View source for Engineering:Delta II

{{Short description|American space launch system}}
{{No orbit for payload}}
{{Infobox rocket
|logo           = Delta II logo.svg
|image          = Delta II Dawn liftoff 1.jpg
|caption        = A Delta II rocket launches from {{wipe|Cape Canaveral Air Force Station}} carrying the [[Engineering:Dawn (spacecraft)|Dawn]] spacecraft.

|name           = Delta II
|function       = [[Engineering:Launch vehicle|Launch vehicle]]
|manufacturer   = [[Company:United Launch Alliance|United Launch Alliance]]
|country-origin = United States

|cpl            = US$51 million in 1987 (7920-10 model) <ref>{{cite web|url=http://www.spaceflight101.com/delta-ii-7920h-10.html|title=Delta II 7920H-10|access-date=July 1, 2014|url-status=dead |archive-url=https://web.archive.org/web/20140714122955/http://www.spaceflight101.com/delta-ii-7920h-10.html|archive-date=14 July 2014}}</ref> US$137 million in 2018 before retirement <ref>{{cite web |url=https://www.faa.gov/about/office_org/headquarters_offices/ast/media/2018_ast_compendium.pdf|title=The Annual Compendium of Commercial Space Transportation: 2018|date=January 2018|website=Federal Aviation Administration's Office of Commercial Space Transportation|publisher=Bryce Space and Technology}} {{PD-notice}}</ref>

|height         = {{cvt|38.9|m}}<ref name="Delta">{{cite web |title=Delta II Data Sheet |url=http://www.spacelaunchreport.com/delta2.html |archive-url=https://archive.today/20140726211308/http://www.spacelaunchreport.com/delta2.html |url-status=usurped |archive-date=26 July 2014 |website=Space Launch Report |access-date=9 March 2021}}</ref>
|diameter       = {{cvt|2.44|m}}
|mass           = {{cvt|152000-286000|kg}}<ref name="Delta"/>

|capacities = 
  {{Infobox rocket/payload
  |location     = [[Astronomy:Low Earth orbit|low Earth orbit]]
  |kilos        = {{cvt|2800-6140|kg}}<ref name="Delta"/>
  }}
  {{Infobox rocket/payload
  |location     = [[Astronomy:Geostationary transfer orbit|geostationary transfer orbit]]
  |kilos        = {{cvt|1140-2190|kg}}<ref name="Delta"/>
  }}
  {{Infobox rocket/payload
  |location     = [[Astronomy:Heliocentric orbit|heliocentric orbit]]
  |kilos        = {{cvt|806-1519|kg}}<ref name="Delta"/>
  }}

|status         = Retired
|sites          = {{wipe|Cape Canaveral Air Force Station}}, SLC-17<br>{{wipe|Vandenberg Air Force Base}}, SLC-2W
|launches       = 155<br>'''Delta 6000:''' 17<br>'''Delta 7000:''' 132<br>'''Delta 7000H:''' 6
|success        = 153<br>'''Delta 6000:''' 17<br>'''Delta 7000:''' 130<br>'''Delta 7000H:''' 6
|fail           = 1 (Delta 7000)
|partial        = 1 (Delta 7000)

