View source for Atlas (rocket family)

{{short description|Family of American missiles and space launch vehicles}}
{{Infobox aircraft
|name=Atlas family
|image=Atlas_EELV_family.png
|caption=Atlas II, III and V comparison  
|type=[[Expendable launch system]] with various applications
|manufacturer=[[Convair]]<br/>[[General Dynamics]]<br/>[[Lockheed Martin]]<br/>[[United Launch Alliance]]
|designer=
|first_flight={{Start date and age|1957|12|17}}<ref name="Rusty Barton">{{cite web | url = http://www.geocities.com/atlas_missile/Chronology.html | title = Atlas ICBM Chronology | author = Rusty Barton |archive-url=https://web.archive.org/web/20060204073649/http://www.geocities.com/atlas_missile/Chronology.html|archive-date=2006-02-04}}</ref>
|introduction=1957
|retired=
|status=[[Atlas V]] (current)
|primary_user=[[United States Air Force]]
|more_users=[[National Aeronautics and Space Administration]]
|produced=1957–2010s (decade)
|number_built=
|unit cost=
|variants=[[SM-65 Atlas]]<br/>[[SM-65D Atlas]]<br/>[[Atlas LV-3C]]<br/>[[Atlas IIIA]]<br/>[[Atlas V]]
}}
'''Atlas''' is a family of US missiles and space [[launch vehicle]]s that originated with the [[SM-65 Atlas]]. The Atlas [[intercontinental ballistic missile]] (ICBM) program was initiated in the late 1950s under the [[Convair]] Division of [[General Dynamics]].<ref>{{cite video
 | year =1959
 | title =Deny Rocket Lag. Atlas Firing Keynotes U.S. Missile Build-Up, 1959/01/29 (1959)
 | url =https://archive.org/details/1959-01-29_Deny_Rocket_Lag
 | publisher =[[Universal Newsreel]]
 | access-date =February 22, 2012
}}</ref> Atlas was a [[liquid propellant rocket]] burning [[RP-1]] kerosene fuel with [[liquid oxygen]] in three engines configured in an unusual "stage-and-a-half" or "parallel staging" design: two outboard booster engines were jettisoned along with supporting structures during ascent, while the center sustainer engine, propellant tanks and other structural elements remained connected through propellant depletion and engine shutdown.

The Atlas name was originally proposed by [[Karel Bossart]] and his design team working at [[Convair]] on project MX-1593.  Using the name of a [[Atlas (mythology)|mighty Titan from Greek mythology]] reflected the missile's place as the biggest and most powerful at the time. It also reflected the parent company of Convair, the [[Atlas Corporation]].<ref>{{cite book|title=Origin of NASA Names|publisher=NASA Science and Technical Information Office|pages=8–9|author1=Helen T. Wells |author2=Susan H. Whiteley |author3=Carrie E. Karegeannes  |name-list-style=amp }}</ref>

The missiles saw only brief ICBM service, and the last squadron was taken off operational alert in 1965. However, from 1962 to 1963 [[Atlas LV-3B|Atlas boosters]] launched the first four US [[astronaut]]s to [[orbital spaceflight|orbit]] the Earth (in contrast to the preceding two [[PGM-11 Redstone|Redstone]] [[suborbital]] launches). The [[Atlas-Agena]] and [[Atlas-Centaur]] satellite launch vehicles were also derived directly from the original Atlas. The Atlas-Centaur was evolved into the [[Atlas II]], various models of which were launched 63 times between 1991 and 2004. There were only six launches of the succeeding [[Atlas III]], all between 2000 and 2005. The [[Atlas V]] is still in service, with launches planned into the mid 2020s.

More than 300 Atlas launches have been conducted from [[Cape Canaveral Space Force Station]] in Florida and 285 from [[Vandenberg Space Force Base]] in California.

==Launch vehicles based on original Atlas ICBM==
The Atlas was used as an [[expendable launch system]], with both the Agena and Centaur upper stages, for the [[Mariner program|Mariner]] space probes used to explore [[Mercury (planet)|Mercury]], [[Venus]], and [[Mars]] (1962–1973); and to launch ten of the [[Mercury program]] missions (1962–1963).{{citation_needed|date=July 2019}}

===SM-65 Atlas missile===
{{Main|SM-65 Atlas}}
The first successful test launch of an SM-65 Atlas missile was on 17 December 1957.<ref name="Rusty Barton"/> Approximately 350 Atlas missiles were built.<ref>{{cite news|title=This week in history - Feb. 26, 1954: Air Force awards contract for Atlas ICBM propulsion system
|date=February 28, 2013|url=https://www.kirtland.af.mil/News/Article-Display/Article/389185/this-week-in-history-feb-26-1954-air-force-awards-contract-for-atlas-icbm-propu/|publisher=U.S. Air Force|access-date=March 29, 2023}}</ref>

