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Atlas Rockets

Atlas Rockets Overview

50 years of Rocketry

Atlas was the name given to Americas first operational ICBM. Although its career as a nuclear armed missile was short-lived, the Atlas has evolved into one of the worlds premier satellite launchers. Over the last 50 years, more than 600 Atlas rockets have flown.

Stage and a Half Propulsion System

One unusual feature of the Atlas rocket is its unique staging system. In the 1950's, rocket designers faced a number of serious challenges. Clearly, there were significant benefits to the concept of 'staging', or the dropping of used engines and fuel tanks to lighten a rocket as it heads toward orbit. However, chemical rockets of this era could not be reliably started. The only way to ensure that a rocket started correctly was to start the engines while the rocket was still on the ground. Using conventional staging, with second stage engines starting in flight, would simply be too unreliable given 1950's technology.

The radical solution developed was two fold. First of all, of the three main rocket engines on the Atlas, only one remained with the Atlas all the way to orbit. The inner engine, sometimes referred to as the sustainer engine, remained permanently attached to the rocket, while the two outer engines, known as booster engines, were used only during the first few minutes of flight.

As the rocket rose into the air, fuel was consumed at a fast rate. After a short period of time, the rocket became light enough and the two booster rockets were dropped. By shedding the weight of the two booster engines, the Atlas was now light enough to fly all the way to orbit using only the sustainer engine.

Balloon Tank Structure

Another design feature of the Atlas was the use of an extremely lightweight structure. The structure, known as a 'balloon' structure, was so lightweight that the fuel tanks needed to be continuously pressurized to avoid collapsing under their own weight! (Atlas rockets on display at museums use an air compressor to keep the tanks pressurized. If the air compressor fails for any reason, the rocket is at risk of collapsing. Some displays have had an internal structure built within the tanks to provide support.)

The lightweight balloon structure, along with the ability to drop the booster engines in flight, allowed the Atlas to approach conventionally staged rockets in performance while still retaining the ability to start and test all main engines while still safely on the ground.


Perhaps the most famous payload launched on the shoulders of Atlas was the Friendship 7 spacecraft in 1962. It was aboard Friendship 7 that John Glenn became the third man to orbit the Earth. Atlas ultimately launched four manned Mercury missions.

Atlas went on to play a critical role in support of project Gemini. Atlas was used to launch heavily modified Agena stages, known as Agena Target Vehicles (ATV), to serve as docking targets for orbiting Gemini spacecraft.

Scientific probes launched on Atlas rockets include the first mission to Mercury (Mariner 10), Venus (Mariner 2), Mars (Mariner 4), Jupiter (Pioneer 10), Saturn (Pioneer 11), and Pluto (New Horizons). Atlas rockets also launched all of the Ranger, Surveyor, and Lunar Orbiter probes to the Moon.

Still Flying

Fifty years after its first orbital flight, Atlas continues to launch American military, commercial, and scientific spacecraft. Continually evolved and improved over the decades, the current version, Atlas V, bears little resemblance to versions first flown in the middle of the last century. With a heritage that spans six decades, Atlas rockets will continue to see service for many years to come.

Atlas-A missile illustration Atlas-B missile illustration Atlas-B Score illustration Atlas-D ICBM illustration Atlas-Able missile illustration Atlas-Agena illustration Atlas-F ICBM illustration Atlas Mercury illustration Atlas-H illustration Atlas-LV-3C Centaur illustration Atlas-SLV-3C illustration Atlas I Centaur Rocket illustration Atlas II Centaur Rocket illustration Atlas IIAS Centaur Rocket illustration Atlas III Centaur Rocket illustration Atlas V 400 Rocket illustration Atlas V 411 Rocket illustration Atlas V 500 Rocket illustration 1.8 Meter Human Figure

Left to right: Atlas-A, Atlas-B, Atlas-B Score, Atlas-D ICBM, Atlas-Able, Atlas-Agena, Atlas-F ICBM, Atlas Mercury, Atlas-H, Atlas-LV-3C Centaur, Atlas-SLV-3C, Atlas I, Atlas II, Atlas IIAS, Atlas III, Atlas V 400, Atlas V 411, Atlas V 500, Human figure for scale (1.8m tall).

View another illustration showing several Atlas rocket versions.

Atlas (Early Models)

Atlas-A missile illustration

Atlas-A missile (PGM-16A)

Atlas-A rockets flew sub-orbital test flights. The missions did not fly with a sustainer engine. Only the two booster engines were included.