|first = {{plainlist|
* '''Delta 6000:''' 14 February 1989 ([[Engineering:USA-35|USA-35]])
* '''Delta 7000:''' 26 November 1990 ([[Engineering:USA-66|USA-66]])
* '''Delta 7000H:''' 7 July 2003 (Opportunity rover)
}}
|last = {{plainlist|
* '''Delta 6000:''' 24 July 1992 ([[Engineering:Geotail|Geotail]])
* '''Delta 7000:''' 15 September 2018 ([[Engineering:ICESat-2|ICESat-2]])
* '''Delta 7000H:''' 10 September 2011 ([[Astronomy:GRAIL|GRAIL]])
}}
{{Infobox rocket/stage
  |type         = booster
  |diff         = 6000 Series
  |name         = Castor 4A
  |number       = 9
  |length       = <!--length of a single booster in metres, use {{cvt}}, optional-->
  |diameter     = <!--diameter of a single booster in metres, use {{cvt}}, optional-->
  |empty        = <!--empty mass of a single booster/stage in kilograms, use {{cvt}}, optional-->
  |gross        = <!--gross (fuelled) mass of a single booster/stage, use {{cvt}}, optional--> 
  |propmass     = <!--propellant mass carried by a single booster/stage in kilograms, use {{cvt}}, optional--> 
  |engines      = Solid
  |solid        = yes
  |thrust       = {{cvt|478|kN}}
  |total        = <!--total thrust for all boosters in kN, use {{convert}}, optional-->
  |SI           = {{cvt|266|isp}}
  |burntime     = 56 seconds
  |propellant   = Aluminum fuel, ammonium perchlorate oxidizer in an HTPB binder
  }}
  {{Infobox rocket/stage
  |type         = booster
  |diff         = 7000 Series
  |name         = [[Engineering:Graphite-Epoxy Motor|GEM 40]]
  |number       = 3, 4, or 9
  |length       = <!--length of a single booster in metres, use {{cvt}}, optional-->
  |diameter     = <!--diameter of a single booster in metres, use {{cvt}}, optional-->
  |empty        = <!--empty mass of a single booster in kilograms, use {{cvt}}, optional-->
  |gross        = <!--gross (fuelled) mass of a single booster, use {{cvt}}, optional--> 
  |propmass     = <!--propellant mass carried by a single booster in kilograms, use {{cvt}}, optional--> 
  |engines      = Solid
  |solid        = yes
  |thrust       = {{cvt|492.9|kN}}
  |total        = <!--total thrust for all boosters in kN, use {{cvt}}, optional-->
  |SI           = {{cvt|274|isp}}
  |burntime     = 64 seconds
  |propellant   = Aluminum fuel, ammonium perchlorate oxidizer in an HTPB binder
  }}
  {{Infobox rocket/stage
  |type         = booster
  |diff         = 7000 Heavy
  |name         = [[Engineering:Graphite-Epoxy Motor|GEM 46]]
  |number       = 9
  |length       = <!--length of a single booster in metres, use {{cvt}}, optional-->
  |diameter     = <!--diameter of a single booster in metres, use {{cvt}}, optional-->
  |empty        = <!--empty mass of a single booster in kilograms, use {{cvt}}, optional-->
  |gross        = <!--gross (fuelled) mass of a single booster, use {{cvt}}, optional--> 
  |propmass     = <!--propellant mass carried by a single booster in kilograms, use {{cvt}}, optional--> 
  |engines      = Solid
  |solid        = yes
  |thrust       = {{cvt|628.3|kN}}
  |total        = <!--total thrust for all boosters in kN, use {{convert}}, optional-->
  |SI           = {{cvt|278|isp}}
  |burntime     = 76 seconds or 178.03 seconds after lift off
  |propellant   = Aluminum fuel, ammonium perchlorate oxidizer in an HTPB binder
  }} 
  {{Infobox rocket/stage
  |type         = stage
  |stageno      = First
  |name         = Thor/Delta XLT(-C)
  |length       = <!--length of a single stage in metres, use {{cvt}}, optional-->
  |diameter     = <!--diameter of a single stage in metres, use {{cvt}}, optional-->
  |empty        = <!--empty mass of a single stage in kilograms, use {{cvt}}, optional-->
  |gross        = <!--gross (fuelled) mass of a single stage, use {{cvt}}, optional--> 
  |propmass     = <!--propellant mass carried by a single stage in kilograms, use {{cvt}}, optional--> 
  |engines      = 1 RS-27 (6000 series) or RS-27A (7000 series) <ref>{{cite web|url=http://www.boeing.com/defense-space/space/delta/delta2/delta2.htm|title=Boeing: Integrated Defense Systems - Delta - Delta II Launch Vehicle Family|access-date=November 3, 2006 |url-status=dead|archive-url=https://web.archive.org/web/20061103194958/http://www.boeing.com/defense-space/space/delta/delta2/delta2.htm|archive-date=November 3, 2006}}</ref>
  |thrust       = {{cvt|1054|kN}}
  |SI           = {{cvt|302|isp}}
  |burntime     = 260.5 seconds
  |fuel         = [[Chemistry:RP-1|RP-1]] / [[Astronomy:LOX|LOX]]
  }}
  {{Infobox rocket/stage
  |type         = stage
  |stageno      = Second
  |name         = Delta K
  |length       = <!--length of a single stage in metres, use {{cvt}}, optional-->
  |diameter     = <!--diameter of a single stage in metres, use {{cvt}}, optional-->
  |empty        = <!--empty mass of a single stage in kilograms, use {{cvt}}, optional-->
  |gross        = <!--gross (fuelled) mass of a single stage, use {{cvt}}, optional--> 
  |propmass     = <!--propellant mass carried by a single stage in kilograms, use {{cvt}}, optional--> 
  |engines      = 1 AJ10-118K
  |thrust       = {{cvt|43.6|kN}}
  |SI           = {{cvt|319|isp}}
  |burntime     = 431 seconds
  |fuel         = [[Chemistry:Dinitrogen tetroxide|N<sub>2</sub>O<sub>4</sub>]] / [[Chemistry:Aerozine 50|Aerozine 50]]
  }}
  {{Infobox rocket/stage
  |type         = stage
  |stageno      = Third
  |name         = [[Engineering:Payload Assist Module|PAM-D]] (optional)
  |length       = <!--length of a single stage in metres, use {{cvt}}, optional-->
  |diameter     = <!--diameter of a single stage in metres, use {{cvt}}, optional-->
  |empty        = <!--empty mass of a single stage in kilograms, use {{cvt}}, optional-->
  |gross        = <!--gross (fuelled) mass of a single stage, use {{cvt}}, optional--> 
  |propmass     = <!--propellant mass carried by a single stage in kilograms, use {{cvt}}, optional--> 
  |engines      = Star 48B
  |solid        = yes
  |thrust       = {{cvt|66|kN}}
  |SI           = {{cvt|286|isp}}
  |burntime     = 87 seconds
  |propellant   = Aluminum fuel, ammonium perchlorate oxidizer in an HTPB binder
  }}
}}

'''Delta II''' was an [[Engineering:Expendable launch system|expendable launch system]], originally designed and built by [[Company:McDonnell Douglas|McDonnell Douglas]], and sometimes known as the Thorad Delta 1. Delta II was part of the Delta rocket family and entered service in 1989. Delta II vehicles included the Delta 6000, and the two later Delta 7000 variants ("Light" and "Heavy"). The rocket flew its final mission [[Engineering:ICESat-2|ICESat-2]] on 15 September 2018, earning the launch vehicle a streak of 100 successful missions in a row, with the last failure being [[Engineering:GPS IIR-1|GPS IIR-1]] in 1997.<ref>{{cite web|url=http://www.spacelaunchreport.com/delta2.html|title=Delta II Data Sheet|first=Ed|last=Kyle|website=spacelaunchreport.com |access-date=2014-07-24|archive-url=https://web.archive.org/web/20140728024436/http://www.spacelaunchreport.com/delta2.html|archive-date=2014-07-28|url-status=usurped}}</ref>

