Atlas is a family of US missiles and space launch vehicles derived from the SM-65 Atlas. The Atlas intercontinental ballistic missile (ICBM) program was initiated in the late 1950s by General Dynamics through its Convair division. 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 mighty Titan from Greek mythology reflected the missile's place as the biggest and most powerful at the time. It also reflected the former parent company of Convair before its General Dynamics acquisition, the Atlas Corporation.

The missiles saw only brief ICBM service, and the last squadron was taken off operational alert in 1965. However, from 1962 to 1963 Atlas boosters launched the first four US astronauts to orbit the Earth (in contrast to the preceding two 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 space probes used to explore Mercury, Venus, and Mars (1962–1973); and to launch ten of the Mercury program missions (1962–1963).

SM-65 Atlas missile

The first successful test launch of an SM-65 Atlas missile was on 17 December 1957. Approximately 350 Atlas missiles were built.

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.

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 satellites.

SM-65B Atlas SCORE launch

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, which was "the first prototype of a communications satellite, and the first test of any satellite for direct practical applications." The communications payload was placed into low Earth orbit on Atlas serial number 10B without an upper stage. Atlas 10B/SCORE, at 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

Atlas D missile-derived SLV-3s were used for orbital launches with the RM-81 Agena and Centaur upper stages. The modified Atlas LV-3B was used for the orbital element of Project Mercury, launching four crewed Mercury spacecraft into low Earth orbit. 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.

Two suborbital stage and a half vehicles were used during Project FIRE as sounding rockets.

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.

Mercury program

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 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 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 Vehicles used during the Gemini program.

Atlas-Agena

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.

Atlas-Centaur

The Atlas-Centaur was an expendable launch system derived from the SM-65D Atlas missile. Launches were conducted from two pads of the 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 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

Following retirement as an ICBM, the Atlas-E, along with the Atlas-F, were refurbished for orbital launches.

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.

Atlas E/F was used to launch the Block I series of GPS satellites 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.

Tabulated 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 Pioneer P-3, Pioneer P-30, Pioneer P-31 2 rockets failed during static firing, and 3 during attempts to launch Pioneer spacecraft to the Moon Atlas LV-3A 1960 1968 49 38 Atlas D Agena Mariner 2, Ranger program, Missile Defense Alarm System The baseline Atlas-Agena sub-family vehicle Atlas LV-3B 1959 1963 9 9 Atlas D none Friendship 7, Aurora 7, Sigma 7, Faith 7 Human-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 Atlas SLV-3B 1966 1966 1 1 Atlas D Agena D Orbiting Astronomical Observatory 1 Atlas LV-3C 1963 1967 11 8 Atlas D Centaur C Surveyor 1 The baseline Atlas-Centaur sub-family vehicle Atlas SLV-3C 1967 1972 17 14 Atlas D Centaur D ? Same as LV-3C stretched Atlas SLV-3D 1973 1983 32 29 Atlas D Centaur D1A Mariner 10 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 Atlas I 1990 1997 11 8 Atlas G derived Centaur D1A derived CRRES Same as Atlas G except strengthened for 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 , engines uprated, added hydrazine roll control, fixed foam insulation, deleted verniers, and Centaur stretched . Development done by General Dynamics (now part of Lockheed Martin). Atlas IIA 1992 2002 23 23 Atlas G derived Centaur D1A derived - Same as Atlas II except Centaur RL10 engines uprated to of thrust and 6.5-second Isp increase from extendible RL10 nozzles Atlas IIAS 1993 2004 30 30 Atlas G derived Centaur D1A derived - Same as Atlas IIA except four Castor IVA strap-on boosters added Atlas D-OV1 1965 1967 7 6 Atlas D none OV (Orbiting Vehicle) flights ICBM refurbished for orbital launch Atlas E 1980 1995 23 21 Atlas E none ICBM refurbished for orbital launch Atlas F 1968 1981 23 22 Atlas F none ? ICBM refurbished for orbital launch Atlas H 1983 1987 5 5 Modified Atlas G Centaur stage removed NOSS satellites Atlas G modified for West Coast Avionics. SLC 3E modified for Space Booster hold down system versus weapon system flyaway

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 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.

Atlas V

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. Atlas V is built in Decatur, Alabama, and maintains two launch sites: Space Launch Complex 41 at Cape Canaveral Space Force Station and 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 boosters can be used to augment first stage thrust. The upper stage remains the Centaur, powered by a single or dual Aerojet Rocketdyne RL10 engines.