The Launch Complex 39 Pads A and B are roughly
octagonal in shape. Each covers about 0.25- square-mile (0.65-square-kilometer)
of land, contained within a high chain link fence. Space Shuttles launch from
the top of the concrete hardstand in the center of the pad. The Pad A stand is
48 feet (14.6 meters) above sea level at its top, while the upper surface at Pad
B is at an elevation of 55 feet (16.8 meters).
Approximately 105 Space Transportation System
(STS) 51-L accident-related pad modifications were made before the STS-26
return-to-flight mission in September 1988. Although pad equipment was not found
to be a contributing factor in the accident, the modifications improved flight
safety margins and corrected possible problems in emergency escape hardware and
Some of the modifications include extensive
changes to the Crew Emergency Egress System. The personnel escape route from the
Shuttle, beginning with the orbiter access arm, has been covered with solid
panels for fire protection. A water spray system also has been incorporated. Two
slidewire baskets have been added to the slidewire system for a total of seven,
along with devices to decelerate the baskets and to improve exit from them. The
old emergency shelter bunker near the end of the slidewires, which the crew
would enter to wait out the emergency, has been replaced by a new version.
Other modifications include the addition of a
solid rocket booster joint heater umbilical to keep booster field joints at or
about 75 degrees Fahrenheit (24 degrees Celsius), and a system to recirculate
launch pad water services to prevent them from freezing. Still other
modifications are improvements to the environmental controls in the Payload
Changeout Room, the addition of a cryogenic liquid-propellant filter device, and
the inclusion of an automatic secondary release system for the Shuttle external
tank hydrogen vent umbilical.
The top of each pad measures 390 feet by 325 feet
(119 meters by 99 meters). The two major items of equipment on each pad are the
Fixed Service Structure and the Rotating Service Structure.