Atlas V finally launches with MUOS – Centaur celebrates milestone

by William Graham, Chris Bergin

United Launch Alliance’s Altas V has launched at the third attempt on Friday at 5:15pm Eastern, lofting the first of five U.S. Navy’s Mobile User Objective System (MUOS) satellites from SLC-41 at Cape Canaveral Air Force Station (CCAFS).  The successful mission also marked the 200th launch of a Centaur upper stage.


With the mission heading into the T-4 minute hold – a nominal 10 minute Built In Hold (BIH) – weather balloon data showed red upper level winds, requiring the new information to be fed into the flight profile of the Atlas V’s onboard computers.

With five minute slips being called during the hold, the target T-0 was eventually moved to the very end of launch window, providing one final shot of launch. With green balloon data received with just moments remaining, the launch was given a go, prior to oversight controllers then calling a hold with around 90 seconds remaining in the count.

Given the hold was called at the end of the window, the decision was to scrub for 24 hours, with Friday’s launch window opening at 5:42pm Eastern.


Going into the count with a 60 percent chance of a weather violation, there was a lack of optimism that the Atlas V would be able to launch. Dark clouds over the launch site were a visual sign of what was three red conditions for launch, in tandem with upper level winds.

Going into the T-4 minute hold, the T-0 was slipped several times, the last of which took the attempt to the end of the launch window, prior to the scrub being called by the launch director. A new launch attempt won’t take place until at least next Wednesday.

“Due to lack of range availability and also the forecast weather conditions for the next several days, the Atlas V vehicle and MUOS will return to the Vertical Integration Facility and will roll back out to the launch pad prior to launch,” noted ULA. “The launch is rescheduled for no earlier than Wednesday, Feb. 22.”

However, according to the ELV officer at the GSFC, the manifest was updated to show February 24 as the latest NET date for the launch, with the window opening at 5:15pm Eastern. ULA later confirmed the Friday target for the third attempt.

Review the countdown events for the first attempt here. To review the second attempt – click here. For the third attempt, refer to the live update link below.

Atlas V launch Preview:

The MUOS-1 satellite will ensure continued mission capability of the existing Ultra-High Frequency Satellite Communications (UHF SATCOM) system, and represents deployment of the first satellite in the next-generation narrowband tactical satellite communications system which will provide significantly improved and assured communications for the mobile warfighter.

MUOS-1 will ultimately replace the current UHF SATCOM system, providing military users with 10 times more communications capability over existing systems, including simultaneous voice (full-duplex), video and data, leveraging 3G mobile communications technology.

The Mobile User Objective System will provide Net-Centric use of UHF SATCOM and provides enabling capabilities, such as beyond-line-of-site, communication-on-the-move to the warfighter with focus on usability, and global communications to connect any set of users, regardless of location with the exception of polar regions.

MUOS will also improved connectivity in stressed environments including urban canyons, mountains, jungle, weather and scintillation and sports a future-proof architecture that is upgradeable with “smarts” on the ground. It also has accessibility to Global Information Grid (GIG), Non-secure Internet Protocol Router Network (NIPRNet), Secure Internet Protocol Router Network (SIPRNet), and Defense Information Systems Network (DISN).

“United Launch Alliance (ULA) is proud to be a part of the deployment of the U.S. Navy’s Mobile User Objective System (MUOS) satellite constellation,” noted Jim Sponnick, Vice President of Mission Operations.

“The MUOS-1 satellite is the first of a five-satellite constellation to be launched and operated by the Navy’s Communications Satellite Program Office, PMW 146. MUOS is the next-generation narrowband tactical satellite communications system designed to significantly improve ground communications to U.S. forces on the move around the globe.

“MUOS will fully support legacy UHF SATCOM terminals and Joint Tactical Radio System terminals, ensuring its users receive the technological advancements needed without a gap during necessary system upgrades. The MUOS constellation will also provide enhanced geo-location capabilities.”

