- Main article: Atlas (rocket family)
Launch of an SM-65A Atlas from LC-12,
Cape Canaveral Air Force Station, 20 February 1958
|Type||Intercontinental Ballistic Missile (ICBM)|
|Place of origin||United States|
|Used by||United States Air Force|
|Number built||350 (all versions)
Peak deployment level of 129
(30 D, 27 E, 72 F).
|Variants||Atlas A, B/C, D, E/F (ICBMs)
SLV-3/3A/3C (NASA use)
|Weight||260,000 lb (117,900 kg)
maximum at launch
|Length||75 ft 10 in (23.11 m)
85 ft 6 in (26.06 m) in ICBM configuration)
|Diameter||10 ft 0 in (3.05 m), (not
including strap-on boosters)
|Crew||None (One on Mercury-Atlas)|
The SM-65 Atlas was the first intercontinental ballistic missile (ICBM) developed and deployed by the United States. It was built for the U.S. Air Force by Convair Division of General Dynamics at the Kearny Mesa assembly plant north of San Diego, California. Atlas became operational as an ICBM in October 1959 and was used as a first stage for satellite launch vehicles for half a century. The Atlas missile's warhead was over 100 times more powerful than the bomb dropped over Nagasaki in 1945.
An initial development contract was given to Consolidated Vultee Aircraft (Convair) on 16 January 1951 for what was then called MX-1593, but at a relatively low priority. The 1953 testing of the first dry fuel H-bomb in the Soviet Union led to the project being dramatically accelerated. The initial design completed by Convair in 1953 was larger than the missile that eventually entered service. Estimated warhead weight was lowered from 8,000 lb (3,630 kg) to 3,000 lb (1,360 kg) based on highly favorable U.S. nuclear warhead tests in early 1954, and on 14 May 1954 the Atlas program was formally given the highest national priority. A major development and test contract was awarded to Convair on 14 January 1955 for a 10-foot (3 m) diameter missile to weigh about 250,000 lb (113,400 kg). Atlas development was tightly controlled by the Air Force's Western Development Division, WDD, later part of the Air Force Ballistic Missile Division. Contracts for warhead, guidance and propulsion were handled separately by WDD. The first successful flight of a highly instrumented Atlas missile to full range occurred 28 November 1958. Atlas ICBMs were deployed operationally from 31 October 1959 to 12 April 1965.
On 18 December 1958, the launch of Atlas 10B sent the missile into orbit around the Earth (without use of an upper stage) carrying the "SCORE" (Signal Communications by Orbiting Relay Equipment) communications payload. Atlas 10B/SCORE, at 8,750 lb (3,970 kg) was the heaviest man-made object then in orbit, the first voice relay satellite, and the first man-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. Many retired Atlas ICBMs would be used as launch vehicles, most with an added spin-stabilized solid rocket motor upper stage for polar orbit military payloads. Even before its military use ended in 1965, Atlas had placed four Project Mercury astronauts in orbit and was becoming the foundation for a family of successful space launch vehicles, most notably Atlas Agena and Atlas Centaur.
Mergers led to the acquisition of the Atlas Centaur line by Lockheed Martin which in turn became part of the United Launch Alliance. Today Lockheed Martin and ULA support a new Atlas rocket family based on the larger "Atlas V" which still uses the unique and highly efficient Centaur upper stage. Atlas V stage one is powered by a Russian RD-180 oxygen/kerosene engine and uses conventional aluminum isogrid tankage rather than the thin-wall, pressure-stabilized stainless steel tanks of the original Convair Atlas. Payload weights have increased along with launch vehicle weights over the years so the current Atlas V family serves many of the same type commercial, DoD, and planetary missions as earlier Atlas Centaurs.
