LOS ANGELES (AP) -- Wanted by the Pentagon: A muscular, outdoorsy specimen. Must be intelligent and, above all, self-driven.
When 20 hulking robotic vehicles face off next month in a rugged race across the Nevada desert, the winning machine -- if any crosses the finish line -- will blend the latest technological bling and the most smarts.
The military sponsors the race to speed the development of unmanned vehicles for combat. The project had an inauspicious start: Last year's inaugural contest ended soon after it began when the robots careered off course or abruptly stalled. One even got tangled in barbed wire.
Fast forward 18 months, and double the prize to $2 million.
Newcomers have joined a few of last year's teams to form a motley mix of garage tinkerers, academia and corporations. All hope that their machines -- fitted with the latest sensors, cameras and computers -- have aged a generation since last year.
Teams have beefed up their vehicles' artificial intelligence through improved computer algorithms that will help them avoid pitfalls such as ditches and boulders strewn across the roughly 150-mile-long course. To get there, the robots must compete in a semifinal showdown that starts Wednesday.
Entrants include several converted sport utility vehicles, souped-up passenger sedans, a modified all-terrain vehicle, a behemoth military truck and a motorcycle.
This year's race shows signs of intense competition. Some vehicles have logged hundreds of self-guided miles in the Southwest desert during summer practice runs. Several tested on last year's course, which spanned the Mojave Desert between Barstow, Calif., and Primm, Nev.
The ramped-up preparation reflects the higher stakes for the so-called Grand Challenge. While sweetening the purse, organizers promise that the course, which this year loops from and to Prime, a casino town on the Nevada-California border, will be tougher and meaner.
Vehicles will have to drive on dirt and gravel, maneuver mountain switchbacks, squeeze through choke points and avoid man-made and natural obstacles.
The sponsor of the Grand Challenge is the research arm of the Pentagon known as the Defense Advanced Research Projects Agency (DARPA), whose best-known success story is the Internet. The Pentagon wants one-third of the military's ground vehicles to be unmanned by 2015.