The spacecraft was launched atop Atlas V AV-030, which is flying in the 551 configuration, with a five metre payload fairing, five solid rocket motors augmenting the first stage, and a single-engined Centaur (SEC) second stage. This is the third time the 551 configuration was used; its previous launch being that of New Horizons and Juno.

The five metre payload fairing had an exact external diameter of 5.4 metres, and is available three different lengths. The “short” fairing is 20.7 metres long, whilst the “medium” length is 23.4 metres, and a “long” fairing 26.5 metres long. The five metre fairings are produced by RUAG, a Swiss company which also produces a similar fairing for the Ariane 5 rocket.

The launch of AV-030 marked the 200th launch of a Centaur upper stage. First flown in 1962, the Centaur has become a workhorse of the US space programme, and has flown on Atlas and Titan rockets. It was also proposed as an upper stage for numerous other vehicles, including Saturn, the Space Shuttle, and even the British Blue Streak rocket.

Centaur was conceived as a cryogenically fuelled high-energy upper stage, with a pressure-stabilised structure formed of balloon tanks and a common, double-walled, bulkhead separating its liquid hydrogen and liquid oxygen tanks. Early Centaurs were powered by two RL10 engines; single-engine Centaurs were not introduced until the Atlas III entered service in 2000.

Development of Centaur began in the late 1950s, both to provide a more capable expendable launch system than existed at the time, and to allow engineers to gain experience with the cryogenically-fuelled rocket stages which would be necessary for the Saturn rockets.

Centaur made its maiden flight aboard an Atlas LV-3C on 9 May 1962, having been delayed seven months by fuel leaks, and problems with the rocket’s guidance system and engines. The only flight of the “Centaur-A” configuration, with RL10A-1 engines, ended in failure 54 seconds after liftoff; the Centaur began leaking liquid hydrogen, which was ignited by the Atlas’ engines, and the rocket exploded.

Following the failure, NASA came under pressure to cancel the Centaur programme, with a variant of the Saturn I rocket with an Agena upper stage replacing the Atlas-Centaur for launching planetary probes and larger satellites.

The programme survived the proposed cancellation because it was determined that Saturn-Agena could not be ready in time to launch the Surveyor missions as precursors to the Apollo programme, and that further Centaur flights would provide useful data to aid the development of Saturn’s cryogenic stages. The second launch, using a Centaur-B powered by RL10A-3 engines, occurred on 27 November 1963.

This flight was successful, placing an instrumentation ring into low Earth orbit. The third test flight, which introduced the Centaur-C, took place in June 1964. Again carrying no payload other than an instrumentation ring, the launch was this time bound for a geosynchronous transfer orbit. The Centaur’s hydraulics failed, resulting in the vehicle failing to achieve orbit.

Following the failure of the next launch, carrying a mass model of a Surveyor spacecraft, during a coast phase, AC-5; the fifth Atlas-Centaur and final rocket to use the Centaur-C, lifted off from LC-36A on 2 March 1965 with the SD-1 spacecraft; a dynamic test article for the Surveyor programme. Two seconds after liftoff, the an engine failure resulted in the rocket falling back onto its launch pad and exploding, causing significant damage to the complex.

Following this failure, construction of a second launch pad at LC-36B, which had been put on hold, was resumed, and the pad was completed later that year. With LC-36A still under repair, the sixth Atlas-Centaur launch, and first flight of the RL10A-3-1 powered Centaur-D, lifted off in August carrying SD-2. Another test flight was made in April 1966, before the Atlas-Centaur deployed its first operational payload, Surveyor 1, in May 1966.

The Atlas LV-3C Centaur-D made seven flights in total; the two initial test flights, then two operational Surveyor launches, another test flight which included the first in-flight restart of a liquid hydrogen-fuelled engine, and two more operational launches.

The Atlas SLV-3C Centaur-D, which featured several modifications to the vehicle, including the re-engineering of the Centaur with the RL10A-3-3, replaced the LV-3C. If first flew in September 1967, and made 17 flights in total. After deploying the last three Surveyor spacecraft, the Atlas-Centaur began to be used for a variety of other payloads, including Advanced Test Satellites (ATS), Orbiting Astronomical Observatories (OAO), and Mariner probes.