The Atlas boosters would collapse under their own weight if not kept pressurized with nitrogen gas in the tanks when devoid of propellants. The Atlas booster was unusual in its use of "balloon" tanks. The rockets were made from very thin stainless steel that offered minimal or no rigid support. It was pressure in the tanks that gave the rigidity required for space flight. In order to save weight they were not painted and needed a specially designed oil to prevent rust. This was the original use of [[WD-40]] water displacement oil.<ref>{{Cite web |title=WD-40 History {{!}} Learn the Stories Behind the WD-40 Brand {{!}} WD-40 |url=https://www.wd40.com/history/ |access-date=2022-06-15 |website=www.wd40.com}}</ref>

The SM-65 Atlas was used as a first stage for satellite launch vehicles for half a century. Many were eventually converted to orbital launch vehicles after they were removed from service as missiles. Missiles converted into [[Atlas E/F]] "space boosters" were used to launch the early "Block I" [[GPS (satellite)|GPS satellites]].<ref>{{cite web | url = http://www.astronautix.com/lvs/atlase.htm | archive-url = https://web.archive.org/web/20020305192516/http://www.astronautix.com/lvs/atlase.htm | url-status = dead | archive-date = March 5, 2002 | title = Atlas E | publisher = Encyclopedia Astronautica |access-date=28 October 2014 }}</ref>

===SM-65B Atlas SCORE launch===
[[File:Atlas-B with Score payload.jpg|thumb|Atlas-B with SCORE payload, at LC-11, 1958]]
Early Atlas rockets were also built specifically for non-military uses. On 18 December 1958, an Atlas was used to launch the Signal Communication by Orbiting Relay Equipment ([[SCORE (satellite)|SCORE]]) satellite, which was "the first prototype of a [[communications satellite]], and the first test of any satellite for direct practical applications."<ref>{{cite web |url=http://www.narmc.amedd.army.mil/patterson/score.htm|title=Project SCORE|publisher=Patterson Army Health Clinic|url-status=dead |archive-url=https://web.archive.org/web/20070624221727/http://www.narmc.amedd.army.mil/patterson/score.htm |archive-date=2007-06-24}}</ref><ref>{{cite web |url=http://www.globalsecurity.org/space/systems/score.htm|title=SCORE (Signal Communication by Orbiting Relay Equipment)|publisher=GlobalSecurity.org|access-date=28 October 2014}}</ref><ref>{{Cite AV media| year=1958|title=Video: Atlas In Orbit. Radios Ike's Message Of Peace To World, 1958/12/22 (1958)|url=https://archive.org/details/1958-12-22_Atlas_In_Orbit|publisher=Universal Newsreels|access-date=20 February 2012}}</ref> The communications payload was placed into [[low Earth orbit]] on Atlas serial number 10B without an upper stage. Atlas 10B/SCORE, at {{convert|8750|lb|-1|abbr=on}} was the heaviest artificial object then in orbit, the first voice relay satellite, and the first human-made object in space easily visible to the naked eye due to the large, mirror-polished stainless steel tank. This was the first flight in what would be a long career for the Atlas as a satellite launcher.

===Atlas-D based launchers===
{{main|Atlas SLV-3}}
Atlas D missile-derived SLV-3s were used for [[orbit]]al launches with the [[RM-81 Agena]] and [[Centaur (rocket stage)|Centaur]] upper stages. The modified '''[[Atlas LV-3B]]''' was used for the orbital element of [[Project Mercury]], launching four [[human spaceflight|crewed]] [[Mercury spacecraft]] into [[low Earth orbit]].<ref name="EA"/> Atlas D launches were conducted from Cape Canaveral Air Force Station, at Launch Complexes 11, 12, 13 and 14, and [[Vandenberg AFB Launch Complex 576]].{{citation needed|date=August 2015}}

Two [[suborbital]] [[stage and a half]] vehicles were used during [[Project FIRE]] as [[sounding rocket]]s.<ref name="EA" />

By 1979, Atlas space launcher variants had been whittled down to just the Atlas-Centaur and some refurbished ICBMs. The launch rate of Atlases decreased in the 1980s due to the advent of the [[Space Shuttle]], but Atlas launches continued until 2004, when the last "classic" Atlas with balloon tanks and the jettisonable booster section launched a comsat for the Air Force.<ref>{{cite news|title=Final Atlas 2 Rocket Orbits Classified U.S. Satellite|author=Tariq Malik |date=August 31, 2004|url=https://www.space.com/296-final-atlas-2-rocket-orbits-classified-satellite.html|website=space.com|access-date=March 29, 2023}}</ref>

