Photos: Robot vehicles race for Grand Challenge Summary: A $2 million prize awaits the winner of DARPA's desert contest for unmanned vehicles. By Bill Detwiler | July 19, 2006 -- 11:36 GMT (04:36 PDT) Follow @billdetwiler Previous | Next Image 11 of 12 walking off course Ghostrider is walked off the course. Topic: Emerging Tech Kick off your day with ZDNet's daily email newsletter. It's the freshest tech news and opinion, served hot. Get it.