== History ==
In the early 1980s, all United States expendable launch vehicles were planned to be phased out in favor of the [[Engineering:Space Shuttle|Space Shuttle]], which would be responsible for all government and commercial launches. Production of Delta, [[Engineering:Atlas-Centaur|Atlas-Centaur]], and Titan 34D had ended.<ref>{{cite book|title=Taming Liquid Hydrogen|last=Dawson|first=Virginia|year=2004|page=233|url=https://history.nasa.gov/SP-4230.pdf|access-date=2017-07-12|archive-url=https://web.archive.org/web/20060929004415/https://history.nasa.gov/SP-4230.pdf|archive-date=2006-09-29|url-status=live}} {{PD-notice}}</ref> The [[Engineering:Space Shuttle Challenger disaster|''Challenger'' disaster]] of 1986 and the subsequent halt of Shuttle operations changed this policy, and President Ronald Reagan announced in December 1986 that the Space Shuttle would no longer launch commercial payloads, and [[Organization:NASA|NASA]] would seek to purchase launches on expendable vehicles for missions that did not require crew or Shuttle support.<ref>{{cite news|url=https://apnews.com/7e6b76c27ec65f93f14fd7913cf95c48|title=Reagan Orders NASA To Halt Launch of Commercial Payloads|date=August 16, 1986|work=Associated Press News|access-date=March 21, 2013|archive-url=https://web.archive.org/web/20140306111634/http://www.apnewsarchive.com/1986/Reagan-Orders-NASA-To-Halt-Launch-of-Commercial-Payloads/id-7e6b76c27ec65f93f14fd7913cf95c48|archive-date=March 6, 2014|url-status=live}}</ref>

McDonnell Douglas, at that time the manufacturer of the Delta family, signed a contract with the {{wipe|United States Air Force}} in 1987 to provide seven Delta II. These were intended to launch a series of [[Engineering:Global Positioning System|Global Positioning System]] (GPS) [[Engineering:GPS satellite blocks|Block II]] satellites, which had previously been manifested for the [[Engineering:Space Shuttle|Space Shuttle]]. The Air Force exercised additional contract options in 1988, expanding this order to 20 vehicles, and NASA purchased its first Delta II in 1990 for the launch of three Earth-observing satellites.<ref name=":0">{{cite book|title=NASA Historical Data Book, Vol. VII: NASA Launch Systems, Space Transportation, Human Spaceflight, and Space Science, 1989-1998|last=Rumerman|first=Judy|publisher=NASA|year=2009|id=NASA SP-4012|pages=49–51|url=https://history.nasa.gov/SP-4012v7ch2.pdf|access-date=2017-07-12|archive-url=https://web.archive.org/web/20171225230629/https://history.nasa.gov/SP-4012v7ch2.pdf|archive-date=2017-12-25|url-status=live}} {{PD-notice}}</ref><ref>{{cite web |url=http://www.losangeles.af.mil/shared/media/document/AFD-130426-024.pdf|title=Archives copy|url-status=dead |archive-url=https://web.archive.org/web/20160414125341/http://www.losangeles.af.mil/shared/media/document/AFD-130426-024.pdf|publisher=Los Angeles Air Force Base|archive-date=14 April 2016}} {{PD-notice}}</ref> The first Delta II launch occurred on 14 February 1989, with a Delta 6925 boosting the first GPS Block II satellite ([[Engineering:USA-35|USA-35]]) from Launch Complex 17A (SLC-17A) at {{wipe|Cape Canaveral Air Force Station}} into a {{cvt|20000|km|mi}} high [[Astronomy:Medium Earth orbit|medium Earth orbit]].<ref>{{cite web|url=http://planet4589.org/space/log/launchlog.txt|title=Launch Log|publisher=Jonathan's Space Report|first=Jonathan|last=McDowell|access-date=10 July 2012|archive-url=https://web.archive.org/web/20091113093423/http://planet4589.org/space/log/launchlog.txt|archive-date=13 November 2009|url-status=live}}</ref>

The first Delta II 7000-series flew on November 26, 1990, replacing the RS-27 engine of the 6000-series with the more powerful RS-27A engine. Additionally, the steel-cased [[Engineering:Castor (rocket stage)|Castor 4A]] solid boosters of the 6000 series were replaced with the composite-cased [[Engineering:Graphite-Epoxy Motor|GEM-40]]. All further Delta II launches except three were of this upgraded configuration, and the 6000-series was retired in 1992 with the last launch being on July 24.<ref>{{cite web|url=http://www.nasaspaceflight.com/2014/07/delta-ii-oco-2-launch-vandenberg/|title=ULA Delta II successfully lofts OCO-2 to orbit|date=July 2, 2014|access-date=July 26, 2014 |website=nasaspaceflight.com|archive-url=https://web.archive.org/web/20140714130852/http://www.nasaspaceflight.com/2014/07/delta-ii-oco-2-launch-vandenberg/|archive-date=July 14, 2014|url-status=live}}</ref>

McDonnell Douglas began [[Engineering:Delta III|Delta III]] development in the mid-1990s as increasing satellite mass required more powerful launch vehicles.<ref name=":0"/> Delta III, with its liquid hydrogen second stage and more powerful [[Engineering:Graphite-Epoxy Motor|GEM-46]] boosters, could bring twice as much mass as Delta II to [[Astronomy:Geostationary transfer orbit|geostationary transfer orbit]], but a string of two failures and one partial failure, along with the development of the much more powerful [[Engineering:Delta IV|Delta IV]], led to the cancellation of the Delta III program.<ref>{{cite web|url=http://www.spacelaunchreport.com/delta3.html|title=Delta III Data Sheet|access-date=July 27, 2014|publisher=Space Launch Report|archive-url=https://web.archive.org/web/20141102030603/http://www.spacelaunchreport.com/delta3.html|archive-date=November 2, 2014|url-status=usurped}}</ref> The upgraded boosters would still find use on the Delta II, leading to the Delta II Heavy.

