No damaged graphite shells were detected. In another test, scientists tacked an RTG to a solid rocket booster and blew it up. In one experiment, engineers fired shrapnel traveling 700 ft. Department of Energy has spent $50 million testing the generators. Coated pellets are then encased by two graphite shells and finally by an aluminum shroud. Each of the 144 plutonium pellets in the generators, designed by General Electric, is surrounded by an iridium shell. NASA has gone to extraordinary lengths to make sure the RTGs are safe. The generators were then redesigned, and in two subsequent accidents in which spacecraft broke apart, no radioactivity is known to have escaped. It is not clear what health effects that might have had. The most significant was in 1964, when a satellite launched by the Air Force burned up over the Pacific, tripling the amount of radioactive plutonium 238 in the environment. The space agency admits that there have been three accidents involving RTG- powered vehicles. NASA used similar generators on 22 space missions, but no one paid much attention until the Challenger tragedy dramatized the risks of space launches. Critics are concerned that the vehicle could collide with the earth during close flybys in 19. To gather momentum, the Galileo spacecraft will first make a swing around Venus and two around the earth before hurtling off to Jupiter. The danger, they say, does not end with a successful takeoff.

Opponents charge that a disaster during launch could spew large amounts of radioactive fallout throughout Florida and cause 2,000 cases of lung, bone and liver cancer. Says Cuddihy: 'The risks of the launch are greater than those originally estimated by the committee.' Their view is shared by Richard Cuddihy, an analyst with the Inhalation Toxicology Research Center in Albuquerque and the lone dissenter on the federal interagency panel that recommended a go-ahead for the Galileo program.

Antinuclear groups, led by the Florida Coalition for Peace and Justice and the Washington-based Christic Institute, have claimed that the generators are unsafe. At issue is the space probe's power source: two radioisotope thermoelectric generators that are fueled by almost 50 lbs. Nonetheless, a sharp controversy has dogged the mission. There the probe will take the first direct measurements of the planet's dense clouds and hurricane-like winds.įew doubt the scientific value of the Galileo flight. Astronauts on Atlantis will release the Galileo spacecraft, setting it on a six-year, 2.5 billion-mile journey to Jupiter. At last the Galileo mission, which has languished for more than a decade because of technical debates and the Challenger explosion, will be getting under way. The shuttle Atlantis lifts off this week from its Cape Canaveral launch pad as planned, astronomers will let out a long-delayed cheer.

Nuclear time