Environmentalists argued in court yesterday that NASA is so anxious to launch the space shuttle Discovery Saturday that it is ignoring the danger that would be posed by radioactivity escaping from a launch accident.

U.S. District Judge Oliver Gasch is expected to rule today on the

request by the Florida Coalition

for Peace and Justice to delay for at least a year the launch of Discovery, which is supposed to carry

the nuclear-powered probe Ulysses on a mission to orbit and study the sun.

Gasch rejected a similar request last year, and the Galileo space probe, containing nearly 50 pounds of plutonium, was sent on a six-year trip to Jupiter. Ulysses carries a reactor powered by about 24 pounds of plutonium.

The launch would be the first of a shuttle in more than five months. Fuel leaks have halted the launch of Columbia three times and delayed the flight of Atlantis.

As Discovery's countdown continued, the space agency announced that an experienced work crew had left a 70-pound beam inside Atlantis's engine compartment and that it had crashed around and dented some insulation when Atlantis was raised to an upright position Wednesday.

Workers at Cape Canaveral found the 8-foot-11-inch-long beam, which had been part of a scaffold, on a pile of cables inside the compartment after the solid fuel booster rockets and external tank were attached to the orbiter, which is scheduled for a secret military flight in early November.