The revelation that the doomed Russian Mars probe had crashed with its plutonium cargo in Bolivia, and not the Pacific Ocean as had originally been reported, has exposed a potential new threat in the US.
Science activists say that a Plutonium powered spacecraft, set to launch in October 1997 from NASA's Cape Canaveral, is a disaster waiting to happen. At the root of their concern are the containers NASA uses to house the radioactive plutonium that powers the craft.
"That container is inadequate," said Hoerst Poehler, a scientist who works on missile safety issues and who was a senior scientist with the Kennedy Space Center until retiring in 1980. "That iridium is the thickness of a fingernail," he said. In the event of a launch failure, the housing "will break up on impact," he claimed.
Federal officials disagree. "We do not expect there to be any health effects of the mission," said Beverly Cook, program director of space and national security programs for the Department of Energy. "Our design was conservative and analysis was rigorous by experts in every field," she said.
The 12-year Cassini mission to Saturn will be powered with more than 70 pounds of plutonium, larger than any quantity NASA has launched into space to date.
"Cassini is the most dangerous mission. They're playing Russian roulette," said Poehler, who was among those who registered public comments on the Galileo and Cassini missions during the period NASA allowed.
Federal scientists have determined that the containers in question are safe enough to withstand intense heat, collisions with space matter, and impact with concrete, land and materials used on the launch pad. The Radioisotope Thermoelectric Generators contain 36 capsules, each housing two pellets of plutonium. Each golfball-sized pellet contains Plutonium 238, a highly radioactive isotope of the element that is formed into Plutonium Oxide, a hard, ceramic-like substance that breaks into big chunks, said Cook.
However, the Titan IV/Centaur booster rocket that will launch Cassini into space has, according to the NASA Jet Propulsion Laboratory, a 1 in 20 chance of failure. JPL claims that an accident would release very low radiation.
Cook remains unfazed. "I have no hesitation in bringing my family to watch the launch of Cassini," he said.