====Mercury program====
[[file:LOC-63C-1556.jpg|thumb|Mercury-Atlas 9 at [[Cape Canaveral Air Force Station Launch Complex 14|Launch Complex 14]]]]
{{main|Atlas LV-3B}}
Atlas boosters were also used for the last four crewed [[Project Mercury]] missions, the first United States crewed space program. On February 20, 1962, it launched [[Mercury-Atlas 6|''Friendship 7'']], which made three Earth orbits carrying [[John Glenn]], the first United States [[astronaut]] to orbit the Earth.  Identical Atlas boosters successfully launched three more crewed Mercury orbital missions from 1962 to 1963.

Atlas saw the beginnings of its "workhorse" status during the [[Mercury-Atlas]] missions, which resulted in Lt. Col. [[John Glenn|John H. Glenn Jr.]] becoming the first American to orbit the Earth in 1962. Atlas was also used throughout the mid-1960s to launch the [[Agena Target Vehicle]]s used during the [[Gemini program]].

====Atlas-Agena====
{{main|Atlas-Agena}}
Beginning in 1960, the [[RM-81 Agena|Agena]] [[multistage rocket|upper stage]], powered by [[hypergolic propellant]], was used extensively on Atlas launch vehicles. The [[United States Air Force]], [[National Reconnaissance Office|NRO]] and [[CIA]] used them to launch [[Signals intelligence|SIGINT]] satellites.<ref>{{cite web | url = http://www.astronautix.com/lvs/atlslv3a.htm | archive-url = https://web.archive.org/web/20020827232121/http://astronautix.com/lvs/atlslv3a.htm | url-status = dead | archive-date = August 27, 2002 | title = Atlas/Agena D SLV-3A | author = Mark Wade | publisher = Astronautix.com|access-date=28 October 2014 }}</ref> NASA used them in the [[Ranger program]] to obtain the first close-up images of the surface of the Moon and for [[Mariner 2]], the first spacecraft to fly by another planet. Each of the [[Agena target vehicle]]s used for the later [[space rendezvous]] practice missions of [[Project Gemini|Gemini]] was launched on an Atlas rocket.

====Atlas-Centaur====
{{main|Atlas-Centaur}}
The Atlas-Centaur was an [[expendable launch system]] derived from the [[SM-65D Atlas]] missile.{{citation needed|date=October 2013}} Launches were conducted from two pads of the [[Cape Canaveral Air Force Station Launch Complex 36|Launch Complex 36]] at [[Cape Canaveral Air Force Station]], Florida. The Atlas' engines were upgraded and the structure reinforced for the large upper stage, along with elongated propellant tanks.

The first launch attempt of an Atlas-Centaur in May 1962 failed, the rocket exploding after take-off.
Footage of this was shown in the penultimate shot of the 1982 art film ''[[Koyaanisqatsi]]'', directed by [[Godfrey Reggio]].

Beginning in 1963, the [[liquid hydrogen]]-fueled [[Centaur (rocket stage)|Centaur]] upper stage was also used on dozens of Atlas launches. [[NASA]] launched the [[Surveyor program]] lunar lander spacecraft and most of the Mars-bound [[Mariner program]] spacecraft with Atlas-Centaur launch vehicles.

===Atlas E/F===
{{main|Atlas E/F}}
Following retirement as an ICBM, the Atlas-E, along with the [[SM-65F Atlas|Atlas-F]], were refurbished for [[orbit]]al launches.<ref name="EA">{{cite web |url=http://www.astronautix.com/lvs/atlasa.htm |title=Encyclopedia Astronautica – Atlas A |publisher=Astronautix.com |access-date=19 July 2013 |url-status=dead |archive-url=https://web.archive.org/web/20130522064526/http://www.astronautix.com/lvs/atlasa.htm |archive-date=22 May 2013 |df=dmy-all }}</ref>

The last Atlas E/F spacecraft launch was conducted on 24 March 1995, using a rocket which had originally been built as an Atlas-E. The last Atlas E/F launch to use a rocket which had originally been built as an Atlas-F was conducted on 23 June 1981.<ref>{{cite web|title=Atlas F|url=https://spacelaunchnow.me/vehicle/launch_vehicle/244/|website=spacelaunchnow.me|access-date=March 29, 2023}}</ref>