The first flight, launched on 11 June 1957, was a failure. A total of eight Atlas-A rockets were launched in 1957 and 1958.

Atlas-B missile illustration

Atlas-B missile

The Atlas-B missile was the first version to include both the jettison-able booster engines, and the sustainer engine.

At launch, all three engines would ignite. Later in the ascent, the two booster engines would shut down and drop away. The sustainer engine would continue firing.

Not an operational missile, the Atlas-B was used to further test components of the Atlas missile.

Ten Atlas-B missiles were launched during 1958 and 1959. Three launches were failures. One missile went into orbit with the SCORE payload (below).

Atlas-B Score illustration

Atlas-B Score

Atlas-B Score was an orbital mission consisting of a modified Atlas-B rocket and a communication experiment known as SCORE (Satellite Communications by Orbiting Relay Equipment). The mission was launched on 18 December 1958. Once in orbit, communication experiments were carried out, including the broadcasting of a Christmas message recorded by President Eisenhower. Additional messages were sent to the spacecraft, recorded, and retransmitted to ground stations.

Planning for the mission was done in secrete. The first public acknowledgment of the mission occurred only after the spacecraft was in orbit.

Atlas-D ICBM illustration

Atlas-D ICBM

Atlas-D was the first operational version of the Atlas missile. The Atlas-D was later used to launch Mercury capsules into Earth orbit.

Atlas-Able missile illustration


Consisting of an Atlas-C or Atlas-D first stage, and an Able upper stage, Atlas-Able rockets launched the Pioneer P-3, P-30, P-31 space probes. All three missions, intended to be Lunar probes, failed.

Atlas-Agena illustration


The Agena, used first as an upper stage on Thor-Agena rockets was adapted for use on Atlas rockets.

Several Agena models were used as the program progressed, including the Agena-A, Agena-B, and Agena-D stages.

Many space probes were launched on Atlas-Agena rockets. Including all nine Ranger lunar probes, the Mariner 2 and 5 Venus flyby spacecraft, the Mariner 3 and 4 Mars probes, and all five Lunar Orbiter missions.

A large number of military spacecraft were launched , including reconnaissance and early warning satellites.

During Project Gemini, Agena upper stages were modified to use as docking targets for Gemini spacecraft.

Agena-A Upper Stage

Agena-B Upper Stage on display at the Air Force Space and Missile Museum. (Photos: Richard Kruse, 2009)

Agena-A Upper Stage overview Agena-A Upper Stage Engine Agena-A fuel tank Agena-A nosecone

Agena-B Upper Stage

Agena-B Upper Stage on display at the Air Force Space and Missile Museum. (Photos: Richard Kruse, 2009)

Agena-B Upper Stage Agena-B Upper Stage Front

Agena-B Upper Stage

Agena-B Upper Stage on display at the Udvar Hazy Center. (Photos: Richard Kruse, 2008)

Agena-B Upper Stage Agena-B Upper Stage Agena-B Upper Stage

Agena Engine

Bell Model 8048 Rocket Engine on display at the National Museum of the United States Air Force. (Photos: Richard Kruse, 2007)

Agena Engine Agena Engine Agena Engine Agena Engine Agena Engine Agena Engine Agena Motor

Atlas-F ICBM illustration

Atlas-F ICBM

Atlas-F was an operational ICBM that first flew on 8 August 1961.

Photos of an Atlas F (10F) on Transporter

Atlas rocket on transporter at the US Space and Rocket Center in Huntsville, Alabama. (Photos: Richard Kruse, 2007)

Atlas Rocket side Atlas Rocket on transporter 1 Atlas Rocket on transporter 2 Atlas Rocket on transporter 3 Atlas Rocket transporter wheels Atlas Rocket transporter back side Atlas Rocket with transporter Atlas Rocket aft view Atlas Rocket detail 1 Atlas Rocket detail 2 Atlas Rocket detail 3 Atlas Rocket detail 4 Atlas Rocket detail 5

Photos of an Atlas F (30F)

Atlas-F rocket on display at Kennedy Space Center. The display includes a dummy Agena stage on top. In reality, almost all Atlas-Agena rockets were "Atlas-D" models.(Photos: Richard Kruse, 2009)

Atlas-F Rocket Atlas-F Rocket Atlas-F Rocket Atlas-F Rocket Atlas-F Rocket Atlas-F Rocket Atlas-F Rocket Atlas-F Rocket Atlas-F Rocket Atlas-F Rocket Atlas-F Rocket Atlas-F Rocket Atlas-F Rocket Atlas-F Rocket Atlas-F Rocket Atlas-F Rocket Atlas-F Rocket Atlas-F Rocket

Atlas Mercury illustration

Atlas Mercury

Atlas-D, the first operational ICBM variant of the Atlas, was used to launch Mercury spacecraft on orbital missions. Ten Atlas-D rockets flew in support of project Mercury, including two failures and four manned missions.

