One of the main launch vehicles currently in use, the Atlas V, has a long heritage commencing in the late forties. This article summarizes the various developments that led to the current launch vehicle and, as the current Atlas V has little in common with the original Atlas missile, other than the name, the Atlas development is considered as a good example of incremental technology development.

Early Experiments
Although the development of the Atlas intercontinental ballistic missile did not commence until 1951, the “thin skin” tank, which had to be pressurized at all times, had been developed in the late forties for the Convair MX-774 missile.

The MX-774 had a length of 9.93m and a diameter of 0.76m and was powered by four Thiokol solid fueled motors. The first launch was on July 13, 1948, with further launches on September 27, 1948, and December 2, 1948.

Further studies were conducted as MX-1593, commencing in January 1951 and, later that year, the military designation XB-65 was assigned to the project.

By 1953, the initial design studies had been completed and envisaged a vehicle with five engines. It was decided to develop a single engined test vehicle powered by a North American XLR43-NA-5 rocket engine and designated as X-11. Some reference sources have suggested that the X11 program covered only one flight, i.e., the prototype of the Atlas A, which was launched on June 11, 1957. The Atlas A, however, was equipped with three engines rather than the single engine that was specified for the X11.

X-11 and X-12
The subsequent X12 was a 1-1/2 stage rocket ballistic test vehicle for the SM65. The program was initiated in 1953 in parallel with the X11 and was a three engine version, with three North American XLR43NA5 rocket engines.

Some reference sources have suggested the X-12 covered the second Atlas A flight, which was launched from Cape Canaveral on September 25, 1957, and was destroyed during the flight. The suggestion that this flight was the X-12 is certainly incorrect and neither the X-11 nor X-12 was ever flown.

The five engine XB-65 version never materialized as nuclear warheads had become lighter in weight. The initial prime contractor of the Atlas was Convair, which later became General Dynamics.

In 1994, the rights to the Atlas launch vehicle were sold to Martin Marietta, which merged with Lockheed in 1995 to become Lockheed Martin.

Atlas
As a missile, the Atlas carried military designations XSM-65A (Atlas A), XSM-65B (Atlas B), XSM-65C (Atlas C), XSM-65D, SM-65D and USM-65D (Atlas D), SM-65E and USM-65E (Atlas E) and SM-65F (Atlas F). On September 18, 1962, those missiles remaining in service were redesignated as CIM-16D (was SM65D0, CTM-16D (was USM-65D), CGN-16E (was SM-65E), CTM-16E (was USM-65E) and HGM-16F (was SM-65F).

As a military missile, substantial numbers of the Atlas were built, but due to their slow response time when under attack, they were gradually replaced by Titan and Minuteman missiles. The Atlas missiles which became available due to this changeover were then used as launch vehicles, either by themselves or in combination with an upper stage. Additionally, development of the missile as a dedicated launch vehicle continued.

In addition to the military missile designations, the basic Atlas first stage received military designations in the LV/SLV and SB series. Table 1 lists these designations — as far as the cross references to the launch vehicle types are concerned, there remain discrepancies in this list. It is probable these designations were only used for flights carrying military satellites.

As a missile, the first launch of an Atlas A missile took place on June 11, 1957, as part of a series of eight test flights from Cape Canaveral — only four were successful. This was followed by 10 launches of the Atlas B missile, of which four were failures, and six Atlas C flights, of which two failed.

The Atlas D version was the initial production version. Known military serials indicate 121 Atlas D missiles were built. The missile test program lasted until January 23, 1961, and involved 49 launches, of which six failed, eight were partially successful and 35 were successful. The final flight was on November 7, 1967.

The use of the missile as a space launcher started on September 9, 1959, and of the 18 launches, four failed and two were sub-orbital. The last launch was on July 27, 1967.

These basic missiles were fitted with an additional upper stage and have also been referred to as Atlas Satar. Those Atlas D launch vehicles used in the Mercury program were also referred to as Atlas-Mercury and could place payloads of 1360 kg into a low orbit. The remainder of the Atlas D missiles were used as first stages in the Atlas configurations with the Agena, Able and Centaur upper stages, although the actual disposition is not known.

The Atlas E was launched successfully for the first time on January 24, 1961. Known serials indicate that 203 missiles were built.

In the ‘80s, surplus Atlas E missiles, which had a length of 28.10m, were used as space launch vehicles after having been fitted with an additional upper stage, allowing them to place a 820 kg payload into a low orbit.

Between December 18, 1981, and March 24, 1995, a total of 25 flights were made, of which two failed. The remainder of the Atlas E missiles were used as first stages in the Atlas configurations the Agena, Able and Centaur upper stages, although the actual disposition is not known.

For two sub-orbital flights, the basic Atlas E was also fitted with a Trident missile as an upper stage. The Trident missile was a three stage missile and it is not clear from references which stage (or all) was used for the Atlas E/Trident launch vehicle.

Atlas F differed from the Atlas E by having a modified fuel system. The version was launched successfully for the first time on August 8, 1961. Known serials indicate 122 missiles were built.