Atlas E/F was used to launch the Block I series of [[GPS satellite]]s from 1978 to 1985. The last refurbished Atlas-F vehicle was launched from Vandenberg AFB in 1995 carrying a satellite for the Defense Meteorological Satellite Program.<ref>{{cite web|last=Krebs|first=Gunter D. |title=DMSP-5D2 F6, 7, 8, 9, 10, 11, 12, 13, 14|publisher=Gunter's Space Page|access-date=April 1, 2023 |url=https://space.skyrocket.de/doc_sdat/dmsp-5d2.htm}}</ref>

===Tabulated===
{| class="toccolours sortable" border="1" cellspacing="0" cellpadding="2"  style="margin:auto; text-align:center; border-collapse:collapse; margin-left:0; margin-right:auto;"
|- style="background:#a0b0ff;"
! Model name !! First launch !! Last launch !! Total launches !! Successes !! ICBM base !! Upper stage !! Notable payloads !! Remarks
|-
| Atlas-Vega<ref>{{cite web|url=http://www.astronautix.com/a/atlasvega.html|archive-url=https://web.archive.org/web/20160824113845/http://www.astronautix.com/a/atlasvega.html|url-status=dead|archive-date=August 24, 2016|title=Atlas Vega|publisher=Astronautix.com|access-date=28 October 2014}}</ref> || - || - || 0 || 0 || Atlas E || storable propellant stage || none || <small>Development was essentially identical to Atlas-Agena, and cancelled accordingly in 1959</small>
|-
| [[Atlas-Able]] || 1959 || 1960 || 3 || 0 || Atlas-D/Able(Delta-A)<ref>{{cite web|url=http://www.astronautix.com/stages/deltaa.htm|archive-url=https://web.archive.org/web/20020525121733/http://www.astronautix.com/stages/deltaa.htm|url-status=dead|archive-date=May 25, 2002|title=Delta A|publisher=Astronautix.com|access-date=28 October 2014}}</ref> || [[Altair (rocket stage)|Altair]] || [[Pioneer P-3]], [[Pioneer P-30]], [[Pioneer P-31]]|| [[File:Atlas-Able.jpg|center|frameless|200x200px]]<small>2 rockets failed during static firing, and 3 during attempts to launch [[Pioneer program|Pioneer]] spacecraft to the Moon</small>
|-
| Atlas LV-3A || 1960 || 1968 || 49 || 38 || Atlas D ||[[Agena (rocket)|Agena]] || [[Mariner 2]], [[Ranger program]], [[Missile Defense Alarm System]] ||  [[File:Atlas_Agena_launching_Lunar_Orbiter_4.jpg|center|frameless|200x200px]]<small>The baseline [[Atlas-Agena]] sub-family vehicle</small>
|-
| [[Atlas LV-3B]] || 1959 || 1963 || 9 || 9 || Atlas D || none || [[Mercury-Atlas 6|''Friendship 7'']], [[Mercury-Atlas 7|''Aurora 7'']], [[Mercury-Atlas 8|''Sigma 7'']], [[Mercury-Atlas 9|''Faith 7'']] || [[File:Mercury-Atlas_2_liftoff.jpg|center|frameless|200x200px]]<small>Human-rated Atlas LV-3A</small>
|-
| [[Atlas SLV-3]] || 1964 || 1968 || 51 || 46 || Atlas D|| [[Agena (rocket)|Agena]] || [[Corona (satellite)|Corona]], [[KH-7 Gambit]] || <small>same as LV-3A except reliability improvements</small>
|-
| [[Atlas SLV-3]]A || 1969 || 1978 || 10 || 9 || Atlas D|| [[Agena (rocket)|Agena]] || [[Canyon (satellite)|Canyon]] || <small>same as SLV-3 except stretched {{cvt|2.97|m|ft|order=flip}}</small>
|-
| [[Atlas SLV-3]]B<ref>{{cite web|url=http://space.skyrocket.de/doc_lau_det/atlas-slv3b_agena-d.htm|title=Atlas-SLV3B Agena-D|publisher=Space.skyrocket.de|access-date=28 October 2014}}</ref> || 1966 || 1966 || 1 || 1 || Atlas D|| [[Agena (rocket)|Agena]] D || [[Orbiting Astronomical Observatory|Orbiting Astronomical Observatory 1]]||
|-
| Atlas LV-3C || 1963 || 1967 || 11 || 8 || Atlas D|| [[Centaur (rocket stage)|Centaur]] C ||[[Surveyor 1]]|| [[File:Surveyor_1_launch.jpg|center|frameless|200x200px]]<small>The baseline [[Atlas-Centaur]] sub-family vehicle</small>
