Launch pad
A launch pad is the area and facilities where rockets or spacecraft lift off. A spaceport
A spaceport or cosmodrome is a site for launching spacecraft, by analogy with seaport for ships or airport for aircraft. The word spaceport, and even more so cosmodrome, has traditionally been used for sites capable of launching spacecraft into orbit around Earth or on interplanetary trajectories...

 (or rocket launch site) can contain one or many launch pads. 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
A countdown is a sequence of counting backward to indicate the seconds, days, or other time units remaining before an event occurs or a deadline expires. Typical events for which a countdown is used include the launch of a rocket or spacecraft, the detonation of a bomb, the start of a race, and the...

. 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 rocket
A rocket is a missile, spacecraft, aircraft or other vehicle which obtains thrust from a rocket engine. In all rockets, the exhaust is formed entirely from propellants carried within the rocket before use. Rocket engines work by action and reaction...

s need stable support for a few seconds after ignition while the engines ramp up and stabilize at full thrust
Thrust is a reaction force described quantitatively by Newton's second and third laws. When a system expels or accelerates mass in one direction the accelerated mass will cause a force of equal magnitude but opposite direction on that system....

. 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.

Transport of rockets to the pad

There are several different types of launch site, determined by the means by which the rocket gets to the pad.
  • The first large rocket, the V-2
    V-2 rocket
    The V-2 rocket , technical name Aggregat-4 , was a ballistic missile that was developed at the beginning of the Second World War in Germany, specifically targeted at London and later Antwerp. The liquid-propellant rocket was the world's first long-range combat-ballistic missile and first known...

    , travelled horizontally with its tail forward to the launch site at Peenemünde
    The Peenemünde Army Research Center was founded in 1937 as one of five military proving grounds under the Army Weapons Office ....

    . This is the most common method of transport to the pad and was used for all large Soviet rockets, even Buran.
  • In a similar manner, at the Soviet launch site near Volgograd
    Volgograd , formerly called Tsaritsyn and Stalingrad is an important industrial city and the administrative center of Volgograd Oblast, Russia. It is long, north to south, situated on the western bank of the Volga River...

    , 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.
  • Like the Saturn V
    Saturn V
    The Saturn V was an American human-rated expendable rocket used by NASA's Apollo and Skylab programs from 1967 until 1973. A multistage liquid-fueled launch vehicle, NASA launched 13 Saturn Vs from the Kennedy Space Center, Florida with no loss of crew or payload...

     and Saturn IB
    Saturn IB
    The Saturn IB was an American launch vehicle commissioned by the National Aeronautics and Space Administration for use in the Apollo program...

     rockets launched from Launch Complex 39 at the Kennedy Space Center
    Kennedy Space Center
    The John F. Kennedy Space Center is the NASA installation that has been the launch site for every United States human space flight since 1968. Although such flights are currently on hiatus, KSC continues to manage and operate unmanned rocket launch facilities for America's civilian space program...

     in the past, the Space Shuttle
    Space Shuttle
    The Space Shuttle was a manned orbital rocket and spacecraft system operated by NASA on 135 missions from 1981 to 2011. The system combined rocket launch, orbital spacecraft, and re-entry spaceplane with modular add-ons...

     vehicles are first assembled vertically in the Vehicle Assembly Building
    Vehicle Assembly Building
    The Vehicle Assembly Building, or VAB, at NASA's Kennedy Space Center was used to assemble and house American manned launch vehicles from 1968-2011. It is the fourth largest building in the world by volume...

     on a Mobile Launcher Platform
    Mobile Launcher Platform
    The Mobile Launcher Platform or MLP is one of three two-story structures used by NASA to support the Space Shuttle stack during its transportation from the Vehicle Assembly Building to Launch Pad 39-A at the Kennedy Space Center as well as serve as the vehicle's launch platform...

     (MLP). The assembled shuttle and MLP ride on top of a Crawler-Transporter
    The crawler-transporters are a pair of tracked vehicles used to transport spacecraft from NASA's Vehicle Assembly Building along the Crawlerway to Launch Complex 39. They were originally used to transport the Saturn IB and Saturn V rockets during the Apollo, Skylab and Apollo–Soyuz programs....

    , which slowly drives to the launch pad. A similar system is used to launch Ariane 5
    Ariane 5
    Ariane 5 is, as a part of Ariane rocket family, an expendable launch system used to deliver payloads into geostationary transfer orbit or low Earth orbit . Ariane 5 rockets are manufactured under the authority of the European Space Agency and the Centre National d'Etudes Spatiales...

     rockets at ELA-3
    ELA-3, short for Ensemble de Lancement Ariane 3 , is a launch pad and associated facilities at the Centre Spatial Guyanais in French Guyana. ELA-3 is operated by Arianespace as part of the expendable launch system for Ariane 5 rockets...

     at Guiana Space Centre, a French spaceport near Kourou
    Kourou is a commune in French Guiana, an overseas region and department of France located in South America.Kourou is the location of the Guiana Space Centre, France and ESA's main spaceport.-Geography:...

     in French Guiana
    French Guiana
    French Guiana is an overseas region of France, consisting of a single overseas department located on the northern Atlantic coast of South America. It has borders with two nations, Brazil to the east and south, and Suriname to the west...

