Atlas II was a member of the
Atlas
An atlas is a collection of maps; it is typically a bundle of maps of Earth or of a region of Earth.
Atlases have traditionally been bound into book form, but today many atlases are in multimedia formats. In addition to presenting geographic ...
family of
launch vehicle
A launch vehicle or carrier rocket is a rocket designed to carry a payload (spacecraft or satellites) from the Earth's surface to outer space. Most launch vehicles operate from a launch pad, launch pads, supported by a missile launch contro ...
s, which evolved from the successful
Atlas missile
The SM-65 Atlas was the first operational intercontinental ballistic missile (ICBM) developed by the United States and the first member of the Atlas rocket family. It was built for the U.S. Air Force by the Convair Division of General Dyna ...
program of the 1950s. The Atlas II was a direct evolution of the
Atlas I
The Atlas I was a US expendable launch system manufactured by General Dynamics in the 1990s to launch a variety of satellites. In June 1987, General Dynamics committed $100M to acquire long-lead procurement items to support build of 18 vehicles f ...
, featuring longer first stage tanks, higher-performing engines, and the option for strap-on solid rocket boosters. It was designed to launch payloads into
low earth orbit
A low Earth orbit (LEO) is an orbit around Earth with a period of 128 minutes or less (making at least 11.25 orbits per day) and an eccentricity less than 0.25. Most of the artificial objects in outer space are in LEO, with an altitude never mor ...
, geosynchronous transfer orbit or geosynchronous orbit. Sixty-three launches of the Atlas II, IIA and IIAS models were carried out between 1991 and 2004; all sixty-three launches were successes, making the Atlas II a highly reliable space launch system. The Atlas line was continued by the
Atlas III
The Atlas III (known as the Atlas II-AR (R for Russian) early in development ) was an American orbital launch vehicle, used in the years between 2000 and 2005. It was developed from the highly successful Atlas II rocket and shared many componen ...
, used between 2000 and 2005, and the
Atlas V
Atlas V is an expendable launch system and the fifth major version in the Atlas (rocket family), Atlas launch vehicle family. It was originally designed by Lockheed Martin, now being operated by United Launch Alliance (ULA), a joint venture be ...
which is still in use.
Background
In May 1988, the US Air Force chose
General Dynamics
General Dynamics Corporation (GD) is an American publicly traded, aerospace and defense corporation headquartered in Reston, Virginia. As of 2020, it was the fifth-largest defense contractor in the world by arms sales, and 5th largest in the Uni ...
(now
Lockheed Martin
The Lockheed Martin Corporation is an American aerospace, arms, defense, information security, and technology corporation with worldwide interests. It was formed by the merger of Lockheed Corporation with Martin Marietta in March 1995. It ...
) to develop the Atlas II vehicle, primarily to launch
Defense Satellite Communications System
The Defense Satellite Communications System (DSCS) is a United States Space Force satellite constellation that provides the United States with military communications to support globally distributed military users. Beginning in 2007, DSCS is be ...
payloads under the Medium Launch Vehicle II (MLV-II) program. Additional commercial and U.S. Government sales resulted in production increases leading to greater than 60 vehicles being produced and launched.
Atlas II was developed from the
Atlas I
The Atlas I was a US expendable launch system manufactured by General Dynamics in the 1990s to launch a variety of satellites. In June 1987, General Dynamics committed $100M to acquire long-lead procurement items to support build of 18 vehicles f ...
and featured numerous upgrades over that vehicle.
[
Atlas II was launched from ]Launch Complex 36
Launch Complex 36 (LC-36)—formerly known as Space Launch Complex 36 (SLC-36) from 1997 to 2010—is a launch complex at Cape Canaveral Space Force Station in Brevard County, Florida. It was used for Atlas launches by NASA and the U.S. Air Force ...
at Cape Canaveral Space Force Station
Cape Canaveral Space Force Station (CCSFS) is an installation of the United States Space Force's Space Launch Delta 45, located on Cape Canaveral in Brevard County, Florida.
