Four teams and some strange machines competed for a quarter-of-a-million dollars from NASA, but all walked away empty-handed. NASA's Regolith Excavation Challenge invited teams to build machines for digging mock moon dirt, or regolith, in a competition held in a one-ton sandbox on Saturday. But all the teams fell well short of the winning requirement of 150 kilograms of regolith deposited in a container in 30 minutes, and no one claimed the $250,000 purse. An excavator built by Technology Ranch of Pismo Beach did the best, collecting just over 65 kilograms (143 pounds) in half an hour. All the other machines broke down while digging. The prize rolls over to next year's competition, which will be worth $750,000.