Category THE DEVELOPMENT. OF PROPULSION. TECHNOLOGY. FOR U. S.. SPACE-LAUNCH. VEHICLES,. 1926-1991

28

Chapter 1 In the meantime, two other rocket programs had contributed to launch-vehicle technology. The Viking sounding rocket made its own contributions and was also, in a sense, the starting point for the second U. S. launch vehicle, Vanguard. Although often regarded

as a failure, Vanguard did launch three satellites. Together with Vi­king, it pioneered use of gimbals for steering in large rockets. In addition, its upper stages contributed significantly to the evolution of launch-vehicle technology.55

Milton W. Rosen, who was responsible for the development and firing of the Viking rockets, went on to become technical director of Project Vanguard and then director of launch vehicles and pro­pulsion in the Office of Manned Space Flight Programs for NASA. Rosen had been working at the Naval Research Laboratory (NRL) during World War II and suggested that his group implement an idea of G. Edward Pendray of the American Rocket Society to use rock­ets for exploration of the upper atmosphere. To prepare himself, he spent about eight months working at JPL in 1946-47. Drawing on what he learned there, some conversations with Wernher von Braun, and other sources, Rosen oversaw the design and testing of a totally new rocket, the Viking,56 another example of information sharing that contributed to rocket development.

Reaction Motors designed the engine, drawing on its own experi­ence as well as data from the V-2, with the Glenn L. Martin Com-

pany designing and building the overall rocket. Martin engineers conceived Viking’s innovative gimballing engine. But to make it work, the Martin staff had to develop careful adjustments, using the advice of Albert C. Hall, who wrote his Ph. D. thesis at MIT on negative feedback. A successful program with 12 launches, Viking prepared Rosen and the Martin engineers for Vanguard.57

Developed under the auspices of the NRL to launch a satellite for the United States during the International Geophysical Year (July 1, 1957, to December 31, 1958), Vanguard became a NASA respon­sibility near the end of the project (on November 30, 1958). NRL appointed astronomer John Hagen as overall director, with Rosen becoming technical director. The navy contracted with Martin on September 23, 1955, to design, build, and test Vanguard in prepara­tion for flight. Martin, in turn, contracted with GE on October 1, 1955, to develop the first-stage engine and with Aerojet on Novem­ber 14, 1955, for the second-stage engine. There were two contracts for alternative versions of a stage-three solid-propellant motor. One in February 1956 went to the Grand Central Rocket Company, with a second going to the Allegany Ballistics Laboratory (ABL), operated by the Hercules Powder Company, Inc., in West Virginia.58

Hampered by a low priority, which caused Martin to split up the experienced Viking team between it and the higher-priority Titan I missile (for which Martin had also contracted), Rosen and his Van­guard engineers had other difficulties, including substantially new technology for all three stages. Contributions from a wide variety of organizations were necessary to develop the three stages. Prob­lems with the first – and second-stage engines caused delays in de­velopment and testing; Sputnik and the cold-war desire to catch up with the Soviets led to unexpected publicity for the first test launch, in which both the problematical second stage and the com­plete guidance/control system were operational. Although three previous tests had been successful, this attempted launch with a small satellite onboard was a spectacular failure. The press did not react charitably but called the vehicle “Kaputnik, Stayputnik, or Flopnik" while Americans, in one historian’s words, “swilled the Sputnik Cocktail: two parts vodka, one part sour grapes."59

Between March 17, 1958, and September 18, 1959, Vanguard launch vehicles orbited three satellites in nine attempts, the last 30 of which used the solid third stage developed at ABL. This hardly Chapter 1 constituted a successful record, but Vanguard nevertheless made important technological contributions. The air force’s Thor-Able launch vehicle used the Thor intermediate-range ballistic missile as a first stage plus modified Vanguard second and third stages, the last

being the original third stage developed by Grand Central Rocket Company. The air force also learned from the problems Vanguard had experienced and thereby avoided them, illustrating a transfer of information from a navy project to a competing military service. Despite interservice rivalries, the federal government encouraged this sort of transfer, limiting the rights of individual contractors to protect discoveries made under federal contract in order to facilitate technology transfer. But the emphasis in the literature on competi­tion rather than cooperation often masks the importance of trans­ferred data.

In January 1959, Rosen proposed to Abe Silverstein, NASA’s di­rector of Space Flight Programs, that the Thor-Able be evolved into what became the Delta launch vehicle. Rosen suggested designing

more reliable control electronics than used on Vanguard, substitu­tion of a stainless-steel combustion chamber for the aluminum one used in the second stage of Vanguard, and incorporation of Bell Tele­phone Laboratories’ radio guidance system then being installed in the Titan ballistic missile, among other changes. Silverstein com­missioned Rosen to develop the Delta launch vehicle along those lines, and it became highly successful. A variant of the ABL third stage for Vanguard, known as the Altair I (X248 A5), became a third stage for Delta and a fourth stage for the Scout launch vehicle. A fol­low-on, also built by Hercules Powder Company (at ABL), became the third stage for Minuteman I. And a fiberglass casing for the ABL third stage was also a feature in these later stages and found many other uses in missiles and rockets. In these and other ways, Van­guard made important contributions to launch-vehicle technology and deserves a better reputation than it has heretofore enjoyed.60

When the von Braun group, relocated to Redstone Arsenal, began de­veloping the Redstone missile, it chose North American Aviation’s XLR43-NA-1 liquid-propellant rocket engine, developed for the

air force’s Navaho missile, as the basis for the Redstone propul­sion unit. A letter contract with NAA on March 27, 1951, provided 120 days of research and development to make that engine comply with the ordnance corps’ specifications and to deliver a mockup and two prototypes of the engine (then to be designated NAA 75-110, referring to 75,000 pounds of thrust operating for 110 seconds). Sup­plemental contracts in 1952 and 1953 increased the number of en­gines to be delivered and called for their improvement. These con­tracts included 19 engines, with subsequent powerplants purchased by the prime contractor, Chrysler, through subcontracts.25

The story of how North American Aviation had initially devel­oped the XLR43-NA-1 illustrates much about the ways launch – vehicle technology developed in the United States. NAA came into existence in 1928 as a holding company for a variety of avia­tion-related firms. It suffered during the Depression after 1929, and General Motors acquired it in 1934, hiring James H. Kindelberger, nicknamed “Dutch," as its president—a pilot in World War I and an engineer who had worked for Donald Douglas before moving to NAA. Described as “a hard-driving bear of a man with a gruff, earthy sense of humor—mostly scatological—[who] ran the kind of flexible operation that smart people loved to work for," he re­organized NAA into a manufacturing firm that built thousands of P-51 Mustangs for the army air forces in World War II, the B-25 Mitchell bomber, and the T-6 Texas trainer. With the more cautious but also visionary John Leland Atwood as his chief engineer, Dutch made NAA one of the principal manufacturers of military aircraft during the conflict, its workforce rising to 90,000 at the height of wartime production before it fell to 5,000 after the end of the war. Atwood became president in 1948, when Dutch rose to chairman of the board and General Motors sold its share of the company. The two managers continued to service the military aircraft market in the much less lucrative postwar climate, when many competitors shifted to commercial airliners.26

Despite the drop in business, NAA had money from wartime production, and Kindelberger hired a top-notch individual to head a research laboratory filled with quality engineers in the fields of elec­tronics, automatic control with gyroscopes, jet propulsion, and mis­siles. He selected William Bollay, a former von Karman student. Fol­lowing receipt of his Ph. D. in aeronautical engineering at Caltech, Bollay had joined the navy in 1941 and been assigned to Annapolis where the Bureau of Aeronautics (BuAer) was working on experimen­tal engines, including the JATOs Robert Truax was developing. At war’s end, Bollay was chief of the Power Plant Development Branch

for BuAer. As such, he was responsible for turbojet engines, and at the time, NAA was developing the FJ-1 Fury, destined to become one of the navy’s first jet fighters. Bollay came to work for NAA during the fall of 1945 in a building near the Los Angeles airport, where he would create what became the Aerophysics Laboratory.27