On 28 March 2003, the Air Force Space Command began the process of deactivating the Delta II launch facilities and infrastructure at Cape Canaveral once the last of the second-generation GPS satellites were launched. However, in 2008, it instead announced that it would transfer all the Delta II facilities and infrastructure to NASA to support the launch of the [[Astronomy:GRAIL|Gravity Recovery and Interior Laboratory]] (GRAIL) in 2011.<ref>{{cite web|last1=Cleary|first1=Mark|title=DELTA II & III SPACE OPERATIONS AT CAPE CANAVERAL 1989–2009|url=http://afspacemuseum.org/library/histories/Delta.pdf|website=afspacemuseum.org |access-date=18 November 2017|archive-url=https://web.archive.org/web/20150530135122/http://www.afspacemuseum.org/library/histories/Delta.pdf|archive-date=30 May 2015|url-status=live}} {{PD-notice}}</ref>

On 14 December 2006, with the launch of [[Engineering:USA-193|USA-193]], was the first launch of the Delta II operated by [[Company:United Launch Alliance|United Launch Alliance]].<ref>{{cite web|title=United Launch Alliance Joint Venture Completes First Launch |url=https://www.ulalaunch.com/missions/missions-details/2006/12/14/united-launch-alliance-joint-venture-completes-first-launch|website=ulalaunch.com|access-date=2020-06-02}}</ref>

The last GPS launch aboard a Delta II, and the final launch from SLC-17A at Cape Canaveral was in 2009. The GRAIL Launch in 2011 marked the last Delta II Heavy launch and the last from Florida. The final five launches would all be from {{wipe|Vandenberg Air Force Base}} in {{wipe|California}}.<ref>{{cite web|title=Delta II|url=http://www.spaceflightinsider.com/hangar/delta-ii/#ELuwclvxe8H5Cdu1.99 |website=spaceflightinsider.com|access-date=18 November 2017|archive-url=https://web.archive.org/web/20171117170205/http://www.spaceflightinsider.com/hangar/delta-ii/#ELuwclvxe8H5Cdu1.99|archive-date=17 November 2017|url-status=live}}</ref>

On 16 July 2012, NASA selected the Delta II to support the [[Chemistry:Orbiting Carbon Observatory|Orbiting Carbon Observatory]] (OCO-2), [[Astronomy:Soil Moisture Active Passive|Soil Moisture Active Passive]] (SMAP), and [[Engineering:Joint Polar Satellite System|Joint Polar Satellite System]] (JPSS-1 - NOAA-20) missions. This marked the final purchase of Delta II. OCO-2 was launched on 2 July 2014, [[Astronomy:Soil Moisture Active Passive|Soil Moisture Active Passive]] (SMAP) was launched on 31 January 2015, and [[Engineering:NOAA-20|JPSS-1]] was launched on 18 November 2017. All three of these launches were placed into orbit from SLC-2 at Vandenberg.<ref>{{cite web|url=http://www.nasa.gov/home/hqnews/2012/jul/HQ_C12-028_RSLP-19_Launch_Services.html|date=16 July 2012|title=NASA Selects Launch Services Contract for Three Missions|publisher=NASA|access-date=7 June 2013|archive-url=https://web.archive.org/web/20130510160219/http://www.nasa.gov/home/hqnews/2012/jul/HQ_C12-028_RSLP-19_Launch_Services.html|archive-date=10 May 2013|url-status=live}} {{PD-notice}}</ref>

The Delta II family launched 155 times. Its only unsuccessful launches were [[Engineering:Koreasat 1|Koreasat 1]] in 1995, and [[Engineering:GPS IIR-1|GPS IIR-1]] in 1997. The Koreasat 1 launch was a partial failure caused by one booster not separating from the first stage, which resulted in the satellite being placed in a lower than intended orbit. By using reserve fuel, it was able to achieve its proper [[Astronomy:Geosynchronous orbit|geosynchronous orbit]] and operated for 10 years.<ref>{{cite web|url=http://space.skyrocket.de/doc_sdat/koreasat-1.htm|title=Koreasat 1, 2 (Mugungwha 1, 2) / Europe*Star B|last=Krebs|first=Gunter Dirk|access-date=2010-10-07|archive-url=https://web.archive.org/web/20100917121608/http://space.skyrocket.de/doc_sdat/koreasat-1.htm|archive-date=2010-09-17|url-status=live}}</ref> The GPS IIR-1 was a total loss as the Delta II exploded 13 seconds after launch. The explosion occurred when a damaged [[Engineering:Solid rocket booster|solid rocket booster]] casing ruptured and triggered the vehicle's flight termination system.<ref>{{Cite web|url=https://www.gizmodo.com.au/tag/science/|archiveurl=https://web.archive.org/web/20090212062143/http://www.gizmodo.com.au/2008/09/the_deadly_aftermath_of_a_rocket_explosion_seconds_after_launch-2.html|url-status=dead|title=Science & Health Archives|archivedate=12 February 2009|website=Gizmodo Australia|accessdate=11 March 2023}}</ref> No one was injured, and the launch pad itself was not seriously impacted, though several cars were destroyed and a few buildings were damaged.<ref>{{cite news |url=http://www.cnn.com/TECH/9701/17/rocket.explosion/index.html|title=Unmanned rocket explodes after liftoff|website=cnn.com|date=1997-01-17|access-date=2009-03-31|archive-url=https://web.archive.org/web/20090423212616/http://www.cnn.com/TECH/9701/17/rocket.explosion/index.html|archive-date=2009-04-23|url-status=live}}</ref>

