Editing Delta II (section)

== History ==
[[Image:Delta rocket evolution.png|thumb|320px|left|Evolution of the modern Delta rockets]]

In the early 1980s, all United States [[expendable launch vehicles]] were planned to be phased out in favor of the [[Space Shuttle]], which would be responsible for all government and commercial launches. Production of Delta, [[Atlas-Centaur]], and [[Titan 34D]] had ended.<ref>{{cite book |title=Taming Liquid Hydrogen - The Centaur Upper Stage Rocket (1958-2002) |last1=Dawson |first1=Virginia P. |last2=Bowles |first2=Mark D. |year=2004 |page=308 |publisher=NASA |url=https://www.nasa.gov/wp-content/uploads/2023/04/sp-4230.pdf |access-date=13 August 2024}} {{PD-notice}}</ref> The [[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 [[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 |first1=Harry F. |last1=Rosenthal |title=Reagan Orders NASA To Halt Launch of Commercial Payloads |date=August 16, 1986 |work=Associated Press News Archive |access-date=13 August 2024 |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 [[U.S. Air Force]] in 1987 to provide seven Delta II. These were intended to launch a series of [[Global Positioning System]] (GPS) [[GPS satellite blocks|Block II]] satellites, which had previously been manifested for the 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 A. |publisher=NASA |year=2009 |id=NASA SP-4012 |pages=49–51 (73–75) |url=https://www.nasa.gov/wp-content/uploads/2023/04/sp-4012v7.pdf |access-date=13 August 2024}} {{PD-notice}}</ref><ref>{{cite web |url=https://www.losangeles.spaceforce.mil/ |title=Delta II, Atlas II, and Atlas III |date=26 April 2013 |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 |url-status=live |access-date=13 August 2024}} {{PD-notice}}</ref> The first Delta II launch occurred on 14 February 1989, with a Delta 6925 boosting the first GPS Block II satellite ([[USA-35]]) from [[Cape Canaveral Space Launch Complex 17|Launch Complex 17A]] (SLC-17A) at [[Cape Canaveral Space Force Station|Cape Canaveral]] into a {{cvt|20000|km|mi}} high [[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 |archive-url=https://web.archive.org/web/20091113093423/http://planet4589.org/space/log/launchlog.txt |archive-date=13 November 2009 |access-date=13 August 2024 |url-status=live}}</ref>

The first Delta II 7000-series flew on 26 November 1990, replacing the [[RS-27]] engine of the 6000-series with the more powerful [[RS-27A]] engine. Additionally, the steel-cased [[Castor (rocket stage)|Castor 4A]] solid boosters of the 6000 series were replaced with the composite-cased [[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=https://www.nasaspaceflight.com/2014/07/delta-ii-oco-2-launch-vandenberg/ |first=William |last=Graham |title=ULA Delta II successfully lofts OCO-2 to orbit |date=July 2, 2014 |access-date=13 August 2024 |website=nasaspaceflight.com}}</ref>

McDonnell Douglas began [[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 [[Graphite-Epoxy Motor|GEM 46]] boosters, could bring twice as much mass as Delta II to [[geostationary transfer orbit]], but a string of two failures and one partial failure, along with the development of the much more powerful [[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 |publisher=Space Launch Report |website=spacelaunchreport.com |date=2 November 2014 |access-date=13 August 2024}}</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 [[GRAIL|Gravity Recovery and Interior Laboratory]] (GRAIL) in 2011.<ref>{{cite web |last=Cleary |first=Mark |title=Delta II and III Space Operations at Cape Canaveral 1989–2009 |url=http://www.afspacemuseum.org/library/histories/Delta.pdf |website=afspacemuseum.org |archive-url=https://web.archive.org/web/20150530135122/http://www.afspacemuseum.org/library/histories/Delta.pdf |access-date=13 August 2024 |archive-date=30 May 2015 |url-status=live}} {{PD-notice}}</ref>

On 14 December 2006, with the launch of [[USA-193]], was the first launch of the Delta II operated by [[United Launch Alliance]].<ref>{{cite web |title=United Launch Alliance Joint Venture Completes First Launch - ULA Demonstrates Commitment to Mission Assurance With Delta II West Coast Liftoff for NRO Customer|url=https://www.ulalaunch.com/missions/missions-details/2006/12/14/united-launch-alliance-joint-venture-completes-first-launch |website=ulalaunch.com |date=14 December 2006 |access-date=13 August 2024}}</ref>

The last GPS launch aboard a Delta II and the final launch from SLC-17A at Cape Canaveral occurred 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 [[Vandenberg Space Force Base|Vandenberg Air Force Base]] in [[California]].<ref>{{cite web |title=The Hangar/Delta II |url=http://www.spaceflightinsider.com/hangar/delta-ii/ |website=spaceflightinsider.com |archive-url=https://web.archive.org/web/20171117170205/http://www.spaceflightinsider.com/hangar/delta-ii/#ELuwclvxe8H5Cdu1.99 |archive-date=17 November 2017 |access-date=13 August 2024 |url-status=live}}</ref>

On 16 July 2012, NASA selected the Delta II to support the [[Orbiting Carbon Observatory]] (OCO-2), [[Soil Moisture Active Passive]] (SMAP), and [[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, [[Soil Moisture Active Passive]] (SMAP) was launched on 31 January 2015, and [[NOAA-20|JPSS-1]] was launched on 18 November 2017. All three of these launches were placed into orbit from [[Vandenberg Space Launch Complex 2|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 |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 |access-date=13 August 2024 |url-status=live}} {{PD-notice}}</ref>

The Delta II family launched 155 times. Its only unsuccessful launches were [[Koreasat 1]] in 1995, and [[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 [[geosynchronous orbit]] and operated for 10 years.<ref>{{cite web |url=https://space.skyrocket.de/doc_sdat/koreasat-1.htm |title=Koreasat 1, 2 (Mugungwha 1, 2) / Europe*Star B / ABS-1A |last=Krebs |first=Gunter Dirk |date=14 January 2023 |access-date=13 August 2024}}</ref> The GPS IIR-1 was a total loss as the Delta II exploded 13 seconds after launch. The explosion occurred when a damaged [[solid rocket booster]] casing ruptured and triggered the vehicle's flight termination system.<ref>{{Cite web |url=http://www.gizmodo.com.au/2008/09/the_deadly_aftermath_of_a_rocket_explosion_seconds_after_launch-2.html |archive-url=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 |title=Science & Health Archives |archive-date=12 February 2009 |website=gizmodo.com.au |access-date=13 August 2024}}</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=14 August 2024 |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 [[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=2009-03-03 |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=14 August 2024 |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 [[ICESat-2]] in 2018, Delta II reached 100 consecutive successful launches.

During its career, Delta II achieved a peak launch rate of 12 launches in a single year, although its infrastructure was capable of supporting up to 15 launches per year.<ref name ="Guide"/>

While all completed Delta II rockets were launched, many flight-qualified spare parts remained in inventory. These spare parts were assembled, alongside a few structural simulators, to create a nearly complete Delta II for exhibition in its 7320-10C configuration. The rocket is displayed vertically at the [[Kennedy Space Center Visitor 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 |date=15 September 2018 |access-date=14 August 2024 |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>