|-
| Atlas SLV-3C || 1967 || 1972 || 17 || 14 || Atlas D|| [[Centaur (rocket stage)|Centaur]] D || ? || <small>Same as LV-3C stretched {{cvt|1.3|m|ft|order=flip}}</small>
|-
| Atlas SLV-3D || 1973 || 1983 || 32 || 29 || Atlas D|| [[Centaur (rocket stage)|Centaur]] D1A ||[[Mariner 10]]|| [[File:Atlas-Centaur_with_Mariner_10_at_LC_36B.jpg|center|frameless|200x200px]]<small>Same as SLV-3C except Centaur uprated and Atlas electronics integrated with Centaur</small>
|-
| [[Atlas G]] || 1984 || 1987 || 6 || 4 || Atlas G|| [[Centaur (rocket stage)|Centaur]] D1A || ? || [[File:Atlas-G.jpg|center|frameless|200x200px]]<small>Same as SLV-3D but Atlas longer by {{cvt|2.06|m|ft|order=flip}}</small>
|-
| [[Atlas I]] || 1990 || 1997 || 11 || 8 || Atlas G derived || [[Centaur (rocket stage)|Centaur]] D1A derived || [[CRRES]]<ref>
{{cite web | url = http://www.astronautix.com/lvs/atlasi.htm | archive-url = https://web.archive.org/web/20020827232043/http://astronautix.com/lvs/atlasi.htm | url-status = dead | archive-date = August 27, 2002 | title = Atlas I | publisher = Encyclopedia Astronautica|access-date=28 October 2014}}</ref> || [[File:Atlas_I_launching_CRRES_satellite1.jpg|center|frameless|200x200px]]<small>Same as Atlas G except strengthened for {{cvt|4.27|m|ft|order=flip}} payload fairing and ring laser gyro added.</small>
|-
| [[Atlas II]] || 1991 || 1998 || 10 || 10 || Atlas G derived || [[Centaur (rocket stage)|Centaur]] D1A derived || [[Eutelsat]] || [[File:DF-SC-99-00074_cropped_and_rotated.jpeg|center|frameless|200x200px]]<small>Same as Atlas I except Atlas stretched {{cvt|2.74|m|ft|order=flip}}, engines uprated, added hydrazine roll control, fixed foam insulation, deleted verniers, and Centaur stretched {{cvt|0.9|m|ft|order=flip}}. Development done by [[General Dynamics]] (now part of [[Lockheed Martin]]).</small>
|-
| [[Atlas IIA]] || 1992 || 2002 || 23 || 23 || Atlas G derived || [[Centaur (rocket stage)|Centaur]] D1A derived || - || <small>Same as Atlas II except Centaur RL10 engines uprated to {{cvt|88|kN|lbf|order=flip}} of thrust and 6.5-second I<sub>sp</sub> increase from extendible RL10 nozzles</small>
|-
| [[Atlas IIAS]] || 1993 || 2004 || 30 || 30 || Atlas G derived{{citation needed|date=October 2013}} || [[Centaur (rocket stage)|Centaur]] D1A derived || - || <small>Same as Atlas IIA except four Castor IVA strap-on boosters added</small>
|-
| [[SM-65D Atlas|Atlas D-OV1]] || 1965 || 1967 || 7 || 6 || Atlas D|| none ||OV (Orbiting Vehicle) flights || [[File:Atlas_D_OV1_with_OV1-2_1965-10-05.gif|center|frameless|200x200px]]<small>ICBM refurbished for orbital launch</small>
|-
| [[Atlas E/F|Atlas E]] || 1980 || 1995 || 23 || 21 || Atlas E|| none || || [[File:Atlas-E-F_with_solid_fuel_upper_stage.jpg|center|frameless|200x200px]]<small>ICBM refurbished for orbital launch</small>
|-
| [[Atlas E/F|Atlas F]] || 1968 || 1981 || 23 || 22 || Atlas F|| none || ? || <small>ICBM refurbished for orbital launch</small>
|-
| [[Atlas H]] || 1983 || 1987 || 5 || 5 ||Modified Atlas G|| [[Centaur (rocket stage)|Centaur]] stage removed ||[[Naval Ocean Surveillance System|NOSS]] satellites ||[[File:Atlas-H.jpg|center|frameless|200x200px]]<small>Atlas G modified for West Coast Avionics. SLC 3E modified for Space Booster hold down system versus weapon system flyaway</small>
|-
|}