On 26 January 1971, the Atlas-Centaur launched its first communications satellite, Intelsat IV F-2. A modified SLV-3C Centaur-D with a Star-37E third stage was launched on 3 March 1972 with Pioneer 10, the first spacecraft to visit Jupiter, and subsequently be placed on a trajectory taking it out of the solar system.

The Atlas SLV-3C Centaur-D experienced three failures and one partial failure. The first failure was on the first post-Surveyor launch in August 1968, carrying the ATS-4 satellite. Following an hour-long coast phase, the Centaur failed to restart for its second burn, leaving the payload in a useless orbit. Almost exactly a year later, control of the Centaur was lost between the end of the final burn and the deployment of the ATS-5 satellite, resulting in the payload being spun in a manner which prevented it from fully completing its mission.

The next failure occurred in November 1970, during the launch of OAO-B. A pyrotechnic bolt holding the fairing onto the rocket failed to fire, resulting in the failure of the fairing to separate. This left the rocket with too much mass to reach orbit. The final failure occurred during the Mariner 8 launch in May 1971, when a problem with the guidance program caused the Centaur to tumble out of control as soon as it separated from the Atlas.

The first flight of the short-lived Atlas SLV-3D Centaur-D1A occurred on 6 April 1973, carrying the Pioneer 11 spacecraft into heliocentric orbit for its flybys of Jupiter and Saturn. As with the Pioneer 10 launch the previous year, a Star-37E third stage was used on that flight.

The new Centaur-D1A upper was intended to improve the stage’s reliability, and reduce operating costs. It incorporated new avionics systems including a 24-bit flight computer which controlled both the Centaur and the Atlas first stage. The avionics also included the ADDJUST system, which allowed data on upper level winds to be loaded during the final stages of the countdown rather than using forecast data further in advance, thereby reducing weather constraints upon launches.

Following the launch of Pioneer 11, the Atlas SLV-3D Centaur-D1A made a further five flights; four carrying Intelsat IV communications satellites, and one deploying Mariner 10, the first spacecraft to visit Mercury. One of the Intelsat launches, that of Intelsat IV F-6, ended in failure, the rocket being destroyed by range safety after an electrical problem during stage separation.

By the 1970s, the Atlas-Centaur was no longer powerful enough to launch NASA’s flagship missions, and a new vehicle was developed, the Titan III(23)E Centaur-D1T, or Titan IIIE. The first Titan-Centaur configuration, the Titan IIIE consisted of a standard Titan-23 core vehicle, derived from the Titan II missile, with two UA-1205 solid rocket boosters, and a Centaur-D1T upper stage powered by two RL10-3-3A engines.

The first of seven Titan IIIE launches occurred on 11 February 1975, carrying the Viking Dynamic Simulator, and NASA’s Sphinx satellite. After failing to ignite, the Centaur was commanded to self-destruct 748 seconds into the flight. The failure was later established to have been caused by the rivet holding a sensor in place in the oxygen tank being too short, and falling out.

The next Titan IIIE launch, this time with a Star-37E fourth stage, occurred in December 1974, carrying the Helios 1 probe to study the Sun. In August and September 1975, the two Viking probes were launched to Mars, and in January 1976 a second Helios spacecraft was launched, again using a Star-37E. The final two Titan IIIE launches occurred in August and September 1977, carrying the Voyager 2 and 1 spacecraft respectively on missions to explore the outer planets. The Voyager 1 launch was success despite the core vehicle severely underperforming.

The Centaur was able to detect the underperformance, and was carrying sufficient surplus propellant to extend its burn to compensate, resulting in the spacecraft still reaching its target trajectory. It was later estimated that the Centaur only had less than three and a half seconds of propellant remaining when it finally shut down.