Headquartered at the nearby Patrick Space Force Base, the station ...
in Florida as well as Space Launch Complex 3E at Vandenberg Space Force Base
Vandenberg Space Force Base , previously Vandenberg Air Force Base, is a United States Space Force Base in Santa Barbara County, California. Established in 1941, Vandenberg Space Force Base is a space launch base, launching spacecraft from th ...
in California. All launches were successful.
Design
Atlas II provided higher performance than the earlier Atlas I
The Atlas I was a US expendable launch system manufactured by General Dynamics in the 1990s to launch a variety of satellites. In June 1987, General Dynamics committed $100M to acquire long-lead procurement items to support build of 18 vehicles f ...
by using engines with greater thrust and longer propellant tanks for both stages. The increased thrust, engine efficiency, and propellant capacity enabled the vehicle to lift payloads of 6,100 pounds (2,767 kg) into geostationary transfer orbit (GTO), or more on later Atlas II variants.
Atlas II also featured lower-cost electronics, an improved flight computer, and longer propellant tanks than its predecessor, Atlas I
The Atlas I was a US expendable launch system manufactured by General Dynamics in the 1990s to launch a variety of satellites. In June 1987, General Dynamics committed $100M to acquire long-lead procurement items to support build of 18 vehicles f ...
.
Atlas II first stage
The Atlas II first stage was in diameter and long. The stage was powered by 3 RS-56
RS-56 was an American liquid-fueled rocket engine, developed by Rocketdyne. RS-56 was derived from the RS-27 rocket engine, which itself is derived from the Rocketdyne H-1 rocket engine used in the Saturn I and Saturn IB. Two variants of this en ...
rocket engines (derived from the RS-27
The RS-27 was a liquid-propellant rocket engine developed in 1974 by Rocketdyne to replace the aging Rocketdyne_S-3D, MB-3 in the Delta. Incorporating components of the venerable MB-3 and the H-1 designs, the RS-27 was a modernized version of t ...
main engine of the Delta II
Delta II was an expendable launch system, originally designed and built by McDonnell Douglas. Delta II was part of the Delta rocket family and entered service in 1989. Delta II vehicles included the Delta 6000, and the two later Delta 7000 va ...
rocket) burning of RP-1
RP-1 (alternatively, Rocket Propellant-1 or Refined Petroleum-1) is a highly refined form of kerosene outwardly similar to jet fuel, used as rocket fuel. RP-1 provides a lower specific impulse than liquid hydrogen (LH2), but is cheaper, is st ...
and liquid oxygen
Liquid oxygen—abbreviated LOx, LOX or Lox in the aerospace, submarine and gas industries—is the liquid form of molecular oxygen. It was used as the oxidizer in the first liquid-fueled rocket invented in 1926 by Robert H. Goddard, an applica ...
. The two booster engines were the RS-56-OBA variants (the complete assembly of both engines and the aft skirt was referred to as the MA-5A), with high thrust but moderate efficiency. The sustainer (center) engine was the RS-56-OSA variant, featuring much less thrust but higher efficiency at high altitudes than the booster engines.
The vernier engines
A vernier thruster is a rocket engine used on a spacecraft for fine adjustments to the attitude or velocity of a spacecraft. Depending on the design of a craft's maneuvering and stability systems, it may simply be a smaller thruster complementin ...
used on the first stage of the Atlas I (and all previous Atlas models) were replaced by a hydrazine
Hydrazine is an inorganic compound with the chemical formula . It is a simple pnictogen hydride, and is a colourless flammable liquid with an ammonia-like odour. Hydrazine is highly toxic unless handled in solution as, for example, hydrazine ...
-fueled roll control system on Atlas II. This system, mounted on the interstage between the first and second stages, utilized small thrusters to control the vehicle's roll. Compared to Atlas I
The Atlas I was a US expendable launch system manufactured by General Dynamics in the 1990s to launch a variety of satellites. In June 1987, General Dynamics committed $100M to acquire long-lead procurement items to support build of 18 vehicles f ...
