DARPA Captive Air Amphibious Transporter

The Captive Air Amphibious Transporter (CAAT) was a research project of the US Defense Advanced Research Projects Agency (DARPA), run jointly with the Office of Naval Research, to move supplies from ship to shore during disaster-relief operations. It revisits the idea of the Second World War amphibious tractors that swam using their tracks.

Design

Like a tank, the CAAT runs on tracks driven by a sprocket, but instead of steel its treads are large buoyant elements, either inflated with air or filled with light foam. These keep the vehicle afloat, and in the water the tread segments open out into flat panels that push against the water like a paddle wheel. On land the soft treads act like tyres, spreading the weight of a vehicle weighing thousands of pounds to a ground pressure of only about 2 psi (roughly 0.14 bar).

Testing

Trials with a small-scale prototype showed it driving straight out of the water onto land, crossing beaches and mud, and climbing a one-foot (30 cm) wall from the water onto the deck of a barge. The intended uses included delivering cargo or troops after a major earthquake or tsunami, across beaches, mud, ice and sea walls.