On October 31, 1945, the army air forces’ Air Technical Service Command released an invitation for leading aircraft firms to bid on studies of guided missiles. NAA proposed a surface-to-surface rocket with a range of 175-500 miles that it designated Navaho (for North American vehicle alcohol [plus] hydrogen peroxide and oxygen). The proposal resulted in a contract on March 29, 1946, for MX-770, the designation of the experimental missile. Other con­tracts for the missile followed. The Navaho ultimately evolved into a complicated project before its cancellation in 1958. It included a rocket booster and ramjet engines with a lot of legacies passed on to aerospace technology, but for the Redstone, only the rocket engine that evolved to become NAA 75-10 is relevant.28

NAA did not originally intend to manufacture the engine. As an early employee of the firm recalled, the company was “forced into the engine business—we had the prime contract for Navaho and couldn’t find a subcontractor who would tackle the engine for it, so we decided to build it for ourselves." NAA’s plans for developing the engine began with the German V-2 as a model but soon led to “an en­tirely new design rated at 75,000 pounds thrust" (as compared with about 56,000 for the V-2). In the spring of 1946, Bollay and his as­sociates had visited Fort Bliss to conduct numerous interviews with many of the Germans who had worked on the V-2, including von Braun, Walter Riedel, and Konrad Dannenberg. By the middle of June 118 1946, Bollay’s team began redesigning the V-2 engine with the aid of

Chapter 3 drawings and other documents obtained from the Peenemunde files. In September, the firm secured the loan of a complete V-2.29

The NAA engineers also conferred with JPL, GE, Bell Aircraft Corp., the National Advisory Committee for Aeronautics’ labora­tory in Cleveland (later Lewis Research Center), the Naval Ord­nance Test Station at Inyokern, and Aerojet about various aspects of rocket technology.30 Thus, the heritage of the Redstone engine went well beyond what NAA had learned from the V-2.

By October 1947, the Astrophysics Laboratory had grown to more than 500 people. This necessitated a move to a plant in nearby Downey in July 1948. By the following fall, the engineers had taken apart and reconditioned the V-2 engine, examining all of its parts carefully. The team had also built the XLR41-NA-1, a rocket engine like the V-2 but using U. S. manufacturing techniques and design

standards, some improved materials, and various replacements of small components. Then, by early 1950, the team had redesigned the engine to a cylindrical shape, replacing the spherical contour of the V-2, which produced efficient propulsion but was hard to form and weld. Bollay’s people kept the propellants for the V-2 (75 per­cent alcohol and liquid oxygen). But in place of the 18-pot design of the V-2, which had avoided combustion instability, NAA engineers developed two types of flat injectors—a doublet version in which the alcohol and liquid oxygen impinged on one another to achieve mixing, and a triplet, wherein two streams of alcohol met one of liquid oxygen. They tested subscale versions of these injectors in small engines fired in the parking lot. Their methodology was purely empirical, showing the undeveloped state of analytical capabilities in this period. They, too, encountered combustion instability. But they found that the triplet type of injector provided slightly higher performance due to improved mixing of the propellants.31

Meanwhile, NAA searched for a place where it could test larger engines. It found one in the Santa Susana Mountains northwest of Los Angeles in Ventura County, California. The firm obtained a permit in November 1947 for engine testing there. It leased the land and built rocket-testing facilities in the rugged area where Tom Mix had starred in western movies, using company funds for about a third of the initial costs and air force funding for the rest. By early 1950, the first full-scale static test on XLR43-NA-1 took place.32

Full-scale engine tests with the triplet injector revealed severe combustion instability, so engineers reverted to the doublet injec­tor that partly relieved the problem. Although the reduced combus­tion instability came at a cost of lower performance, the XLR43- NA-1 still outperformed the V-2, enabling use of the simpler and less bulky cylindrical combustion chamber that looked a bit like a farmer’s milk container with a bottom that flared out at the nozzle. The engine delivered 75,000 pounds of thrust at a specific impulse 8 percent better than that of the V-2. Further enhancing perfor­mance was a 40 percent reduction in weight. The new engine re­tained the double-wall construction of the V-2 with regenerative and film cooling. Tinkering with the placement of the igniter plus injection of liquid oxygen ahead of the fuel solved the problem with combustion instability. The engine used hydrogen peroxide – powered turbopumps like those on the V-2 except that they were smaller and lighter. It also provided higher combustion pressures.

Like the V-2, the XLR43-NA-1 began ignition with a preliminary stage in which the propellants flowed at only some 10 to 15 percent of full combustion rates. If observation suggested that the engine

was burning satisfactorily, technicians allowed it to transition to so-called main stage combustion. To enable the engineers to ob­serve ignition and early combustion, von Braun, who was working with the NAA engineers by this time, suggested rolling a small, surplus army tank to the rear of the nozzle. By looking at the com­bustion process from inside the tank, engineers could see what was happening while protected from the hot exhaust, enabling them to reduce problems with rough starts by changing sequencing and im­proving purges of the system in a trial-and-error process. Through such methods, the XLR43-NA-1 became the basis for the Redstone missile’s NAA 75-110.33

Having supervised the development of this engine and the ex­pansion of the Aerophysics Laboratory to about 2,400 people on staff, Bollay left North American in 1951 to set up his own com­pany, which built army battlefield missiles. In 1949, he had hired Samuel K. Hoffman, who had served as a design engineer for Fair­child Aircraft Company, Lycoming Manufacturing Company, and the Allison Division of General Motors. He then worked his way up from project engineer with the Lycoming Division of the Aviation Corporation to become its chief engineer, responsible for the design, development, and production of aircraft engines. In 1945 he became a professor of aeronautical engineering at his alma mater, Penn State University, the position he left in 1949 to head the Propulsion Sec­tion of what became NAA’s Aerophysics Laboratory.

As Hoffman later recalled, Bollay had hired him for his practi­cal experience building engines, something the many brilliant but young engineers working in the laboratory did not possess. Hoffman succeeded Bollay in 1951. Meanwhile, he and Bollay had overseen 120 the development of a significantly new rocket engine. Although it Chapter 3 had used the V-2 as a starting point and bore considerable resem­blance to the cylindrical engine developed at Peenemunde before the end of the war, it had advanced substantially beyond the Ger­man technology and provided greater thrust with a smaller weight penalty. Also, it marked the beginnings of another rocket-engine manufacturing organization that went on to become the Rocket- dyne Division of NAA in 1955, destined to become the foremost producer of rocket engines in the country.34

Development of the NAA 75-110 engine for the Redstone mis­sile did not stop in 1951. Improvements continued through seven engine types, designated A-1 through A-7. Each of these engines had fundamentally the same operational features, designed for identical performance parameters. The engines were interchangeable, requir­ing only minor modifications in their tubing for them to be installed

in the Redstone missile. All of them except A-5 flew on Redstone tests between August 20, 1953, and November 5, 1958, with A-1 be­ing the prototype and A-2, for example, having an inducer added to the liquid-oxygen pump to prevent cavitation (bubbles forming in the oxidizer, causing lower performance of the turbopump and even damage to hardware as the bubbles imploded).35

During the course of these improvements, the Chrysler Corpo­ration had become the prime contractor for the Redstone missile, receiving a letter contract in October 1952 and a more formal one on June 19, 1953. Thereafter, it and NAA had undertaken a product – improvement program to increase engine reliability and reproduc­ibility. A comparison of the numbers of components in the pneu­matic control system for the A-1 and A-7 engines, used respectively in 1953 and 1958, illustrates the results (see table 3.1).36

Obviously, the fewer components needed to operate a complex system like the engine for a large missile, the fewer things there are that can go wrong in its launching and flight. Thus, this threefold reduction in components on a single system for the engine must have contributed significantly to the reliability of its operation. This was especially true since Rocketdyne engineers (as they be­came after 1955) tested each new component design both in the lab­oratory and in static firings before qualifying it for production. They also simulated operating conditions at extreme temperatures, levels of humidity, dust, and the like, because the Redstone was scheduled for deployment and use by the army in the field. Static engine tests showed reliability higher than 96 percent for the engines.

