Editing Launch pad (section)

== Facilities ==
=== Transport of rockets to the pad ===
{{main|Mobile launcher platform}}
{{original research|section|date=November 2018}}
[[File:Soyuz Rolls Out.jpg|thumb|upright=1.2|Transport of [[Soyuz rocket]] to pad by train]]
[[File:STS-114 rollout.jpg|thumb|upright=1.2|Transport of [[Space Shuttle]] and [[Mobile launcher platform|MLP]] to pad on [[Crawler-transporter]]]]
[[File:Falcon 9 preparing to launch DSCOVR (16673054016).jpg|thumb|upright=1.2|[[SLC-40]] with SpaceX [[Falcon 9]] launch infrastructure. The four towers surrounding the rocket are [[lightning arrester]]s, and acts like a giant [[Faraday cage]]]]
[[File:Pas-de-tir-du-lanceur-KSLV-II-à-Naro-3.jpg|thumb|upright=1.2|The second launch pad at [[Naro Space Center]] in South Korea is a fixed launch tower.]]
Each launch site is unique, but a few broad types can be described by the means by which the [[space vehicle]] gets to the pad.{{cn|date=November 2018}}

* Horizontally integrated rockets travel horizontally with the tail forward to the launch site on a [[transporter erector launcher]] and are then raised to the vertical position over the flame duct. Examples include all large Soviet rockets, including [[Soyuz (rocket family)|Soyuz]], [[Proton (rocket)|Proton]], [[N1 (rocket)|N1]], and [[Energia (rocket)|Energia]]. This method is also used by the [[SpaceX launch vehicles|SpaceX]] and [[Electron (rocket)|Electron]] launch vehicles.
* Silo launched rockets are assembled inside of a [[missile silo]]. This method is only used by converted ICBMs due to the difficulty and expense of constructing a silo that can contain the forces of a rocket launch.
* Vertically integrated rockets can be assembled in a separate [[hangar]] on a [[mobile launcher platform]] (MLP). The MLP contains the umbilical structure and is carried to the launch site on a large vehicle called [[Crawler-transporter]]. [[Launch Complex 39]] at the [[Kennedy Space Center]] is an example of a facility using this method.<ref>{{cite web |url=http://www-pao.ksc.nasa.gov/kscpao/release/1985/252-85r.htm |title=LAUNCH COMPLEX 39, PADS A AND B |publisher=NASA KSC |year=1992 |url-status=dead |archive-url=https://web.archive.org/web/20080921222509/http://www-pao.ksc.nasa.gov/kscpao/release/1985/252-85r.htm |archive-date=2008-09-21 }}</ref> A similar system is used to launch [[Ariane 5]] rockets at [[ELA-3]] at [[Guiana Space Centre]].
* Vertically assembled vehicles can also be transported on a mobile launcher platform resting on two parallel standard gauge railroad tracks that run from the integration building to launch area. This system is in use for the [[Atlas V]] and future [[Vulcan (rocket)|Vulcan]].
* At [[Vandenberg AFB Space Launch Complex 6|SLC-6]] and [[Cape Canaveral Air Force Station Launch Complex 37|SLC-37]], rockets are assembled on the launch mount. A windowless rail-mounted building encloses the launch pad and gantry to protect the vehicle from the elements, and for purposes of military secrecy. Prior to launch,<ref>{{cite web |url=https://cpsblaunchpad.com/cpsb-launchpad-4/ |title=Cpsb Launchpad |publisher=Viswanath |year=2023 |url-status=dead |access-date=2023-06-16 |archive-date=2023-06-16 |archive-url=https://web.archive.org/web/20230616125001/https://cpsblaunchpad.com/cpsb-launchpad-4/ }}</ref> the building is rolled away. This method is also used at [[Kagoshima Space Center|Kagoshima]] for the [[M-V]].
* The former [[Sea Launch]] service used the converted self-propelled oil drilling platform ''[[Ocean Odyssey]]'' to transport [[Zenit 3SL]] rockets horizontally to the [[Equator]], and then to erect and launch them from a [[floating launch platform]] into [[geostationary transfer orbit]]s.

=== Service structure ===
{{main|Service structure}}
A service structure is a steel framework or tower that is built on a launch pad to facilitate assembly and servicing. 