, the Atlas II first stage was taller.
The Atlas II was the last Atlas rocket to use the "stage-and-a-half" technique, where it ignited all 3 RS-56
RS-56 was an American liquid-fueled rocket engine, developed by Rocketdyne. RS-56 was derived from the RS-27 rocket engine, which itself is derived from the Rocketdyne H-1 rocket engine used in the Saturn I and Saturn IB. Two variants of this en ...
engines at liftoff and then jettisoned the 2 RS-56-OBA side engines and their support structure during ascent. The two RS-56-OBA engines were integrated into a single unit called the MA-5A and shared a common gas generator
A gas generator is a device for generating gas. A gas generator may create gas by a chemical reaction or from a solid or liquid source, when storing a pressurized gas is undesirable or impractical.
The term often refers to a device that uses a ...
. They burned for approximately 164 seconds before being jettisoned, when acceleration reached approximately 5.0-5.5 g. The central sustainer engine on the first stage, an RS-56-OSA, would burn for an additional 125 seconds after their jettison. It featured better efficiency at high altitudes than the RS-56-OBAs.
The first stage also had the option to be fitted with 4 Castor 4A solid rocket boosters as part of the IIAS version, each providing an additional of thrust for 56 seconds. The first two boosters were ignited at liftoff, and the other two were ignited after the first two burnt out. Both pairs of boosters were jettisoned shortly after their respective burns.
Centaur II upper stage
The second stage of Atlas II, the Centaur II, was the result of over 3 decades of flights and enhancements of the Centaur upper stage. Centaur II featured 2 RL-10A-3-3A engines, burning liquid hydrogen and liquid oxygen. It featured propellant tanks 0.9 meters longer than its predecessor, Centaur I, giving the stage more propellant and therefore higher performance. Due to the super cold propellants inside Centaur, foam insulation was installed onto the outer metal skin on the stage to help mitigate propellant boiloff inside the tank. Centaur II's foam insulation was permanently attached to the side of the stage, whereas previous versions of the stage (including Centaur I) jettisoned their insulation panels during flight.
The Centaur II upper stage (along with all other Centaur variants) used a pressure-stabilized propellant tank design and cryogenic propellants. The two stainless steel propellant tanks were separated by a common bulkhead, which helped keep mass down. Centaur II was long, carrying almost of fuel. The stage also featured 12 hydrazine
Hydrazine is an inorganic compound with the chemical formula . It is a simple pnictogen hydride, and is a colourless flammable liquid with an ammonia-like odour. Hydrazine is highly toxic unless handled in solution as, for example, hydrazine ...
thrusters to orient the stage and settle the propellants prior to engine ignition.
For the IIA and IIAS versions, Atlas used the Centaur IIA variant which featured 2 RL-10A-4 engines, providing higher thrust and efficiency over the RL-10A-3-3A. The two engines could be fitted with extendable nozzles, which would provide an increase in efficiency and therefore performance.
Centaur II was further refined to create the Centaur III, which flew on the Atlas III
The Atlas III (known as the Atlas II-AR (R for Russian) early in development ) was an American orbital launch vehicle, used in the years between 2000 and 2005. It was developed from the highly successful Atlas II rocket and shared many componen ...
and continues to fly today on the Atlas V
Atlas V is an expendable launch system and the fifth major version in the Atlas (rocket family), Atlas launch vehicle family. It was originally designed by Lockheed Martin, now being operated by United Launch Alliance (ULA), a joint venture be ...
. Atlas II was the final Atlas rocket that only had a dual-engine Centaur available, future rockets had the option for one or two RL-10 engines on Centaur. However, the Centaur V flying on the Vulcan rocket
Vulcan Centaur is a two-stage-to-orbit, heavy-lift launch vehicle that is under development by the United Launch Alliance (ULA) since 2014 with an initial flight expected in early 2023. It is principally designed to meet launch demands for the ...
will only utilize two RL-10 engines.
