Shuttle Liftoff Due Today After Winds Force Delay

Treacherous high-altitude winds forced the postponement of the planned launch of the space shuttle Atlantis and its classified military cargo Thursday, and NASA rescheduled the liftoff for this morning.

Air Force weather forecasters gave a 70% probability that the weather would be favorable for a launch early today, although winds were expected to worsen during the three-hour launch window.

Officials briefed by weather experts late Thursday gave the go-ahead to fuel the spacecraft again. Giant spotlights illuminated the shuttle as technicians, repeating many of the tasks they performed the night before, began pumping in 500,000 gallons of volatile liquid hydrogen and liquid oxygen unloaded from the ship’s giant external tank earlier in the day.

Exceeded Guidelines

The cancellation of Thursday’s launch, space agency officials said, came when 91-knot winds and wind shear conditions at 42,000 feet exceeded their stringent new weather guidelines.

Weather forecasts on Wednesday had made it clear that prospects for a liftoff were iffy, but the National Aeronautics and Space Administration decided to continue with the countdown anyway, hoping conditions would improve. However, rapidly changing wind direction and speed at high altitudes, as well as heavy cloud cover, forced the scrubbing of the flight.

“As predicted, the weather was the most troublesome item associated with this launch,” said Robert B. Sieck, shuttle launch director at the Kennedy Space Center.

Atlantis’ five-man, all-military crew “took it (the postponement) in stride,” Sieck said. “We’ve been talking of the threat of this, so it wasn’t unexpected.”

The astronauts would suit up and climb aboard the spacecraft again this morning if the revised countdown went as planned, Sieck said. They were aiming for a liftoff during a three-hour period beginning at 3:32 a.m. PST, but, if the weather grew worse, NASA said, the operation would again be put off for a day.

Lawrence G. Williams, deputy manager of the shuttle engineering office at the Johnson Space Center in Houston, said the spacecraft is capable of flying through moderate wind shear conditions, but called Thursday’s winds “pretty extreme,” with wind speed and direction changing unpredictably.

Trying to punch Atlantis through the winds would put intolerable stresses on the orbiter’s stubby wings, Williams said.

“It wouldn’t fail,” he said. “But you don’t want to fly it close to the point where it would fail.”

NASA tried a computer simulation of a slight alteration to the craft’s liftoff trajectory to miss the winds, but conditions were still unacceptable, he added.

Although wind shear was the chief reason for scrubbing Thursday’s launch, NASA officials were also concerned about clouds that hovered at 7,000 feet a half hour before the three-hour launch window was to close. NASA guidelines call for an 8,000 foot clearance.

In addition, weather conditions at “trans-Atlantic abort” landing sites were considered marginal, officials said. The shuttle flight path allows for emergency landings in Spain or Morocco in case of trouble early in the flight.