This was a remarkably high figure, considering that Rocketdyne purchased about half of Redstone engine components (or parts thereof) from outside suppliers; but the parts had to be built to a higher standard than those used in conventional aircraft. The rea­son was that the stresses of an operating rocket engine were greater than those for an airplane. All welds for stressed components had to undergo radiographic inspection to ensure reliability. The army then required a minimum of four static engine tests to prove each new model worked satisfactorily before the service would accept the system. Two of these tests had to last for 15 seconds each, and a third was for the full rated duration. This, presumably, was 110 sec­onds, but according to Chrysler’s publication on the Redstone, the engine ultimately produced 78,000 pounds of thrust for a duration of 117 seconds.37

In the meantime, Thiokol had teamed up with General Electric in the Hermes project to produce a solid-propellant missile (initially

known as the A-2) that was much larger than the Sergeant sounding rocket. It operated on a shoestring budget until canceled, but it still made significant progress in solid-propellant technology.16

The original requirements for the A-2 were to carry a 500-pound warhead to a range as far as 75 nautical miles, but these changed to a payload weighing 1,500 pounds, necessitating a motor with a diameter of 31 inches. Thiokol started developing the motor in May 1950, a point in time that allowed the project to take advantage of work on the Sergeant sounding rocket and of Larry Thackwell’s ex­perience with it. By December 1951, the program had successfully completed a static test of the 31-inch motor. From January 1952 through March 1953, there were 20 more static tests at Redstone Arsenal and four flight tests of the missile at Patrick AFB, Florida.

230 In the process, the missile came to be designated the RV-A-10. The Chapter 6 project encountered unanticipated problems with nozzle erosion and combustion instability that engineers were able to solve.17

The four flight tests achieved a maximum range of 52 miles (on flight one) and a maximum altitude of 195,000 feet (flight two) us­ing a motor case 0.20 inch thick and a propellant grain featuring a star-shaped perforation with broad tips on the star. The propellant was designated TRX-110A. It included 63 percent ammonium per­chlorate by weight as the oxidizer. The propellant took advantage of an air force-sponsored project (MX-105) titled “Improvement of Polysulfide-Perchlorate Propellants" that had begun in 1950 and is­sued a final report (written by Thiokol employees) in May 1951. On test motor number two a propellant designated T13, which con­tained polysulfide LP-33 and ammonium perchlorate, achieved a specific impulse at sea level of more than 195 lbf-sec/lbm at 80°F but also experienced combustion instability. This led to the shift to TRX-110, which had a slightly lower specific impulse but no com­bustion instability.18

Thiokol had arrived at the blunter-tipped star perforation as a re­sult of Thackwell’s experience (at JPL) with the Sergeant test vehi­cle and of photoelastic studies of grains performed at the company’s request by the Armour Institute (later renamed the Illinois Institute of Technology). This, together with a thicker case wall than JPL had used with the Sergeant sounding rocket, eliminated JPL’s prob­lems with cracks and explosions. However, TRX-110 proved not to have enough initial thrust. The solution was to shift the size of the ammonium perchlorate particles from a mixture of coarse and fine pieces to one of consistently fine particles, which yielded not only higher initial thrust but also a more consistent thrust over time—a desirable trait. Meanwhile, the Thiokol-GE team gradually learned

about the thermal environment to which the RV-A-10 nozzles were exposed. Design of the nozzles evolved through subscale and full – scale motor tests employing various materials and techniques for fabrication. The best materials proved to be SAE 1020 steel with carbon inserts, and a roll weld proved superior to casting or forging for producing the nozzle itself.19

Another problem encountered in fabricating the large grain for the RV-A-10 was the appearance of cracks and voids when it was cured at atmospheric pressure, probably the cause of a burnout of the liner on motor number two. The solution proved to be twofold: (1) Thiokol poured the first two mixes of propellant into the motor chamber at a temperature 10°F hotter than normal, with the last mix 10°F cooler than normal; then, (2) Thiokol personnel cured the propellant under 20 pounds per square inch of pressure with a layer of liner material laid over it to prevent air from contacting the grain. Together, these two procedures eliminated the voids and cracks.20

With these advances in the art of producing solid-propellant mo­tors, the RV-A-10 became the first known solid-propellant rocket motor of such a large size—31 inches in diameter and 14 feet, 4 inches long—to be flight tested as of February-March 1953. Among its other firsts were scaling up the mixing and casting of polysulfide propellants to the extent that more than 5,000 pounds of it could be processed in a single day; the routine use of many mixes in a single motor; the use of a tubular igniter rolled into coiled plastic tubing (called a jelly roll) to avoid the requirement for a heavy clo­sure at the nozzle end to aid in ignition; and one of the early uses of jet vanes inserted in the exhaust stream of a large solid-propellant rocket to provide thrust vector control.

As recently as December 1945, the head of the Office of Scientific Research and Development during World War II, Vannevar Bush, had stated, “I don’t think anybody in the world knows how [to build an accurate intercontinental ballistic missile] and I feel confident it will not be done for a long time to come." Many people, even in the rocket field, did not believe that solid-propellant rockets could be efficient enough or of long enough duration to serve as long-range missiles. The RV-A-10 was the first rocket to remove such doubts from at least some people’s minds.21 Arguably, it provided a signifi­cant part of the technological basis for the entire next generation of missiles, from Polaris and Minuteman to the large solid boost­ers for the Titan IIIs and IVs and the Space Shuttle, although many further technological developments would be necessary before they became possible (including significant improvements in propellant performance).

Following Redstone and Vanguard, the Atlas, Thor, and Jupiter mis­siles brought further innovations in rocket technology and became the first stages of launch vehicles themselves, with Atlas and Thor having more significance in this role than Jupiter. All three pro­grams illustrated the roles of interservice and interagency rivalry and cooperation that were both key features of rocket development in the United States. They also showed the continued use of both theory and empiricism in the complex engineering of rocket sys­tems. “It was not one important ‘breakthrough’ that enabled this advance; rather, it was a thousand different refinements, a hundred thousand tests and design modifications, all aimed at the develop­ment of equipment of extraordinary power and reliability," accord­ing to Milton Rosen, writing in 1962.61

Atlas was a much larger effort than Vanguard, and it began to create the infrastructure in talent, knowledge, data, and capability necessary for the maturation of launch-vehicle technology in the decade of the 1960s. However, until the air force became serious about Atlas, that service had lagged behind the army and the navy in the development of purely ballistic missiles.62

The process began in a significant way on January 23, 1951, when 32 the air force awarded the Consolidated Vultee Aircraft Corporation Chapter 1 (Convair) a contract for MX-1593, the project that soon became Atlas. (MX-1593 had been preceded by MX-774B and a number of other air force missile contracts in the late 1940s, with a total of $34 million devoted to missile research in fiscal year 1946, much re-

duced in subsequent years.) But the specifications for the MX-1593 missile changed drastically as technology for nuclear warheads evolved to fit more explosive power into smaller packages. This new technology plus the increased threat from the Soviets provided one condition for greater air force support of Atlas and other bal­listic missiles.