Shortly before his death, John von Neumann headed the top secret von Neumann ICBM committee. Its purpose was to decide on the feasibility of building an ICBM large enough to carry a thermonuclear weapon. Von Neumann had long argued that while the technical obstacles were indeed formidable, they could be overcome in time. Events were proving him right. The weapons had become smaller, and Diode-transistor logic enabled the construction of compact guidance computers. (Atlas A, B, C, and D had no onboard computers, but Atlas E (1960) and F (1961) did.) The committee approved a "radical reorganization" and speeding up of the Atlas program. Atlas was informally classified as a "stage-and-a-half" rocket; both engines were started at launch time, and there was only a single set of propellant tanks. One engine was jettisoned about 135 seconds into the flight. (A "stage" of a liquid propellant rocket is normally thought of as tanks and engine(s) together. The jettisoned engine therefore constitutes a "half stage".) The booster engine consisted of two large thrust chambers fed by a single common set of turbopumps. The sustainer engine consisted of a single large thrust chamber and two small verniers, once again fed by a single common set of turbopumps. The verniers provided roll control and final velocity trim. The total sea level thrust of all five thrust chambers was 360,000 lb for Atlas D. Later model Atlas E and F variants were built with two separate booster engines, each with a single large thrust chamber and its own independent set of turbopumps. Total sea level thrust for these three-engine Atlas Es and Fs was 389,000 lb (176,400 kg).
The first Atlas flown was the Atlas A in 1957–1958. It was a test model designed to verify the structure and propulsion system, and had no sustainer engine or separable stages. This was followed by the Atlas B and C in 1958–1959. The B had full engines and booster engine staging capability. An Atlas B was used to orbit the SCORE satellite in December 1958, which was the Atlas' first space launch. The C was a slightly more developed model using even thinner skin in the propellant tanks. Finally, the Atlas D, the first operational model and the basis for all Atlas space launchers, debuted in 1959. Atlas D weighed 255,950 lb (116,100 kg) (without payload) and had an empty weight of only 11,894 lb (5,395 kg), the other 95.35% was propellant. Dropping the 6,720 lb (3,048 kg) booster engine and fairing reduced the dry weight to 5,174 lb (2,347 kg), a mere 2.02% of the initial gross weight of the vehicle (still excluding payload). This very low dry weight allowed Atlas D to send its thermonuclear warhead to ranges as great as 9,000 miles (14,500 km) or orbit payloads without an upper stage. The final variants of the Atlas ICBM were the E and F, introduced in 1960–1961. E and F had fully self-contained inertial navigation systems (INS) and were identical to each other except for interfaces associated with their different basing modes (underground silo for F).
By 1965, with the second-generation Titan II having reached operational status, the Atlas was obsolete as a missile system, and was gradually phased out in the mid-1960s. Many of the retired Atlas D, E and F missiles were used for space launches into the 1990s.
Atlas, named for the Atlas of Greek mythology and the contractor's parent Atlas Corporation, got its start in 1946 with the award of an Army Air Forces research contract to Consolidated Vultee Aircraft (later Convair) for the study of a 1,500-to-5,000-mile (2,400 to 8,000 km) range missile that might, at some future date carry a nuclear armed warhead. At the time (the late 1940s), no missile conceived could carry even the smallest nuclear warheads then thought possible. The smallest atomic warheads were all larger than the maximum theoretical payloads of the planned long range missiles. The Convair team was led by Karel Bossart. This was the MX-774 or Hiroc project. It was for this reason that the contract was canceled in 1947 but the Army Air Forces allowed Convair to launch the three almost-completed research vehicles using the remaining contract funds. The three flights were only partially successful. However they did show that balloon tanks, and gimbaled rocket engines were valid concepts. In the mid-1950s after practical thermonuclear weapons had been demonstrated and an independent design breakthrough drastically reduced the weight of such weapons, along with the CIA learning that the Soviet ICBM program was making progress, Atlas became a crash program of the highest national importance.
The missile was originally given the military designation XB-65, thus making it a bomber; from 1955 it was redesignated SM-65 ('Strategic Missile 65') and, from 1962, it became CGM-16. This letter "C" stood for "coffin" or "Container", the rocket being stored in a semi-hardened container; it was prepared for launch by being raised and fueled in the open. The Atlas-F (HGM-16) was stored vertically underground, but launched after being lifted to the surface.
