Atlas

by Jean-Jacques Serra
Launchers operated by Lockheed Martin Launch Services, formerly General Dynamics. Since mid-1995 the launchers are marketed by ILS

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External resources

http://www.lmco.com/ILS/

Origins of Atlas

Atlas without top stage

Atlas with an Agena stage

Atlas with solid top stage

Atlas with a Centaur stage


Origin: Inter Continental Ballistic Missile (ICBM) of first generation

In January 1955 the General Dynamics' Convair division was selected to build the Atlas system. In 1946 this firm was awarded a contract to design a 8000 km range ICBM: the MX-774. Three of those were launched in 1948 before the project was cancelled. Notheless those studies had lead to 3 major innovations: the engine with gimbaled nozzle, the monocoque structure and the releasable payload.

In the mid-50ies the problems related to high altitude ignition of liquid ergol engines were not solved. The only known solution was to ignite them all at takeoff: the Russians picked a bundle structure for their Semiorka while the Americans opted for a one-and-a-half stage vehicle. A main Rocketdyne LR105 sustainer of 670 kN was supported by 2 LR89 boosters. The propulsion bay containing 3 motors was named MA-1. Those engines consumed ergols (liquid oxygen and kerosene) provided by the same tanks. On each side a vernier LR101 rocket of 4.45 kN provided fine tuning of the thrust. The missile itself was 3.05 m diameter and 22.9 m in height (with an Mk2 Reentry Vehicle) and weighed over 110 tons.

On 11 Jun 1957 for its first test, the missile was only propulsed by its lateral motors... but it failed. The first success occured at the third try, on 17 Dec 1957. On 2 Aug 1958 the first 3-motor Atlas (named version B) ranged over 4000 km and the nominal range was achieved on 28 Nov 1958 (version C). Less than a month later on 18 Dec 1958 Atlas was used for a space mission: Score.

The propulsion system kept on evolving, first as a missile then as a space launcher. The first improved MA-2 was used for the Atlas-D ICBM. Then the MA-3 was introduced as a simplified version for the Atlas-E and -F ICBMs and derived launchers. The MA-5 was a civilian version of the MA-2; it was used by Atlas SLV-3 until the MA-5A version became available for Atlas-2.

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Atlas propulsion system

Designation	Year of first launch	Main engine Thrust (kN)	Main engine SI (sec.)	Additional engines Thrust (kN)	Additional engines SI (sec.)	Application
MA-1	1957	240	210	1335	245	Atlas A, B, C
MA-2	1958	255	213	1375	248	Atlas D
MA-3	1960	255	214	1470	250	Atlas E, F, launchers
MA-5	1961	270	220	1680	259	launchers
MA-5A	1991	270	220	1885	264	launchers

Atlas was equipped with the top stages of Thor Able -derived from those of Vanguard- in 1959. This launcher named Atlas Able was to launch the Pioneer probes to the Moon. But after 3 failures between November 1959 and December 1960 it was abandonned.

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Statistics

Between 1956 and 1989, 189 MA-1/MA-2, 238 MA-3 and 213 MA-5 propulsion systems were manufactured that is 640 Atlas. The great majority of those Altas were used as ICBM. Thus the 150th Atlas was fired on 7 Nov 1962 and within those 150 rockets only 31 did launch satellites.

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