But it also took two heterogeneous engineers to nudge the new­est armed service and the Department of Defense (DoD) in a new direction. One of them was Trevor Gardner, assistant for research and development to Secretary of the Air Force Harold Talbott in the Eisenhower administration. The other key promoter of ballistic missiles was the “brilliant and affable" polymath, John von Neu­mann, who was research professor of mathematics at Princeton’s Institute for Advanced Study and also director of its electronic com­puter project. In 1953, he headed a Nuclear Weapons Panel of the Air Force Scientific Advisory Board, which confirmed beliefs that in the next six to eight years, the United States would have the capability to field a thermonuclear warhead weighing about 1,500 pounds and yielding 1 megaton of explosive force. This was 50 times the yield of the atomic warhead originally planned for the Atlas missile, fit in a much lighter package. This and a report (dated February 1, 1954) for von Neumann’s Teapot Committee set the stage for extraordi­nary air force support for Atlas.63

In May 1954 the air force directed that the Atlas program be­gin an accelerated development schedule, using the service’s high­est priority. The Air Research and Development Command within the air arm created a new organization in Inglewood, California, named the Western Development Division (WDD), and placed Brig. Gen. Bernard A. Schriever in charge. Schriever, who was born in Germany but moved to Texas when his father became a prisoner of war there during World War I, graduated from the Agricultural and Mechanical College of Texas (since 1964, Texas A&M Univer­sity) in 1931 with a degree in architectural engineering. Tall, slen­der, and handsome, the determined young man accepted a reserve commission in the army and completed pilot training, eventu­ally marrying the daughter of Brig. Gen. George Brett of the army air corps in 1938. Placed in charge of the WDD, Schriever in es­sence took over from Gardner and von Neumann the role of het­erogeneous engineer, promoting and developing the Atlas and later missiles.64

Gardner had been intense and abrasive in pushing the develop­ment of missiles. Schriever was generally calm and persuasive. He selected highly competent people for his staff, many of them be-

coming general officers. An extremely hard worker, like von Braun he demanded much of his staff; but unlike von Braun he seemed somewhat aloof to most of them and inconsiderate of their time— frequently late for meetings without even realizing it. Good at plan­ning and organizing, gifted with vision, he was poor at management, often overlooking matters that needed his attention—not surprising because he spent much time flying back and forth to Washington, D. C. His secretary and program managers had to watch carefully over key documents to ensure that he saw and responded to them. One of his early staff members (later a lieutenant general), Otto J. Glasser, said Schriever was “probably the keenest planner of any­body I ever met" but he was “one of the lousiest managers."

Later Lt. Gen. Charles H. Terhune Jr., who became Schriever’s deputy director for technical operations, called his boss a “superb front man" for the organization, “very convincing. . . . He had a lot of people working for him [who] were very good and did their jobs, but Schriever was the one who pulled it all together and represented them in Congress and other places." Glasser added, “He was just superb at. . . laying out the wisdom of his approach so that the Congress wanted to ladle out money to him." Glasser also said he was good at building camaraderie among his staff.65

To facilitate missile development, Schriever received from the air force unusual prerogatives, such as the Gillette Procedures. Designed by Hyde Gillette, a budgetary expert in the office of the secretary of the air force, these served to simplify procedures for managing intercontinental ballistic missiles (ICBMs). Schriever had complained that there were 40 different offices and agencies he had to deal with to get his job done. Approval of his annual develop­ment plans took months to sail through all of these bodies. With the new procedures (granted November 8, 1955), Schriever had to deal with only two ballistic missile committees, one at the secretary – of-defense and the other at the air-force level. Coupled with other arrangements, this gave Schriever unprecedented authority to de­velop missiles.66

Another key element in the management of the ballistic mis­sile effort was the Ramo-Wooldridge Corporation. Simon Ramo and Dean Wooldridge, classmates at Caltech, each had earned a Ph. D. there at age 23. After World War II, they had presided over an 34 electronics team that built fire-control systems for the air force at Chapter 1 Hughes Aircraft. In 1953, they set up their own corporation, with the Thompson Products firm buying 49 percent of the stock. For a variety of reasons, including recommendations of the Teapot Com­mittee, Schriever made Ramo-Wooldridge into a systems engineer-

ing-technical direction contractor to advise his staff on the man­agement of the Atlas program. The air force issued a contract to the firm for this task on January 29, 1955, although it had begun working in May 1954 under letter contract on a study of how to redirect the Atlas program. This unique arrangement with Ramo- Wooldridge caused considerable concern in the industry (especially on the part of Convair) that Ramo-Wooldridge employees would be in an unfair position to use the knowledge they gained to bid on other contracts, although the firm was not supposed to produce hardware for missiles. To ward off such criticism, the firm created a Guided Missile Research Division (GMRD) and kept it separate from other divisions of the firm. Louis Dunn, who had served on the Teapot Committee, became the GMRD director, bringing sev­eral people with him from JPL. This arrangement did not put an end to controversy about Ramo-Wooldridge’s role, so in 1957, GMRD became Space Technology Laboratories (STL), an autonomous divi­sion of the firm, with Ramo as president and Dunn as executive vice president and general manager.67

Some air force officers on Schriever’s staff objected to the con­tract with Ramo-Wooldridge, notably Col. Edward Hall, a propul­sion expert. Hall had nothing good to say about Ramo-Wooldridge (or Schriever), but several engineers at Convair concluded that the firm made a positive contribution to Atlas development.68

The Ramo-Wooldridge staff outnumbered the air force staff at WDD, but the two groups worked together in selecting contrac­tors for components of Atlas and later missiles, overseeing their performance, testing, and analyzing results. For such a large under­taking as Atlas, soon joined by other programs, there needed to be some system to inform managers and allow them to make decisions on problem areas. The WDD, which became the Air Force Ballistic Missile Division on June 1, 1957, developed a management control system to collect information for planning and scheduling.

Schriever and his program directors gathered all of this data in a program control room, located in a concrete vault and kept under guard at all times. At first, hundreds of charts and graphs covered the walls, but WDD soon added digital computers for tracking infor­mation. Although some staff members claimed Schriever used the control room only to impress important visitors, program managers benefited from preparing weekly and monthly reports of status, be­cause they had to verify their accuracy and thereby keep abreast of events. Separate reports from a procurement office the Air Force Air Materiel Command assigned to the WDD on August 15, 1954, pro­vided Schriever an independent check on information from his own

managers. The thousands of milestones—Schriever called them inchstones—in the master schedule kept him and his key manag­ers advised of how development matched planning. All of the infor­mation came together on “Black Saturday" meetings once a month starting in 1955. Here program managers and department heads presented problem areas to Schriever, Ramo, and Brig. Gen. Ben I. Funk, commander of the procurement office. As problems arose, discussion sometimes could resolve them in the course of the meet­ing. If not, a specific person or organization would be assigned to come up with a solution, while the staff of the program control room tracked progress. Sometimes, Ramo brought in outside experts from industry or academia to deal with particularly difficult problems.69

Because the process of developing new missile systems entailed considerable urgency when the Soviet threat was perceived as great and the technology was still far from mature, Schriever and his team used a practice called concurrency that was not new but not routinely practiced in the federal government. Used on the B-29 bomber, the Manhattan Project, and development of nuclear vessels for the U. S. Navy, it involved developing all subsystems and the facilities to test and manufacture them on overlapping schedules; likewise, the systems for operational control and the training sys­tem for the Strategic Air Command, which took over the missiles when they became operational.

Schriever claimed that implementing concurrency was equiva­lent to requiring a car manufacturer to build the automobile and also to construct highways, bridges, and filling stations as well as teach drivers’ education. He argued that concurrency saved money, but this seems doubtful. Each model of the Atlas missile from A to F involved expensive improvements, and the F models were housed in silos. Each time the F-model design changed, the Army Corps of Engineers had to reconfigure the silo. There were 199 engineering change orders for the silos near Lincoln, Nebraska, and these raised the costs from $23 million to more than $50 million dollars—to give one example of costs added by concurrency. What concurrency did achieve was speed of overall development and the assurance that all systems would be available on schedule.70

A further tool in WDD’s management portfolio was parallel de­velopment. To avoid being dependent on a single supplier for a sys – 36 tem, Schriever insisted on parallel contractors for many of them.