  • At Cape Canaveral Air Force Station, two parallel standard gauge railroad tracks were used to transport the Titan launch vehicle and its mobile launcher platform from the integration building to the launch areas at Complex 40 and 41, and continue to be used for the Atlas V.
  • In the 1920s, Hermann Oberth
    Hermann Oberth
    Hermann Julius Oberth was an Austro-Hungarian-born German physicist and engineer. He is considered one of the founding fathers of rocketry and astronautics.- Early life :...

     described a method in which the rocket is assembled vertically on a floating barge, which he used in the movie Frau im Mond
    Frau im Mond
    Woman in the Moon is a science fiction silent film that premiered October 15, 1929. It is often considered to be one of the first "serious" science fiction films...

    . This has never been used, although it was seriously considered for use at Kennedy Space Center Launch Complex 39 for the Saturn V. It was rejected for that application due to the instability of the top-heavy unfuelled rocket and gantry.
  • At Vandenberg Air Force Base
    Vandenberg Air Force Base
    Vandenberg Air Force Base is a United States Air Force Base, located approximately northwest of Lompoc, California. It is under the jurisdiction of the 30th Space Wing, Air Force Space Command ....

    , in California, the Titan series of rockets were set up vertically in a gantry in a windowless building at SLC-4
    Vandenberg AFB Space Launch Complex 4
    Space Launch Complex 4 , was a launch site at Vandenberg Air Force Base, used by Atlas and Titan rockets between 1963 and 2005. It consisted of two separate launch pads, SLC-4W and SLC-4E, which were formerly designated PALC2-3 and PALC2-4 respectively. Both pads were originally built for use by...

    , the outside walls of which would be rolled away just at launch. This was done for purposes of military secrecy. Similar systems are used at SLC-6
    Vandenberg AFB Space Launch Complex 6
    Space Launch Complex-6 at Vandenberg Air Force Base in California is a launch pad and support area. It was originally designed for the launching of the Titan III in support of the cancelled Manned Orbiting Laboratory, and was later rebuilt for the Space Shuttle, which also never used it due to...

     and LC37
    Cape Canaveral Air Force Station Launch Complex 37
    Cape Canaveral Air Force Station Space Launch Complex 37 , previously Launch Complex 37 , is a launch complex on Cape Canaveral, Florida. Construction began in 1959 and the site was accepted by NASA to support the Saturn I program in 1963. The complex consists of two launch pads...

     at Cape Canaveral Air Force Station for the Delta IV rocket
    Delta IV rocket
    Delta IV is an active expendable launch system in the Delta rocket family. Delta IV uses rockets designed by Boeing's Integrated Defense Systems division and built in the United Launch Alliance facility in Decatur, Alabama. Final assembly is completed at the launch site by ULA...

    , ELA-1
    ELA-1, short for Ensemble de Lancement Ariane 1 , also known as Ensemble de Lancement Vega, ELV, and CECLES, is a launch pad at the Centre Spatial Guyanais in French Guyana...

     & 2
    ELA-2, short for Ensemble de Lancement Ariane 2 , was a launch pad at the Centre Spatial Guyanais in French Guiana. It was used by Arianespace for all 116 Ariane 4 launches between 1988 and 2003. Following the retirement of the Ariane 4 in favour of the Ariane 5, ELA-2 was deactivated...

     at CSG for the Ariane 1-4, and Kagoshima for the M-V.
  • Zenit 3SL rockets of Sea Launch
    Sea Launch
    Sea Launch is a spacecraft launch service that uses a mobile sea platform for equatorial launches of commercial payloads on specialized Zenit 3SL rockets...

     are transported horizontally by sea aboard the Ocean Odyssey
    Ocean Odyssey
    |-External links:*...

     converted oil rig, which is then used to erect and launch them.
  • Dnepr rockets are transported vertically and then inserted into a silo.

See also

  • Spaceport
    A spaceport or cosmodrome is a site for launching spacecraft, by analogy with seaport for ships or airport for aircraft. The word spaceport, and even more so cosmodrome, has traditionally been used for sites capable of launching spacecraft into orbit around Earth or on interplanetary trajectories...

  • List of rocket launch sites
  • Launch vehicle
    Launch vehicle
    In spaceflight, a launch vehicle or carrier rocket is a rocket used to carry a payload from the Earth's surface into outer space. A launch system includes the launch vehicle, the launch pad and other infrastructure....

  • Pad abort test
    Pad abort test
    A pad abort test is a test of a launch escape system to determine how well the system could get the crew of a spacecraft to safety in an emergency on the launch pad.- Project Mercury :Section sources....

  • Non-rocket spacelaunch‎
  • Rocket launch
    Rocket launch
    A rocket launch is the takeoff phase of the flight of a rocket. Launches for orbital spaceflights, or launches into interplanetary space, are usually from a fixed location on the ground, but may also be from a floating platform such as the San Marco platform, or the Sea Launch launch...

  • Launch tower
  • Gantry (rocketry)
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