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Delta IV
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== History == The latest evolutionary development of the [[Delta (rocket family)|Delta rocket family]], Delta IV was introduced to meet the requirements of the United States Air Force's (USAF) [[Evolved Expendable Launch Vehicle]] (EELV, now [[National Security Space Launch]] (NSSL)) program. While the Delta IV retains the name of the Delta family of rockets, major changes were incorporated. Perhaps the most significant change was the switch from kerosene to [[liquid hydrogen]] fuel, with new tankage and a new engine required.<ref>{{Cite web |last=Kelly |first=Emre |title=The last ever 'single stick' Delta IV scheduled to launch; here's what that means |url=https://www.floridatoday.com/story/tech/science/space/2019/08/15/united-launch-alliance-set-launch-last-ever-single-stick-delta-iv-rocket-cape-canaveral-florida/2008221001/ |access-date=2021-04-19 |website=Florida Today |language=en-US}}</ref><ref name="planner guide2013" /> During the Delta IV's development, a small variant was considered. This would have featured the [[Delta II]] second stage, an optional [[Thiokol]] [[Star (rocket stage)|Star 48B]] third stage, and the Delta II payload fairing, all atop a single [[Common Booster Core]] (CBC).<ref>[http://www.astronautix.com/lvs/delsmall.htm "Delta IV Small"] {{webarchive |url=https://web.archive.org/web/20061105183541/http://www.astronautix.com/lvs/delsmall.htm|date=2006-11-05}} Astronautix.com</ref> The Small variant was dropped by 1999.<ref>[http://space.skyrocket.de/doc_lau/delta-4.htm Gunter's Space page - Delta IV]</ref><ref>{{Cite press release |title=Boeing Signs agreement for Delta IV Integration Facility |date=January 28, 1999 |publisher=Boeing |url=http://www.boeing.com/news/releases/1999/news_release_990128b.html |url-status=dead |archive-url=https://web.archive.org/web/20121010230340/http://www.boeing.com/news/releases/1999/news_release_990128b.html |archive-date=October 10, 2012}}</ref> In 2002, the Delta IV was first launched, with the [[RS-68]] becoming the first large [[liquid-propellant rocket]] engine designed in the United States since the [[RS-25|Space Shuttle main engine]] (SSME) in the 1970s.<ref name="slrdiv">{{Cite web |date=26 Apr 2021 |title=Space Launch Report: Delta IV Data Sheet |url=http://www.spacelaunchreport.com/delta4.html |url-status=usurped |archive-url=https://web.archive.org/web/20220406013823/http://www.spacelaunchreport.com/delta4.html |archive-date=6 Apr 2022}}</ref> The [[L3 Technologies]] Redundant Inertial Flight Control Assembly (RIFCA) guidance system originally used on the Delta IV was common to that carried on the [[Delta II]], although the software was different because of the differences between the Delta II and Delta IV. The RIFCA featured six [[ring laser gyroscope]]s and [[accelerometer]]s each, to provide a higher degree of reliability.<ref>[http://www.l-3com.com/spacenav/space_and_nav/space_products/RIFCA-Trihex.htm "L-3 Space & Navigation's RIFCA Trihex"] {{webarchive|url=https://web.archive.org/web/20061015192521/http://www.l-3com.com/spacenav/space_and_nav/space_products/RIFCA-Trihex.htm|date=2006-10-15}}</ref> [[Boeing]] initially intended to market Delta IV commercial launch services. However, the Delta IV entered the space launch market when global capacity was already much higher than demand. Furthermore, as an unproven design it had difficulty finding a market in commercial launches, and Delta IV launch costs are higher than comparable vehicles of the same era. In 2003, Boeing pulled the Delta IV from the commercial market, citing low demand and high costs. In 2005, Boeing stated that it sought to return the Delta IV to commercial service.