Mercury-Atlas 6, launched on 20 February 1962, placed John Glenn into orbit. Given the call sign "Friendship 7", the successful three-orbit mission was Americas first manned orbital mission.

Mercury-Atlas 7, placed Scott Carpenter into orbit on 24 May 1962. On 3 October 1962, Walter Schirra was launched into orbit with Mercury-Atlas 8. Mercury-Atlas 9, the final Mercury mission, was piloted by Gordon Cooper and launched on 14 May 1963.

Atlas-D Rocket Photos

Atlas D (37D) Displayed in Mercury-Atlas configuration.

Atlas-D rocket on display at Kennedy Space Center. (Photos: Richard Kruse, 2009)

Atlas-D Rocket Atlas-D Rocket Atlas-D Rocket Atlas-D Rocket Atlas-D Rocket Atlas-D Rocket Atlas-D Rocket Atlas-D Rocket Atlas-D Rocket Atlas-D Rocket Atlas-D Rocket Atlas-D Rocket Atlas-D Rocket Atlas-D Rocket Atlas-D Rocket

Atlas-H illustration


Atlas-H was first flown in 1983. A total of five Atlas-H launches took place.

Atlas Centaur

The Centaur upper stage, powered by two Pratt and Whitney RL-10 rocket engines, was the worlds first hydrogen fueled, high energy upper stage.

Hydrogen fuel can offer a significant performance increase over other fuels, especially in upper stages.

RL-10 Rocket Engine on display at the United States Space and Rocket Center

(Photos: Richard Kruse, 2007)

RL-10 Rocket RL-10 Rocket RL-10 Rocket RL-10 Rocket RL-10 Rocket RL-10 Rocket RL-10 Rocket RL-10 Rocket

RL-10 Rocket Engine on Display at the Chicago Museum of Science and Industry

(Photos: Richard Kruse, 2008)

RL-10 Rocket Motor RL-10 Rocket Motor RL-10 Rocket Motor RL-10 Rocket Motor RL-10 Rocket Motor

Atlas-LV-3C Centaur illustration

Atlas-LV3C Centaur

Centaur D-1 upper stage.

Atlas-LV3C was the first Atlas rocket to use the Centaur upper stage (right). The first launch attempt, conducted on 8 May 1962, failed. The second test flight, launched on 27 November 1963, succeeded.

Several Surveyor Lunar landing probes were launched on Atlas-LV3C-Centaur rockets.

Atlas-SLV-3C illustration

Atlas-SLV3C Centaur

The last three Surveyor Lunar landing probes were launched on Atlas-SLV3C-Centaur rockets.

Atlas Centaur rockets also launched the Mariner 6 and 7 Mars flyby spacecraft, the Mariner 9 Mars orbiter mission, and the Mariner 10 mission. Mariner 10, the first spacecraft to visit two planets, conducted flybys of both Venus and Mercury.

A number of Pioneer missions also flew on Atlas-Centaur rockets. Pioneer 10, the first spacecraft to visit Jupiter, was launched on 2 March 1972. Pioneer 11, launched on 5 April 1973, conducted flybys of both Jupiter and Saturn. The Pioneer-Venus Multi-Probe was launched on 8 August 1978, and the Pioneer-Venus orbiter was launched on 20 May 1978.

Atlas I

Atlas I Centaur Rocket illustration

Atlas I

Atlas I, first flown on 25 July 1990, evolved from the successful Atlas-Centaur rocket. Improvements included an enlarged payload fairing.

Atlas II

Atlas II Centaur Rocket illustration

Atlas II

The Atlas II was first flown on 10 June 1992

Atlas IIAS Centaur Rocket illustration

Atlas IIAS

The Atlas IIAS, first flown on 16 December 1993, improved performance by adding four Castor-4A strap-on boosters to the rocket.

The Solar and Heliospheric Observatory (SOHO) was launched on an Atlas IIAS on 2 December 1995.

Atlas III

Atlas III Centaur Rocket illustration

Atlas III

The Atlas III, first flown on 24 May 2000, replaced the 'stage and a half' three chambered rocket system with a two chambered RD-180 engine.

