ROBERT, La. — The most ambitious bid yet to stop the worst oil spill in U.S. history ended in failure Saturday after BP was unable to overwhelm the gusher of crude with heavy fluids and junk. President Obama called the setback ‘as enraging as it is heartbreaking.’ The oil giant immediately began readying its next attempted fix, using robot submarines to cut the pipe that’s gushing the oil and cap it with funnel-like device, but the only guaranteed solution remains more than two months away. The company determined the ‘top kill’ had failed after it spent three days pumping heavy drilling mud into the crippled well 5,000 feet underwater. It’s the latest in a series of failures to stop the crude that’s fouling marshland and beaches, as estimates of how much oil is leaking grow more dire. The spill is the worst in U.S. history - exceeding even the 1989 Exxon Valdez disaster - and has dumped between 18 million and 40 million gallons into the Gulf, according to government estimates. ‘This scares everybody, the fact that we can’t make this well stop flowing, the fact that we haven’t succeeded so far,’ BP PLC Chief Operating […]