Saturday’s space shuttle disaster has stirred grassroots opposition to the Bush administration’s recently announced plan to develop nuclear-powered space rockets. “If there had been a nuclear reactor on board (the Columbia space shuttle), this debris field they’re warning people not to come too close to would be a considerably bigger mess,” said physicist Edward Lyman, head of the private Nuclear Control Institute in Washington, D.C. But many space enthusiasts say nuclear-powered spaceships offer the only way to penetrate the deepest, darkest corners of the solar system. Out there, billions of miles from Earth, sunlight is too weak to energize existing forms of solar-electric cells.