WASHINGTON — Pioneering moonwalking astronauts Neil Armstrong and Eugene Cernan on Wednesday accused the Obama administration of hastily concocting an ill-conceived road map for manned space exploration in its move to shelve NASA's back-to-the-moon program. Armstrong, who took man's first steps on the moon in 1969, and Cernan, who took the last steps in 1972, told the Senate Committee on Commerce, Science and Transportation that President Barack Obama's plans to end shuttle flights and shift responsibility for building manned spacecraft to commercial companies was a risky strategy that reflected a predilection for developing commercial spacecraft industry at all costs.