==RD-180 era==
=== Atlas III ===
The first stage of the [[Atlas III]] discontinued the use of three engines and 1.5 staging in favor of a single Russian-built [[NPO Energomash|Energomash]] [[RD-180]] engine, while retaining the stage's balloon tank construction. The Atlas III continued to use the Centaur upper stage, available with single or dual [[RL10]] engines.<ref>{{cite web |title=Space Launch Report: Atlas III Data Sheet |url=http://www.spacelaunchreport.com/atlas3.html |archive-url=https://web.archive.org/web/20220406013818/http://www.spacelaunchreport.com/atlas3.html |archive-date=6 Apr 2022 |date=1 Dec 2005 |url-status=usurped}}</ref>

===Atlas V===
{{Main|Atlas V}}
{{multiple image
| align             = right
| width1            = 110
| alt1              = 
| caption1          = 2005 Launch of [[Mars Reconnaissance Orbiter]]
| image2            = Atlas V(401) launches with LRO and LCROSS cropped.jpg
| width2            = 100
| alt2              = 
| caption2          = Launch of an Atlas V 401 carrying the LRO and LCROSS
| footer            = 
}}
The Atlas V, currently in service, was developed by [[Lockheed Martin]] as part of the US Air Force [[Evolved Expendable Launch Vehicle]] (EELV) program. The first was launched on August 21, 2002. In 2006, operation was transferred to [[United Launch Alliance]] (ULA), a joint venture between Lockheed Martin and [[Boeing]]. Lockheed Martin continued to market the Atlas V to commercial customers until September 2021, when it announced that the rocket will be retired after fulfilling the remaining 29 launch contracts.<ref>{{cite web|url=http://www.lockheedmartin.com/news/press_releases/2009/1111_ss_cls.html |title=Lockheed Martin Ready For Launch Of Intelsat 14 Spacecraft |date=November 11, 2009 |publisher=[[Lockheed Martin]] |access-date=28 October 2014 |url-status=dead |archive-url=https://web.archive.org/web/20111217062420/http://www.lockheedmartin.com/news/press_releases/2009/1111_ss_cls.html |archive-date=17 December 2011 }}</ref><ref name="Verge">{{cite news |last1=Roulette |first1=Joey |title=ULA stops selling its centerpiece Atlas V, setting path for the rocket's retirement |url=https://www.theverge.com/2021/8/26/22641048/ula-boeing-lockheed-end-sales-atlas-v-rocket-russia-rd180 |access-date=1 September 2021 |publisher=The Verge |date=26 August 2021}}</ref> Atlas V is built in [[Decatur, Alabama]], and maintains two launch sites: [[Cape Canaveral Air Force Station Space Launch Complex 41|Space Launch Complex 41]] at [[Cape Canaveral Space Force Station]] and [[Vandenberg AFB Space Launch Complex 3|Space Launch Complex 3-E]] at [[Vandenberg Space Force Base]].

The Atlas V's first stage is called the [[Common Core Booster]] (CCB), which continues to use the Energomash [[RD-180]] introduced in the Atlas III, but employs a rigid framework instead of balloon tanks. The rigid fuselage is heavier, but easier to handle and transport, eliminating the need for constant internal pressure. Up to five [[Aerojet Rocketdyne]] strap-on [[solid rocket booster]]s can be used to augment first stage thrust. The upper stage remains the [[Centaur (rocket stage)|Centaur]], powered by a single or dual Aerojet Rocketdyne [[RL10]] engines.<ref name=afsp200903>{{cite web|url=http://www.afspc.af.mil/library/factsheets/factsheet.asp?id=3643 |title=Evolved Expendable Launch Vehicle |date=March 2009 |publisher=Afspc.af.mil |access-date=28 October 2014 |url-status=dead |archive-url=https://web.archive.org/web/20140427031225/http://www.afspc.af.mil/library/factsheets/factsheet.asp?id=3643 |archive-date=27 April 2014 }}</ref>