In 2007, Delta II completed its 75th consecutive successful launch, surpassing the 74 consecutive successful launches of the [[Engineering:Ariane 4|Ariane 4]].<ref>{{cite web|url=http://media.digitalglobe.com/index.php?s=press_release_popup&item=135|title=DigitalGlobe Successfully Launches Worldview-1|publisher=DigitalGlobe|access-date=2007-09-21|archive-url=https://web.archive.org/web/20090302000726/http://media.digitalglobe.com/index.php?s=press_release_popup&item=135|archive-date=2009-03-02|url-status=dead}}</ref><ref>{{cite web |url=http://www.spacedaily.com/reports/Ariane_5s_impressive_75_in_a_row_launch_record_999.html|title=Ariane 5's impressive 75 in-a-row launch record|publisher=SpaceDaily|access-date=2017-11-19|archive-url=https://web.archive.org/web/20171201080916/http://www.spacedaily.com/reports/Ariane_5s_impressive_75_in_a_row_launch_record_999.html|archive-date=2017-12-01|url-status=live}}</ref> With the launch of [[Engineering:ICESat-2|ICESat-2]] in 2018, Delta II reached 100 consecutive successful launches.

While all completed Delta II rockets have launched, many flight-qualified spare parts remain. These spare parts were assembled to create a nearly-complete Delta II, for exhibition in its 7420-3 configuration. The rocket is displayed vertically at the Kennedy Space Center Visitors Complex, and bears its popular "shark teeth" livery on its fairing, which was painted on past Delta II rockets for the GPS launches.<ref>{{cite web|url=https://spaceflightnow.com/2018/09/15/leftover-delta-2-rocket-to-go-on-display-at-kennedy-space-center/|title=Leftover Delta 2 rocket to go on display at Kennedy Space Center|publisher=Spaceflight Now|website=spaceflightnow.com|access-date=2018-09-17|archive-url=https://web.archive.org/web/20190129220657/https://spaceflightnow.com/2018/09/15/leftover-delta-2-rocket-to-go-on-display-at-kennedy-space-center/|archive-date=2019-01-29|url-status=live}}</ref>

== Vehicle description ==
[[Image:Foguete Delta II 7425 - Corte esquematico.jpg|thumb|270px|left|Delta II 7425 diagram]]
[[File:Delta II second stage.jpg|thumb|270px|right|A Delta-K stage]]

The first stage of the Delta II was propelled by a Rocketdyne RS-27 main engine burning [[Chemistry:RP-1|RP-1]] and [[Physics:Liquid oxygen|liquid oxygen]]. This stage was technically referred to as the "Extra-Extended Long Tank Thor", a derivative of the [[Engineering:PGM-17 Thor|Thor]] ballistic missile <ref>{{cite web|url=http://www.spacelaunchreport.com/thorh12.html|title=Space Launch Report|website=spacelaunchreport.com|access-date=2013-02-05|archive-url=https://web.archive.org/web/20120418063513/http://www.spacelaunchreport.com/thorh12.html|archive-date=2012-04-18|url-status=usurped}}</ref> as were all Delta rockets until the [[Engineering:Delta IV|Delta IV]]. The RS-27 used on the 6000-series Delta II produced {{cvt|915|kN|lbf}},<ref>{{cite web|url=http://www.astronautix.com/engines/rs27.htm|title=RS-27|access-date=July 27, 2014|website=Astronautix|url-status=dead |archive-url=https://web.archive.org/web/20111011044326/http://astronautix.com/engines/rs27.htm|archive-date=October 11, 2011}}</ref> while the upgraded RS-27A used by the 7000-series produced {{cvt|1054|kN|lbf}}.<ref>{{cite web|url=http://www.astronautix.com/engines/rs27a.htm|title=RS-27A|access-date=July 27, 2014|website=astronautix.com|url-status=dead |archive-url=https://web.archive.org/web/20140805141506/http://astronautix.com/engines/rs27a.htm|archive-date=August 5, 2014}}</ref> The stage was {{convert|26|m|ft|sp=us}} long and {{convert|2.4|m|ft|sp=us}} wide, weighted over {{convert|100|t|lb}} when fueled, and burned for 260&nbsp;seconds.<ref name=slrd2>{{cite web|url=http://www.spacelaunchreport.com/delta2.html|title=Delta II Data Sheet|access-date=July 27, 2014|publisher=Space Launch Report|archive-url=https://web.archive.org/web/20140728024436/http://www.spacelaunchreport.com/delta2.html|archive-date=July 28, 2014|url-status=usurped}}</ref> In addition, two LR101-NA-11 vernier engines provided guidance for the first stage.

