NASA readies Ulysses satellite for slingshot ride around Jupiter to the sun

October 05, 1990|By Luther Young

NASA hopes to end a frustrating five-month drought in shuttle flights tomorrow morning with the scheduled launch aboard Discovery of the Ulysses nuclear-powered satellite, seven years overdue to begin a 2-billion-mile journey to the sun.

Barring bad weather or hydrogen fuel leaks like those that have grounded its two sister shuttles since spring, Discovery is set to lift off on the joint NASA/European Space Agency mission at 7:35 a.m. from Kennedy Space Center with a crew of five astronauts.

"I'm very enthusiastic about Ulysses, despite the problems and delays during the 13 years since we started," said Derek Eaton, project manager for ESA, which built the spacecraft and will operate it during the five-year, $750 million mission under NASA management.

National Aeronautics and Space Administration officials express confidence that Discovery -- the last shuttle to fly, with the Hubble Space Telescope in late April -- is free of the fuel leaks that continue to delay Columbia and Atlantis.

But Ulysses is not the easiest mission NASA could have picked to end its launch jinx and begin to salvage what's left of the once-ambitious 1990 shuttle schedule.

Anti-nuclear groups have filed suit to halt the launch, claiming that the on-board nuclear power supply -- fueled by 23.7 pounds of plutonium -- could shower the deadly material over Florida in the event of a Challenger-like accident.

A hearing was held yesterday in Washington, before U.S. District Court Judge Oliver Gasch, who agreed last October with NASA's contention that the risk is slight and refused to stop Atlantis from lifting off with the plutonium-powered Galileo probe to Jupiter. Judge Gasch's decision in the case is expected today.

Also complicating NASA's comeback plans is that Ulysses must be launched by Oct. 23 or face a 13-month delay for the proper alignment of Earth, the sun and Jupiter, whose gravity will boost the 807-pound spacecraft on its way to the sun.

"It's a unique mission that will revolutionize our understanding of the sun," said Klaus-Peter Wenzel, project scientist for ESA. "All measurements so far from Earth or space have been made only over the sun's equator. The poles are unexplored territory."

Deep space probes are typically launched in the same direction the Earth spins, west to east, into the plane of the sun's equator, or the ecliptic, taking advantage of our planet's orbital speed to escape the powerful tug of gravity.

But Ulysses -- on an unprecedented trajectory perpendicular to the ecliptic -- will be going against the motion of the Earth. And, even though the spacecraft will be one of the smallest ever on the shuttle, no rocket booster is powerful enough to send it directly toward the sun.

"So we use Jupiter like a slingshot," Mr. Eaton explained. After release from Discovery, Ulysses will be accelerated toward the giant planet by a three-stage rocket to 36,000 miles per hour, the fastest escape speed ever attained by a man-made spacecraft.

Sixteen months later, it will whip around Jupiter, down and away from the ecliptic on a looping arc that will bring it over the sun's south pole between June and October 1994 and the north pole between June and September 1995.

The satellite is named in honor of Ulysses, the mythological Greek adventurer who, according to Dante's "Inferno," set out "to venture the uncharted distances . . . of the uninhabited world beyond the sun . . . to follow after knowledge and excellence."

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