The Atlas Space-Launch Vehicle and Its Upper Stages, 1958-90

Even before it began service as a missile, the Atlas had started to function as a launch vehicle. In December 1958, an entire Atlas (less two jettisoned booster engines) went into orbit carrying a re­peater satellite in Project Score. Then, simultaneously with their role in Project Mercury, modified Atlas missiles served as space – launch vehicles for both the air force and NASA in a variety of missions. The basic Atlas was standardized, uprated, lengthened, and otherwise modified in a variety of configurations, often indi­vidually tailored for specific missions. Engineers mated the vehicle with a number of different upper stages, of which the Agena and Centaur were the best known and most important. In these various configurations, Atlas space boosters launched satellites and space­craft for such programs as Samos, Midas, Ranger, Mariner, Pioneer, International Telecommunications Satellite Consortium (Intelsat), the Fleet Satellite Communications System (FLTSATCOM), the Defense Meteorological Satellite Program, and the Navstar Global Positioning System. Following the end of the period covered in this book, some Atlases even used strap-on solid motors to supplement their thrust at liftoff.33

After initial failures of three Atlas-Ables in 1959-60, Atlas-Agena 62 had a number of problems but became a successful launch combi – Chapter 2 nation. From February 26, 1960, until June 27, 1978, Atlas-Agenas flew approximately 110 missions, many of them classified. Mean­while, in 1962 NASA urged the air force to upgrade the Atlas D basic launch vehicle to a standardized launch configuration known as Space Launch Vehicle 3 (SLV-3), which was much more reliable than the Atlas D (96 versus 81 percent successful). A further up­grade after 1965 known as SLV-3A featured longer tanks, allowing heavier payloads in conjunction with other modifications. Because of the classified nature of many Agena missions, precise and reliable

statistics are not available, but by May 1979, on Thor, Atlas, and Titan boosters, Agena had proved itself to be a workhorse of space, achieving a reported success rate of higher than 93 percent.34

With the exception of Agena, most of the upper stages used with Atlas were derivatives from other programs. The Centaur, however, was a derivative, in a sense, of Atlas in that it used the steel-balloon tank structure envisioned by Charlie Bossart and developed for the Atlas missile. Adapting that structure to the liquid-hydrogen fuel used on the Centaur proved to be a major challenge, however. It required a lot of engineering changes when problems occurred, a major reorganization of the way Centaur was managed, and a great deal of testing. But after initial delays, it worked well.35

If Agena was the workhorse of space, Centaur was the Clydes­dale. Its powerful engines enabled it to carry heavier payloads into orbit or farther into space than Agena could manage. The Centaur could do this because it burned liquid hydrogen as well as liquid oxygen. Hydrogen offered more thrust per pound of fuel burned per second than any other chemical propellant then available—about 35 to 40 percent more than RP-1 (kerosene) when burned with liq­uid oxygen.36

This added performance allowed various versions of Atlas – Centaur to support such NASA missions as landing on the lunar surface in the Surveyor project and orbiting High-Energy Astron­omy Observatories, as well as placing 35 communications satel­lites into orbit through 1989. As with other upper stages flying on Atlas vehicles, not all of the Centaur missions were successful, but most were.37

The intellectual push for Centaur came from Convair Division of General Dynamics engineer Krafft Ehricke, who had worked for von Braun at Peenemunde and Huntsville and for Bell Aircraft be­fore moving to Convair. When General Dynamics managers asked him to design an upper stage for Atlas, he and some other engineers, including Bossart, decided that liquid hydrogen and liquid oxygen were the propellants they needed. Aware to some degree that liquid hydrogen’s very low density, extremely cold boiling point (-423°F), low surface tension, and wide range of flammability made it unusu­ally difficult to work with, Ehricke faced funding limitations under an air force contract that precluded performing as many tests as the propellant required—an important restriction on normal rocket­engineering practice.38

This, among other issues, prevented Convair engineers from dis­covering problems occasioned by liquid hydrogen’s unique properties as early as they otherwise might have done, necessitating redesign.

