Setback for Saturn

As the Saturn 5 lifted off its Cape Kennedy launching pad with dramatic precision last week, ground controllers had visions of a repeat of last November's near-perfect maiden flight of the giant rocket. Their optimism was premature. Only six minutes after lift off, Saturn encountered the first of a series of troubles that may cause a delay of months in landing the first astronauts on the moon.

After igniting successfully, two of the five second-stage J-2 engines inexplicably shut down nearly 2 1/2 minutes early, reducing thrust by 400,000 lbs Although Saturn's sophisticated guidance-and- control system automatically ordered the remaining three engines to fire longer, the rocket had not achieved its programmed velocity by the time the third stage was ready to take over. Thus to achieve orbital velocity of 17,500 m.p.h., the third stage was required to fire 23 seconds longer than planned, consuming 20,000 extra pounds of fuel.

If a three-man moon crew had been aboard, they would still have been safe enough. The makeshift maneuvers successfully inserted the third stage and the unmanned Apollo 6 spacecraft into a 218-mile by 113-mile elliptical orbit (instead of the planned 115-mile circular orbit). But there was more trouble to come.

Mysterious Breakup. When controllers ordered the third-stage engine to restart--in an effort to shove it from its parking orbit to a distance of 320,000 miles on a simulated moon trip-- nothing happened. Still attempting to salvage the mission, the controllers next separated Apollo 6 from the dead third stage and used the spacecraft's engine to push it to an altitude of 13 822 miles. From that height, it plunged back into the atmosphere and parachuted to a safe landing and recovery in the Pacific Ocean. Later, NASA reported the orbiting third stage mysteriously broke into "thousands of pieces."

At week's end, disappointed space scientists were picking through telemetry attempting to discover what had gone wrong with the previously reliable Saturn. Preliminary analysis suggested that the two second-stage rocket engines might have been damaged during the separation of the first stage and that an electrical malfunction had prevented the third stage from restarting in orbit The misfires dimmed NASA's hope that the next Saturn shot would carry three astronauts into orbit. Instead, if further diagnosis shows that the rocket's ills are serious, it may be necessary to prove them cured in another unmanned flight.

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