Surplus military missiles were fitted with an additional upper stage and were used as space launch vehicles from April 6, 1968, to June 23, 1981. They had a payload capacity of 820 kg into a low orbit. A total of 20 flights were made, of which one was a failure.

The remainder of the Atlas F missiles were used as first stages for the Agena, Able, Burner and Centaur upper stages.

A number of Atlas F missiles were fitted with a Trident missile as upper stage and used in a sub-orbital flight program. The Trident missile was a three stage missile and it is not clear from references which stage (or all) was used for the Atlas F/Trident launch vehicle.

The Atlas A, B, C, D, E and F were powered by two Rocketdyne LR89-NA-5 and one Rocketdyne LR-105-NA-5 rocket engines and, where appropriate, a second stage.

The Atlas G version was to be powered by the further improved Rocketdyne LR89-NA-7 and one Rocketdyne LR-105-NA-7 engines. The Atlas G was specifically developed as a first stage for the Atlas Centaur combination and was not flown as a launch vehicle without the upper stage.

The Atlas H version had engines similar to the Atlas G and was used five times between February 9, 1983, and May 15, 1987, as a space launch vehicle for payload of up to 3630 kg into a low orbit.

The Atlas SLV-3 was a version of the basic Atlas (probably Atlas D) without an upper stage used to launch the Prime SV5D re-entry test vehicles into a sub-orbital flight trajectory. Three flights took place between December 21, 1966, and April 19, 1967.

Atlas Able
To increase the launch capability, the Atlas D basic stage was combined with the Able IV and V upper stages developed by Aerojet and Allegheny Ballistic Laboratories for the Vanguard launch vehicle. After three failed flights between November 26, 1959, and December 15, 1960 it became evident that the Atlas Able combination was not successful and further development was abandoned. The length of the vehicle was up to 35 m and it would have been capable to launch a payload of 170 kg into a low orbit.

Atlas Vega
The Atlas Vega was a proposed development of the Atlas Able. The second stage was to have been propelled by a General Electric GE 405H liquid fueled engine (similar to the one used for the first stage of the Vanguard), while a third stage was to be propelled by a liquid fueled engine to be developed by the Jet Propulsion Laboratory. An orbiting capability of 2270 kg into a low orbit was envisaged.

At one stage it was intended to use the Atlas Vega for seven lunar fly-bys, a Mars fly-by in October of 1960, a Venus fly-by in January of 1961, a lunar hard lander in July 1961, a lunar satellite in September of 1961, a Venus lander and orbiter in August of 1962 and a Mars lander in November of 1962. It was also considered as the launch vehicle for the Mercury Mk II, later Gemini, crewed spacecraft.

The first flight was envisaged in August 1960 but development was cancelled on December 11, 1959, in favor of the Atlas Agena B vehicle. The cause of the failure was the delay in development, by which time the development of the Centaur upper stage was proceeding successfully.

Atlas Agena
The Atlas D first stage was also mated with the Lockheed Agena upper stage, which had been developed for the US military reconnaissance satellite programs.

The Atlas Agena A combination was capable of placing a 490 kg payload into orbit and four were launched between February 26, 1960, and January 31, 1961, of which two failed. It had a maximum length of 31.10 m.

The Atlas Agena B introduced an improved and longer Agena engine. Between July 12, 1961, and June 7, 1966, 28 were launched, of which five failed. The combination, which had a length of up to 33m, was capable of placing a payload of 2627 kg into low orbit. Commencing with the Atlas Agena B, NASA procured launch vehicles directly from the contractor and not through the U.S. Air Force.

The Atlas Agena D combination, with a length of up to 35m, was capable of orbiting payloads of up to 2718 kg. The first flight was on July 12, 1963, and until the last flight on April 8, 1978, 76 were launched, of which five failed. Many of these launches placed multiple satellites into orbit.

Atlas Antares II
The Atlas launch vehicle was also combined with an Antares-II solid fueled sounding rocket as upper stage. It was used on May 22, 1965, for a sub-orbital flight designated as Fire-2.

Atlas Burner II
The Atlas F was matched with the Burner II upper stage. The vehicle had an orbiting capacity of 215 kg into low orbit and between August 16, 1968, and February 24, 1979, three flights were conducted, of which one failed.

Atlas Centaur
The Centaur upper stage was initially developed by General Dynamics to place military communications satellites into orbit. This upper stage was fitted with two Pratt & Whitney RL-10A-3 rocket engines. When the program was cancelled, the launcher was handed over for civilian use by NASA.

The first stage was based on surplus military Atlas D, E and F missiles. The Atlas G was also used as a first stage after all Atlas D, E, and F first stages had been depleted. These first stages only differed in minor detail and no information is known to match the missile’s originated first stage with the Atlas Centaur launch vehicle, the latter being identified by an AC number only.

The Centaur upper stage allowed the combination, which had a length of up to 38m, depending on the size of the payload bay, to have an initial orbiting capability of 4670 kg into low orbit but this has been improved over time. In two instances (viz. the Pioneer-10 and -11 launches) a further Thiokol TE-M-364 upper stage was carried.

