CAPE CANAVERAL, Fla. - Discovery and an International Space Station construction crew have a green light for NASA's 100th shuttle flight, but windy weather could blow away a Monday night opportunity to get the milestone mission under way.

Mission Discovery

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With a suspect bolt no longer a concern and a new fuel valve installed, Discovery and its crew now are firmly scheduled for a launch attempt at 8:05 p.m. Eastern Daylight Time Monday (Tuesday, 00:05 GMT).

But forecasters say there is a 70 percent chance that stiff winds could prompt yet another delay in the launch, which was scrubbed last Thursday to give NASA enough time to wrestle with a pair of technical problems.

"We're definitely going to be breezy," said shuttle weather officer Johnny Weems. "The big concern will be which direction the wind is coming from."

Strict NASA flight rules call for a launch to be scrubbed if winds top 17.25 miles per hour (27.6 kilometers per hour) at Kennedy Space Center's swamp-surrounded shuttle runway.

The concern is that stiff crosswinds could make it dangerous for a shuttle commander to make an emergency landing at the runway if serious problems cropped up early in flight.

Crosswinds at the runway are expected to be "right on the edge" of safety limits, and there's also a chance that low clouds could block the view of the landing strip on final approach.

Mission managers nonetheless cleared Discovery for flight after coming to grips with a pair of technical problems over the weekend.~

Bolt issue cleared

After a five-day engineering analysis, managers decided Sunday that there is little chance a suspect bolt on the shuttle's 15-story external tank could trigger an orbital collision between Discovery and its massive fuel reservoir.

A close up of the protruding bolt on the external tank from Atlantis' Sept. 2000 mission is clearly evident in this frame thanks to a tell-tale shadow pointing to the upper-left. NASA image.

The 14-inch (35.5 centimeter) bolt is designed to draw back into the tank after it is jettisoned from the shuttle about nine minutes into flight.

A film review last week showed that an identical bolt failed to fully retract after the Sept. 8 launch of Atlantis, prompting an 11th-hour engineering analysis of the situation.

Further analysis showed the same situation had cropped up on a half-dozen previous flights. But engineers ultimately decided that even in a worst-case scenario, a protruding bolt would not endanger a shuttle or its astronaut crew.

"They engineering community came back and concluded that we're safe to fly," said Kennedy Space Center spokesman Bruce Buckingham. "They feel like there is no indication that the bolt can come in contact with the orbiter."

Shuttle Upgrades

Changes to the Space Shuttle through the first 100 flights are detailed in this FLASH graphic. Need Flash 4?

The concern had been that a protruding bolt might bump into the orbiter, causing the tank to pitch up and collide with the ship.

The culmination of the bolt review came a day after NASA contractor technicians replaced a sluggish main propulsion system valve in Discovery's cramped rear engine compartment.

The valve - which controls the flow of liquid oxygen into the shuttle's three main engines - failed to open and close properly during routine turnaround operations after NASA called off an initial launch attempt last Thursday.

A spare valve was put in place Saturday and then tested at KSC's launch pad 39A, where Discovery now stands poised for flight.

"The bird is in great shape," said NASA Test Director Steve Altemus. "We're not working any technical issues whatsoever and the ground systems are performing well as we expected."

A launch Monday would lead to a docking at the International Space Station two days later. Five days of construction work then would follow to put in place the first piece of the station's metal backbone and a new shuttle docking port.

Landing back at KSC is tentatively scheduled for 4:16 p.m. EDT (20:16 GMT) Oct. 20.