Meanwhile, modifications made to the Centaur for use with the Titan III were applied to the Atlas-Centaur, with the Atlas SLV-3D Centaur-D1AR replacing the the D1A in 1975. The D1AR made 26 launches, mostly carrying communications satellites although three HEAO astronomy satellites and two Pioneer missions to Venus were also launched.

The D1AR configuration experienced two failures, the first of which occurred during the September 1977 launch of Intelsat IVA F-5, when a first stage gas generator began leaking hot gas around 55 seconds into the flight. The vehicle failed to achieve orbit. The second was the launch of FLTSATCOM-5 in August 1981, during which the payload fairing collapsed, damaging the spacecraft.

The Atlas SLV-3D Centaur-D1AR was the last Atlas-Centaur to bear that name; in 1984 it was replaced by the Atlas G. This featured a Centaur-D1AR with a new first stage; a two-metre stretch of the Atlas SLV-3D. Seven were launched, of which two failed. The first failure came on the maiden flight, in June 1984, when the Centaur’s oxidiser tank was damaged during staging, resulting in a leak.

The other failure occurred on 26 March 1987, when a relaxed interpretation of flight weather rules led to the rocket being launched into a thunderstorm. The rocket was struck by lightning, which disrupted its guidance system and resulted in a loss of control. These failures resulted in the loss of the Intelsat V F-9 and FLTSATCOM-6 satellites respectively. The last Atlas-G launch occurred in September 1989, carrying another FLTSATCOM spacecraft, and was the final launch to be conducted by NASA before the privatisation of launch services.

In July 1990. the Atlas I made its first flight. The first member of the Atlas family to be identified using a numeral rather than a letter, the Atlas I featured improved guidance systems, including digital components. The Centaur was powered by RL10A-3-3A engines rather than the previous RL10A-3-3s. Eleven Atlas I launches were conducted carrying an array of communications satellites, as well as the CRRES research satellite, three GOES weather satellites, and the BeppoSAX astronomy satellite.

All but three of the launches were successful; the first failure occurred in April 1991, when the Centaur failed to ignite resulting in the loss of B.S-3h. Following an identical failure during the launch of Galaxy 1R in August 1992, the problem was traced to icing in the Centaur turbopump. The third failure was caused by first stage underperformance during the launch of the UFO-1 satellite in March 1993.

The Atlas II, featuring a 2.7-metre longer re-engined Atlas, and a 1-metre longer Centaur, first flew in December 1991. It was joined in 1992 by the Atlas IIA with an uprated Centaur powered by RL10A-4 engines, increasing its capacity. The Atlas IIAS, which added four Castor-4A solid rocket motors to the Atlas IIA, first flew in 1993.

The Atlas II made 10 flights, the IIA 23, and the IIAS 30, for an overall total of 63 launches, all successful, making the Atlas II one of the most reliable rockets ever built. Its final launch came on 31 August 2004, when an Atlas IIAS orbited USA-179; a Satellite Data System spacecraft for the US National Reconnaissance Office. The Atlas II also introduced a launch complex at Vandenberg Air Force Base, SLC-3E. Although only three Atlas IIAS launches were made from the pad, it would later be refurbished as an Atlas V complex.

During the 1990s, the Titan-Centaur was reintroduced in the form of the Titan IV(401)A. Using lessons learned from the Titan IIIE, and an aborted attempt to use the Centaur as an upper stage for the Space Shuttle, the 401A had a Centaur-T third stage with two RL10-3-3A engines. It made nine flights, carrying Milstar, Trumpet, Mercury and Mentor satellites into orbit. In August 1998, the final flight, NROL-7 carrying a Mercury satellite, ended in failure after the guidance system lost power, causing the rocket to go off course and be destroyed by range safety.

The Titan IV(401)B used the same core vehicle and Centaur-T as the 401A, but replaced the ‘A’s UA-1207 boosters with SRMUs. The first 401B was launched on 15 October 1997, carrying the Cassini and Huygens spacecraft on their mission to Saturn. Seven were launched in all; in addition to the Cassini launch, four launched Milstar communications satellites, and two launched Menor ELINT spacecraft. The final Titan-Centaur launch occurred on 9 September 2003, with the USA-171 (NROL-19) satellite.

