Below are a few excerpts about nuclear energy by Neil deGrasse Tyson from Natural History Magazine, July-August 2005
Source: Hayden Planetarium
Since the early 1960s, space vehicles have commonly relied on the heat from radioactive plutonium as a power supply. Several of the Apollo missions to the Moon, Pioneer 10 and 11(now more than 8 billion miles from Earth, and headed for interstellar space), Viking 1 and 2 (to Mars), Voyager 1 and 2 (also destined for interstellar space and, in the case of Voyager 1,farther along than the Pioneers), and Cassini (now orbiting Saturn), among others, have all used plutonium for their radioisotope thermoelectric generators, or RTGs. An RTG is an inefficient but long-lasting source of nuclear power. Much more efficient, and much more energetic, would be a nuclear reactor that could supply both power and propulsion.
Nuclear power in any form, of course, is anathema to some people. Good reasons for this view are not hard to find. Inadequately shielded plutonium and other radioactive elements pose great danger; uncontrolled nuclear chain reactions pose an even greater danger. And it's easy to draw up a list of proven and potential disasters: the radioactive debris spread across northern Canada in 1978 by the crash of the nuclear-powered Soviet satellite Cosmos 954; the partial meltdown in 1979 at the Three Mile Island nuclear power plant on the Susquehanna River near Harrisburg, Pennsylvania; the explosion at the Chernobyl nuclear power plant in 1986 in what is now Ukraine; the plutonium in old RTGs currently lying in (and occasionally stolen from) remote, decrepit lighthouses in northwestern Russia. The list is long. Citizens' organizations such as the Global Network Against Weapons and Nuclear Power in Space remember these and other similar events.
But so do the scientists and engineers who work on NASA's Project Prometheus.
Rather than deny the risks of nuclear devices, NASA has turned its attention to maximizing safeguards. In 2003 the agency charged Project Prometheus with developing a small nuclear reactor that could be safely launched and could power long and ambitious missions to the outer solar system. Such a reactor would provide onboard power and could drive an electric engine with ion thrusters—the same kind of propulsion tested in Deep Space 1.
To appreciate the advance of technology, consider the power output of the RTGs that drove the experiments on the Vikings and Voyagers. They supplied no more than a hundred watts, about what your desk lamp uses. The RTGs onCassini do a bit better: they could power your thousand-watt microwave oven. The nuclear reactor that will emerge from Prometheus should yield as much as 200,000 watts of power, equivalent to the energy needs of a small school—or a single SUV. To exploit the Promethean advance, an ambitious scientific mission has been proposed: the Jupiter Icy Moons Orbiter, or JIMO. Its destinations would be Callisto, Ganymede, and Europa—three of the four moons of Jupiter discovered by Galileo in 1610. (The fourth, Io, is studded with volcanoes and is flaming hot.) The lure of the three frigid Galilean moons is that beneath their thick crust of ice may lie vast reservoirs of liquid water that harbor, or once harbored, life.