal energy, temperature differences in the ocean, to move in the water. So far, a two-month test has been conducted with the vehicle, which does not use a propeller to move along.

The six-foot (1.5-meter) long, 132-pound (60-kilogram) vehicle changes its height under the water by pumping fluid back and forth between bladders that are located on the interior and exterior of the hull. The hull’s diameter is about 8.4 inches (21.3 centimeters).

In relatively warm water, wax positioned inside a chamber melts and expands. Such action makes a pumping action that pushes the water from the interior to the exterior bladder.

The Slocum glider can descend to 6,500 feet (2,000 meters) for a time period of about five years. It has a maximum range of 24,800 miles (40,000 kilometers).

To move up, fluid is pumped from the interior bladder to the exterior one. Thus, its volume increases as the exterior bladder expands in size. Such an arrangement increases the buoyancy of the vehicle, and it rises in the water.

When the vessel reaches the ocean’s surface, the pumps are recharged as wax melts and again expands. Fluid is drawn back into the interior bladder from the exterior one, and the vessel submerges back down into the water.

Fins on the vessel give forward momentum as it rises and falls in the water. It can move at a horizontal speed of about one mile (1.4 kilometer) per hour, as it moves up and down about 4,000 feet in a cycle all with a temperature difference of about 43 degrees (Fahrenheit).

Long-duration batteries transmit data from the vessel through a RF (radio-frequency) modem, ARGOS satellite-based ground system, and Iridium satellite system.

The Slocum glider is expected to help measure ocean currents, sea surface heights, temperatures, and various other properties of ocean waters. Because of its small cost to operate, Webb Research foresees that many such vehicles could be used in the future in order to study and map the dynamic features of subsurface coastal waters.

Please turn the page to learn more about Webb Research Corporation and its founder Douglas Webb, along with additional information about Joshua Slocum.