An umbilical tower also usually includes an [[elevator]] which allows maintenance and crew access. Immediately before ignition of the rocket's motors, all connections between the tower and the craft are severed, and the bridges over which these connections pass often quickly swing away to prevent damage to the structure or vehicle.{{Citation needed|date=October 2021}}

=== Flame deflector systems ===
{{main|Flame deflector}}
A flame deflector, flame diverter or flame trench is a structure or device designed to redirect or disperse the flame, heat, and [[exhaust gas]]es produced by [[rocket engine]]s or other propulsion systems.<ref name=":1">{{Cite web |title=Moonport, CH11-7 |url=https://www.hq.nasa.gov/pao/History/SP-4204/ch11-7.html |access-date=2023-09-01 |website=www.hq.nasa.gov |archive-date=2023-09-01 |archive-url=https://web.archive.org/web/20230901192218/https://www.hq.nasa.gov/pao/History/SP-4204/ch11-7.html |url-status=live }}</ref> The amount of thrust generated by a rocket launch, along with the sound it produces during liftoff, can damage the [[Launch pad|launchpad]] and [[service structure]], as well as the launch vehicle.<ref name=":0">{{Cite web |last=Wessels |first=Wessel |date=2022-10-26 |title=The Purpose Of A Flame Trench At A Rocket Launch Site |url=https://headedforspace.com/flame-trench/ |access-date=2023-09-01 |website=Headed For Space |language=en-US |archive-date=2023-09-01 |archive-url=https://web.archive.org/web/20230901192219/https://headedforspace.com/flame-trench/ |url-status=live }}</ref> The primary goal of the diverter is to prevent the flame from causing damage to equipment, infrastructure, or the surrounding environment. Flame diverters can be found at [[rocket launch sites]] and [[Engine test stand|test stands]] where large volumes of exhaust gases are expelled during engine testing or vehicle launch.

=== Sound suppression systems ===
{{main|Sound suppression system}}
Sites for launching large rockets are often equipped with a sound suppression system to absorb or deflect [[Sound|acoustic energy]] generated during a rocket launch.  As engine exhaust gasses exceed the [[speed of sound]], they collide with the ambient air and [[Shock wave|shockwaves]] are created, with noise levels approaching 200 db. This energy can be reflected by the [[Transporter erector launcher|launch platform]] and pad surfaces, and could potentially cause damage to the launch vehicle, payload, and crew. For instance, the maximum admissible overall [[sound power]] level (OASPL) for payload integrity is approximately 145 db.<ref>Dougherty, N. S., &amp; Guest, S. H. (2012, August 17). A correlation of scale model and flight aeroacoustic data for the Space Shuttle Vehicle. ''Aeroacoustics Conferences''. Retrieved November 16, 2022, from https://arc.aiaa.org/doi/10.2514/6.1984-2351</ref> Sound is dissipated by huge volumes of water distributed across the launch pad and launch platform during liftoff.<ref name=":0sss">{{Cite journal|last=Lubert|first=Caroline Parsons|date=2017|title= Sixty years of launch vehicle acoustics|journal= The Journal of the Acoustical Society of America|volume=142|issue=4 |page=040004|doi=10.1121/1.5014084|bibcode=2017ASAJ..142.2489L|doi-access=free}}</ref><ref>{{Cite journal|last1=Walsh|first1=E. J.|last2=Hart|first2=P.M.|date=Nov 1982|title=Liftoff Ignition Overpressure-A Correlation|journal=Journal of Spacecraft and Rockets|language=en|volume=19|issue=6|pages=550–556|doi=10.2514/3.62300|bibcode=1982JSpRo..19..550W|issn=0022-4650}}</ref>

Water-based acoustic suppression systems are common on launch pads.  They aid in reducing acoustic energy by injecting large quantities of water below the launch pad into the exhaust plume and in the area above the pad. [[Flame deflector|Flame deflectors]] or flame trenches are designed to channel rocket exhaust away from the launch pad but also redirect acoustic energy away.<ref name=":0sss" /><ref>{{Cite web|url=https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19710023719.pdf|title=Acoustic Loads Generated by the Propulsion System (NASA SP-8072)|last=|first=|date=June 1971|website=|access-date=}}</ref>

=== Hydrogen burn-off systems ===
In rockets using [[liquid hydrogen]] as their source of [[Rocket propellant|propellant]], hydrogen burn-off systems (HBOI), also known as radially outward firing igniters (ROFI), can be utilized to prevent the build up of free gaseous hydrogen (GH2) in the aft engine area of the vehicle prior to engine start. Too much excess hydrogen in the aft during engine start can result in an [[overpressure]] blast wave that could damage the launch vehicle and surrounding pad structures.<ref>{{cite web |last=Gebhardt |first=Chris |title=Heritage hardware: Testing the hydrogen burn off system for SLS |url=https://www.nasaspaceflight.com/2015/06/heritage-hardware-hydrogen-burn-off-system-sls/ |website=NASASpaceFlight.com |date=June 1, 2015}}</ref>