<ref>{{Cite news |date=March 25, 2005 |title=Boeing's Delta IV may return to commercial launches |url=http://www.ocregister.com/ocr/2005/03/25/sections/business/business_nation/article_456341.php |url-status=dead |archive-url=https://web.archive.org/web/20061114073317/http://www.ocregister.com/ocr/2005/03/25/sections/business/business_nation/article_456341.php |archive-date=November 14, 2006 |publisher=Orange County Register}}</ref> As of 2009, the USAF funded Delta IV EELV engineering, integration, and infrastructure work through contracts with Boeing Launch Services (BLS). On 8 August 2008, the USAF [[Space and Missile Systems Center]] increased the "cost plus award fee" contract with BLS for US$1.656 billion to extend the period of performance through the 30 September 2008 ([[Fiscal year|FY09]]). In addition, a US$557.1 million option was added to cover FY10.<ref name="Def_Contract_Aug2008">{{Cite web |date=8 August 2008 |title=DefenseLink Contracts for Friday, August 08, 2008 |url=http://www.defenselink.mil/contracts/contract.aspx?contractid=3837 |access-date=6 January 2009 |publisher=US Department of Defense}}</ref> In February 2010, naturalized citizen Dongfan Chung, an engineer working with Boeing, was the first person convicted under the [[Economic Espionage Act of 1996]]. Chung passed on classified information on designs including the Delta IV rocket to China and was sentenced to 15 years.<ref>{{Cite news |last=Whitcomb |first=Dan |date=8 February 2010 |title=Ex-Boeing engineer gets 15 years in U.S. spy case |url=https://www.reuters.com/article/idUSN0821290920100208 |url-status=live |archive-url=https://web.archive.org/web/20100212070059/http://www.reuters.com/article/idUSN0821290920100208 |archive-date=12 February 2010 |work=Reuters}}</ref> In March 2015, ULA announced plans to phase out the Delta IV Medium by 2018.<ref>{{Cite web |date=3 March 2015 |title=ULA Targets 2018 for Delta 4 Phase-out, Seeks Relaxation of RD-180 Ban |url=http://spacenews.com/ula-targets-2018-for-delta-4-phase-out-seeks-relaxation-of-rd-180-ban/ |access-date=2015-03-03 |publisher=SpaceNews.com}}</ref> With the exception of the first launch, which carried the [[Eutelsat 33B|Eutelsat W5]] commercial communications satellite, all Delta IV launches have been paid for by the US government. In 2015, ULA stated that a [[Delta IV Heavy]] is sold for nearly US$400 million.<ref name="sfn-20150422">{{Cite news |last=Clark |first=Stephen |date=22 April 2015 |title=ULA needs commercial business to close Vulcan rocket business case |url=http://spaceflightnow.com/2015/04/22/ula-needs-commercial-business-to-close-vulcan-rocket-business-case/ |access-date=23 April 2015 |publisher=Spaceflight Now}}</ref> === RS-68A booster engine upgrade === The possibility of a higher performance Delta IV was first proposed in a 2006 [[RAND Corporation]] study of national security launch requirements out to 2020. A single [[National Reconnaissance Office]] (NRO) payload required an increase in the lift capability of the Delta IV Heavy.<ref>{{Cite web |last=Forrest McCartney |display-authors=etal |year=2006 |title=National Security Space Launch Report |url=https://www.rand.org/pubs/monographs/2006/RAND_MG503.pdf |publisher=RAND |pages=6β7}}</ref> Lift capacity was increased by developing the higher-performance [[RS-68#Variants|RS-68A]] engine,<ref>{{Cite press release |title=Three Pratt & Whitney Rocketdyne RS-68A Engines Power Delta IV Heavy Upgrade Vehicle on Inaugural Flight |url=http://www.prnewswire.com/news-releases/three-pratt--whitney-rocketdyne-rs-68a-engines-power-delta-iv-heavy-upgrade-vehicle-on-inaugural-flight-160868765.html |access-date=November 9, 2014 |website=prnewswire.com}}</ref> which first flew on 29 June 2012.<ref name="ULA-PR-Jun12">{{Cite press release |title=United Launch Alliance Upgraded Delta IV Heavy rocket successfully Launches Second Payload in Nine Days for the National Reconnaissance Office |date=2012-06-29 |publisher=United Launch Alliance |url=http://www.ulalaunch.com/site/pages/News.shtml#/109/ |access-date=2011-01-21 |url-status=dead |archive-url=https://web.archive.org/web/20131207160150/http://www.ulalaunch.com/site/pages/News.shtml#/109/ |archive-date=2013-12-07}}</ref> ULA phased out the baseline RS-68 engine with the launch of Delta flight 371 on 25 March 2015. All following launches used the RS-68A,<ref name="Spaceflight Now">{{Cite web |date=27 March 2015 |title=Delta 4 rocket evolving to upgraded main engine |url=http://spaceflightnow.com/2015/03/27/delta-4-rocket-evolving-the-upgraded-main-engine/ |access-date=28 March 2015 |publisher=Spaceflight Now}}</ref> and the engine's higher thrust allowed the use of a single standardized CBC design for all Delta IV Medium and M+ versions. This upgrade reduced cost and increased flexibility, since any standardized CBC could be configured for zero, two, or four [[solid-propellant rocket]] boosters. However, the new CBC led to a slight performance loss for most medium configurations.