The Atlas A-D used radio guidance: the missile sent information from its inertial system to a ground station by radio, and received course correction information in return. The Atlas E and F had completely autonomous inertial guidance systems.
Atlas was unusual in its use of balloon tanks for fuel, made of very thin stainless steel (with the uncoated steel necessitating the development by Convair of the anti-corrosive spray WD-40) with minimal or no rigid support structures. Pressure in the tanks provides the structural rigidity required for flight. An Atlas rocket would collapse under its own weight if not kept pressurized, and had to have 5 psi (34 kPa) nitrogen in the tank even when not fuelled. The only other known use of balloon tanks at the time of writing is the Centaur high-energy upper stage, although some rockets (such as the Falcon series) use partially pressure-supported tanks. The rocket had two small thrust chambers on the sides of the tank called vernier rockets. These provided fine adjustment of velocity and steering after the sustainer engine shut down.
Atlas also had a unique and somewhat odd staging system. Most rockets stage by dropping both engines and fuel tanks simultaneously. However, when the Atlas missile was being developed, there were considerable doubts as to whether or not a rocket motor could be ignited in space. Therefore, the decision was made to ignite all of the Atlas' engines at launch; later the booster engine(s) would be discarded, while the sustainer continued to burn. Rockets using this technique are sometimes called stage-and-a-half boosters. This technique is made possible by the extremely light weight of the balloon tanks. The tanks make up such a small percentage of the total booster weight that the weight penalty of lifting them to orbit is less than the technical and weight penalty required to throw half of them away mid-flight. Depending on how you look at it, this makes Atlas a single-stage-to-orbit booster (though most call it a 1.5 stage to orbit).
Sergey Korolyov made a similar choice for the same reason in the design of the R-7, the first Soviet ICBM and the launcher of Sputnik and Vostok. The R-7 had a central sustainer section, with four boosters attached to its sides. All engines were started before launch, eliminating the then unexplored task of igniting a large liquid fuel engine at high altitudes. Like the Atlas, the R-7 used cryogenic oxidizer and could not be kept in the state of flight readiness indefinitely. Unlike the Atlas, the R-7 had large side boosters, which required use of an expensive launch pad and prevented launching the rocket from a silo.
Convair XSM-16A/X-11/SM-65A Atlas 
The Convair XSM-16A (later X-11) was the first testbed for what became the Atlas missile. Later the Convair X-12 became a second, more advanced testbed. A total of 12 X-11's were built and tested. The first three were involved in static tests only. X-11 Number 4 and 6, were destroyed in launch accidents. All others performed successful test flights. The test series began on June 11, 1957 and ended on June 3, 1958.
It was developed into the SM-65A Atlas, or Atlas A, which was the first full-scale prototype of the Atlas missile, which first flew on 11 June 1957. Unlike later versions of the Atlas missile, the Atlas A did not feature the stage and a half design. Instead, the booster engines were fixed in place, and the sustainer engine was omitted.
The Atlas A conducted eight test flights, of which four were successful. All test flights were conducted from Cape Canaveral Air Force Station, at either Launch Complex 12 or Launch Complex 14. Atlas A flights were powered by a single engine consisting of two large thrust chambers fed by a single set of turbopumps.
Convair X-12/SM-65B Atlas 
The Convair X-12 was the second, more advanced testbed for the Atlas rocket program. It was designed with 2 engines, the booster engine used on the predecessor X-11 plus a sustainer engine. This combination of booster plus sustainer engines was designated the MA-1 engine system. MA-1 was used in Atlas B and Atlas C. MA-1 was the direct predecessor of the MA-2 engine system of Atlas D which in turn was the direct predecessor of the MA-5 engine system used in Atlas Agena and Atlas Centaur launch vehicles. The first flight of X-12 (Atlas B) was in July 1958. The X-12 pioneered the use of these 1.5 stage rocket engines that became a hallmark of the Atlas rocket program. It was also the first rocket to achieve a flight distance that could be considered intercontinental when it flew 6,325 miles (10,180 km).