Chapter 1 Eventually, when Thor and Titan I came along, the testing program became overwhelming, and Glasser argued that Ramo-Wooldridge just ignored the problem. He went to Schriever, who directed him to come up with a solution. He decided which systems would go on

Atlas, which on Titan and Thor, in the process becoming the deputy for systems management and the Atlas project manager.71

A final component of the management structure for Schriever’s west-coast operation consisted of the nonprofit Aerospace Corpora­tion. It had come into existence on June 4, 1960, as a solution to the problems many people saw in Space Technology Laboratories’ serv­ing as a systems-engineering and technical-direction contractor to the air force while part of Thompson Ramo Wooldridge (later, just TRW), as the company had become following an eventual merger of Ramo-Wooldridge with Thompson Products. STL continued its operations for programs then in existence, but many of its person­nel transferred to the Aerospace Corporation for systems engineer­ing and technical direction of new programs. Further complicat­ing the picture, a reorganization occurred within the air force on April 1, 1961, in which Air Force Systems Command (AFSC) re­placed the Air Research and Development Command. On the same date, within AFSC, the Ballistic Missile Division split into a Ballis­tic Systems Division (BSD), which would retain responsibility for ballistic missiles (and would soon move to Norton Air Force Base [AFB] east of Los Angeles near San Bernardino); and a Space Systems Division (SSD), which moved to El Segundo, much closer to Los Angeles, and obtained responsibility for military space systems and boosters. There would be further reorganizations of the two offices, but whether combined or separated, they oversaw the development of a variety of missiles and launch vehicles, ranging from the Atlas and Thor to Titans I through IV.72

To return specifically to the Atlas program, under the earlier (1946-48) MX-774B project, Convair had developed swiveling of en­gines (a precursor of gimballing); monocoque propellant tanks that were integral to the structure of the rockets and pressurized with nitrogen to provide structural strength with very little weight pen­alty (later evolving into what Convair called a steel balloon); and separable nose cones so that the missile itself did not have to travel with a warhead to the target and thus have to survive the aerody­namic heating from reentering the atmosphere.73

Other innovations followed under the genial leadership of Karel (Charlie) Bossart. Finally, on January 6, 1955, the air force awarded a contract to Convair for the development and production of the Atlas airframe, the integration of other subsystems with the airframe and one another, their assembly and testing. The contractor for the At­las engines was North American Aviation, which built upon earlier research done on the Navaho missile. NAA’s Rocketdyne Division, formed in 1955 to handle the requirements of Navaho, Atlas, and

Redstone, developed one sustainer and two outside booster engines for the Atlas under a so-called stage-and-a-half arrangement, with the boosters discarded after they had done their work. Produced in

1957 and 1958, the early engines ran into failures of systems and components in flight testing that also plagued the Thor and Jupiter engines, which were under simultaneous development and shared many component designs with the Atlas.74

But innovation continued, partly through engineers making “the right guess or assumption" or simply learning from problems. De­spite repeated failures and (trial-and-error) modifications to elimi­nate their causes, development proceeded from Atlas A through At­las F with a total of 158 successful launches for all models against 69 failures—a success rate of only 69.6 percent. The Atlas D became the first operational version in September 1959, with the first E and F models following in 1961. All three remained operational until 1965, when they were phased out of the missile inventory, with many of them later becoming launch-vehicle stages.75

Meanwhile, fearing (unnecessarily) that an ICBM like the Atlas could not be deployed before 1962, a Technology Capabilities Panel headed by James R. Killian Jr., president of MIT, issued a report in mid-February 1955 recommending the development of both sea – and land-based intermediate-range ballistic missiles (IRBMs). In Novem­ber 1955, the Joint Chiefs of Staff recommended, in turn, that the air force develop the land-based version while the army and navy collaborate on an IRBM that could be both land and sea based. Thus were born the air force’s Thor and the army’s Jupiter, with the navy eventually developing the solid-propellant Polaris after initially try­ing to adapt the liquid-propellant Jupiter to shipboard use.76

Arising out of this decision was the “Thor-Jupiter Controversy," which the House of Representatives Committee on Government Operations called a “case study in interservice rivalry." The Thor did not use the extremely light, steel-balloon structure of Atlas but a more conventional aluminum airframe. Its main engine consisted essentially of half of the booster system for Atlas. In 1957 and 1958, it experienced 12 failures or partial successes out of the first 18 launches. Before the air force nevertheless decided in September

1958 that Thor was ready for operational deployment, problems with the turbopumps (common to the Atlas, Thor, and Jupiter) and

38 differences of approach to these problems had led to disagreement Chapter 1 between the Thor and Jupiter teams.77

Von Braun’s engineers, working on the Jupiter for the army, di­agnosed the problem first and had Rocketdyne design a bearing re­tainer for the turbopump that solved the problem, which the Thor

program would not admit at first, suspecting another cause. Once the Jupiters resumed test flights, they had no further turbopump problems. Meanwhile, failures of an Atlas and a Thor missile in April 1958, plus subsequent analysis, led the air force belatedly to accept the army’s diagnosis and a turbopump redesign. The first Thor squadron went on operational alert in Great Britain in June 1959, with three others following by April 1960. When the Atlas and Titan ICBMs achieved operational readiness in 1960, the last Thors could be removed from operational status in 1963, making them available for space-launch activities.78

While the Western Development Division and the successor Air Force Ballistic Missile Division were developing the Thor in con­junction with contractors, von Braun’s group at what had become the Army Ballistic Missile Agency (ABMA) in Alabama and its con­tractors were busily at work on Jupiter without a clear indication whether the army or the air force would eventually deploy the mis­sile. At ABMA, the forceful and dynamic Maj. Gen. John B. Medaris enjoyed powers of initiative roughly analogous to those of Schriever for the air force. On December 8, 1956, the navy left the Jupiter program to develop Polaris, but not before the sea service’s require­ments had altered the shape of the army missile to a much shorter and somewhat thicker contour than the army had planned. With Chrysler the prime contractor (as on the Redstone), Medaris reluc­tantly accepted the same basic engine North American Rocketdyne was developing for the Thor except that the Jupiter engine evolved from an earlier version of the powerplant and ended as somewhat less powerful than the air force counterparts.79

With a quite different vernier engine and guidance/control sys­tem, the Jupiter was a decidedly distinct missile from the Thor. The first actual Jupiter (as distinguished from the Jupiter A and Jupiter C, which were actually Redstones) launched on March 1, 1957, at Cape Canaveral. Facing the usual developmental problems, including at least one that Medaris blamed on the thicker shape resulting from the navy’s requirements, the Jupiter nevertheless achieved 22 sat­isfactory research-and-development flight tests out of 29 attempts. The air force, instead of the army, deployed the missile, with initial operational capability coming on October 20, 1960. Two squadrons of the missile became fully operational in Italy as of June 20, 1961. A third squadron in Turkey was not operational until 1962, with all of the missiles taken out of service in April of the following year. Three feet shorter, slightly thicker and heavier, the Jupiter was more accurate but less powerful than the Thor, with a comparable range. The greater average thrust of the Thor may have contributed

to its becoming a standard first-stage launch vehicle, whereas Jupi­ter served in that capacity to only a limited degree. Another factor may have been that there were 160 production Thors to only 60 Ju­piter missiles.80

Although much has rightly been made of the intense interservice rivalry between the army and the air force over Thor and Jupiter, even those two programs cooperated to a considerable extent and exchanged much data. Medaris complained about the lack of infor­mation he received from the air force, but Schriever claimed that his Ballistic Missile Division had transmitted to ABMA a total of 4,476 documents between 1954 and February 1959. By his count, BMD withheld only 28 documents for a variety of reasons, including con­tractors’ proprietary information.81 This was one of many examples showing that—although interservice and interagency rivalry helped encourage competing engineers to excel—without sharing of infor­mation and technology, rocketry might have advanced much less quickly than in fact it did.