<ref>{{Cite web |date=15 June 2012 |title=New Delta 4 Engine Variant is Part of ULA Cost Cutting Strategy |url=http://www.spacenews.com/article/new-delta-4-engine-variant-part-ula-cost-cutting-strategy |website=spacenews.com}}</ref> The Delta IV Heavy required non-standard CBCs for the core and boosters.<ref>{{Cite web |date=March 2010 |title=Ongoing Launch Vehicle Innovation at United Launch Alliance |url=http://ulalaunch.com/site/docs/publications/ULA-Innovation-March-2010.pdf |archive-url=https://web.archive.org/web/20140328201054/http://ulalaunch.com/site/docs/publications/ULA-Innovation-March-2010.pdf |archive-date=2014-03-28 |access-date=July 13, 2014 |publisher=ULA}}</ref> '''Payload capacities after RS-68A upgrade''' {| class="wikitable sortable" |- style="background:#ffdead;" ! Version ! Fairing ! CBCs ! SRBs ! Payload to [[Low Earth orbit|LEO]] 407 km x 51.6Β° ! Payload to [[Geostationary transfer orbit|GTO]] 1800 m/s residual ! Launches |- | Medium | 4 m | 1 | 0 | 8,510 kg<ref name=":0">{{Cite web |title=Delta IV |url=http://www.spacelaunchreport.com/delta4.html |url-status=usurped |archive-url=https://web.archive.org/web/20100821062352/http://www.spacelaunchreport.com/delta4.html |archive-date=21 August 2010 |publisher=SpaceLaunchReport.com}}</ref> | 4,440 kg<ref name=":1">{{Cite web |date=June 2013 |title=Delta IV User's Guide |url=http://www.ulalaunch.com/uploads/docs/Launch_Vehicles/Delta_IV_Users_Guide_June_2013.pdf |archive-url=https://web.archive.org/web/20140710005717/http://www.ulalaunch.com/uploads/docs/Launch_Vehicles/Delta_IV_Users_Guide_June_2013.pdf |archive-date=2014-07-10 |access-date=July 10, 2014 |publisher=ULA}}</ref> | 0 |- | M+ (4,2) | 4 m | 1 | 2 | 12,000 kg<ref name=":0" /> | 6,390 kg<ref name=":1" /> | 2 |- | M+ (5,2) | 5 m | 1 | 2 | 10,220 kg<ref name=":0" /> | 5,490 kg<ref name=":1" /> | 2 |- | M+ (5,4) | 5 m | 1 | 4 | 12,820 kg<ref name=":0" /> | 7,300 kg<ref name=":1" /> | 4 |- | Heavy | 5 m | 3 | 0 | 25,980 kg<ref name=":0" /> | 14,220 kg<ref name=":1" /> | 9 |} '''Payload capacities with original RS-68''' {| class="wikitable sortable" ! Version ! Fairing ! CBCs ! SRBs ! Payload to [[Low Earth orbit|LEO]] 407 km x 51.6Β° ! Payload to [[Geostationary transfer orbit|GTO]] 1800 m/s residual ! Launches |- | Medium | 4 m | 1 | 0 | 8,800 kg<ref name=":0" /> | 4,540 kg<ref name=":2">{{Cite web |date=September 2007 |title=Delta IV Payload Planner's Guide |url=https://www.scribd.com/doc/16924978/Boeing-Delta-IV-Payload-Planners-Guide}}</ref> | 3 |- | M+ (4,2) | 4 m | 1 | 2 | 11,920 kg<ref name=":0" /> | 6,270 kg<ref name=":2" /> | 13 |- | M+ (5,2) | 5 m | 1 | 2 | 10,580 kg<ref name=":0" /> | 5,430 kg<ref name=":2" /> | 1 |- | M+ (5,4) | 5 m | 1 | 4 | 13,450 kg<ref name=":0" /> | 7,430 kg<ref name=":2" /> | 4 |- | Heavy | 5 m | 3 | 0 | 22,980 kg<ref name=":0" /> | 13,400 kg<ref name=":2" /> | 7 |} <nowiki>*</nowiki>Masses include a Payload Attach Fitting (240 kg to 1,221 kg depending on payload).<ref name=":1" /> === Proposed upgrades that were not implemented === Possible future upgrades for the Delta IV included adding extra strap-on solid motors, higher-thrust main engines, lighter materials, higher-thrust second stages, more (up to eight) strap-on CBCs, and a cryogenic propellant cross feed from strap on boosters to the common core.<ref name="Growth">{{Cite web |title=Delta Launch 310 β Delta IV Heavy Demo Media Kit - Delta Growth Options |url=http://www.boeing.com/defense-space/space/delta/kits/d310_d4heavy_demo.pdf |url-status=dead |archive-url=https://web.archive.org/web/20121006021346/http://www.boeing.com/defense-space/space/delta/kits/d310_d4heavy_demo.pdf |archive-date=October 6, 2012 |publisher=Boeing}}</ref> At one point, NASA planned to use Delta IV or Atlas V to launch the proposed [[Orbital Space Plane Program|Orbital Space Plane]],<ref>{{Cite web |last=Whitesides |first=Loretta Hidalgo |date=July 9, 2008 |title=Why NASA Isn't Trying to Human-Rate the Atlas V or Delta IV Rockets |url=https://www.wired.com/wiredscience/2008/07/why-nasa-isnt-t/ |publisher=Wired |quote="You could launch a smaller human vehicle on a current expendable rocket [...] In fact, before the Columbia disaster NASA teams were working on an Orbital Space Plane (OSP) designed to do just that".