Space Shuttle Cleared for Launch but Weather May Not Cooperate

Though NASA has cleared the space shuttle Columbia for liftoff today--launch attempt No. 6--the weather may force another delay.

A sixth postponement would have Columbia tie its own record for shuttle launch scrubs.

Forecasters expect only a 20% chance of good weather for the scheduled 6:46 a.m. PDT launch. The main concerns are heavy rain and wind associated with recent tropical storms.

Columbia’s 16-day laboratory-research mission has been repeatedly delayed by equipment failures and Hurricane Opal.

The latest setback was a crack found in a test engine in Mississippi. NASA wanted to make sure Columbia’s engines did not have similar flaws and delayed Saturday’s launch to allow time for ultrasonic tests, which found the shuttle’s three main engines in good shape.

Bill Dowdell, shuttle test director, insists age is not a factor in Columbia’s track record. Columbia made the first shuttle flight in 1981; this will be its 18th trip.

Officials also maintain that Columbia’s recent overhaul is not related to mechanical problems of the past 2 1/2 weeks: a leaky engine valve, sluggish hydraulics and a failed computer signal-relay unit--all of which caused delays. One of Columbia’s primary computers and a unit that formats computer data also had to be replaced.

Seven astronauts are assigned to the flight, originally scheduled to begin Sept. 28. Once in orbit, they will produce semiconductor and protein crystals, study fluids and conduct other experiments.

The last time delays lasted this long, a Columbia satellite delivery mission was put off six times before finally getting under way in January, 1986.