One Titan IV(401)B launch failed; on 30 April 1999 whilst attempting to deploy the a Milstar satellite, USA-143, into a geosynchronous orbit. A misprogrammed Centaur performed three burns during its first orbit which had been planned to occur later in the flight, resulting in the payload reaching an incorrect and unusable orbit. This was the third consecutive failure of a Titan IV rocket, coming less than a month after the failure of a Titan IV(402)B with a solid-fuelled IUS upper stage to deploy a DSP missile defence satellite. The launch before that had been the Titan IV(401)A with NROL-7.

The twenty-first century saw the end of Titan launches, with the Evolved Expendable Launch Vehicles entering service to replace the Titan, Atlas and Thor-Delta families of rockets. As a pathfinder for the Atlas V EELV, the Atlas III was developed. First flying in May 2000, the Atlas IIIA offered a similar payload capacity to the Atlas IIAS, whilst the Atlas IIIB offered increased capacity through a stretched Centaur.

The Atlas III introduced a conventional first stage design, rather than the stage-and-a-half concept inherited from the Atlas missile. The first stage was powered by the Russian-built RD-180 main engine, developed from the Zenit’s RD-170 for the Atlas V. The Atlas III also introduced the option of single or dual engine Centaurs, with all but one launch using the new single-engine configuration. Two Atlas IIIAs were launched, along with one Atlas IIIB with a conventional twin-engine Centaur, and three IIIBs with the newer single-engine model. The last Atlas III flew in February 2005, carrying two NOSS satellites for the NRO.

In August 2002, the Atlas V made its maiden flight, carrying the Hot Bird 6 satellite for Eutelsat. A more flexibile launch system, it introduced the option of four and five metre fairings, and multiple SRM configurations. Although both single and dual engine Centaurs are available, all launches to date have used the single-engine configuration. The CST-100 spacecraft, which is expected to fly in 2015, will require the dual engine Centaur.

The launch of MUOS-1 marked the Atlas V’s twenty-ninth flight. To date, only the launch of USA-194 has been other than successful, with a valve problem resulting in the premature cutoff of the Centaur, however the payload was able to correct its own orbit. The Atlas V’s past payloads have included the Mars Reconnaissance Orbiter, Mars Science Laboratory, the Lunar Reconnaissance Orbiter, the New Horizons mission to Pluto, the Juno mission to Jupiter, and the Solar Dynamics Laboratory, as well as numerous communications satellites, reconnaissance and intelligence satellites, two X-37B spacecraft, a weather satellite and a group of small technology demonstration satellites.

In addition to its use with Atlas and Titan, Centaur has also been proposed as part of several other rockets. It was originally intended to form part of the Saturn family of rockets, a role for which it was designated S-V. The Saturn I was originally intended to be a three-stage rocket, with the Centaur being used to propel an Apollo spacecraft on a circumlunar mission. This proposal was abandoned, however the first four Saturn I launches carried mockups of the original upper stage configuration, including the Centaur.

In the 1980s, Centaurs were to have been deployed from the Space Shuttle, with the Centaur-G and G Prime optimised for use within the orbiters’ payload bays. Cancelled after a risk-reassessment in light of the Challenger accident, the first Centaur mission had been expected to occur in May 1986 with Challenger deploying the Ulysses spacecraft during STS-61F. This would have been followed five days later by Atlantis deploying Galileo during STS-61G.

Atlantis and Challenger were the only orbiters which could carry the Centaur; Atlantis having been built to accommodate it Centaur, whilst Challenger was modified after construction. Following the cancellation of Shuttle-Centaur, Ulysses and Galileo were deployed from the Shuttle using Inertial Upper Stages instead.

