Kennedy Space Center Launch Complex 39
Launch Complex 39 actually refers to LC39A and LC39B at the John F. Kennedy Space Center on Merritt Island in Florida, USA, which are currently launch pads for the space shuttle.
History
The initial design of the launch complex contained 5 pads that were evenly space 8700 feet apart to avoid damage in the event of a pad explosion. 3 were scheduled for construction (shown), 2 reserved for future use (1 shown). The numbering of the pads at the time was from north to south, with the northern most being Pad A, and the southern being Pad C. Pad A was never built, and Pad C became Pad A in 1963. With today's numbering, Pad C would be north of Pad B. Pad D (visible as an outline on the photograph to the right) would have been due west of Pad C. Pad E (not shown) would due north of the mid-distance between Pad C and Pad D, with Pad E forming the top of a triangle, and equidistant from Pad C and D. Today, crawler way stubs are visible that would lead to these pads. The stubs are located 1 mile west of Pad A, and 1.5 south of Pad B. TerraServer Image The accompanying map also shows the unbuilt Nuclear Assembly Building (NAB).
The pads were previously used for launches of the Saturn V rocket for the Project Apollo moon missions. The original structure of the pads were remodeled for the needs of the shuttle, first starting with LC39A after the last Saturn V launch, which carried Skylab, in 1973, and in 1977 for LC39B after the Apollo-Soyuz Test Project in 1975. LC39 during the Apollo era were just launchpads - the umblical/service towers were attached to the launch platform--the only modification made was the so-called "milkstool" which allowed the Saturn IB rocket to use the Saturn V launch tower. For the shuttle, the pad has a fixed tower (leftover from the Apollo-Saturn era) and a rotating service platform, used to protect the Shuttle Orbiter and to install vertically-handled payloads into the payload bay.
The first use of LC39 came in 1967 with the first Saturn V launch, carrying the unmanned Apollo 4 spacecraft. LC39B was used for the unmanned Apollo 6 mission, with LC39A being used for Apollo 8, the first manned lunar flight. With the exception of Apollo 10, which used LC39B (due to NASA's all-up program, resulting in a two-month turnaround between missions), all Apollo launches, commencing with Apollo 8 in December 1968 to Apollo 17 in December 1972, were launched from LC39A. LC39A was decommissioned as an Apollo-Saturn pad in 1974 and was reconfigured for Space Shuttle operations, being used for the first Columbia launch (STS-1) in 1981. LC39B underwent a similar Apollo-Saturn decommission in 1977. However, due to necessary modifications, along with budgetary restraints, it was not ready until 1986, and the first Shuttle launch to use it was the ill-fated STS 51-L flight - the Challenger Disaster.
Space shuttle usage
Before shuttles are launched at either of the LC39 pads, they are assembled in the Vehicle Assembly Building (VAB). A Mobile Launcher Platform (MLP) loaded atop a Crawler-Transporter is stationed in the VAB. The various segments of the Solid Rocket Boosters (SRB's) are attached to the MLP, then the External Tank is mounted between them. The SRB's are already fueled, as the solid fuel mixture is loaded in the SRB fuel segments prior to their railcar transportation to the Kennedy Space Center. The empty external tank is transported by barge from its manufacturing location in Louisiana, and is fueled with cryogenic liquid hydrogen and liquid oxygen during the countdown before launch. The shuttle is attached to the SRB-ET assembly, and then the Crawler-Transporter moves the whole assembly the 3-4 miles to one of the launch pads, which takes about 8 hours. The Mobile Launch Platform is affixed to several pedestals on the launch pad, and the Crawler-Transporter is moved away to a safe distance. The vehicle can be accessed for service and protected by the elements by a two-piece access tower system. The two pieces of the Tower are the Fixed Service Structure (FSS) and the Rotating Service Structure (RSS). The RSS contains a clean room and offers access to the orbiter's payload bay, so that gear that will fly with the shuttle can be installed or seviced shortly before launch while the shuttle waits on the launch pad. The shuttle can be kept on the pad in fairly severe weather inside the protection of the Rotating Service Structure which, according to NASA regulation, can protect the launch vehicle in wind speeds up to 60 knots.
Shortly before launch, the External Tank is fueled from tanks of liquid hydrogen and liquid oxygen, which are connected to the launch pad by pipelines.
The closest one can get to a LC during launch is three miles; the Launch Control facilities and the VAB are almost exactly three miles away. If the launch vehicle were to explode on the pad, three miles is considered the closest safe distance for KSC employees and special visitors.
Future usage
After the retirement of the Space Shuttle in 2010 both pads will be extensively modified to accommodate the future Heavy Lift Cargo launcher, derived from the Space Shuttle, which will be used for the return to the Moon. The only difference with Apollo is that the crew will not be launched from these launch pads. Two launches a year are expected, starting in 2018.
Some information taken from a pamphlet handed out at Kennedy Space Center. Rest from memory of tour.