The Shuttle Endeavor launch set for Sunday at 7:13PM EDT [23:13 GMT] yesterday was scrubbed with a mere nine minutes to go on the countdown. The Decision was made due to high winds moving in the area. These winds were moving in opposing directions as were the cause of concern throughout central Florida. Tornado Warnings were in effect in Seminole County due to the rotation caused by the opposing winds.
Just before the Flight Director called the launch off some had speculated that it was being called due to the approaching thunderstorms. But these storms were not close enough at the time and while of concern were not the major factor in the scrub decision.
Winds have always been a concern for space launches, if they are too violent the space vehicle can be pushed out of the launch corridor. If the winds are opposing and strong enough, it can make it impossible for the launch to maintain proper attitude [again resulting in the space craft drifting out of the launch corridor]. In the days of the Apollo program they were even more concerning as any aborted launch would put the command module capsule in risk of landing on land. In an abort a tower jet would eject the capsule away from the rest of the launch vehicle and the parachutes would deploy. A normal launch trajectory would put the capsule out off the coast of Florida in the Atlantic Ocean. However, if the winds were strong enough and blowing in a westerly direction the capsule could potentially be pushed back over land. This could very likely result in injury of the astronauts in the capsule and was not something that was to be taken lightly.
It was during Apollo 7 that the wind issue was put into greatest concern. Apollo 7 was to be the first manned launch of the Apollo. However the couches that the crew would sit in were not rated for a land impact. There were newer couches to fix this issue in production but they would not be ready by the launch date. To ensure crew safety a rule was put in place to abort the launch if the winds were blowing to the west and over 35 MPH.
It was not until Apollo 12 that lightning was considered a major concern for space launches. During the early seconds of that flight, not one but two bolts of lightning struck the Saturn V rocket and trailed all the way back down to the tower. The electrical discharge caused an apparent failure of the navigation platform, along with many other instrument errors including the attitude indicator [called the 8-ball]. These errors caused all three fuel cells to be taken offline by on board safety systems. The removal of the three fuel cells put Apollo 12 on battery which resulted in a failure of one of the AC inverters; this failure caused most of the alarms on the Command Module, Yankee Clipper, to go off.
If it were not for the quick thinking of EECOM John Aaron, who remembered the pattern of failures from stress tests conducted earlier, the mission might have been a failure. However he was able to relay a solution to the crew. They needed to switch their Signal Conditioning Equipment to Aux. Unfortunately neither Pete Conrad nor Richard Gordon [In fact the Flight Director and the CapComm as well] knew what that solution meant. It was not until Al Bean remembered the command [and switch] from a simulated incident from over a year ago that the switch was set to Aux. After that Apollo 12 began sending telemetry data correctly to Huston and the mission looked to be saved.
Although the Space Shuttle is more protected from this type of event, lightning is a very real concern to this day and when thunderstorms roll in they can be cause for any mission to be scrubbed. Wind still remains a concern for aborted launches as the shuttle would effectively become a large and ungainly glider in unfavorable weather, not exactly a good thing.
The next window for launch is today at 6:51PM EDT.