U.S. military’s crawler prototype drives on water, land and everything in between

As the nation's armed forces think tank, the Defense Advance Research Projects Agency tends to think about problems most of us didn't know needed solutions -- like how worrying about communications during a nuclear war led DARPA to create the foundations of the Internet. Among its projects are ways to haul supplies in disaster-struck areas, such as flooded cities, and this is one proposed solution: a tractor that doesn't care whether it's on land or water.

One of DARPA's priorities has been to investigate how the U.S. military might better deliver aid to places struck by natural or man-made disasters, where airports, docks and roads may be destroyed. The central idea involves using a container ship packed with materials -- including vehicles that themselves can fit inside a standard shipping container, then be built on site to deliver goods.

The Captive Air Amphibious Transporter, or CAAT, runs on an old principle that the U.S. Army has been testing since the early 1960s. By combining a tank trend with low-pressure air bags, the CAAT can spread its weight over a massive area while using air pressure to stay afloat in aquatic territory. It's not just open water; the one-fifth-sized tester shown in the video below weighs about a ton, but can glide over muddy swamps that would suck in people on foot.

DARPA says it lacks the money to make a full-scale version of the CAAT for real-world testing, and given how infrequently such a craft might be used, the idea might have little interest among private firms. But with weather-related disasters on the rise around the globe, having a craft that could carry several tons from land to water and back without stopping is an idea worth remembering.