Atlas (rocket family)
Atlas is a family of United States space launch vehicles. The original Atlas missile was designed in the late 1950s and produced by the Convair Division of General Dynamics, to be used as an intercontinental ballistic missile (ICBM). It was a liquid-fuel rocket burning liquid oxygen and RP-1 in three engines configured in an unusual "stage-and-a-half" or "Parallel Staging" design: its two outboard booster engines were jettisoned during ascent, while its center sustainer engine, fuel tanks and other structural elements were retained into orbit.
The missiles saw only brief ICBM service, and the last squadron was taken off operational alert in 1965. From 1962 to 1963, Atlas boosters launched the first four American astronauts to orbit the Earth. Various Atlas II models were launched 63 times between 1991 and 2004. There were only six launches of the Atlas III, all between 2000 and 2005. The Atlas V is still in service, with launches planned until 2020.
Atlas family evolution 
Intercontinental ballistic missile 
The first successful test launch of an SM-65 Atlas missile was on December 17, 1957. Approximately 350 Atlas missiles were built. 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 satellites.
Early Atlas rockets were also built specifically for non-military uses. On December 18, 1958, an Atlas was used to launch the Signal Communication by Orbiting Relay Equipment (SCORE) satellite, which was, "The first prototype of a communications satellite, and the first test of any satellite for direct practical applications." The satellite broadcast President Eisenhower’s pre-recorded Christmas message around the world.
The Atlas boosters would collapse under their own weight if not kept pressurized with nitrogen gas in the tank, even when not fueled. The Atlas booster was unusual in its use of balloon tanks for holding its fuel. 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.
Atlas boosters were also used for the last four manned Project Mercury missions, the first United States manned space program. On February 20, 1962 it launched 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 manned Mercury orbital missions from 1962 to 1963.
Beginning in 1960, the Agena upper-stage, powered by hypergolic propellant, was used extensively on Atlas launch vehicles. The United States Air Force, NRO and CIA used them to launch SIGINT satellites. 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 vehicles used for the later space rendezvous practice missions of Gemini was launched on an Atlas rocket.
Beginning in 1963, the liquid hydrogen-fueled 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.
Launch vehicles based on original Atlas ICBM 
|Model name||First launch||Last launch||Total launches||Successes||ICBM base||Upper stage||Notable payloads||Remarks|
|Atlas-Vega||-||-||0||0||Atlas E||storable propellant stage||none||Development was essentially identical to Atlas-Agena, and cancelled accordingly in 1959|
|Atlas-Able||1959||1960||3||0||Atlas-D/Able(Delta-A)||Altair||none||2 rockets failed during static firing, and 3 during attempts to launch Pioneer spacecrafts to the Moon|
|Atlas LV-3A||1960||1968||49||38||Atlas D||Agena||Gemini, Mariner 2, Ranger program, Missile Defense Alarm System||The baseline Atlas-Agena sub-family vehicle|
|Atlas LV-3B||1959||1962?||9||9||Atlas D||Agena||Mercury-Atlas 1||Man-rated Atlas LV-3A|
|Atlas SLV-3||1964||1968||51||46||Atlas D||Agena||Corona, KH-7 Gambit||same as LV-3A except reliability improvements|
|Atlas SLV-3A||1969||1978||10||9||Atlas D||Agena||Canyon||same as SLV-3 except stretched 2.97 m|
|Atlas LV-3C||1963||1967||11||8||Atlas D||Centaur C||?||The baseline Atlas-Centaur sub-family vehicle|
|Atlas SLV-3C||1967||1972||17||14||Atlas D||Centaur D||?||Same as LV-3C stretched 1.3 m|
|Atlas SLV-3D||1973||1983||32||29||Atlas D||Centaur D1A||?||Same as SLV-3C except Centaur uprated and Atlas electronics integrated with Centaur|
|Atlas G||1984||1987||6||4||Atlas G||Centaur D1A||?||Same as SLV-3D but Atlas longer by 2.06 m|
|Atlas I||1990||1997||11||8||Atlas G derived||Centaur D1A derived||CRRES||Same as Atlas G except strengthened for 4.27 m payload fairing and ring laser gyro added.|
|Atlas II||1991||1998||10||10||Atlas G derived||Centaur D1A derived||Eutelsat||Same as Atlas I except Atlas stretched 2.74 m, engines uprated, added hydrazine roll control, fixed foam insulation, deleted verniers, and Centaur stretched 0.9 m. Development done by General Dynamics (now Lockheed Martin).|
|Atlas IIA||1992||2002||23||23||Atlas G derived||Centaur D1A derived||-||Same as Atlas II except Centaur RL10 engines uprated to 88 kN of thrust and 6.5 Isp increase from extendible RL10 nozzles|
|Atlas IIAS||1993||2004||30||30||Atlas G derived||Centaur D1A derived||-||Same as Atlas IIA except 4 Castor IVA strap-on boosters added|
|Atlas D Space||1965||1967||7||6||Atlas D||none||?||ICBM refurbished for orbital launch|
|Atlas E Space||1980||1995||23||21||Atlas E||none||?||ICBM refurbished for orbital launch|
|Atlas F Space||1968||1981||23||22||Atlas F||none||?||ICBM refurbished for orbital launch|
|Atlas H Space||1983||1987||5||5||Atlas D||Centaur stage removed||?||ICBM refurbished for orbital launch, Atlas D upgraded with Atlas E/F avionics|
Current Atlas family 
The Atlas III was a major revised version from Atlas II, which both dropped balloon tank design, together with the 1.5 stage in previous Altas family. It is the first Atlas rocket that adopted Russian-designed RD-180 engine at the first stage.