For additional thrust during launch, the Delta II used solid boosters. For the 6000-series, Delta II used Castor 4A boosters, while the 7000-series used [[Engineering:Graphite-Epoxy Motor|Graphite-Epoxy Motor]]s manufactured by [[Company:Alliant Techsystems|ATK]]. The vehicle could be flown with three, four, or, most commonly, nine boosters. When three or four boosters were used, all ignited on the ground at launch, while models that used nine boosters would ignite six on the ground, then the remaining three in flight after the burnout and jettison of the first six.<ref name=slrd2/>

The second stage of Delta II was the [[Engineering:Delta-K|Delta-K]], powered by a restartable [[Company:Aerojet|Aerojet]] [[Engineering:AJ10|AJ10]]-118K engine burning hypergolic Aerozine-50 and {{N2O4|link=https://en.wikipedia.org/wiki/Dinitrogen_tetroxide}}. These propellants are highly toxic and corrosive, and once loaded the launch had to occur within approximately 37 days or the stage would have to be refurbished or replaced.<ref>{{cite web|url=http://dawn.jpl.nasa.gov/mission/journal_7_15_07.asp|title=DAWN Journal|access-date=2008-09-06|author=Dr. Marc D. Rayman|date=2007-07-15|publisher=JPL NASA|archive-url=https://web.archive.org/web/20081012160553/http://dawn.jpl.nasa.gov/mission/journal_7_15_07.asp|archive-date=2008-10-12|url-status=live}} {{PD-notice}}</ref> This stage also contained a combined [[Engineering:Inertial platform|inertial platform]] and [[Engineering:Guidance system|guidance system]] that controlled all flight events. The Delta-K stage was {{convert|6|m|ft|sp=us}} long and {{convert|2.4|m|ft|sp=us}} wide, containing up to {{convert|6|t|lb}} of propellant, and burned for up to 430&nbsp;seconds.<ref name=slrd2/>

For low Earth orbit, Delta II was not equipped with a third stage. Payloads bound for higher energy orbits such as [[Astronomy:Geostationary transfer orbit|GTO]] or to reach Earth escape velocity for trans-Mars injection or other destinations beyond Earth used a solid propellant third stage. This stage was spin-stabilized and depended on the second stage for proper orientation prior to stage separation, but was sometimes equipped with a nutation control system to maintain proper spin axis.<ref name="D2PG"/> It also included a yo-weight system to induce tumbling in the third stage after payload separation to prevent recontact, or a [[Engineering:Yo-yo de-spin|yo-yo de-spin]] mechanism to slow the rotation before payload release.<ref name="D2PG">{{cite web|title=Delta II Payload Planner's Guide 2007 |url=http://www.ulalaunch.com/uploads/docs/DeltaIIPayloadPlannersGuide2007.pdf|website=ulalaunch.com|access-date=24 July 2014|archive-url=https://web.archive.org/web/20110919175556/http://www.ulalaunch.com/site/docs/product_cards/guides/DeltaIIPayloadPlannersGuide2007.pdf|archive-date=19 September 2011|url-status=live}}</ref>

== Naming system ==
The Delta II family used a four-digit system to generate its technical names:<ref>{{cite web|url=http://kevinforsyth.net/delta/vehicle.htm|title=Vehicle Description and Designations|last=Forsyth|first=Kevin S. |access-date=2008-03-15|date=2007-08-10|work=History of the Delta Launch Vehicle|archive-url=https://web.archive.org/web/20110808102239/http://kevinforsyth.net/delta/vehicle.htm|archive-date=2011-08-08|url-status=live}}</ref>
* The '''first digit''' was either 6 or 7, denoting the 6000- or 7000-series Delta.
* The '''second digit''' indicated the number of boosters. Most Delta II rockets flew with 9 boosters, but some flew with 3 or 4.
* The '''third digit''' was always 2, denoting a second stage with an Aerojet AJ10 engine. Only Deltas prior to the 6000-series used a different engine, the TR-201.
* The '''last digit''' denoted the third stage. 0 denoted no third stage, 5 indicated a [[Engineering:Payload Assist Module|Payload Assist Module]] (PAM) stage with Star 48B solid motor, and 6 indicated a Star 37FM motor.
* An '''H''' following the four digits denoted that the vehicle used the larger Delta III GEM-46 boosters. The Heavy variant could be launched only from Cape Canaveral (as Vandenberg's pad wasn't modified to handle the larger SRBs), and was retired with the closure of that launch site in 2011.<ref name="nsfoco">{{cite web|last1=Graham|first1=William|title=ULA Delta II successfully lofts OCO-2 to orbit |url=http://www.nasaspaceflight.com/2014/07/delta-ii-oco-2-launch-vandenberg/|website=NASASpaceflight.com|access-date=July 23, 2014|date=July 2, 2014|archive-url=https://web.archive.org/web/20140714130852/http://www.nasaspaceflight.com/2014/07/delta-ii-oco-2-launch-vandenberg/|archive-date=July 14, 2014|url-status=live}}</ref>
* Numbers and letters following those indicate the type of fairing. -9.5 means that the vehicle had a {{cvt|9.5|ft}} diameter fairing, -10 means a metallic {{cvt|10|ft}} diameter fairing, -10C means a composite {{cvt|10|ft}} diameter fairing, and -10L indicates a lengthened {{cvt|10|ft}} diameter composite fairing. In some early Delta II flights, an 8-foot diameter fairing (from older Delta rockets) was flown, and those vehicles had a -8 designation.

For example, a Delta 7925H-10L used an RS-27A, nine GEM-46 boosters, a PAM third stage, and a lengthened {{cvt|10|ft}} diameter fairing. A Delta 6320–9.5 is a two-stage vehicle with an RS-27 first stage engine, three Castor 4A boosters, a {{cvt|9.5|ft}} diameter fairing, and no third stage.

