Anti-nuclear activists are in a tizzy again, planning rallies and mass protest meetings. What riles them is an item buried in the Bush Administration's proposed budget that would allot $125 million in fiscal year 2003 to begin designing a fleet of nuclear powered spacecraft. Some and this is what has the activists most agitated would have nuclear reactors aboard. A launch pad accident or an inadvertent reentry into Earth's atmosphere, the more extreme of the activists say, could cause millions of deaths.
NASA scoffs at these fears, and remains adamant. "If we are ever going to aggressively explore the planets and send humans there," says NASA space science chief Ed Weiler, "if we are ever going to do more than simply fly by planets like Neptune and Pluto, chemical energy just doesn't do it. We've got to go to nuclear reactors."
In fact, NASA has been using nuclear power, in one form, for years. The Pioneers, Viking, the Voyagers and even the manned Apollo spacecraft were equipped with plutonium-filled radioisotope thermoelectric generators, or RTGs, to supplement the electricity produced by their solar panels. NASA now has only one RTG left on the shelf for future deep-space missions, however, and one of the goals of the new program is to build more of the units with an improved design that should produce three times as much power for a given mass of plutonium.
Still, even these new RTGs will provide only several hundred watts of power, barely enough to light a few living room lamps and hardly enough for robust exploratory missions. That's why NASA is turning to reactors that will produce megawatts of inexhaustible power that could cut flight time to distant planets, moons, perhaps even nearby stars, and provide for locomotion and heavy work digging for water or evidence of life, for example after landing on alien surfaces.
What about safety? The new RTGs, like their predecessors, will have their plutonium encased in layers of protective material that can withstand explosions and impacts. Indeed, in one earlier NASA failed launch, after the unmanned craft crashed back to Earth, its RTG was recovered intact and used on a later mission. And craft with reactors aboard will be launched by conventional chemical rockets, their reactors remaining inactive, or "cold" until they are a safe distance from Earth.
That hardly mollifies the activists. For example, when the Cassini spacecraft, on its way to Saturn, was scheduled to pass close to Earth in 1999 (to get a boost in speed from terrestrial gravity), the anti-nuke groups demanded that the billion dollar mission be scrapped by diverting the craft away from Earth. They charged that Cassini could be incinerated during an inadvertent reentry into Earth's atmosphere, and that the plutonium released from its RTG's could kill as many as 40 million people. That, of course, is absolute rubbish, supported by not a bit of medical or scientific evidence. Fortunately, cooler heads prevailed, Cassini stayed on course, and is now well on its way to a 2004 rendezvous with Saturn.
Never mind, say the anti-nukes. To avoid the risks, they claim, we could have used solar panels on Cassini instead of RTGs. Really? Saturn is ten times as far as Earth from the Sun. This means that to deliver as much electrical power that solar panels now provide to Earth satellites, Cassini's panels would have to be a hundred times greater in area, a clearly impossible requirement.
But the activists are hardly deterred by facts. The European Space Agency has developed new and more efficient solar cells, they point out, and will be fixing them to the non-nuclear Rosetta spacecraft, scheduled to be launched next year for a 2011 rendezvous and fly-along with a comet that will take it beyond the orbit of Jupiter. Why use nukes, they say, when these new cells will soon be available? Did they bother to verify their claims? Of course not.
But we did. TIME contacted the Marcello Coradini, coordinator of solar system missions for the ESA, who ought to know. The anti-nuke people are wrong, he says, "and no one should be led to believe otherwise." For a substantial portion of Rosetta's travels with the comet, the electrical systems will be dormant, and its instruments and experiments inoperative as the craft is pulled along by the comet's gravity. Only when the comet comes much closer to the sun will Rosetta's solar cells be able to generate sufficient electricity. "If we want to go beyond Mars, to Saturn, Europa, Jupiter," says Coradini, "there is no alternative today to non-solar energy systems which essentially means nuclear."
Never underestimate the resilience of the activists. When I confronted one of the anti-nuke leaders with this irrefutable evidence, he hardly blinked an eye. "So why don't we wait then until some capable non-nuclear power system is developed," he said. "After all, the planets have been there and will be there for a long time."
That remark conjured up a vision of a Queen Isabella interview with a petitioner. "What's the hurry, Columbus?" asks the Queen. "The New World has been there and will be there for a long time. Why not be easy on yourself and wait until someone invents a flying machine?"