The newest version of Atlas, the Atlas V, is an Atlas in name alone, as it contains little Atlas technology. It no longer uses balloon tanks nor 1.5 staging, but incorporates a rigid framework for its first stage booster, much like the Titan family of vehicles. The rigid fuselage is heavier, but easier to handle and transport, eliminating the need for constant internal pressure.
Ironically, given Atlas' origin as a military ICBM weapon against the Soviet Union/Russia, the Atlas III and Atlas V use Russian-designed/built NPO Energomash RD-180 engines. These engines are now prepared for production under license by Pratt & Whitney in the United States. The Atlas V is built in Denver, Colorado by United Launch Alliance, a joint venture of Lockheed Martin and Boeing. Future[when?] production will be shifted to Decatur, Alabama.
|Model name||First launch||Last launch||Total launches||Successes||1st stage engines||Upper stage engines||Notable payloads||Remarks|
|Atlas IIIA||2000||2000||1||1||1xRD-180||1xRL-10A||Eutelsat W4||major revision of Atlas IIA, with new RD-180 first-stage engine, normal staging, first stage stretched 4.4 m and strengthened.|
|Atlas IIIB||2002||2005||4||4||1xRD-180||2xRL-10A||Same as Atlas IIIA, except for dual-engine Centaur stage and Centaur stretched 1.7 m.|
|Atlas V 400||2002||-||25||24||1xRD-180||1xRL-10A||major revision of Atlas IIIA, with new first stage structure (CCB).|
|Atlas V 500||2002||-||12||12||1xRD-180||1xRL-10A||major revision of Atlas V 400, with optional solid strap-on boosters, and Centaur stage encapsulated inside 5.4 m payload fairing.|
Atlas future developments 
Atlas V HLV 
The Atlas V HLV (Heavy Lift Vehicle) would use three Common Core Booster (CCB) stages strapped together to provide the capability necessary to lift 25 tonne payload to low Earth orbit. Approximately 95% of the hardware required for the Atlas HLV has already been flown on the Atlas V single core vehicles.
A report, prepared by RAND Corporation for the Office of the Secretary of Defense in 2006, stated that Lockheed Martin had decided not to develop an Atlas V heavy-lift vehicle (HLV). 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, Stockpile, or U.S. development of an RD-180 replacement."
The lifting capability of the Atlas V HLV is roughly equivalent to the Delta IV Heavy. The latter utilizes RS-68 engines developed and produced domestically by Pratt & Whitney Rocketdyne.
Atlas Phase 2 
With the merger[when?] of Boeing and Lockheed-Martin space operations into United Launch Alliance, the Atlas V program gained access to the tooling and processes for 5-meter-diameter stages, used on Delta IV. At 5 meters, a stage can accept dual RD-180 engines.[clarification needed]
The conceptual heavy-lift vehicle was called "Atlas Phase 2" or "PH2" in the 2009 Augustine Report report. An Atlas V PH2-Heavy (three 5 m stages in parallel; six RD-180s) along with 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. The Atlas PH2 HLV concept vehicle would have notionally been able to launch a payload mass of approximately 70 metric tons into an orbit of 28.5 degree-inclination.
See also 
- Deny Rocket Lag. Atlas Firing Keynotes U.S. Missile Build-Up, 1959/01/29 (1959). Universal Newsreel. 1959. Retrieved February 22, 2012.
- Rusty Barton. "Atlas ICBM Chronology". Archived from the original on 2006-02-04.
- "Atlas E". Encyclopedia Astronautica.
- "Project SCORE". Patterson Army Health Clinic.
- "SCORE (Signal Communication by Orbiting Relay Equipment)". GlobalSecurity.org.
- Mark Wade. "Atlas/Agena D SLV-3A".
- "Atlas I". Encyclopedia Astronautica.
- National Security Space Launch Report (PDF). RAND Corporation. 2006. p. 29.
- National Security Space Launch Report (PDF). RAND Corporation. 2006. p. xxi.
- Atlas V EELV – Lockheed-Martin Retrieved on 2008-02-08. Globalsecurity.org. Retrieved on 2011-11-19.
- HSF Final Report: Seeking a Human Spaceflight Program Worthy of a Great Nation, October 2009, Review of U.S. Human Spaceflight Plans Committee, graphic on p. 64, retrieved 2011-02-07.