Bad weather grounds space shuttle for third time in four days

About the only things leaving the ground at the Kennedy Space Center today were the turkey vultures. Bad weather once again left a fully tanked space shuttle and a crew more than primed for space with another frustrated launch attempt.

The message for the seven-member crew aboard the shuttle Endeavour: "It wasn't our weather today."

That was the word from Mike Moses, who heads the mission management team, after the mission was scrubbed.

"When the time is right, we'll be ready," replied mission commander Mark Polansky from the crew module.

Today's launch cancellation was the mission's fifth in a month. The first two scrubs were triggered by a pesky hydrogen leak involving a fixture on the side of the shuttle's external fuel tank.

If there was any good news coming out of the latest delays, it was that the repairs to the tank are doing their job. On the hardware side of things, "we've been really clean," Mr. Moses said of the shuttle systems' performance.

Mission managers are now shooting for a launch on Wednesday at 6:03 P.M. EDT.

Planners could have tried again tomorrow. But the weather forecast for launch time on Tuesday looked as iffy as the weather turned out to be today. Forecasters predict a 60 percent chance that the weather will violate launch requirements tomorrow; on Wednesday, that falls to a 40 percent chance.

Rather than put the shuttle and supports crews through what likely would be another false start, NASA managers opted to try for a Wednesday launch.

The delay also buys time to replace Tyvek covers that protect the shuttle's nose thrusters from catching rain while on the pad. The shuttle sheds the covers in the early stages of lift-off.

One cover had come loose, potentially allowing rain to get into the thruster nozzle. The presence of water, especially if it remains in the nozzle and freezes during the shuttle's ascent, could lead to false readings from thruster sensors, leaving the shuttle's computers with the wrong information about whether the thruster would work when it comes time to use them.

The space shuttle Endeavour and its crew are scheduled to spend 12 days of a 16-day mission docked to the International Space Stationto install the final pieces of Japan's laboratory module Kibo as well as perform a variety of maintenance tasks.

Astronauts are scheduled to perform five spacewalks to get everything done -- if the shuttle can launch Wednesday.

If the mission gets put off until Thursday, another iffy weather day, mission managers will have to knock one spacewalk off the agenda in order to have enough time to complete all of the major jobs astronauts need to tackle.

And if they can't launch Thursday, the next opportunity comes on July 26.