Chill May Delay Today’s Planned Shuttle Launch

NASA officials decided Tuesday against easing the Challenger-inspired cold-weather launch rules as the shuttle Discovery awaited liftoff on a secretive military mission.

Discovery was scheduled to blast off at 3:59 a.m. PST today with five astronauts and a Defense Department satellite believed to be a reconnaissance spacecraft, but low temperatures were forecast.

Cold weather contributed to the 1986 explosion of the Challenger, which was caused by a leak in a joint on a solid fuel rocket booster. It was 36 degrees during Challenger’s liftoff, 15 degrees lower than for any previous launch.

The temperature early today was expected to be 47 degrees before launch with winds of about 4 1/2 m.p.h.

Meteorologists put the odds of acceptable launch weather at 60%. They said their only worry was that conditions might violate the National Aeronautics and Space Administration’s rule prohibiting launch if the temperature dipped below 47 degrees with winds below 5 3/4 m.p.h. for more than 30 minutes once fueling began.

Mission managers had considered easing the rule so Discovery would have a better chance of lifting off as scheduled. Although data collected by an engineering team suggested that the guidelines are “extremely conservative,” managers decided against changing the criteria so close to launch.