== Launch profile ==
; [[Engineering:Launch vehicle|Launch vehicle]] build-up: A Delta II launch vehicle was assembled vertically on the launch pad. Assembly started by hoisting the first stage into position. The solid rocket boosters were then hoisted into position and mated with the first stage. Launch vehicle build-up then continued with the second stage being hoisted atop the first stage.<!-- Is there a better source for this info? --><ref>{{cite web |url=http://www.nasa.gov/centers/kennedy/launchingrockets/status/2007/elvstatus-20070606.html|title=Expendable Launch Vehicle Status Report|date=June 6, 2007|publisher=NASA|access-date=June 8, 2007|archive-url=https://web.archive.org/web/20070608140719/http://www.nasa.gov/centers/kennedy/launchingrockets/status/2007/elvstatus-20070606.html|archive-date=June 8, 2007|url-status=live}} {{PD-notice}}</ref>
; Fueling: It took approximately 20 minutes to load the first stage with {{cvt|10000|USgal|L|-2|order=flip|sp=us}} of fuel.<ref>{{cite web|url=http://www.nasa.gov/mission_pages/swift/launch/pad.html |title=Swift Launch Pad Activities|date=2004-11-18|access-date=2007-12-20|archive-url=https://web.archive.org/web/20070808154914/http://www.nasa.gov/mission_pages/swift/launch/pad.html|archive-date=2007-08-08 |url-status=live}} {{PD-notice}}</ref>

: At T-45 minutes, fueling completion was confirmed. At T-20 minutes, the FTS pyros were armed. At T-20 minutes and T-4 minutes, two built in holds occurred. During these holds, final launch checkouts were performed. At T-11 seconds SRB igniters were armed. Ignition of the main engine was at T-0.4 seconds. The ascent profile varies between missions.
; SRB staging: If 9 solid rocket boosters were used, only six were ignited at launch. After about a minute, once the first six were depleted, three air-start motors would ignite for another minute and the ground-start motors would separate.<ref>{{Cite book |last=Squyres |first=Steve |title=Roving Mars: Spirit, Opportunity, and the Exploration of the Red Planet |publisher=Hachette Books |year=2005 |isbn=9781401308513}}</ref> The air-start motors had nozzles optimized for high-altitude as they operated mostly in a near-vacuum during the flight.
: If only 3 or 4 boosters were used, all were ignited on the ground and jettisoned at the same time.

== Delta II launches ==
{{Main article|Engineering:List of Delta 2 launches}}
[[File:Lancement Spirit fusee Delta IIs 10062003.jpg|thumb|270px|right|Delta II lifting off with MER-A on 10 June 2003.]]
[[File:Mer-b-final-launch.jpg|right|thumb|270px|Delta II Heavy (7925H-9.5) lifting off from pad 17-B carrying [[Engineering:Opportunity (rover)|MER-B]].]]

=== Notable payloads ===
Earth-orbiting
{{div col|colwidth=15em}}
* [[Astronomy:Fermi Gamma-ray Space Telescope|GLAST]]
* [[Physics:Gravity Probe B|Gravity Probe B]]
* 24 GPS satellites
* 60 [[Engineering:Iridium satellite constellation|Iridium]] satellites
* [[Engineering:ICESat-2|ICESat-2]]
* [[Astronomy:Kepler space telescope|Kepler space telescope]]
* OSTM/Jason-2
* [[Engineering:Radarsat-1|Radarsat-1]]
* [[Engineering:Polar (satellite)|Polar (satellite)]]
* [[Astronomy:ROSAT|ROSAT]]
* [[Astronomy:Spitzer Space Telescope|Spitzer Space Telescope (SIRTF)]]
* STSS-ATRR
* Swift
* [[Astronomy:THEMIS|THEMIS]]
* USA 193 (NROL-21)
* WIND
* [[Astronomy:Wide-field Infrared Survey Explorer|WISE]]
* [[Astronomy:Wilkinson Microwave Anisotropy Probe|WMAP]]
{{div col end}}

Extra-planetary
{{div col|colwidth=15em}}
* [[Astronomy:2001 Mars Odyssey|2001 Mars Odyssey]]
* [[Astronomy:CONTOUR|CONTOUR]]
* [[Engineering:Dawn (spacecraft)|Dawn]]
* ''[[Engineering:Deep Impact (spacecraft)|Deep Impact]]''
* [[Astronomy:Deep Space 1|Deep Space 1]]
* [[Engineering:Genesis (spacecraft)|Genesis]]
* [[Astronomy:GRAIL|GRAIL]]
* [[Astronomy:Mars Climate Orbiter|Mars Climate Orbiter]]
* [[Astronomy:Mars Exploration Rover|Mars Exploration Rover]]s
* [[Astronomy:Mars Global Surveyor|Mars Global Surveyor]]
* [[Astronomy:Mars Pathfinder|Mars Pathfinder]]
* [[Engineering:Phoenix (spacecraft)|Mars Phoenix]]
* [[Astronomy:Mars Polar Lander|Mars Polar Lander]]
* [[Astronomy:MESSENGER|MESSENGER]]
* [[Astronomy:NEAR Shoemaker|NEAR]]
* [[Astronomy:STEREO|STEREO]]
{{div col end}}