Other problems arose with Centaur engines, designed by Pratt & Whitney Division of United Aircraft Corporation. The extreme cold of liquid hydrogen required completely new design features, includ­ing the use of aluminum coated with Teflon in place of rubber gas­kets to seal pipe joints. Despite such problems plus burnthroughs of the combustion chamber that necessitated redesigns, Pratt & Whit­ney engineers conducted a successful engine run in September 1959, less than a year from the date of the initial contracts with their com­pany and Convair.39

However, explosions in engines in late 1960-early 1961 revealed other problems. One of these required an adjustment to the method of feeding the hydrogen to the combustion chamber. Because of such difficulties and resultant delays, an Atlas-Centaur did not launch on a test flight until May 8, 1962, 15 months later than planned. At the point of maximum dynamic pressure, 54.7 seconds into the launch, an explosion occurred as the liquid-hydrogen tank split open. Engineers did not discover the real cause of the problem until five years later, but meanwhile the delays and problems resulted in a complete reorganization of the Centaur program to provide better control and coordination. Funding also improved.40

Solutions to further problems and programmatic changes fol­lowed, but finally, on May 30, 1966, an Atlas-Centaur successfully launched Surveyor 1 to the Moon on the first operational Atlas – Centaur flight. Atlas-Centaur performed satisfactorily on all of the Surveyor launches, although two of the spacecraft had problems. But five of the seven missions were successful, providing more than 87,000 photographs and much scientific information valuable both for Apollo landings and for lunar studies. On Surveyors 5-7 the At­lases used longer tanks with greater propellant volumes and pay­load capacity than the earlier versions. With the longer tanks, the weight of payload that the Atlas-Centaur combination could place in 300-nautical-mile orbit rose from 8,500 pounds on the shorter version to 9,100 pounds.41

64 The longer-tank Atlas (SLV-3C) and the original Centaur (known Chapter 2 as Centaur D) launched on March 2, 1972, with a Delta third-stage solid-propellant motor, the Thiokol TE-M-364-4 (Star 37E), on the spectacular Pioneer 10 mission that was NASA’s first to the outer planets and the first to reach escape velocity from the solar system. Well before this launch, NASA, which had taken over the program from the air force, had decided to upgrade the Centaur with an im­proved guidance/control computer. The new computer allowed General Dynamics to simplify the Atlas to the SLV-3D configura­tion by removing the autopilot, programming, and telemetry units

FIG. 2.7 An Atlas – Centaur launch vehicle with the Mariner 9 space probe undergoing radio­frequency interference tests at Kennedy Space Center in 1971. (Photo courtesy of NASA)

from the earlier, long-tank SLV-3C and having the Centaur perform those functions. The new Centaur had two configurations, the D-1A for use with Atlas and the D-1T for use with Titan space-launch vehicles. The differences between the two configurations involved details of external insulation, payload-fairing diameter, battery ca­pacity, and the like.42

The first use of the Centaur D-1A and SLV-3D was on the launch of Pioneer 11, which had the same mission as Pioneer 10 plus making detailed observations of Saturn and its rings. As on Pioneer 10, the mission also employed the Star 37 motor in a third stage. Launched on April 5, 1973, Pioneer 11 returned much data about Saturn, in­cluding discoveries of Saturn’s 11th moon and two new rings. Be­tween 1973 and May 19, 1983, 32 SLV-3Ds launched with Centaur

FIG. 2.8

Launch of a Titan-Centaur vehicle from Cape Canaveral Air Force Station, Febru­ary 11, 1974. The two solid – rocket motors and the core stages of the Titan appear below the Centaur upper stage. (Photo courtesy of NASA)