The Russian designed RD-180 engine is fueled with kerosene and liquid oxygen. The new engine represented a significant improvement in both efficiency and reliability over the previous Atlas engines. The switch to the RD-180 engine allowed Atlas to remain viable in the increasingly competitive commercial launch market.

Atlas V

The Atlas V booster uses the RD-180 engine first used on the Atlas III. The rocket family features a stretched Centaur stage (right) allowing increased performance over previous versions. The new Centaur second stage can have either one or two RL-10A-4-2 rocket engines, allowing performance to better match payload. All previous Centaur versions had two RL-10 engines.

Atlas V rockets are given a three-digit model designation. The first digit indicates the payload fairing diameter (4 or 5). The second number indicates the number of solid rocket boosters attached (this number can be from 0 to 5). The third number indicates the number of RL-10A-4-2 engines on the Centaur stage (this will always be either a 1 or 2).

Atlas V 400 Rocket illustration

Atlas V 400

Centaur D3 SEC upper stage.

The first Atlas V 400, a 401 model, launched on 21 August 2002.

The Atlas V 400, like earlier Atlas variants, features a four meter payload fairing. The fairing is available in a variety of lengths to meet payload requirements.

Performance can be increased by adding up to three solid rocket boosters.

Notable payloads include the Lunar Reconnaissance Orbiter (LRO), and the Lunar Crater Observation and Sensing Satellite (LCROSS), both launched on 18 June 2009. The booster was a 401 model.

The Solar Dynamics Observatory was launched on an Atlas V-401 on 11 February 2010.

Atlas V 411 Rocket illustration

Atlas V 411

The Atlas V 411 model includes the four meter fairing, and a single solid rocket booster.

Among the payloads launched on the Atlas V 411, was the OSIRIS-REx asteroid mission in 2016.

Atlas V 500 Rocket illustration

Atlas V 500

Centaur D-3 stages with payloads.
Atlas V Interplanetary Payloads
Illustration showing Centaur stages with the New Horizons Pluto probe and the Mars Science Lander spacecraft. Both missions were launched on Atlas V Rockets. (An astronaut is included as a scale reference.)

Atlas V 500 performance can be adjusted by adding up to five solid rocket boosters. The large 5 m payload fairing is available in several lengths.

The first Atlas V 500, a 521 model, launched on 17 July 2003.

Missions have included several communications satellites and National Reconnaissance Office payloads

An Atlas V, 551 model, was used to launch the New Horizons mission to Pluto. The New Horizons launch, on 19 January 2006, imparted a velocity of 16.26 kilometers per seconds to the probe. This is the fastest speed of any space probe so far. New Horizons is on a solar-escape trajectory and will make a close fly-by of Pluto in July of 2015.

An Atlas V, 541 model, launched the Mars Science Laboratory in November of 2011.

Atlas Sustainer Rocket Motor

Photos of an Atlas Sustainer Motor being restored at the Michigan Space Science Center. (Photos: Richard Kruse, 2008)

Atlas Sustainer Rocket Motor Atlas Sustainer Rocket Motor Front Atlas Sustainer Rocket Motor Atlas Sustainer Rocket Motor Atlas Sustainer Rocket Motor Thrust Chamber Atlas Sustainer Rocket Motor Data Plate Atlas Sustainer Rocket Motor Closeup Atlas Sustainer Rocket Motor Power Head Atlas Sustainer Rocket Motor Power Head

Atlas Vernier Rocket Motor

Early Atlas rockets used two Rocketdyne LR-101 vernier engines to provide directional control. Versions of the LR-101 engine were also used on Thor and Delta rockets.

Photos of an Atlas Vernier Motor at the Air Force Space and Missile Museum. (Photos: Richard Kruse, 2008)

LR-101 vernier engine side view LR-101 vernier engine LR-101 vernier engine front view LR-101 vernier engine

Atlas Rockets Illustration

Atlas Family of Rockets
1Atlas B 1958Drawing of Atlas Rockets
2Atlas B Score 1958
3Atlas Agena 1960
4Atlas F ICBM 1961
5Mercury Atlas 1962
6Atlas Centaur 1962
7Atlas H 1983
8Atlas IIA 1992
9Atlas IIAS 1993
10Atlas IIIA 2000
11Atlas V 400 2002
12Atlas V 500 2003
Creative Commons License Images by Richard Kruse are licensed under a Creative Commons Attribution-Noncommercial 3.0 United States License.

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