{{clear}}

{| class="toccolours sortable" border="1" cellspacing="0" cellpadding="2"  style="margin:auto; text-align:center; border-collapse:collapse; margin-left:0; margin-right:auto;"
|- style="background:#a0b0ff;"
! Model name !! First launch !! Last launch !!Total launches !! Successes !! 1st-stage engines !! Upper-stage engines !! Notable payloads !! Remarks
|-
| [[Atlas IIIA]] || 2000 || 2004 || 2 || 2 || 1x[[RD-180]]|| 1x[[RL10]]A || [[Eutelsat]] W4 || [[File:Atlas_III_Centaur.jpg|center|frameless|200x200px]]<small>Major revision of Atlas IIA, with new [[RD-180]] first-stage engine, normal staging, first stage stretched 4.4 m and strengthened.  First single RL10 engine Centaur.</small>
|-
| [[Atlas IIIB]] || 2002 || 2005 || 4 || 4 || 1x[[RD-180]]|| 1x[[RL10]]A || || <small>Same as Atlas IIIA, except for Centaur stretched 1.7 m and an optional dual engine Centaur.</small>
|-
| [[Atlas V]] 400 || 2002 || 2022 || 59 || 58 || 1x[[RD-180]]|| 1x[[RL10]]A ||[[Lunar Reconnaissance Orbiter]], [[Lunar Crater Observation and Sensing Satellite|LCROSS]], [[Mars Reconnaissance Orbiter]] || [[File:Atlas_V(401)_launches_with_LRO_and_LCROSS_cropped.jpg|center|frameless|200x200px]]<small>Major revision of Atlas III, with new first-stage structure ([[Common Core Booster|CCB]]) and with optional solid strap-on boosters.</small>
|-
| [[Atlas V]] 500 || 2003 || - || 18 || 18 || 1x[[RD-180]]|| 1x[[RL10]]A || [[New Horizons]], [[USA-212|X-37B]], [[Mars Science Laboratory]]|| [[File:Atlas_V_501_launch_with_NROL-41.jpg|center|frameless|200x200px]]<small>Revision of Atlas V 400, with optional solid strap-on boosters, and Centaur stage encapsulated inside 5.4 m payload fairing.</small>
|-
| [[Atlas V]] N22 || 2019 || - || 3 || 3 || 1x[[RD-180]]|| 2x[[RL10]]A || [[Boeing CST-100 Starliner|Starliner]] [[Boeing Orbital Flight Test|Boeing OFT]]|| [[File:Boeing_OFT-2_Liftoff_(KSC-20220519-PH-KNO01_0022).jpg|center|frameless|200x200px]]<small>Revision of Atlas V with optional two solid strap-on boosters, and no Centaur 5.4 m payload fairing, but the [[Boeing Starliner|Starliner]] spacecraft.</small>
|-
|}

===RD-180 phaseout===
In 2014, [[US Congress]] passed legislation restricting the purchase and use of the [[Russia|Russian-supplied]] [[RD-180]] engine used on the first stage booster of the Atlas V.<ref>{{cite web|url=http://spacenews.com/ula-could-buy-as-many-as-30-more-russian-made-rd-180-engines/|publisher=SpaceNews|title=ULA Could Buy as Many as 30 More Russian-made RD-180 Engines|date=2015-01-20|access-date=2015-04-13}}</ref> Formal study contracts were issued in June 2014 to a number of US rocket engine suppliers.<ref name=sn20140917>
{{cite news |last1=Ferster|first1=Warren |title=ULA To Invest in Blue Origin Engine as RD-180 Replacement |url=http://www.spacenews.com/article/launch-report/41901ula-to-invest-in-blue-origin-engine-as-rd-180-replacement |archive-url=https://archive.today/20140918114236/http://www.spacenews.com/article/launch-report/41901ula-to-invest-in-blue-origin-engine-as-rd-180-replacement |url-status=dead |archive-date=September 18, 2014 |access-date=2014-09-19 |work=Space News |date=2014-09-17 }}</ref>

In September 2014, ULA announced that it had entered into a partnership with [[Blue Origin]] to develop the [[BE-4]] [[LOX]]/[[Liquid methane|methane]] engine to replace the RD-180 on the new [[Vulcan (rocket)|Vulcan rocket]]. The new stage and engine first flew in 2024.

In December 2014, legislation to prevent the award of further military launch contracts to vehicles that use Russian-made engines was approved by the [[United States Congress|US Congress]]. The bill allows ULA to continue to use the 29 RD-180 engines already on order at the time.<ref>{{cite news |last1=Petersen|first1=Melody |title=Congress OKs bill banning purchases of Russian-made rocket engines |url=http://www.latimes.com/business/la-fi-russian-rocket-ban-20141213-story.html |access-date=2014-12-14 |newspaper=LA Times |date=2014-12-12 }}</ref> In September 2021, ULA announced that Atlas V will be retired after they fulfill their remaining launch contracts, and that all remaining RD-180s for the remaining rockets have been delivered.<ref name="Verge"/>

===Formerly proposed launch vehicles===
Prior to the April 2015 announcement of the [[Vulcan launch vehicle]], during the first decade since ULA was formed from Lockheed Martin and Boeing, there were a number of proposals and concept studies of future launch vehicles.  None were subsequently funded for full-up development.  Two of those concepts were the ''Atlas V Heavy'' and the ''Atlas Phase 2''.