D-1A upper stages. With the first launch of the Intelsat У with more relay capacity (and weight) on December 6, 1980, the Centaur be­gan to use engines that were adjusted to increase their thrust. Of the 66 total 32 SLV-3D/D-1A (and the slightly modified D-1AR) launches, Chapter 2 only 2 failed. This marked a 93.75 percent success rate, with no fail­ures caused by the Centaur stage.43

During the early 1980s, General Dynamics and Pratt & Whit­ney converted to new versions of Atlas and Centaur. The Atlas G was 81 inches longer than the SLV-3D because of additions to the lengths of the propellant tanks. It developed 438,000 pounds of thrust. Pratt & Whitney made several changes to the Centaur. The first Atlas G-Centaur launched on June 9, 1984, attempting to place an Intelsat У into orbit. It did so, but the orbit was not the intended

one and was unusable for communications purposes. After a modi­fication to fix the problem, there were four successes and one failure (caused by a lightning strike). Then, on September 25, 1989, an At­las G-Centaur launched the 5,100-pound FLTSATCOM F-8 satellite into geosynchronous transfer orbit. This was the last in a series of such navy ultra-high-frequency satellites, part of a worldwide com­munications system for the DoD.44

Meanwhile, forces had been building for commercializing launch- vehicle services. The air force had become unhappy with the idea, promoted by NASA, that all DoD payloads should be transported on the Space Shuttles instead of expendable launch vehicles. There was already competition from the Ariane launch vehicle in Europe, with prospects that other countries would sell launch-vehicle ser­vices to communications-satellite purveyors and other users. On January 28, 1986, the explosion of the shuttle Challenger grounded the remaining shuttles for more than two years. Early in 1987, General Dynamics announced that it would sell Atlas-Centaur as a commercial launch vehicle. NASA then signed a commercial con­tract with the company. General Dynamics decided to designate the commercial vehicles with Roman numerals, the first being Atlas I. All would have Centaur upper stages. On July 25, 1990, the first Atlas I successfully launched the joint NASA/Air Force Combined Release and Radiation Effects Satellite into a highly elliptical geo­synchronous transfer orbit.45

Through this launch, the Centaur had had a 95 percent success rate on 76 flights. This included 42 successes in a row for Centaur D-1 and D-1A between 1971 and 1984. The Centaur had led to the use of liquid-hydrogen technology on both upper stages of the Saturn launch vehicle and in the space shuttle main engines (SSMEs). It had thus made major contributions to U. S. launch-vehicle technology.46

Partway through the history of Centaur and the various Atlas models used to launch it, the air force contracted with General Dy­namics, beginning on February 14, 1966, to modify Atlas Es and Fs that had been in storage since their decommissioning as missiles in 1965. The process began with the newer F models. Rocketdyne in­spected each of the MA-3 engines and fixed or replaced any part that failed to meet specifications. In 1969, the rocket division started a more extensive program of refurbishment to ensure that the engines in storage would work when called upon. After two launch failures in 1980-81, Rocketdyne rebuilt the engines at its plant, performing static tests before installing them on a launch vehicle.47

Six Atlas Ds and four Fs joined forces in launching Orbiting Vehicle One (OV-1) spacecraft, beginning with a failed launch on

January 21, 1965, by a D model and ending on August 6, 1971, with the successful launch of OV-1 20 and OV-1 21 by an F model. A number of the Atlas launch vehicles carried multiple OV-1 satel­lites, each of which included an FW-4S solid-propellant rocket motor built by the Chemical Systems Division (CSD) of United Technologies Corporation, the organization that also provided the solid-rocket motors (SRMs) for the Titan III. Although the satellite failed to orbit for a variety of causes on four of the OV-1 launches, the air force’s Aerospace Research Support Program placed 117 space experiments in orbit to study a variety of phenomena.48

