Strategic Air Command

 

Atlas Missile Performance

    There were six versions of the Atlas Missile:

Atlas A - range 600 miles
     Originating as the X-11, Atlas A was the name given to the first series of Atlas missiles delivered to Cape Canaveral for flight testing.   Their primary purpose was to test the airframe and propulsion system and was designed to fly with two North American booster engines, each of which provided a thrust of 120,000 pounds at liftoff.   It was the only "single stage" Atlas but that was all that was needed for it's short-range flights.  The Atlas A also had vernier engines, located on opposite sides of the missile above the booster engine fairing.  They controlled the roll of the missile and trim its final flight velocity.
     The Atlas A made a pre-programmed turn to a ballistic trajectory at an altitude of about 20,000 feet. The two booster engines shut down about two and one-half minutes into the flight.   In a flight profile unique to the Atlas A, the two booster engines did not need to be jettisoned after shutdown, and remained attached to the missile's main body to water impact.   About ten seconds following booster engine shutdown, the two vernier engines shut down, and the nose cone separated. By this time, the nose cone had been guided to its proper flight path, and could reach its target without further guidance.
     On June 11, 1957 an Atlas A became  the first Atlas launched from Cape Canaveral. The missile strayed off course and was destroyed by the Range Safety Officer less than one minute into its flight. Only  three of the eight Atlas A missiles launched from Cape Canaveral completed their flights as planned.  In spite of that, all of the flights helped to prove that the airframe was strong enough to survive violent twists, turns and loops in low-altitude "heavy air."   The A Series Tests also determined that the Atlas launch system and gimbaled engine flight control system worked effectively
Atlas B - range 6,000 miles
     This was the second series of Atlas missiles delivered to Cape Canaveral for flight testing.  They were built to test booster and nose cone separation as well as the overall propulsion system.  This required longer-range flights, thus the Atlas B employed an operating one and one-half stage booster/sustainer engine combination. To meet all test requirements, It needed to fly nearly ten times farther than the Atlas A.
     The Atlas B employed two North American booster engines and one North American sustainer engine. The sustainer engine was located in between the two booster engines. The engines each had a thrust of 120,000 pounds at liftoff.  It also used two vernier engines to control roll and trim final velocity. All engines were fed by liquid oxygen/RP-1 (kerosene) liquid propellant.
     On its first test flight, July 19, 1958. The missile lost thrust about 43 seconds into the flight, exploded,  and fell into the Atlantic Ocean about three miles downrange.  A second Atlas B was launched from Cape Canaveral on November 28, 1958.  All engines ignited at liftoff.  When it reached an altitude of 16,000 feet, the Atlas B performed a pre-programmed turn to a ballistic trajectory.  About two minutes into the flight, the two booster engines shut down and were jettisoned. The sustainer engine remained firing for about an additional two minutes, staying attached to the missile body to its final water impact. Following sustainer engine cutoff, the two vernier engines remained firing for about 30 seconds. Following cutoff of the vernier engines, the nose cone separated, continuing on toward its target without further guidance.  It successfully completed the first full-range Atlas test flight and flew about 6,000 miles. 
Atlas C - range 6,000 miles
      Designed for long-range guidance and nose cone tests, the Atlas C was configured very closely to what would become the operational Atlas ICBM.   It was powered by two Rocketdyne booster engines, each with a thrust of 165,000 pounds. A single Rocketdyne sustainer engine produced a thrust of 57,000 pounds while two Rocketdyne vernier engines produced a thrust of 1,000 pounds each. All were fed by liquid oxygen/RP-1 (kerosene) liquid propellant, and all engines were ignited at liftoff.
     Considered a semi-operational training and test vehicle, an Atlas C was first launched from Cape Canaveral on December 23, 1958. The missile's flight data capsule was not recovered, but all other test objectives were met.   An Atlas C carried the first recoverable ablative technology nose cone. During the last Atlas C test on August 24, 1959, the missile's nose cone was recovered following a successful 6,000-mile, full-range flight.
