Launch pad

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''This article refers to the structure from which rockets are launched. For other uses see the disambiguation page at Launchpad.

The launch pad refers to the facilities where rockets or spacecrafts liftoff. A typical launch pad consists of the service and umbilical structures. The service structure provides an access platform to inspect the launch vehicle prior to launch. Most service structures can be moved or rotated to a safe distance. The umbilical structure has propellent loading, gas, power, and communication links to the launch vehicle. The launch vehicle sits atop of the launch platform, which has the flame deflection structure to withstand the intense heat and load generated by rocket engines during liftoff.

Most cryogenic launch vehicles need to be continuously topped off as scheduled liftoff approaches. This is particularly necessary as various holds are placed on the liftoff and then removed as support personnel correct problems or verify they are not serious. Without the ability to top off the launch vehicle, the launch would have to be scrubbed when problems slowed down the countdown. gantries are commonly designed and constructed on launch pads to meet these types of servicing requirements both during launch and in the preparation period leading up to it.

Most rockets need stable support for a few seconds after ignition while the engines ramp up and stabilize at full thrust. This stability requirement is commonly met by the use of explosive bolts to connect the launch vehicle to the pad. When the vehicle is stable and ready to fly the bolts explode, severing the vehicle's ties to the launch pad and structures on the ground.

There are five different types of launch site, determined by the means by which the rocket gets to the pad.

The first large rocket, the V-2, travelled horizontally with its tail forward to the launch site at Peenemünde. This is the most common; it was used for all large Soviet rockets, even Buran.
In a similar manner, at the Soviet launch site near Volgograd, a silo used to launch test rockets would have its top opened and a second stage and payload would be driven in horizontally and tilted on top of a first stage already in the silo, the nose cone and some of the second stage remaining visible above ground. Hence no surface pad is used; Russian silos are reusable. This method was only used for the Cosmos series of small satellite launching vehicles.
All forms of the Saturn of Project Apollo, as well as the Space Shuttle, are set up vertically in the Vehicle Assembly Building on a Mobile Launcher Platform which sets on top of Crawler-Transporter, which slowly drives to the launch site.
In the 1920s, Hermann Oberth stated a similar method which had the rocket float vertically on a barge, which he used in the movie Frau im Mond. This has never been used.
At Vandenberg Air Force Base, in California, the Titan III series of rockets were set up vertically in a gantry in a windowless building, the outside walls of which would be rolled away just at launch. This was done for purposes of military secrecy.

Launch pad

See also