====Atlas V Heavy====
{{main|Atlas V#Atlas V Heavy}}
The ''Atlas V Heavy'' was a ULA concept proposal that would have used three [[Common Core Booster]] (CCB) stages strapped together to provide the capability necessary to lift a {{convert|25|t|lb|order=flip|adj=on}} payload to [[low Earth orbit]].{{Citation needed|date=August 2011}}  ULA stated that approximately 95% of the hardware required for the Atlas HLV had already been flown on the Atlas V single-core vehicles.{{Citation needed|date=August 2011}}

A 2006 report, prepared by RAND Corporation for the [[Office of the Secretary of Defense]], stated that Lockheed Martin had decided not to develop an Atlas V heavy-lift vehicle (HLV).<ref>{{Cite book| url=https://www.rand.org/pubs/monographs/2006/RAND_MG503.pdf| title=National Security Space Launch Report| publisher=RAND Corporation| year=2006| page=29| access-date=28 October 2014 }}</ref> The report recommended for the Air Force and the National Reconnaissance Office to "determine the necessity of an EELV heavy-lift variant, including development of an Atlas V Heavy", and to "resolve the RD-180 issue, including coproduction, [[stockpiling|stockpile]], or U.S. development of an RD-180 replacement."<ref>{{cite book| url=https://www.rand.org/pubs/monographs/2006/RAND_MG503.pdf| title=National Security Space Launch Report| publisher=RAND Corporation| year=2006| page=xxi|access-date=28 October 2014 }}</ref>{{update after|2015|4|13}}

The lifting capability of the Atlas V HLV was to be roughly equivalent to the [[Delta IV Heavy]]. The latter utilizes [[RS-68]] engines developed and produced domestically by Pratt & Whitney [[Rocketdyne]].<ref>[http://www.globalsecurity.org/space/systems/atlas-v.htm Atlas V EELV – Lockheed-Martin Retrieved on 2008-02-08]. Globalsecurity.org. Retrieved on 2011-11-19.</ref>

====Atlas V Phase 2====
{{main|Atlas V#Atlas V Phase 2}}
After December 2006, with the merger of Boeing and Lockheed-Martin space operations into [[United Launch Alliance]], the Atlas V program gained access to the tooling and processes for {{cvt|5.4|m|ft|order=flip}} diameter stages used on [[Delta IV]].  An 18&nbsp;ft diameter stage could have conceivably accepted dual RD-180 engines. The resulting conceptual heavy-lift vehicle was called ''"Atlas Phase 2"'' or "PH2" in the 2009 [[Review of United States Human Space Flight Plans Committee|Augustine Report]].  An Atlas V PH2-Heavy (three 5 m stages in parallel; six RD-180s) along with [[Shuttle-Derived Launch Vehicle|Shuttle-derived]], [[Ares V]] and Ares V Lite, were considered as a possible heavy lifter concept for use in future space missions in the Augustine Report.<ref name="hsf200910" />  The Atlas PH2 HLV concept vehicle would have notionally been able to launch a payload mass of approximately {{convert|70|t|lb|order=flip}} into an orbit of 28.5&nbsp;degree [[Orbital inclination#Natural and artificial satellites|inclination]].<ref name=hsf200910>{{cite web|url=http://www.nasa.gov/pdf/396093main_HSF_Cmte_FinalReport.pdf|title=HSF Final Report: Seeking a Human Spaceflight Program Worthy of a Great Nation|date=October 2009|quote=''Review of U.S. Human Spaceflight Plans Committee''|page=64|access-date=2011-02-07|archive-date=2019-02-16|archive-url=https://web.archive.org/web/20190216063908/https://www.nasa.gov/pdf/396093main_HSF_Cmte_FinalReport.pdf|url-status=dead}}</ref>
The concept did not proceed onto full development, and was never built.

==See also==
* [[Comparison of orbital launcher families]]
* [[Delta (rocket family)]]
* [[List of Atlas launches]]

==References==
{{Reflist|30em}}

==Further reading==
* Gainor, Christopher, "The Atlas and the Air Force: Reassessing the Beginnings of America's First Intercontinental Ballistic Missile," ''Technology and Culture'' 54 (April 2013), 346–70.

==External links==
* [https://web.archive.org/web/20080229161820/http://www.astronautix.com/lvfam/atlas.htm Atlas at Encyclopedia Astronautica]

{{Atlas rockets}}
{{USAF space vehicles}}
{{Rocket families}}
{{Expendable launch systems}}
{{Project Mercury}}

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[[Category:Atlas (rocket family)| ]]
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[[Category:United Launch Alliance space launch vehicles]]
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