Atlas-Centaur

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Atlas-Centaur
Surveyor 1 launch.jpg
An Atlas-Centaur launching Surveyor 1
Function Expendable launch system
Manufacturer Convair
General Dynamics
Country of origin United States
Launch history
Status Retired
Launch sites LC-36, Cape Canaveral and Vandenberg Space Launch Complex-3 East
Total launches 197
Successes 181
Failures 13
Partial failures 3
First flight 8 May 1962
Last flight 31 August 2004

The Atlas-Centaur was an American expendable launch system derived from the SM-65 Atlas D missile. Launches were conducted from Launch Complex 36 at Cape Canaveral Air Force Station, Florida.

Early development and testing[edit]

Convair, the manufacturer of the Atlas, developed the Centaur upper stage specifically for that booster, sharing its inflated balloon skin. It was also the first production rocket stage to utilize liquid hydrogen and liquid oxygen as propellant. Despite high performance, LH2 nonetheless had problems because it had to be chilled at extremely low temperatures (lower than LOX) and its light molecular density meant that large fuel tanks were needed.

The first attempt at using a LH2/LOX-fueled engine was the Air Force's top-secret Lockheed CL-400 Suntan reconnaissance aircraft program in the mid-1950s, but it was judged too unsafe, expensive, and impractical for that purpose. However, the progress made during the aborted venture was picked up by Convair and others for rocket stage use.

Convair developed a specially-enhanced version of the Atlas D vehicle for mating with Centaur stages; the Atlas's engines were upgraded and the structure reinforced for the large upper stage, along with elongated fuel tanks. The first Atlas-Centaur, Vehicle F-1, arrived at Cape Canaveral in October 1961 and was erected at the newly completed LC-36A, a pad built specifically for A/C flights. However, technical problems and other delays caused it to sit there for 7 months. The mission at last got under way on 8 May 1962. All went well until about T+53 seconds when the Centaur stage ruptured and disintegrated, taking the Atlas with it in a matter of seconds.

The failure was determined to be caused by an insulation panel that ripped off the Centaur during ascent, causing the LH2 tank to overheat and eventually explode. As the liquid hydrogen spilled down the side of the launch vehicle, it ignited on contact with the Atlas's engine exhaust, leading to the complete destruction of the launch vehicle. The panel had been meant to jettison at 50 miles up when the air was thinner, but the mechanism holding it in place was designed inadequately and led to premature separation. Testing was suspended while efforts were made to correct the Centaur's design flaws. A Congressional investigation in June called the overall management of the Centaur program "weak" and Wernher von Braun recommended that it be cancelled in favor of a Saturn I with an Agena upper stage for planetary missions. In addition, the production Centaur stage had less lift capacity than originally planned, leading to ARPA cancelling Project Advent. NASA transferred Centaur development from MSFC to the Lewis Center in Ohio where a team headed by Abe Silverstein worked to correct the insulation panel problems and various other design flaws.[1]

Meanwhile, the Department of Defense had settled on the Titan family for its heavy lift launching needs and so the Atlas-Centaur would remain a civilian launch vehicle used by NASA to fly scientific and commercial payloads.

More than a year later, the second test took place a few days after President Kennedy's assassination. The redesigned Centaur stage functioned without any problems, reaching a low Earth orbit, firing its engine again, and moving to a geosynchronous orbit.

Flight number three, which carried a dummy Surveyor probe, in June 1964 was a partial success. The Centaur reached orbit, but could not be restarted due to a fuel leak. Flight four (December 1964) was completely successful.

The 5th flight on 2 March 1965 proved a complete disaster as the Atlas's fuel prevalves accidentally snapped shut one second after liftoff, causing the booster to fall back onto LC-36A in the biggest pad explosion ever seen at Cape Canaveral. As a result, NASA was forced to finish work on LC-36B, constructed as a backup pad, but abandoned when it was 90% completed.[2]The accident was found to be the result of an improperly installed pressure transducer that sent a signal to close the prevalves. It also marked the first failure of an Atlas in a space launch since Midas 8 in May 1963, a new record at the time of 26 consecutive flights with only malfunctions of the upper stages or payload.