    The Atlas A and B were 75 feet 10 inches long.  Beginning with the Atlas C, all later models were 82 feet 6 inches long. 
Atlas D - range 10,360 miles
      The Atlas D was initially a prototype of the operational Atlas ICBM. Designed for testing of all Atlas operating systems, it became the first operational US ICBM.   SAC was so optimistic about the missile that it began constructing operational launch sites before the Atlas D test flights had even begun.  This was largely motivated by a perceived "missile gap" existed between the U.S. and the Soviet Union.
    The Atlas D was nearly identical to the Atlas C, although the two booster engines were upgraded to provide a combined thrust of 367,000 pounds at liftoff, compared to 330,000 pounds for the Atlas C. The thrust of the sustainer engine and vernier engines remained the same. Test-flight profiles for the Atlas D were designed specifically to simulate operational conditions of a deployed and activated ICBM.
    Optimism soon turned to dismay.  The first Atlas D was launched from Cape Canaveral on April 14, 1959, followed by ones May 18th and June 6th.  All three missiles exploded less than three minutes into their flights.
    The fourth Atlas D launched from the Cape completed a successful test flight on July 28, 1959.  One out of four wasn't bad, so the Atlas D was declared operational a little over two months later.  They were deployed at Vandenberg Air Force Base, California, Offutt Air Force Base, Nebraska and Warren Air Force Base, Wyoming. These first operational Atlas D missiles were intended to be launched from a vertical storage position on surface-level gantry-serviced launch pads. But to increase safety and security, facilities were modified to allow the Atlas D to be stored horizontally in a concrete surface bunker. The missile could be raised then fueled for a quick launch, which could typically be accomplished in as little as 15 minutes.  
Atlas E - range 11,500 miles
     Essentially an upgraded and modified Atlas D missile, the Atlas E featured an upgraded  propulsion system that increased liftoff thrust by about 8%, resulting in greater range.  It also had an all-inertial guidance system that reduced dependence on ground crews, which afforded a significant technical advantage to the operational Atlas ICBM fleet, effectively removing pressure from ground stations during flight.  On July 6, 1961 a Cape-launched Atlas E completed a successful test flight of 9,054 miles. This established a distance record for the Atlas ICBM which was never broken.
       Atlas E was specifically designed to be housed in underground facilities at Fairchild Air Force Base, Washington, Forbes Air Force Base, Kansas and Warren Air Force Base, Wyoming.  They were stored horizontally in underground hardened shelters.  Prior to launch, they would be raised to their vertical position then fueled.  These shelters were nicknamed "coffins" and the Atlas E was nicknamed "the coffin bird" because the missile was often covered with a thin layer of earth while in storage. Covering the Atlas E missile body with earth, much as an actual coffin would be covered with earth during burial, provided about 25 pounds per square-inch of pressure on the missile body, helping to prevent overpressure when the missile was in storage.
Atlas F - range 11,500 miles
    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 with either RP-1 (kerosene) liquid fuel or liquid oxygen. Atlas F missiles were deployed at Schilling Air Force Base, Kansas, Plattsburg Air Force Base, New York, Lincoln Air Force Base, Nebraska, Altus Air Force Base, Oklahoma, Dyess Air Force Base, Texas and Walker Air Force Base, New Mexico.

Later Atlas
      The Atlas proved to be a reliable and versatile launch vehicle and the Atlas D became the primary booster for Atlas space launch vehicles which would follow. In general terms, Atlas D-based space launch vehicles were classified as Space Launch Vehicle-3 (SLV-3). However, they have historically been better known by the Atlas name in combination with the name of associated upper stages or mission assignments. These variants include the Atlas-Able, Atlas-Agena A, Atlas-Centaur A, Atlas-Centaur B, Atlas-Centaur C and Mercury-Atlas.
      Once SAC removed its E and F models from operational status, some were sent to Vandenberg AFB, California and others to Cape Kennedy,  where they were used to launch satellites.