Even though the Viking rocket used alcohol and the Vanguard first stage adopted kerosene as its fuel, the next major advance in alcohol and kerosene propulsion technology came with the Atlas missile. As with the Redstone, North American Aviation designed and built the Atlas engines, which also owed a great deal to NAA’s work for the Navaho. Unlike the Redstone, the Atlas engines burned kero­sene rather than alcohol. (Both used liquid oxygen as the oxidizer.) Kerosene that would work in rocket engines was another legacy of the protean Navaho program. In January 1953, Lt. Col. Edward Hall and others from Wright-Patterson AFB insisted to Sam Hoffman that he convert from alcohol to a hydrocarbon fuel for a 120,000-pound – 122 thrust Navaho engine. Hoffman protested because the standard Chapter 3 kerosene the air force used was JP-4, whose specifications allowed a range of densities. JP-4 clogged a rocket engine’s slim cooling lines with residues. The compounds in the fuel that caused these prob­lems did not affect jet engines but would not work easily in rocket powerplants. To resolve these problems, Hoffman initiated the Rocket Engine Advancement Program, resulting in development of the RP-1 kerosene rocket fuel, without JP-4’s contaminants and variations in density. This fuel went on to power the Atlas, Thor, and Jupiter engines. The specifications for RP-1 were available in January 1957, before the delivery date of the Atlas engines.38

On October 28, 1954, the Western Development Division and Special Aircraft Projects (procurement) Office that Air Force Ma­teriel Command had located next to it issued a letter contract to NAA to continue research and development of liquid-oxygen and

kerosene (RP-1) engines for Atlas. The cooperating air force organi­zations followed this with a contract to NAA for 12 pairs of rocket engines for the series-A flights of Atlas, which tested only two outside booster engines and not the centrally located sustainer en­gine for the Atlas. The Rocketdyne Division, formed to handle the requirements of Navaho, Atlas, and Redstone, also developed the sustainer engine, which differed from the two boosters in having a nozzle with a higher expansion ratio for optimum performance at higher altitudes once the boosters were discarded.39

Using knowledge gained from the Navaho and Redstone engines, the NAA engineers began developing the MA-1 Atlas engine system for Atlases A, B, and C in 1954. (Atlas B added the sustainer engine to the two boosters; Atlas C had the same engines but included improvements to the guidance system and thinner skin on the pro­pellant tanks. Both were test vehicles only.) The MA-1, like its suc­cessors the MA-2 and MA-3, was gimballed and used the brazed "spaghetti" tubes forming the inner and outer walls of the regen­eratively cooled combustion chamber. NAA had developed the ar­rangement used in the MA-1 in 1951, perhaps in ignorance of the originator of the concept, Edward Neu at Reaction Motors. NAA/ Rocketdyne began static "hot-fire" tests of the booster engines in 1955 and of all three MA-1 engines in 1956 at Santa Susana. The two booster engines, designated XLR43-NA-3, had a specific im­pulse of 245 lbf-sec/lbm and a total thrust of 300,000 pounds, much more than the Redstone engine. The sustainer engine, designated XLR43-NA-5, had a lower specific impulse (210 lbf-sec/lbm) and a total thrust of 54,000 pounds.40

Produced in 1957 and 1958, these engines ran into failures of systems and components in flight testing that also plagued the Thor and Jupiter engines, which were under simultaneous develop­ment and shared many component designs with the Atlas. They used high-pressure turbopumps that transmitted power from the turbines to the propellant pumps via a high-speed gear train. Both Atlas and Thor used the MK-3 turbopump, which failed at high al­titude on several flights of both missiles, causing the propulsion system to cease functioning. Investigations showed that lubrication was marginal. Rocketdyne engineers redesigned the lubrication sys­tem and a roller bearing, strengthening the gear case and related parts. Turbine blades experienced cracking, attributed to fatigue from vibration and flutter. To solve this problem, the engineers ta­pered each blade’s profile to change the natural frequency and added shroud tips to the blades. These devices extended from one blade to the next, restricting the amount of flutter. There was also an explo-

sion of a sustainer engine caused by rubbing in the oxygen side of the turbopump, solved by increasing clearances in the pump and installing a liner.

Another problem encountered on the MA-1 entailed a high – frequency acoustic form of combustion instability resulting in vi­bration and increased transfer of heat that could destroy the engine 124 in less than a hundredth of a second. The solution proved to be rect – Chapter 3 angular pieces of metal called baffles, attached to a circular ring near the center of the injector face and extending from the ring to the chamber walls. Fuel flowed through the baffles and ring for cooling. The baffles and ring served to contain the transverse oscillations in much the way that the 18 pots on the V-2 had done but without the cumbersome plumbing. Together with changing the injection pat­tern, this innovation made the instability manageable. These im­provements came between the flight testing of the MA-1 system and the completion of the MA-3 engine system (1958—63).41 They showed the need to modify initial designs to resolve problems that appeared in the process of testing and the number of innovations that resulted, although we do not always know who conceived them or precisely how they came about. (But see the account below of Rocketdyne’s Experimental Engines Group for some of the explanations.)

National Aeronautics and Space Administration Lewis Research Center

The MA-2 “was an uprated and simplified version of the MA-1," used on the Atlas D, which was the first operational Atlas ICBM and later became a launch vehicle under Project Mercury. Both MA-1 and MA-2 systems used a common turbopump feed system in which the turbopumps for fuel and oxidizer operated from a single gas gen­erator and provided propellants to booster and sustainer engines. For the MA-2, the boosters provided a slightly higher specific im­pulse, with that of the sustainer also increasing slightly. The overall thrust of the boosters rose to 309,000 pounds; that of the sustainer climbed to 57,000 pounds. An MA-5 engine was initially identical to the MA-2 but used on space-launch vehicles rather than missiles. In development during 1961-73, the booster engines went through several upratings, leading to an ultimate total thrust of 378,000 pounds (compared to 363,000 for the MA-2).

The overall MA-3 engine system contained separate subsystems for each of the booster and sustainer engines. Each engine had its own turbopump and gas generator, with the booster engines being identical to one another. The MA-3 exhibited a number of other changes from the MA-2, including greater simplification and bet­ter starting reliability resulting from hypergolic thrust-chamber ig­nition. A single electrical signal caused solid-propellant initiators and gas-generator igniters to begin the start sequence. Fuel flow

FIG. 3.6

Technical drawing of an injector for an MA-5 booster engine, used on the Atlas space-launch vehicle, 1983. (Photo courtesy of NASA)

National Aeronautics and Space Administration Lewis Research Center

through an igniter fuel valve burst a diaphragm holding a hypergolic cartridge and pushed it into the thrust chambers. Oxygen flow oc­curred slightly ahead of the fuel, and the cartridge with its triethyl aluminum and triethyl boron reacted with the oxygen in the thrust chamber and began combustion. Hot gases from combustion oper­ated the turbopump, a much more efficient arrangement than previ­ous turbopumps operated by hydrogen peroxide in rockets like the 126 V-2 and Redstone.

Chapter 3 The MA-3 sustainer engine had a slightly higher specific impulse of almost 215 lbf-sec/lbm but the same thrust (57,000 pounds) as the MA-2 sustainer. The total thrust of the boosters, however, went up to 330,000 pounds with a climb in specific impulse to about 250 lbf-sec/lbm. Both specific impulses were at sea level. At altitude the specific impulse of the sustainer rose to almost 310 and that of the boosters to nearly 290 lbf-sec/lbm. The higher value for the sustainer engine at altitude resulted from the nozzles that were de­signed for the lower pressure outside Earth’s atmosphere. The MA-3 appeared on the Atlas E and F missiles, with production running from 1961 to 1964.42

Most of the changes from the MA-1 to the MA-3 resulted from a decision in 1957 by Rocketdyne management to create an Experi­mental Engines Group under the leadership of Paul Castenholz, a

design and development engineer who had worked on combustion devices, injectors, and thrust chambers. He “enjoyed a reputation at Rocketdyne as a very innovative thinker, a guy who had a lot of en­ergy, a good leader." The group consisted of about 25 mostly young people, including Dick Schwarz, fresh out of college and later presi­dent of Rocketdyne. Bill Ezell, who was the development supervi­sor, had come to NAA in 1953 and was by 1957 considered an “old- timer" in the company at age 27. Castenholz was about 30. Before starting the experimental program, Ezell had just come back from Cape Canaveral, where there had been constant electrical problems on attempted Thor launches. The Atlas and Thor contracts with the air force each had a clause calling for product improvement, which was undefined, but one such improvement the group sought was to reduce the number of valves, electrical wires, and connections that all had to function in a precise sequence for the missile to operate.

