Atlas ballistic missile

The Atlas was the first intercontinental ballistic missile (ICBM) in the western world. The program started when the United States Air Force (USAF) discovered that their standpoint about such type of weapon was wrong. This concept of ICBM was recognized as feasible in February 1954. Intimidated by the magnitude of the task, the USAF stablished a completely new directive structure and created a special company (Ramo-Woolridge Inc.) to direct the program under a new department of the USAF, denominated Western Development Division. The command of this department was entrusted to a young, dynamic and brilliant brigadier general, Bernard A. Schriever. In 1954 these developments did not went unnoticed for the Convair Division of General Dynamics. Years before, in 1946, this company had been the only one in going ahead with the proposal of the USAAF (United States Army Air Force, predecessor of the USAF) to build an ICBM having 8000 kilometers of range. Under the direction of Karel J. Bossart, the team Vultee Field built a test vehicle, the MX-774, which flew thrice in 1948 and tested characteristics so advanced as an engine mounted in suspension, a detachable conical nose and a structure built in stainless steel, so thin that it should be kept inflated like a globe.

In January 1955, Convair was awarded the main contract for the huge Weapon System 107A, denominated Atlas, albeit the missile received as well the designation SM-65. It was a very important program, to the point that in the following month of June it was granted the highest national priority, and to carry it out the engineers of the team led by Bossart were installed in a large facility of recent construction, denominated Convair Astronautics and which was built in Kearney Mesa, in the outskirts of San Diego. As far as possible, it was followed the "principle of coincidence"; the hundred thousand different precision pieces - coming from about 3500 suppliers - were developed simultaneously and to make them all compatible was precisely one of the problems in a weapon which, even with the basis provided by the former project Navaho, was opening its own way in every direction. Some of the decisions that had to be taken in 1955 resulted wrong, but that was part of the price paid for a truncated development cycle. To nobody was allowed to seriously delay or reduce the weapon system that was sought.

One of the decisions was to use inflatable fuel deposits built with very thin walls and fill them with liquid oxygen and RP-1 fuel to feed the Rocketdyne engines of a type that had been already developed. Other was unique: because it was known not much about the ignition in the upper atmosphere of large combustion chambers and an ICBM required to be able to detach the phases that constituted its propulsion systems already used, the Atlas was projected as an "one phase and half" missile. In the conic base of the inflatable deposit there was a mounting for a lift rocket LR 89 of 25855 kilograms of thrust at sea level. Around the base there was a ring for a booster unit, of creased structure (because it was not pressurized), which carried two engines LR 105 of 68040 kilograms of thrust each (or 74884 kilograms in the last versions). At each side of the ring in the base there was a little engine Vernier LR 101 of 454 kilograms of thrust for the final adjustment of the trajectory. The five engines consumed fuel from the main deposits and all of them were ignited before the launching. Elapsed about two minutes and 20 seconds, the booster unit turned off and detached. The lift rocket and the two Vernier burned then during another three minutes in a maximum range flight.



The first launching was of an Atlas 4A - which was provided only with the booster rockets - and it took place from Cape Canaveral the 11th June 1957. One of the boosters turned off prematurely and the missile was destroyed by the security range officer, after its inflatable deposit effectuated violent jumps and turns. The Atlas 6A made it slightly better the following 25th September. The Atlas 12A was already a complete success and the second missile of the B series, fitted with an operative lifter, effectuated a flight of 4000 kilometers the 2nd August 1958. The range set in the project was achieved in November of the same year and a launching in charge of a crew of the Strategic Air Command (SAC), from an operative terrestrial installation, took place in September 1959. The primitive missiles Atlas C employed fascinating radio-inertial guides, which in some aspects were considered more precise than the first exclusively inertial systems. In 1958 it was decided to connect this system - GE/Burroughs - to the Titan and the Atlas was fitted with an inertial guide.

The payload of the Atlas C consisted of the reentry vehicle General Electric Mk 2, with a protection in copper to endure the friction of the atmosphere. Many of these models C were used for the training of troops in the first complex of Atlas, in Vanderberg Airbase, California, in charge of the 576th Strategic Missiles Squadron. The first version deployed in large number was the Atlas D, also designated as SM-65D and later CGM-16D, with the reentry vehicle of blunt surface and superior characteristics General Electric Mk 3. It had also an airier profile and protective skirts for the exhaust flames. It reached operative status in 1960 in Warren Airbase, Wyoming. In this place, the 574th Squadron occupied six non-protected emplacements, completely above the surface and with a sliding ceiling to allow the missiles to be erected for the fuel load and subsequent launching. The 565th Strategic Missiles Squadron had three triple emplacements, spaced each other to give them dispersion and with sliding ceilings of side opening that could save precious minutes in the required reaction time, which was estimated in about half a hour. The 549th Squadron was provided with semiprotected "tomb" installations, embedded in the ground and very separated of each other.

In October 1961, the airbases Fairchild (Washington State) and Forbes (Kansas) reached operative status, with buried missiles and a microwave communications system capable of operating in situations of great overpressure. Due to the non-expected development of Soviet ICBM it was taken the belated decision - in 1959 - of placing the rest of the force of Atlas in protected silos. They were required gigantic silos, of about 53 meters in depth and 16 meters in diameter, with the missile placed in vertical position, which was raised to the surface - with the deposits already filled - by means of a hydraulic system which required 150 tonnes of counterweight. The next complex, in the headquarters of the SAC in Offutt, Nebraska, was already too advanced for the silos, but it had three squadrons each one of three Atlas E (CGM-16E), with more powerful boosters and often the reentry vehicle Avco Mk 4. The Atlas for training, USM-65D and USM-65E, were turned into the CTM-16D and CTM-16E.

Emplacement in silos required a substantially readapted missile. This one was the Atlas F, designated SM-65F and later HGM-16F. They were emplaced in 1961-63 and Lincoln Airbase, in Nebraska, had nine of them, while there were twelve in each of the following bases: Walker (New Mexico), Schilling (Kansas), Dyses (Texas), Altus (Oklahoma) and Plattsburgh (New York). The emplacements in the Southern States were possible because it was achieved to increase the range initially provided in the project to almost the double. Much was what was learnt with this prominent ICBM. Maybe recklessly, its full force was deactivated in 1965-67. Later, the old Atlas E and Atlas F were reconditioned as launchers for numerous space programs. In 1978, less than 30 exemplars survived.

Categories: Missiles - Cold War - 20th Century - [General] - [General]

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Article submitted: 2015-01-05