Atlas B was first flown on 19 July 1958, and was the first version of the Atlas rocket to use the stage and a half design. Ten flights were made. Nine of these were sub-orbital test flights of the Atlas as an Intercontinental Ballistic Missile, with five successful missions and four failures. The seventh flight, launched on 18 December 1958, was used to place the SCORE satellite into low Earth orbit, the first orbital launch conducted by an Atlas rocket.
SM-65C Atlas 
The SM-65C Atlas, or Atlas C was a prototype of the Atlas missile. First flown on 24 December 1958, the Atlas C was the final development version of the Atlas rocket, prior to the operational Atlas D. It was originally planned to be used as the first stage of the Atlas-Able rocket, but following an explosion during a static test on 24 September 1959, this was abandoned in favor of the Atlas D.
SM-65D Atlas 
The SM-65D Atlas, or Atlas D, was the first operational version of the Atlas missile. It first flew on 14 April 1959. Atlas D missiles were also used for orbital launches, both with upper stages, such as the RM-81 Agena, and on their own as a stage and a half vehicle. The Atlas D was used for the orbital element of Project Mercury, launching four manned Mercury spacecraft into low Earth orbit. The modified version of the Atlas D used for Project Mercury was designated Atlas LV-3B.
Most Atlas D launches were sub-orbital missile tests, however several were used for other missions, including orbital launches of manned Mercury, and unmanned OV1 spacecraft. Two were also used as sounding rockets, as part of Project FIRE. A number were also used with upper stages to launch satellites.
SM-65E Atlas 
The SM-65E Atlas, or Atlas-E, was the first 3-engine operational variant of the Atlas missile, the third engine resulting from splitting the two booster thrust chambers into separate engines with independent sets of turbopumps. It first flew on 11 October 1960, and was deployed as an operational ICBM from September 1961 until March 1965. Following retirement as an ICBM, the Atlas-E, along with the Atlas-F, was refurbished for orbital launches as the Atlas E/F. The last Atlas E/F launch was conducted on 24 March 1995, using a rocket which had originally been built as an Atlas-E.
SM-65F Atlas 
The SM-65F Atlas, or Atlas-F, was the final operational variant of the Atlas missile. It first flew on 8 August 1961, and was deployed as an operational ICBM between September 1962 and April 1965. Following retirement as an ICBM, the Atlas-F, along with the Atlas-E, was refurbished for orbital launches as the Atlas E/F. 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.
It was also 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.
The warhead of the Atlas D was originally the G.E. Mk 2 "heat sink" re-entry vehicle with a W-49 bomb, combined weight 3,700 lb (1,680 kg) and yield of 1.44 megatons (MT). The W-49 was later placed in a Mk 3 ablative RV, combined weight 2,420 lb (1,100 kg) The Atlas E and F had an AVCO Mk 4 re-entry vehicle containing a W-38 thermonuclear bomb with a yield of 3.75 MT which was fuzed for either air burst or contact burst. The Mk 4 RV also deployed penetration aids in the form of mylar balloons which replicated the radar signature of the Mk 4 RV. The Mk 4 plus W-38 had a combined weight of 4,050 lb (1,840 kg).
Operational deployment 
Strategic Air Command deployed 11 operational Atlas ICBM squadrons between 1959 and 1962. Each of the three missile variants, the Atlas D, E, and F series, were deployed and based in progressively more secure launchers.
Atlas-D deployment 
To provide the United States with an interim or emergency ICBM capability, in September 1959 the Air Force deployed three SM-65D Atlas missiles on open launch pads at Vandenberg AFB, California, under the operational control of the 576th Strategic Missile Squadron, 704th Strategic Missile Wing. Completely exposed to the elements, the three missiles were serviced by a gantry crane. One missile was on operational alert at all times. They remained on alert until 1 May 1964.