The experimental engineers wanted a system with one wire to start the engine and one to stop it. Buildup of pressure from the turbopump would cause all of the valves to “open automatically by using the. . . propellant as the actuating fluid." This one-wire start arrangement became the solid-propellant mechanism for the MA-3, but the engineers under Castenholz first used it on an X-1 ex­perimental engine on which Cliff Hauenstein, Jim Bates, and Dick Schwarz took out a patent. They used the Thor engine as the start­ing point and redesigned it to become the X-1. Their approach was mostly empirical, which was different from the way rocket devel­opment had evolved by the 1980s, when the emphasis had shifted to more analysis on paper and with a computer, having simulation precede actual hardware development. In the period 1957 to the early 1960s, Castenholz’s group started with ideas, built the hard­ware, and tried it out, learning from their mistakes.

Stan Bell, another engineer in Castenholz’s group, noted a further difference from the 1980s: “We were allowed to take risks and to fail and to stumble and to recover from it and go on. Now, everything has got to be constantly successful." Jim Bates added that there were not any “mathematical models of rocket engine combustion processes" in the late 1950s and early 1960s. “There weren’t even any computers that could handle them," but, he said, “we had our experience and hindsight."

The reason the engineers in the group moved to a hypergolic ig­niter was that existing pyrotechnic devices required a delicate bal­ance. It proved difficult to get a system that had sufficient power for a good, assured ignition without going to the point of a hard start that could damage hardware. This led them to the hypergolic cartridge

(or slug) used on the MA-3. In the process of developing it, however, the group discovered that a little water in the propellant line ahead of the slug produced combustion in the line but not in the chamber; there the propellants built up and caused a detonation, “blow[ing] hell out of an engine," as Bill Ezell put it. They learned from that experience to be more careful, but Ezell said, “there’s probably no degree of analysis that could have prevented that from happening." There were simply a lot of instances in rocket-engine development where the experimenters had to “make the right guess or assump­tion"; otherwise, there was “no way to analyze it. So you’ve got to get out and get the hard experience." Ezell also opined that “with­out the Experimental Engine program going, in my opinion there never would have been a Saturn I," suggesting a line of evolution from their work to later engines.43

The experiences and comments of the members of Castenholz’s group illuminate the often dimly viewed nature of early rocket en­gineering. Without the product-improvement clauses in the Atlas and Thor contracts, a common practice of the Non-Rotating Engine Branch of the Power Plant Laboratory at Wright-Patterson AFB, the innovations made by this group probably would not have occurred. They thus would not have benefited Thor and Atlas as well as later projects like Saturn I. Even with the clauses, not every company would have put some 25 bright, young engineers to work on pure experiment or continued their efforts after the first engine explo­sion. That Rocketdyne did both probably goes a long way toward explaining why it became the preeminent rocket-engine producer in the country.

The changes in the Atlas engines to the MA-3 configuration as 128 a result of the experimental group’s work did not resolve all of the Chapter 3 problems with the Atlas E and F configurations. The Atlas lifted off with all three engines plus its two verniers (supplementary en­gines) firing. Once the missile (or later, launch vehicle) reached a predetermined velocity and altitude, it jettisoned the booster en­gines and structure, with the sustainer engine and verniers then continuing to propel the remaining part of the rocket to its destina­tion. The separation of the booster sections occurred at disconnect valves that closed to prevent the loss of propellant from the feed lines. This system worked through the Atlas D but became a major problem on the E and F models, with their independent pumps for each engine (rather than the previous common turbopump for all of them). Also, the E and F had discarded the use of water in the regen­erative cooling tubes because it reacted with the hypergolic slug. The water had ensured a gentle start with previous igniters. With

the hypergolic device, testing of the engines by General Dynamics had produced some structural damage in the rear of the missile. Design fixes included no thought of a large pressure pulse when the new models ignited.

On June 7, 1961, the first Atlas E launched from Vandenberg AFB on the California coast at an operational launch site that used a dry flame bucket rather than water to absorb the missile’s thrust. The missile lifted off and flew for about 40 seconds before a failure of the propulsion system resulted in destruction of the missile, with its parts landing on the ground and recovered. Rocketdyne specialists analyzed the hardware and data, concluding that a pressure pulse had caused the problem. The pulse had resulted in a sudden up­ward pressure from the dry flame bucket back onto fire-resistant blankets called boots that stretched from the engines’ throat to the missile’s firewall to form a protective seal around the gimballing engines. The pressure caused one boot to catch on a drain valve at the bottom of a pressurized oil tank that provided lubrication for the turbopump gearbox. The tank drained, and the gearbox ceased to operate without lubrication. To solve this problem, engineers re­sorted to a new liquid in the cooling tubes ahead of the propellants to soften ignition and preclude pressure pulses.

Repeated failures of different kinds also occurred during the flight-test program of the E and F models at Cape Canaveral. Control instrumentation showed a small and short-lived pitch upward of the vehicle during launch. Edward J. Hujsak, assistant chief engineer for mechanical and propulsion systems for the Atlas airframe and as­sembly contractor, General Dynamics, reflected about the evidence and spoke with the firm’s director of engineering. Hujsak believed that the problem lay with a change in the geometry of the propellant lines for the E and F models that allowed RP-1 and liquid oxygen (ex­pelled from the booster engines when they were discarded) to mix. Engineers “did not really know what could happen behind the mis­sile’s traveling shock front" as it ascended, but possibly the mixed propellants were contained in such a way as to produce an explosion. That could have caused the various failures that were occurring.

The solution entailed additional shutoff valves in the feed lines on the booster side of the feed system, preventing expulsion of the propellants. Engineers and technicians had to retrofit these valves in the operational missiles. However, the air force decided that since there could be no explosion if only one of the propellants were cut off, the shutoff valves would be installed only in the oxygen lines. A subsequent failure on a test flight convinced the service to approve installation in the fuel lines as well, solving the problem.44 Here

130

Chapter 3

was a further example of engineers not always fully understanding how changes in a design could affect the operation of a rocket. Only failures in flight testing and subsequent analysis pinpointed prob­lem areas and provided solutions.

At the beginning of recent solid-propellant development during World War II, the vast majority of rockets produced for use in com­bat employed extruded double-base propellants. These were limited in size by the nature of the extrusion process used at that time to produce them. In extrusion using a solvent, nitrocellulose was sus­pended in the solvent, which caused the nitrocellulose to swell. It was formed into a doughlike composition and then extruded (forced) through dies to form it into grains. This process of production lim­ited the size of the grains to thin sections so the solvent could evap­orate, and the elasticity of the grain was too low for bonding large charges to the motor case. With a solventless (or dry) process, there 232 were also limitations on the size of the grain and greater hazards of Chapter 6 explosion than with extrusion using a solvent.