The Atlas Centaur A version was the prototype of which one was launched on May 8, 1962. The launch failed. The next prototype was the Atlas Centaur B. Only one was flown on November 27, 1963. Three Atlas Centaur C launch vehicles were flown between June 30, 1964, and March 2, 1965, but only one was successful. The Atlas Centaur D was the first production version of which 24 were flown between August 11, 1965, and August 21, 1972. Two of these were failures. Six examples of the Atlas Centaur D1A were flown between April 6, 1973, and May 22, 1975. One of these failed.

The next version was the Atlas Centaur D1AR, which flew for the first time on September 26, 1975. Thirty-three were launched up to September 25, 1989, including two failures. Since then, the Atlas Centaur has been referred to as simply Atlas I or Atlas II. The reason for the name change — other than for marketing purposes — is not known.

The Atlas I was similar to the earlier Atlas Centaur and had a length of up to 43.90m, depending on the payload bay employed. It had a capability to place 3,630 kg into a low orbit. The first stage engines were comprised of two Rocketdyne LR89-NA-7 and one Rocketdyne LR-105-NA-7.
The first flight designated as such was on July 25, 1990, and 11 were launched until April 25, 1997. Two of these were failures. Some sources use the number ‘1’ to indicate this version, but formal sources (i.e., Lockheed Martin) use the Roman numeral. The basic Atlas II had an improved engines (two Rocketdyne RS-56-OBA and one Rocketdyne RS-56-OSA) as well as a larger tankage. With a length of up to 47.40m, the orbiting capability was up to 6580 kg into low orbit. Thirteen were launched between December 7, 1991, and October 9, 1998.

The Atlas IIA introduced an improved engine on the Centaur stage (two Pratt & Whitney RL-10A-4), thereby increasing the orbiting capability to 7280 kg into low orbit. It had a length of 47.40m.

Another major change was the deletion of the two small Rocketdyne LR101 vernier engines, which had been used on previous versions to provide directional control during the launch. Instead a hydrazine roll control system was fitted. The first flight was on August 3, 199,4 and 20 flights were conducted until December 5, 2002.

The Atlas IIAS incorporated two Thiokol Castor solid fueled boosters, which were attached to the first stage. This enhanced the orbiting capability to as much as 8610 kg into low orbit. The length was 47.40m. The first flight was on December 16, 1993 and 30 were launched until August 31, 2004.

Atlas IIIA
Initially known as Atlas IIAR, the Atlas III differed from the traditional Atlas II launch vehicle in that the first stage was propelled by a single Energomash RD-180 engine. The RD-180 was expected to be more reliable than the traditional Atlas. Matched with the Centaur upper stage. it was capable to deliver 8640 kg into a low orbit.

For the Atlas IIIA version. the Centaur stage was fitted with a single engine. The length of the launch vehicle was 51.88m. The first flight of an Atlas IIIA was on May 24, 2000 and only two were launched.

The Atlas AIIIB was similar to the Atlas IIIA, except that the Centaur stage had two engines. The launch vehicle had a length of 53.10m and the first flight was on February 21, 2002, and to the close of 2008, four were launched.

Atlas V
The latest development of the Atlas vehicle is the Atlas V (there was no Atlas IV) to meet the U.S. Air Force’s Evolved Expendable Launch Vehicle (EELV) program requirements.
The feature that sets the Atlas V apart is the new rigid body Common Core Booster (CCB) that serves as the rocket’s first stage. The CCB replaces the “balloon” pressure-stabilized stage used by previous Atlas vehicles. The stage is common and will be used in all the various configurations of the Atlas V family. The stretched Centaur also will be common across the Atlas V fleet. The total length of the launch vehicle is 58.28m with the type 4 payload fairing, and 62.18m with the type 5 payload fairing. The different configurations are achieved via different sizes of payload bays as well as the number of solid-fueled rockets strapped to the first stage. In addition, the number of Centaur engines can be varied.

There are three distinct versions of Atlas V rockets — the 400 series, 500 series and Heavy — each dedicated to launching a certain class of satellite cargo into orbit. In this designation, the first digit indicates the payload bay (4m or 5m), the second digit the number of strap-ons, and the third digit the number of engines on the Centaur upper stage.

Atlas V Versions
The first Atlas V flight was on August 21, 2002, and to mid July of 2010, a total of 21 flights of the various versions have been conducted. Not all the listed versions have flown as of this writing.

Future Developments
The future of the Atlas V launch vehicle as one of the two mainstays of the U.S. space effort (the other being the Delta IV) is fairly well assured. The new launch vehicles currently under development (such as Falcon 9) may make a small impact on the market share enjoyed by the Atlas V, but are unlikely to jeopardize the on-going use of the Atlas V.

About the author
Jos Heyman is the Managing Director of Tiros Space Information, a Western Australian consultancy specializing in the dissemination of information on the scientific exploration and commercial application of space for use by educational as well as commercial organisations. An accountant by profession, Jos is the editor of the TSI News Bulletin.