File:CentaurIIA-GOES-L-ARRIVES-AT-LC36A.jpg, Centaur IIA arrives at Launch Complex 36A for the launch of GOES-L.
File:CentaurIIA-GOES-L-LIFT.jpg, Centaur IIA before mating with Atlas II booster.
File:CentaurIIA-GOES-L-ENGINE-LOOK.jpg, A close-up view of the RL-10 engines of Centaur IIA.
File:CentaurIIA-TDRS-I-LIFT.jpg, Centaur IIA, to be used to launch TDRS-I, is lifted for integration.
Integrated Apogee Boost Stage
The Integrated Apogee Boost Stage was an optional upper stage, used only as an apogee kick stage when launching Defense Satellite Communications System III satellites (which were designed to be delivered directly to geostationary orbit
A geostationary orbit, also referred to as a geosynchronous equatorial orbit''Geostationary orbit'' and ''Geosynchronous (equatorial) orbit'' are used somewhat interchangeably in sources. (GEO), is a circular geosynchronous orbit in altitud ...
using the Transtage
Transtage, given the United States Air Force designation SSB-10A, was an American upper stage used on Titan III rockets, developed by Martin Marietta and Aerojet.
History
Transtage was developed in anticipation of a requirement to launch milita ...
or Inertial Upper Stage
The Inertial Upper Stage (IUS), originally designated the Interim Upper Stage, was a two-stage, solid-fueled space launch system developed by Boeing for the United States Air Force beginning in 1976 for raising payloads from low Earth orbit to h ...
, and so were not capable of performing their own circularization burn at the apogee of their geostationary transfer orbit
A geosynchronous transfer orbit or geostationary transfer orbit (GTO) is a type of geocentric orbit. Satellite, Satellites that are destined for geosynchronous orbit, geosynchronous (GSO) or geostationary orbit (GEO) are (almost) always put into ...
) on board the Atlas II and, later, the Delta IV
Delta IV is a group of five expendable launch systems in the Delta (rocket family), Delta rocket family introduced in the early 2000s. Originally designed by Boeing's Defense, Space and Security division for the National Security Space Launch, ...
. It was powered by two R-4D
The R-4D is a small hypergolic rocket engine, originally designed by Marquardt Corporation for use as a reaction control system thruster on vehicles of the Apollo crewed Moon landing program. Today, Aerojet Rocketdyne manufactures and markets m ...
engines, and could operate on-orbit for up to twelve days before deploying its payload, allowing additional flexibility in mission planning. The IABS measured 2.9 m in diameter, and 0.68 m in length, carrying 1303 kg of propellant with a dry mass of 275 kg.
Payload fairing
Three fairing models were available for the Atlas II:
*Medium, with a diameter of , a height of , and a mass of
*Large, with a diameter of , a height of , and a mass of
*Extended, with a diameter of , a height of , and a mass of
The Medium variant was not commonly used for Atlas II but was often used in earlier Atlas rockets. The Large and Extended fairing options were also later used on the Atlas III and Atlas V rockets. For the Atlas V, these fairings were part of the 400-series of that rocket, and a further extended option ("Extra Extended") was available. The 4-meter Atlas fairing last flew in 2022.
Atlas II rockets flying with a Medium fairing could move the most payload to orbit, as that fairing was the lightest. Similarly, rockets with Large or Extended fairings suffered slight hits to their payload capacity.
Versions
Atlas II was developed from the Atlas I
The Atlas I was a US expendable launch system manufactured by General Dynamics in the 1990s to launch a variety of satellites. In June 1987, General Dynamics committed $100M to acquire long-lead procurement items to support build of 18 vehicles f ...
and was available in 3 versions.