}}</ref> which eventually became the [[Crew Exploration Vehicle]] and then the [[Orion (spacecraft)|Orion]]. Orion was intended to fly on the [[Ares I]] launch vehicle, then the [[Space Launch System]] after Ares I was cancelled. In 2009, [[The Aerospace Corporation]] reported on [[NASA]] results of a study to determine the feasibility of modifying Delta IV to be [[Human-rating certification|crew-rated]] for use in NASA [[human spaceflight]] missions. According to [[Aviation Week & Space Technology]] the study, "found that a Delta IV heavy [...] could meet NASA's requirements for getting humans to low Earth orbit".<ref>{{Cite web |last=Frank Morring, Jr. |date=June 15, 2009 |title=Study Finds Human-rated Delta IV Cheaper |url=http://www.aviationweek.com/aw/generic/story_channel.jsp?channel=space&id=news/Study061509.xml |publisher=Aviation Week}}{{Dead link|date=October 2023 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> A proposed upgrade to the Delta IV family was the addition of extra solid motors. The Medium+ (4,4) would have used existing mount points to pair the four GEM 60s of the M+ (5,4) with the upper stage and fairing of the (4,2). An M+ (4,4) would have had a GTO payload of {{cvt|7500|kg}}, a LEO payload of {{cvt|14800|kg}}, and could have been available within 36 months of the first order. It was also considered to add extra GEM 60s to the M+ (5,4), which would have required adding extra attachment points, structural changes to cope with the different flight loads, and launch pad and infrastructure changes. The Medium+ (5,6) and (5,8) would have flown with six and eight SRBs respectively, for a maximum of up to {{cvt|9200|kg}} to GTO with the M+ (5,8). The Medium+ (5,6) and (5,8) could have been available within 48 months of the first order.<ref>{{Cite web |date=September 2007 |title=Delta IV Payload Planners Guide |url=http://www.ulalaunch.com/site/docs/product_cards/guides/DeltaIVPayloadPlannersGuide2007.pdf |archive-url=https://web.archive.org/web/20110722081616/http://www.ulalaunch.com/site/docs/product_cards/guides/DeltaIVPayloadPlannersGuide2007.pdf |archive-date=2011-07-22 |publisher=ULA |pages=10β15, 16}}</ref> === Successors === The [[Vulcan Centaur]] is planned to replace the [[Atlas V]] and Delta IV rockets. Vulcan Centaur had been projected to enter service by 2023, using the [[BE-4]] [[methane]]-fueled rocket engine,<ref>{{Cite news |last=Mike Gruss |date=13 April 2015 |title=ULA's Next Rocket To Be Named Vulcan |url=http://spacenews.com/ulas-next-rocket-to-be-named-vulcan/ |publisher=Space News}}</ref><ref>{{Cite web |last=Roulette |first=Joey |date=10 October 2022 |title=United Launch Alliance's debut Vulcan mission slips to 2023 -CEO |url=https://www.reuters.com/lifestyle/science/united-launch-alliances-debut-vulcan-mission-slips-2023-ceo-2022-10-10/ |access-date=24 October 2022 |website=[[Reuters]]}}</ref> but the first Vulcan launched on 8 January 2024.<ref>{{Cite news |last=Belam |first=Martin |date=2024-01-08 |title=Nasa Peregrine 1 launch: Vulcan Centaur rocket carrying Nasa moon lander lifts off in Florida β live updates |url=https://www.theguardian.com/science/live/2024/jan/08/nasa-peregrine-1-launch-rocket-moon-latest-news-updates-live |access-date=2024-01-08 |work=the Guardian |language=en-GB |issn=0261-3077}}</ref> The Atlas V is expected to stay in service for a few years after Vulcan's inaugural launch, and the Delta IV Heavy was discontinued in April 2024.<ref>{{Cite news |last=Stephen Clark |date=19 August 2019 |title=ULA's second launch of the month scheduled for Thursday |url=https://spaceflightnow.com/2019/08/19/ulas-second-launch-of-the-month-scheduled-for-thursday/ |publisher=Spaceflight Now}}</ref>
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