In September 1959 the first operational Atlas ICBM squadron equipped with six SM-65D Atlas missiles based in above-ground launchers, went on operational alert at F.E. Warren AFB, Wyoming. Three additional Atlas D squadrons, two near F.E. Warren AFB, Wyoming and one at Offutt AFB, Nebraska, were based in above-ground launchers that provided blast protection against over-pressures of only 5 pounds per square inch (34 kPa). These units were:
- Francis E. Warren AFB, Wyoming (2 September 1960-1 July 1964)
- 564th Strategic Missile Squadron (6 missiles)
- 565th Strategic Missile Squadron (9 missiles)
The first site at Warren for the 564th SMS consisted of six launchers grouped together, controlled by two launch operations buildings, and clustered around a central guidance control facility. This was called the 3 x 2 configuration: two launch complexes of three missiles each constituted a squadron.
At the second Warren site for the 565th SMS and at Offutt AFB, Nebraska for the 549th SMS, the missiles were based in a 3 x 3 configuration: three launchers and one combined guidance control/launch facility constituted a launch complex, and three complexes comprised a squadron. At these later sites the combined guidance and control facility measured 107 by 121 ft (33 by 37 m) with a partial basement. A dispersal technique of spreading the launch complexes were 20 to 30 miles (30 to 50 km) apart was also employed to reduce the risk that one powerful nuclear warhead could destroy multiple launch sites.
Atlas-E deployment 
The SM-65E Atlas squadrons deployed later in 1961 were also deployed horizontally, but the majority of the launcher was buried underground. These launchers were designed to withstand over-pressures of 25 psi (170 kPa). These units were:
- Fairchild Air Force Base, Washington (28 September 1961-17 February 1965)
- 567th Strategic Missile Squadron, (9 missiles)
- Francis E. Warren AFB, Wyoming (20 November 1961-4 January 1965)
- 566th Strategic Missile Squadron (9 missiles)
The major enhancement in the Atlas E was the new all-inertial system that obviated the need for ground control facilities. Since the missiles were no longer tied to a central guidance control facility, the launchers could be dispersed more widely in what was called a 1 x 9 configuration, with one missile silo located at one launch site each for the 9 missiles assigned to the squadron.
The Atlas Es were based in "semi-hard" or "coffin" facilities that protected the missile against over-pressures up to 25 psi (170 kPa). In this arrangement the missile, its support facilities, and the launch operations building were housed in reinforced concrete structures that were buried underground; only the roofs protruded above ground level.
Atlas-F deployment 
The six SM-65F Atlas squadrons were the first ICBMs to be stored vertically in underground silos. Built of heavily-reinforced concrete, the huge silos were designed to protect the missiles from over-pressures of up to 100 psi (690 kPa).
The Atlas F was the final and most advanced version of the Atlas ICBM and was essentially a quick-firing version of the Atlas E, modified to be stored in a vertical position inside underground concrete and steel silos. When stored, the Atlas F sat atop an elevator. If a missile was placed on alert, it was fueled with RP-1 (kerosene) liquid fuel, which could be stored inside the missile for extended periods. If a decision was made to launch the missile, it was fueled with liquid oxygen. Once the liquid oxygen fueling was complete, the elevator raised the missile to the surface for launching.
This method of storage allowed the Atlas F to be launched in about ten minutes, a saving of about five minutes over the Atlas D and Atlas E, both of which were stored horizontally and had to be raised to a vertical position before being fueled.
Service history 
The number of Atlas intercontinental ballistic missiles in service, by year:
CGM-16D Atlas Intercontinental Ballistic Missiles assigned:
CGM-16E Atlas Intercontinental Ballistic Missiles assigned:
HGM-16F Atlas Intercontinental Ballistic Missiles assigned:
Launch history 
After the solid-fuel LGM-30 Minuteman had become operational in early 1963, the Atlas became rapidly obsolete. By October 1964, all Atlas D missiles had been phased out, followed by the Atlas E/F in April 1965. About 350 Atlas ICBMs of all versions were built, with a peak deployment level of 129 (30 D, 27 E, 72 F). Despite its relatively short life span, Atlas served as the proving ground for many new missile technologies. Perhaps more importantly, its development spawned the organization, policies, and procedures that paved the way for all of the later ICBM programs.