Atlas II
The original Atlas II was based on the Atlas I and its predecessors. Its lengthened propellant tanks and improved electronics over the Atlas I offered better performance. It was designed to work as part of the US Air Force's Medium Launch Vehicle II program. This version flew between 1991 and 1998.
Atlas IIA
Atlas IIA was a derivative of the Atlas II designed to service the commercial launch market. The main improvement was the switch from the RL10A-3-3A to RL10A-4 engine on the Centaur upper stage, increasing the stage's performance and the vehicle's payload capability. The IIA version flew between 1992 and 2002.
Atlas IIAS
Atlas IIAS was largely identical to IIA, but added four Castor 4A solid rocket boosters to increase performance. These boosters were ignited in pairs, with one pair igniting on the ground, and the second igniting in the air shortly after the first pair separated. The half-stage booster section would then drop off as usual. IIAS was used between 1993 and 2004, concurrently with IIA.
Specifications
**Primary contractor: Lockheed Martin – airframe, assembly, avionics, test and systems integration [Spaceflight Now]
Atlas IIAS
(accessed September 24, 2014)
**Principal subcontractors: Rocketdyne (First stage engines), Pratt & Whitney (Centaur RL-10 engines), Honeywell & Teledyne (avionics), and Thiokol (Castor 4A SRBs)
**Power Plant: Two Rocketdyne RS-56-OBA engines (making up the MA-5A), one RS-56-OSA, two Pratt & Whitney RL-10A-3-3A or RL10A-4 Centaur engines
**Thrust: 494,500 lbf (2,200 kN)
**Length: Up to 156 ft (47.54 m); 16 ft (4.87 m) high engine cluster
**Core Diameter: 10 feet (3.04 m)
**Gross Liftoff Weight: 414,000 lb (204,300 kg)
**Fairing options: 3 (Medium, Large, Extended)
**Models: II, IIA, and IIAS
**Launch Sites: Cape Canaveral SFS
Cape Canaveral Space Force Station (CCSFS) is an installation of the United States Space Force's Space Launch Delta 45, located on Cape Canaveral in Brevard County, Florida.
Headquartered at the nearby Patrick Space Force Base, the station ...
Launch Complex 36
Launch Complex 36 (LC-36)—formerly known as Space Launch Complex 36 (SLC-36) from 1997 to 2010—is a launch complex at Cape Canaveral Space Force Station in Brevard County, Florida. It was used for Atlas launches by NASA and the U.S. Air Force ...
, Florida
Florida is a state located in the Southeastern region of the United States. Florida is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia, to the east by the Bahamas and Atlantic Ocean, and to ...
and Vandenberg Space Force Base
Vandenberg Space Force Base , previously Vandenberg Air Force Base, is a United States Space Force Base in Santa Barbara County, California. Established in 1941, Vandenberg Space Force Base is a space launch base, launching spacecraft from th ...
Space Launch Complex 3E, California
California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...
See also
* Comparison of orbital launchers families
This article compares different orbital launcher families (although many launchers that are significantly different from other members of the same 'family' have their own separate entries). The article is organized into two tables: the first tabl ...
* Atlas I
The Atlas I was a US expendable launch system manufactured by General Dynamics in the 1990s to launch a variety of satellites. In June 1987, General Dynamics committed $100M to acquire long-lead procurement items to support build of 18 vehicles f ...
* Atlas III
The Atlas III (known as the Atlas II-AR (R for Russian) early in development ) was an American orbital launch vehicle, used in the years between 2000 and 2005. It was developed from the highly successful Atlas II rocket and shared many componen ...
* Atlas (rocket family)
Atlas is a family of US missiles and space launch vehicles that originated with the SM-65 Atlas. The Atlas intercontinental ballistic missile (ICBM) program was initiated in the late 1950s under the Convair Division of General Dynamics. Atlas was ...
References
USAF Atlas II Fact Sheet
External links
{{US launch systems
Atlas (rocket family)
Lockheed Martin space launch vehicles