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Cassini: Controversies abound
(CNN) -- After some 15 years of detailed planning, the $3.4 billion Cassini mission to alluring Saturn is one of the most complex and ambitious ventures in the history of space exploration.
The U.S.-European joint venture, still another 11 years from completion, is also one of the most controversial, having provoked the biggest, most strident crusade against a nuclear-powered spacecraft.
A small but vociferous group of anti-nuclear activists are questioning the substance powering Cassini -- 72 pounds of highly radioactive, highly carcinogenic plutonium 238.
Although the United States has launched some two dozen nuclear-powered spacecraft since 1961, this will be the largest amount of plutonium ever rocketed into space.
Cassini critics, fearing a radioactive shower in the event of a rocket explosion during the October 15 launch, vowed to disrupt the event. But there was little chance of that threat succeeding; security was so tight that the launch complex -- a seaside pad that sheltered the massive TitanB rocket and, on it, Cassini -- was a virtual fortress.
So, anti-nuclear protesters could do little more than watch as on a moonlit, pre-dawn sky, the Cassini spacecraft safely blasted off from Florida's Cape Canaveral Air Station.
Critics fear Earth fly-by
Still, activists say the danger is far from over.
Opponents also say they are terrified of the planned Earth fly-by in August 1999, a maneuver designed to give the explorer the gravity assist that will sling it out toward Saturn.
While NASA insists that the fallout, if any, from an accident would pose a minimum risk, anti-nuclear activists, pacifists and even a retired space safety officer have banded together to expose what they believe are government lies. They say if the rocket accidentally plunges into the atmosphere during the fly-by, it could shoot lethal plutonium onto Earth.
Protesters contend if the probe comes too close , it could re- enter the Earth's atmosphere at 42,000 mph and vaporize, releasing plutonium. The radiation from P-238 is harmless under most circumstances, but breathing in particles can have lethal consequences, opponents say.
"Winds can blow (plutonium) into Disney World, Universal City, into the citrus industry, and destroy the economy of central Florida," says Michio Kaku, a nuclear physics professor at the City University of New York.
Kaku was among those who staged a protest against the mission at Cape Canaveral just a week before the planned launch. Opponents also have launched a Stop Cassini Homepage on the Web.
Richard Spehalski, Cassini program manager at the Jet Propulsion Laboratory, contends Kaku and others like him are spreading fear, not facts. "Their techniques are very much like walking into a crowded movie theater and yelling 'Fire!" he says
A 2-foot thick document details the government's six-year safety analysis of Cassini; every fact has been substantiated by independent experts.
NASA summarizes the risk odds this way: there's a 1 in 1,400 chance of an accident early in the launch that would cause a plutonium release; a 1 in 476 chance of such a mishap later in the launch; and a less than 1 in 1 million chance of Cassini re-entering the atmosphere and releasing plutonium during its Earth fly-by.
"It's demonstrated to be safe, and it's reliable, no moving parts, not a reactor," says Spehalski. "It's not fissionable. It's not weapons-grade material."
Other missions
In the past, NASA has had a better than average success rate with its nuclear-powered space missions: 23 hits and three flops. In1968, two plutonium converters plummeted into the Pacific Ocean off the California coast following the failed launch of a weather satellite. They were retrieved intact from 300 feet of water, reinforced, and reflown. And in the most famous failure, the plutonium unit from Apollo 13's lunar lander sunk in the South Pacific near Fiji, where it remains, apparently whole.
As for the space agency's most prominent successes, each of the six Apollo landers on the moon carried plutonium, as did the Pioneer, Viking and Voyager spacecraft. Solar energy a safer option
Solar energy a safer option
Critics say that in the case of Cassini, NASA had safer options to plutonium. They point out that breakthrough solar-cell power could be harnessed if Cassini were redesigned.
But the agency argues that since sunlight on Saturn is only 1 percent as strong as it is on Earth, it will not be an efficient power source. And, officials add, neither batteries nor fuel cells would have lasted the length of the mission.
By the time Cassini reaches the sixth planet from the sun in 2004, it will have traversed some 2.2 billion miles and completed fly-bys of Venus, Earth and Jupiter.
Then the spacecraft, named after the Italian astronomer who discovered the largest gap in Saturn's rings, will spend four years orbiting and scrutinizing the planet.
Given the distance and complexity of the mission, NASA says it had no choice but to turn to radioisotope thermal generators (RTGs) which convert the natural radioactive decay of plutonium into electricity. They say the three RTGs on Cassini -- each costing $50 million -- have been tested to resist intense heat.
Cassini's RTGs are the latest, safest version, similar to those used on Galileo and Ulysses. Each of the 216 marshmallow-sized pellets onboard is encased in heat- resistant iridium. Two pellets are then wrapped in a graphite shell with a thermal slipcover. Two of these shells are encased in a graphite block about the size of a handheld tape recorder, and 18 of these blocks go into each of the RTGs.
Space: The new marketing frontier?
The anti-Cassini backlash isn't fazing NASA, however; the agency has tentative plans for plutonium explorers to distant Pluto and Europa, Jupiter's moon. There's even talk of sending nuclear rockets to Mars, an idea that alarms activists like says Bruce Gagnon, state coordinator of the Florida Coalition for Peace and Justice, which opposes the Cassini mission.
"Space is being identified as a new market, if you will, for nuclear power, so it's not just 'Oh Cassini!' My God, there's a whole slew of these things in future years," he says. "God forbid if they do launch Cassini, we hope everything goes well. But sooner or later... you're going to have a problem."
The Associated Press contributed to this report.
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