After its retirement from operational ICBM service in 1965, the ICBMs were refurbished and used over twenty years as space launch vehicles.
NASA use 
Though never used for its original purpose as a weapon, Atlas was suggested for use by the United States Air Force in what became known as Project Vanguard. This suggestion was ultimately turned down as Atlas would not be operational in time and was seen by many as being too heavily-connected to the military for use in the U.S.'s International Geophysical Year satellite attempt.
The Atlas was used as the 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).
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 (Major Yuri A. Gagarin, a Soviet cosmonaut, was the first human in orbit in 1961.) Atlas was also used throughout the mid-1960s to launch the Agena Target Vehicles used during the Gemini program.
Direct Atlas descendants were continued to be used as satellite launch vehicles into the 21st century. An Atlas rocket is shown exploding, in the 1983 art film Koyaanisqatsi, directed by Godfrey Reggio, in the penultimate shot. The vehicle shown in the movie was the first launch attempt of an Atlas-Centaur in May 1962.
- HGM-16F Atlas is on display at the National Museum of the United States Air Force in Dayton, Ohio. For years the missile was displayed outside the museum. In 1998 it was removed from display. It was restored by the museum's restoration staff and returned to display in the museum's new Missile Silo Gallery in 2007. The white nose cone atop the museum's Atlas is an AVCO IV re-entry vehicle built to contain a nuclear warhead. This nose cone actually stood alert in defense of the United States, as it was initially installed on an Atlas on 2 October 1962 at a Denton Valley launch site near Clyde, Texas.
(The National Museum of the United States Air Force does not have an Atlas on display currently; they do claim to have one in storage.)
- Atlas 5A (56-6742) is on display on the lawn in front of the Canada Science and Technology Museum in Ottawa, Canada.
(5A was on display throughout the 1960s at the former location of the Air Force Museum, at Wright-Patterson AFB Building 89 near Xenia Drive in Fairborn, Ohio. Formerly a static-test article, it is the only surviving Atlas in the original A-series configuration, before the boat-tail modifications that solved thermal issues which caused the early termination of the first two Atlas test flights, 4A and 6A.)
- Atlas 8A is displayed in front of the Strategic Air and Space Museum in Nebraska; reconfigured as an Atlas D.
- Atlas 2E is on display in front of the San Diego Aerospace Museum at Gillespie Field, El Cajon, California.
- Atlas 2D mounted with a Mercury capsule is on display in the Rocket Garden at the Kennedy Space Center Visitor Complex, Merritt Island, Florida
Specifications (Atlas ICBM) 
- Length: 75 ft 1 in (22.89 m) with Mk 2 re-entry vehicle, 82 ft 6 in (25.15 m) with Mk 3
- Span of outboard engine fairings: 16 ft 0 in (4.88 m)
- Diameter: 10 ft 0 in (3.05 m)
- Launch weight: 255,950 lb (116,100 kg) for Atlas D w/o payload, 260,000 lb (117,900 kg) for Atlas D with Mk 2/3 RV and W49 warhead, 268,000 lb (121,560 kg) for Atlas E&F with Mk 4 RV and W38 warhead
- Range: 9,000 mi (14,480 km)
- Powerplant: 1 × Rocketdyne LR105 rocket engine with 57,000 lbf (254 kN) thrust, 1 × Rocketdyne XLR89 rocket engine with two 150,000 lbf (670 kN) thrust chambers (Atlas D), 2 × Rocketdyne LR101 vernier rocket engines with 1,000 lbf (4.4 kN) of thrust (propellant feed from LR105 sustainer engine turbopumps); 2 × LR89 booster engines (independent turbopumps) with 165,000 lbf (734 kN) (Atlas E&F)
- Warhead:Mk 2 or Mk 3 re-entry vehicle with W-49 warhead (1.44 MT yield) (Atlas D); Mk 4 re-entry vehicle with W-38 warhead (3.75 MT yield) (Atlas E&F)
- CEP: 4,600 ft (1,400 m)