The last Delta II launch was the [[Engineering:ICESat-2|ICESat-2]] satellite in September 2018.<ref name="nsfoco"/><ref>{{cite web|url=http://www.marketwatch.com/story/nasa-selects-launch-services-contract-for-three-missions-2012-07-16|archive-url=https://archive.today/20130129044229/http://www.marketwatch.com/story/nasa-selects-launch-services-contract-for-three-missions-2012-07-16|url-status=dead|archive-date=29 January 2013|title=NASA Selects Launch Services Contract For Three Missions|date=16 July 2012|access-date=16 July 2012|publisher=MarketWatch}}</ref><ref>{{cite web|url=http://www.nasa.gov/centers/kennedy/news/releases/2013/release-20130222b.html|title=NASA Selects Launch Services for ICESat-2 Mission|date=22 February 2013|access-date=15 March 2013|publisher=NASA Kennedy Space Center|archive-url=https://web.archive.org/web/20130708083045/http://www.nasa.gov/centers/kennedy/news/releases/2013/release-20130222b.html|archive-date=8 July 2013|url-status=live}}</ref>

In 2008, ULA indicated that it had "around half a dozen" unsold Delta II rockets on hand,<ref name=until2015>{{cite web|url=http://www.space.com/businesstechnology/080630-busmon-delta-2.html|title=Delta 2 Rockets to Remain Competitive Until 2015|first=Brian|last=Berger|publisher=Space News|date=2008-06-30|access-date=2008-07-03|archive-url=https://web.archive.org/web/20080703100017/http://www.space.com/businesstechnology/080630-busmon-delta-2.html|archive-date=2008-07-03|url-status=live}}</ref> but ULA CEO Tory Bruno stated in October 2017 that there are no complete, unbooked Delta II rockets left in the ULA inventory; and though there are leftover Delta II parts, there are not enough to build another launch vehicle.<ref>{{cite tweet |user=torybruno|number=920249741082062853|title=Less than 1. Last 2 complete DIIs are ordered, JPSS is flying next. Most of a 3rd DII's parts remain in inventory|date=17 October 2017 |access-date=7 August 2019}}</ref> The final Delta II rocket is located at the [[Engineering:Rocket garden|Kennedy Space Center rocket garden]].<ref>{{Cite web|url=https://www.space.com/delta2-rocket-garden-nasa-display|title=Last Delta II takes root in Kennedy Space Center rocket garden|author1=Robert Z. Pearlman|date=23 March 2021|website=Space.com|accessdate=11 March 2023}}</ref>

== Comparable rockets ==
[[Image:Delta rocket evolution.png|thumb|270px|Delta rocket evolution]]
* [[Engineering:Antares (rocket)|Antares]]
* [[Engineering:Ariane 4|Ariane 4]] (retired)
* [[Engineering:Geosynchronous Satellite Launch Vehicle|GSLV]]
* [[Engineering:Long March 4B|Long March 4B]]
* [[Engineering:Polar Satellite Launch Vehicle|PSLV]]
* [[Engineering:Soyuz (rocket family)|Soyuz]]
* [[Engineering:Tsyklon-3|Tsyklon-3]] (retired)
* [[Engineering:Vega (rocket)|Vega]]

== Space debris ==
The only person on record ever hit by space debris was hit by a piece of a Delta II rocket. Lottie Williams was exercising in a park in Tulsa on 22 January 1997 when she was hit in the shoulder by a {{convert|6|in|cm|adj=on|order=flip|sp=us}} piece of blackened metallic material. U.S. Space Command confirmed that a used Delta II rocket from the April 1996 launch of the [[Astronomy:Midcourse Space Experiment|Midcourse Space Experiment]] had crashed into the atmosphere 30 minutes earlier. The object tapped her on the shoulder and fell off harmlessly onto the ground. Williams collected the item and NASA tests later showed that the fragment was consistent with the materials of the rocket, and Nicholas Johnson, the agency's chief scientist for orbital debris, believes that she was indeed hit by a piece of the rocket.<ref>{{cite news|title=Space Junk Survivor |url=https://abcnews.go.com/Technology/story?id=98700&page=1|access-date=2 January 2018|date=3 March 2017|archive-url=https://web.archive.org/web/20180103072647/http://abcnews.go.com/Technology/story?id=98700&page=1|archive-date=3 January 2018|url-status=live}}</ref><ref>{{cite news|last1=Long|first1=Tony|title=January 22, 1997: Heads Up, Lottie! It's Space Junk!|url=https://www.wired.com/2009/01/jan-22-1997-heads-up-lottie-its-space-junk/|access-date=2 January 2018|date=22 January 1997|archive-url=https://web.archive.org/web/20180102224533/https://www.wired.com/2009/01/jan-22-1997-heads-up-lottie-its-space-junk/|archive-date=2 January 2018|url-status=live}}</ref>

Delta rockets have been involved in multiple fragmentation events as they were routinely left in orbit with enough fuel to explode. A large amount of current "space junk" Is Delta rocket debris.<ref>{{cite web |title=Micrometeoroids and Orbital Debris (MMOD) |url=https://www.nasa.gov/centers/wstf/site_tour/remote_hypervelocity_test_laboratory/micrometeoroid_and_orbital_debris.html |access-date=20 March 2023}}</ref>

== See also ==
* [[Engineering:Comparison of orbital launchers families|Comparison of orbital launchers families]]
* [[Astronomy:Comparison of orbital launch systems|Comparison of orbital launch systems]]

== References ==
{{reflist|2}}

== External links ==
* [https://web.archive.org/web/20061103194958/http://www.boeing.com/defense-space/space/delta/delta2/delta2.htm Delta II page] at Boeing.com
* [https://web.archive.org/web/20110718145330/http://space.skyrocket.de/doc_lau/delta.htm Delta I, II und III launch data] at Skyrocket.de
* [http://kevinforsyth.net/delta/ History of the Delta launch vehicle]
* [http://www.nasa.gov/sites/default/files/633163main_delta-2-weather.pdf Delta II Launch Weather Commit Criteria]

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