The Darpa Robotics Challenge (DRC) involves eight tasks: driving a car; getting out of the car; opening and walking through a door;opening a valve; Using a drill to cut a hole drawn onto a wall; crossing a debris-filled terrain – either by clearing a path for itself or walking over the rubble; climbing up steps and a mystery event, that will only be disclosed to the teams on Friday. The crews can provide remote guidance – for example helping their robot identify the valve – but cannot control specific movements. The robot has to keep all the energy on board using batteries. Contestants only have an hour to complete the circuit. “It is, in my estimation, 10 times harder than before,” said Dr Gill Pratt, the challenge’s manager. Between favorites was a team of Google but they has quit the contest because the company had concerns about being linked to a military-backed event. $3.5m (£2.3m) worth of prizes are announced.