The first stage of the Atlas V is the Common Core Booster (CCB). Like the Common Booster Cores used on the Delta IV, the CCB was designed to be stacked in parallel, allowing a “Heavy” Atlas V with three CCBs. This has never flown, with development being abandoned in favour of the Delta IV Heavy. It is possible; however, that it may be needed to support manned commercial missions in the future.

The Common Core Booster is fuelled by RP-1 propellant, oxidised by liquid oxygen. A single RD-180 engine powers the stage. The Centaur second stage is powered by an RL10A-4-2 burning liquid hydrogen in liquid oxygen. The five solid rocket motors were manufactured by Aerojet, and provide an average of around 1.1 mega-newtons of thrust each.

The launch of MUOS began with the ignition of the RD-180 main engine, 2.7 seconds before the countdown reached zero. At T-0, the solid rocket motors ignited, and about 1.1 seconds later AV-030 began a fast climb away from Cape Canaveral. A second after liftoff, the vehicle reached maximum thrust, and after another 1.7 seconds it began to manoeuvre to the correct attitude for its ascent to orbit.

About 34.5 seconds into its mission, AV-030 passed through Mach 1, beginning supersonic flight. A little under twelve seconds later it experienced Max-Q, the area of maximum dynamic pressure. The solid boosters burned out 85 to 90 seconds after launch, and 104 seconds into the flight they were jettisoned.

Three minutes and 24.9 seconds into the flight, the payload fairing separated from around the satellite. After this, the forward load reactor, which helped to dampen vibrations within the fairing, was also jettisoned. Around 233 seconds after launch the RD-180 engine throttled down to maintain a constant acceleration of 5G, in order to limit stresses on the payload.

Booster Engine Cutoff, the end of first stage flight, came with the depletion of the CCBs propellant, about four minutes and 27.2 seconds after launch. Six seconds later the CCB separated from the Centaur, which then ignited ten seconds after separation to begin the first of two burns.

The 462-second Centaur first burn concluded with Main Engine Cutoff 1 (MECO-1), injecting the vehicle into a low-Earth parking orbit.
Following MECO-1, the Centaur and spacecraft (SC) entered an 8.4-minute coast period. Based on a guidance-calculated start time, the Centaur was re-started (MES-2) then steered into an intermediate transfer orbit. The second Centaur burn duration was 361 seconds and concluded with Main Engine Cutoff (MECO-2), initiated by guidance command once the targeted orbital parameters were achieved.

The Centaur and spacecraft then entered a 2.5-hour coast period. Based on a guidance-calculated start time, the Centaur was re-started (MES-3) and then steered into the spacecraft separation transfer orbit. The third Centaur burn duration was just 54 seconds and concluded with Main Engine Cutoff (MECO-3), initiated by guidance command once the targeted orbital parameters were achieved.

Spacecraft separation was initiated 219 seconds after MECO-3, at 3 hours, 1 minute, 23.2 seconds after liftoff.

Also a major part of placing the satellite into space were the five Aerojet AJ60 Solid Rocket Boosters (SRBs), which increased the launch thrust of ULA’s Atlas V rocket by more than 1.9 million pounds at igniton.

All Atlas V launches requiring extra boost performance have flown Aerojet-produced SRBs. These motors have demonstrated a 100 percent success record in flight, having flown 15 missions over the past 10 years with vehicle configurations ranging from one to five SRBs.

Eight Aerojet retro rockets will also assist with the Atlas Centaur separation from the launch vehicle approximately 4.5 minutes into flight. In addition, 12 Aerojet monopropellant (hydrazine) thrusters on the Atlas V Centaur upper stage provided roll, pitch and yaw control as well as settling burns for the upper stage main engine.

Once separated from the launch vehicle, MUOS used 12 Aerojet 0.2 lbf and six Aerojet 5 lbf thrusters for in-flight maneuvers and final de-orbit.

Aerojet manufactured the Atlas V Solid Rocket Boosters at its Sacramento, Calif. facility. The retro rockets were designed and developed by Aerojet in Gainesville, Va. and manufactured in Redmond, Wash.

(Images via ULA, NASA and L2 Historical).

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