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SM-65 Atlas

The SM-65 Atlas was a missile built by the Convair Division of General Dynamics. Originally designed as an ICBM in the late 1950s, Atlas was the foundation for a family of successful space launch vehicles now built by United Launch Alliance. The Atlas rocket family is today used as a launch platform for commercial and military satellites, and other space vehicles.

History

The Atlas, first tested in 1957, was the United States' first successful ICBM (Intercontinental Ballistic Missile). It was a "1.5 stage", liquid-fueled (LOX and RP-1) rocket, with three engines producing 1,590 kN of thrust.

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 Convair for the study of a 1,500 to 5,000 mi. (2,400 to 8,000 km) range nuclear armed missile. The Convair team was led by Karel Bossart. This was the MX-774 or Hiroc project. 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 1955, the CIA learned that the Soviet ICBM program was making progress so 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" 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.

Operational Atlas D were first deployed in "soft" sites featuring a "hardened" Launch Control Center and three "soft" launch pads. The guidance stations and antennas were also "soft". Later Atlas D bases were in "semi-hard" "coffin" sites where the missile was stored in a concrete structure horizontally and erected before fueling and launch. The Atlas E missiles were deployed in buried "semi-hardened" (harder than the D coffins) which functioned in the same fashion but each missile had its own LCC, allowing "salvo" launches. The Atlas-F was deployed in a 175 foot deep underground missile silo that were "hardened" against all but a direct nuclear hit. Each silo had its own LCC. An Atlas F site could take an overpressure of 100 PSI and lateral ground movement of 1 foot. These silos were usually located together in groups of 12 silos throughout the Midwest.

The only exception to this deployment strategy was the Atlas squadron that was deployed at Plattsburgh AFB in New York State. This location placed these Atlas missiles within striking range of soft targets located in the southern part of the Russian Federation and the Ukraine, of the then Union of Soviet Socialist Republics (USSR). This was the first and thus far the only instance where land-based ICBMs, loaded with live nuclear payloads, were deployed east of the Mississippi River.

The 551st Strategic Missile Squadron (551st SMS) located in Southeastern Nebraska is an example of the underground silo. From the mid-1960s, the Atlas (and its "bigger brother", the Titan) were phased out in favor of the LGM-30 Minuteman, a solid-fueled rocket which could be stored for long periods and launched, without fueling, at the turn of a key.

The warhead of the Atlas D was originally the G.E. Mk 2 "heat sink" re-entry vehicle with a W-38 bomb. 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 megatons 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.

Though never used in combat, the Atlas was used as the expendable launch system with both the Agena and Centaur upper stages for the Mariner space probes used to study Mercury, Venus, and Mars (1962–1973); and to launch ten of the Mercury program missions (1962–1963). Atlas was suggested for use by the United States Air Force in what became known as Project Vanguard. This suggestion was ultimately turned down, however, 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.

However, the 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 on February 20, 1962 (Major Yuri A. Gagarin, a Soviet cosmonaut, was the first human in orbit on April 12, 1961.) Atlas was also used throughout the mid-1960s to launch the Agena Target Vehicles used during the Gemini program. Direct Atlas descendants have continued to be used as satellite launch vehicles into the 21st century. An Atlas rocket is shown exploding, in the 1983 documentary film Koyaanisqatsi, directed by Godfrey Reggio, in the penultimate shot.

Design

Atlas was unusual in its use of balloon tanks for fuel, made of very thin stainless steel 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 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 rocket motors 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. 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 three of the Atlas' engines at launch—later, two of the engines would be discarded, while the third 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 Soviet's first ICBM, and the launcher of Sputnik and Vostok. He had a central sustainer section, with four boosters attached to its sides. All engines were started before launch, eliminating the then unexplored problem of igniting a large liquid fuel engine at high altitudes.

Current Atlas Family

The Atlas II series had 63 successful flights with the last launched August 31, 2004, it is considered one of the most reliable launchers in the world.

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's 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 license production by Pratt and Whitney company in the US.


Service history

The Atlas missiles were assigned to the following Strategic Air Command units:

Fairchild AFB, Vandenberg AFB, , Walker AFB, Dyess AFB, Altus AFB, Forbes AFB, Schilling Air Force Base, Lincoln AFB, Offutt AFB and Plattsburgh AFB.

The number of Atlas intercontinental ballistic missiles in service, by year:

CGM-16D Atlas Intercontinental Ballistic Missiles assigned:

  • 1959 - 6
  • 1960 - 12
  • 1961 - 32
  • 1962 - 32
  • 1963 - 28
  • 1964 - 13

CGM-16E Atlas Intercontinental Ballistic Missiles assigned:

  • 1961 - 32
  • 1962 - 32
  • 1963 - 33
  • 1964 - 30

HGM-16F Atlas Intercontinental Ballistic Missiles assigned:

  • 1961 - 1
  • 1962 - 80
  • 1963 - 79
  • 1964 - 75

Specifications (Atlas ICBM)

  • Length: 75 ft. 1 in. (22.9 m) with Mk 2 re-entry vehicle, 82 ft. 6 in. (25.2 m) with Mk 3
  • Diameter: 10 ft. 0 in. (3.05 m)
  • Launch weight: 255,000 lb. (116,000 kg) for Atlas D, 260,000 lb. (118,000 kg) for Atlas E and F
  • Range: 10,360 miles (16,670 km) for Atlas D, 11,500 miles (18,500 km) for Atlas E and F
  • Powerplant: 1 × Rocketdyne LR105 rocket engine with 57,000 lbf (254 kN) thrust, 2 × Rocketdyne LR89 rocket engines with 150,000 lbf (670 kN) thrust, 2 × Rocketdyne LR101 vernier rocket engines with 1,000 lbf (4.4 kN) of thrust
  • Warhead: Mk 4 re-entry vehicle with W-38 warhead (4 MT yield) (Atlas F)
  • CEP: 4,600 ft (1,400 m)

fin length 6ft 1 in

References

  • Gunston, Bill (1979). Illustrated Encyclopedia of the World's Rockets & Missiles. London: Salamander Books. ISBN 0-517-26870-1
  • Walker, Chuck, & Powell, Joel (2005). Atlas The Ultimate Weapon Burlington, Ontario, Canada: Appogee Books. ISBN 1-894959-18-3

External links

See also

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