An Atlas F successfully launched a radar calibration target and a radiation research payload for the air force’s Space Test Program on October 2, 1972, using the Burner II solid-propellant upper stage that usually paired with the Thor booster. Another solid-propellant upper stage that operated only once with an Atlas E or F was the Pay­load Transfer System (PTS), which used the same basic TE-M-364-4 Thiokol motor as the Stage Vehicle System (SVS), employed mul­tiple times (as a different upper-stage system from PTS) with Atlas Fs and Es. On July 13, 1974, an Atlas F and the PTS successfully launched Navigation Technology Satellite (NTS) 1 to test the first atomic clocks placed in space to confirm their design and opera­tion and provide information about signal propagation to confirm predictions for the Navstar Global Positioning System (GPS). GPS was then in development and destined to become a vital naviga­tional aid, far more sophisticated and accurate than anything that preceded it.49

SVS, built by Fairchild Space and Electronics Company of Ger­mantown, Maryland, used two TE-M-364-4 motors in two upper stages to place NTS-2 and six Navigation Development System (NDS) spacecraft into orbit between June 23, 1977, and April 26, 1980. The NDS-7 launch failed on December 18, 1981, when the Atlas E launch vehicle went out of control. The other seven satel­lites all supported the development of GPS.50

68 The air force used a different upper stage, known as SGS-II, to – Chapter 2 gether with the Atlas E to launch NDS-8 through NDS-11 between July 14, 1983, and October 8, 1985, all four launches being success­ful. McDonnell Douglas Astronautics Company made the upper stage, using two Thiokol TE-M-711-8 (Star 48) motors, also featured on the Payload Assist Module (PAM), which the Space Shuttle and Delta launch vehicle had employed since 1980. Thiokol began de­veloping the motor in 1976. It used the same hydroxy-terminated polybutadiene (HTPB)-based propellant as Thiokol’s Antares III

rocket motor, a third-generation, third-stage propulsion unit for the Scout launch vehicle.51

The Atlas Es and Fs used other upper stages to launch satellites, including one Agena D. On June 26, 1978, an Atlas F—modified to mate with the Agena and to carry the Seasat-A oceanographic satellite—placed its payload into orbit. The other major upper stage used by the Atlas Es and Fs was the Integrated Spacecraft System (ISS), with a Thiokol TE-M-364-15 motor (Star 37S). In 1977-78, this was the latest in the Star 37 series of motors, also used as an upper stage on the Thor for launching weather satellites. Beginning with a launch of Tiros N from an Atlas F on October 13, 1978, the ISS served as an upper stage for launching the NOAA-6 through NOAA-11 polar orbiting meteorological satellites plus a number of DMSP satellites. The only failure in the series was NOAA-B on May 29, 1980.52

In February 1983, the air force began operating a derivative of the SLV-3D known as the Atlas H. It used most of the basic systems on the SLV but employed GE radio-inertial guidance. The particular solid-propellant upper stage used with the Atlas H and previous At­las Es and Fs to launch the White Cloud Naval Ocean Surveillance System (NOSS) satellites was classified. The White Cloud NOSS satellites provided the DoD (primarily the navy) with ocean surveil­lance. Overall, the Atlas E and F launch vehicles had only 4 failures in 41 launches by the end of 1990, yielding a success rate of more than 90 percent. All 5 launches with the Atlas H were successful.53

Conceived as a missile, the Atlas became a successful and ver­satile launch vehicle, mated with a great variety of upper stages. Featuring a controversial but “brilliant, innovative, and yet simple" concept (the steel-balloon tank design), both the Atlas and the Cen­taur proved to be flexible and effective. With commercialization, the Atlas and the Centaur continued to provide launch-vehicle ser­vices beyond the period of this book and into the 21st century. The Centaur proved to be especially difficult to develop because of the peculiar properties of liquid hydrogen. But it was also hampered by initial funding arrangements and other avoidable problems. As with many rocket programs, engineers found that the existing fund of knowledge was inadequate to predict all of the problems that would occur in developing and launching an extraordinarily com­plex machine. Unforeseen problems continued into the 1990s, and engineers had to relearn the lesson that continual and sophisticated testing was the price of success, even if it did not always preclude unanticipated failures.54