Ten more Atlas-Centaur failures occurred, but most of them were high altitude events that occurred late in the launch. There were two exceptions. The first was the attempted launch of an Intelsat communications satellite on AC-43 on 28 September 1977. Shortly after liftoff, abnormal temperatures were detected in the Atlas's engine compartment and continued to rise as the booster ascended. At T+33 seconds, a fire broke out, causing control of the vehicle to gradually fail. At T+55 seconds, the sustainer engine shut down and the Atlas pitched over, causing the entire launch vehicle to disintegrate from structural stress. The payload fairing and satellite were stripped from the booster, followed by the Atlas breaking in half and exploding. The Centaur was ejected and flew free until Range Safety issued the destruct command at T+60 seconds. NASA and Air Force officials, already busy investigating the launch failure of a Delta booster three weeks earlier, dredged the Atlas's engines from the ocean floor and sent them to Convair for examination. It was concluded that a gas generator leak caused by improper brazing of a pipe led to overheating and fire in the boattail of the Atlas. The pipe also suffered corrosion from six years of sitting in a warehouse in the salty air along the Florida coast (the Atlas had been delivered to Cape Canaveral back in 1971 but kept in storage for an extended period of time) and the damage was in an area not visible during preflight examination.

The second involved the launch of a Navy FLTSATCOM satellite in March 1987. Weather conditions were extremely poor that day, with thick clouds and heavy precipitation. Although engineers objected to launching, the NASA program directors gave the go-ahead anyway. The Atlas disappeared into the cloud cover shortly after liftoff and was struck by a lightning bolt. This had the effect of altering a single word in the guidance computer, causing the vehicle to pitch sharply downward and break apart from structural stress. Range Safety issued the destruct command, but there was no evidence that the booster ever received it. Debris rained out of the clouds onto the pad area. This accident was the culmination in the string of disasters that had befallen the US space program since the Titan 34D failure of August 1985 and caused significant reappraisals of weather guidelines at Cape Canaveral.

With the retirement of the Agena stage in 1978, all Atlases flown from that point onward were paired with Centaurs except for a few military flights involving decommissioned Atlas E/F missiles.

Originally designed and built by Convair Division of General Dynamics in San Diego, California, production of Atlas Centaurs at Convair ended in 1995 but was resumed at Lockheed-Martin in Colorado. The list of Atlas Centaur ID numbers began with AC-1 launched on 8 May 1962 and ended with the last Atlas III (Centaur), AC-206, launched on 3 February 2005.

The Rocketdyne-powered Atlas-Centaur was sometimes referred to as a 21/2 stage launch vehicle because the Atlas first stage (in most cases) jettisoned the twin-thrust-chamber booster engine prior to the completion of the first stage burn. Atlas Centaurs with a Rocketdyne-powered first stage were used for 167 launches between 1962 and 2004 by which time they had been superseded by Atlas Vs with a new first stage powered by a much more powerful Russian RD-180 engine. (Atlas Vs are not generally referred to as "Atlas Centaurs" and do not share the AC- serial numbers of the original Atlas Centaurs that had the Rocketdyne-powered first stages.)

Initially, a modified Atlas D, designated LV-3C, was used as the first stage[3] This was quickly replaced by SLV-3C, and later the SLV-3D, both derived from the standard Atlas SLV-3 rocket. Two spaceflights, with the Pioneer 10 and Pioneer 11 space probes to Jupiter, Saturn and exiting the Solar System, used a spin-stabilized "Star-37E" solid propellant final stage weighing 2473 pounds and contributing 8000 mph to the velocities of the spacecraft.[4]

Variants[edit]

Name First launch Last launch Launches Successes Failures Partial failures Remarks
Atlas LV-3C Centaur-A 1962-05-08 1 0 1 0
Atlas LV-3C Centaur-B 1963-11-27 1 1 0 0
Atlas LV-3C Centaur-C 1964-06-30 1965-03-03 3 0 2 1
Atlas LV-3C Centaur-D 1965-08-11 1967-07-14 7 7 0 0
Atlas SLV-3C Centaur-D 1967-09-08 1972-08-21 17 14 3 0 One flight with Star-37E upper stage
Atlas SLV-3D Centaur-D1A 1973-04-06 1975-05-22 6 5 1 0 One flight with Star-37E upper stage
Atlas SLV-3D Centaur-D1AR 1975-09-26 1983-05-19 26 24 1 1
Designations for later model Atlas Centaurs
Atlas G 1984-06-09 1989-09-25 7 5 2 0 (Atlas G Centaur-D1AR)
Atlas I 1990-07-25 1997-04-25 11 8 3 0
Atlas IIA/IIAS 1991-12-07 2004-08-31 63 63 0 0
Designations for RD-180 powered Atlases with Centaur 2nd stage
Atlas III 2000-05-24 2005-02-03 6 6 0 0
Atlas V 2002-08-21 Active 49 48 0 1

References[edit]