These factors created the need for castable double-base propel­lants. But before a truly viable process for producing large castable propellants could be developed, the United States, because it was at war, needed a variety of rockets to attack such targets as ships (including submarines), enemy fortifications, gun emplacements, aircraft, tanks, and logistical systems. The development of these weapons did not lead directly to any launch-vehicle technology, but the organizations that developed them later played a role in furthering that technology. Two individuals provided the leader­ship in producing the comparatively small wartime rockets with extruded grains. One was Clarence Hickman, who had worked with Goddard on rockets intended for military applications during World War I. He then earned a Ph. D. at Clark University and went to work at Bell Telephone Laboratories. After consulting with God­dard, in June 1940 Hickman submitted a series of rocket proposals to Frank B. Jewett, president of Bell Labs and chairman of a divi­sion in the recently created National Defense Research Committee (NDRC). The upshot was the creation of Section H (for Hickman) of the NDRC’s Division of Armor and Ordnance. Hickman’s section had responsibility for researching and developing rocket ordnance. Although Section H was initially located at the Naval Proving Ground at Dahlgren, Virginia, it worked largely for the army.

Hickman chose to use wet-extruded, double-base propellants (em­ploying a solvent) because he favored the shorter burning times they afforded compared with dry-extruded ones. He and his associates worked with this propellant at Dahlgren, moved to the Navy Pow­der Factory at Indian Head, Maryland, and finally to Allegany Ord­nance Plant, Pinto Branch, on the West Virginia side of the Potomac

River west of Cumberland, Maryland. There at the end of 1943 they set up Allegany Ballistics Laboratory, a rocket-development facility operated for Section H by George Washington University. By using traps, cages, and other devices to hold the solvent-extruded, double­base propellant, they helped develop the bazooka antitank weapon, a 4.5-inch aircraft rocket, JATO devices with less smoke than those produced by Aerojet using Parson’s asphalt-based propellant, and a recoilless gun.22 Under different management, ABL later became an important producer of upper stages for missiles and rockets.

Hickman’s counterpart on the West Coast was physics professor Charles Lauritsen of Caltech. Lauritsen was vice chairman of the Division of Armor and Ordnance (Division A), and in that capacity he had made an extended trip to England to observe rocket devel­opments there. The English had developed a way to make solvent­less, double-base propellant by dry extrusion. This yielded a thicker grain that would burn longer than the wet-extruded propellant but required extremely heavy presses for the extrusion. However, the benefits were higher propellant loading and the longer burning time that Lauritsen preferred.

Convinced of the superiority of this kind of extrusion and be­lieving that the United States needed a larger rocket program than Section H could provide with its limited facilities, Lauritsen argued successfully for a West Coast program. Caltech then set up opera­tions in Eaton Canyon in the foothills of the San Gabriel Moun­tains northeast of the campus in Pasadena. It operated from 1942 to 1945 and expanded to a 3,000-person effort involving research, development, and pilot production of rocket motors; development of fuses and warheads; and static and flight testing. The group pro­duced an antisubmarine rocket 7.2 inches in diameter, a 4.5-inch barrage rocket, several retro-rockets (fired from the rear of airplanes at submarines), 3.5- and 5-inch forward-firing aircraft rockets, and the 11.75-inch “Tiny Tim" rocket that produced 30,000 pounds of thrust and weighed 1,385 pounds. (This last item later served as a booster for the WAC Corporal.)

By contrast with Section H, Section L (for Lauritsen) served mainly the navy’s requirements. In need of a place to test and eval­uate the rockets being developed at Eaton Canyon, in November 1943 the navy established the Naval Ordnance Test Station (NOTS) in the sparsely populated desert region around Inyokern well north of the San Gabriel Mountains. Like the Allegany Ballistics Labora­tory, NOTS was destined to play a significant role in the history of U. S. rocketry, mostly with tactical rockets but also with contribu­tions to ballistic missiles and launch vehicles.

One early contribution was the “White Whizzer" 5.0-inch rocket developed by members of the Caltech team who had already moved to NOTS but were still under direction of the university rather than the navy. By about January1944, combustion instability had become a problem with the 2.25-inch motors for some of the tactical rock­ets. These rockets used tubular, partially internal-burning charges of double-base propellant. Radial holes in the grain helped solve se­vere pressure excursions—it was thought, by allowing the gas from the burning propellant to escape from the internal cavity. Edward W. Price, who had not yet received his bachelor’s degree but would later become one of the nation’s leading experts in combustion in­stability, suggested creating a star-shaped perforation in the grain for internal burning. He thought this might do a better job than the 234 radial holes in preventing oscillatory gas flow that was causing the Chapter 6 charges of propellant to split. He tested the star perforation, and it did produce stable burning.

In 1946, Price applied this technique to the White Whizzer, which featured a star-perforated, internal-burning grain with the outside of the charge wrapped in plastic to inhibit burning there. This ge­ometry allowed higher loading of propellant (the previous design having channels for gas flow both inside and outside the grain). And since the grain itself protected the case from the heat in the internal cavity, the case could be made of lightweight aluminum, providing better performance than heavier cases that were slower to accelerate because of the additional weight. Ground-launched about May 1946, the White Whizzer yielded a speed of 3,200 feet per second, then a record for solid rockets. The internal-burning, aluminum-cased design features later appeared in the 5.0-inch Zuni and Sidewinder tactical missiles. The internal-burning feature of the design also came to be applied to a great many other solid rock­ets, including ballistic missiles and stages for launch vehicles. This apparently was the first flight of a rocket using such a grain design in the United States, preceding JPL’s use of a similar design, known as the Deacon, and also flight testing of the first member of the Vicar family to be flown.23

Jupiter, Thor, and Atlas marked a huge step forward in the matura­tion of U. S. rocketry, but before the technology from those missiles came to significant use in launch vehicles, the navy’s development of the Polaris inaugurated a solid-propellant breakthrough in mis­sile technology that also profoundly affected launch vehicles.82 Un­til Polaris A1 became operational in 1960, all intermediate-range and intercontinental missiles in the U. S. arsenal had employed liq­uid propellants. These had important advantages in terms of perfor­mance but required extensive plumbing and large propellant tanks that made protecting them in silos difficult and expensive. Such factors also virtually precluded their efficient use onboard ships, especially submarines. Once Minuteman I became operational in 1962, the U. S. military began to phase out liquid-propellant stra­tegic missiles. To this day, Minuteman III and the solid-propellant fleet ballistic missiles continue to play a major role in the nation’s strategic defenses because they are simpler and cheaper to operate than liquid-propellant missiles.

Because of the higher performance of some liquid propellants and 40 their ability to be throttled as well as turned off and on by the use of Chapter 1 valves, they remained the primary propellants for space-launch ve­hicles. However, since solid-propellant boosters could be strapped on the sides of liquid-propellant stages for an instant addition of high thrust (because their thrust-to-weight ratio is higher, allowing

faster liftoff), solid-propellant boosters became important parts of launch-vehicle technology. The technologies used on Polaris and Minuteman transferred to such boosters and also to upper stages of rockets used to launch satellites. Thus, the solid-propellant break­through in missiles had important implications for launch-vehicle technology. By the time that Polaris got under way in 1956 and Minuteman in 1958, solid-propellant rocketry had already made tremendous strides from the use of extruded double-base propel­lants in World War II tactical missiles. But there were still enor­mous technical hurdles to overcome before solid-propellant missiles could hope to launch strategic nuclear warheads far and accurately enough to serve effectively as a deterrent or as a retaliatory weapon in case of enemy aggression.83

With a much smaller organization than the army or air force, a navy special projects office under the leadership of Capt. (soon-to-be Rear Adm.) William F. Raborn pushed ahead to find the right tech­nologies for a submarine-launched, solid-propellant missile, a daunt­ing task since a solid propellant with the necessary performance did not yet exist. Capt. Levering Smith—who, at the Naval Ord­nance Test Station (NOTS), had led the effort to develop a 50-foot solid-propellant missile named “Big Stoop" that flew 20 miles in 1951—joined Raborn’s special projects office in April 1956. Smith contributed importantly to Polaris, but one key technical discovery came from the Atlantic Research Corporation (ARC), a chemical firm founded in 1949 with which the Navy Bureau of Ordnance had contracted to improve the specific impulse of solid propellants (the ratio of thrust a rocket engine or motor produced to the amount of propellant needed to produce that thrust).84

ARC’s discovery that the addition of comparatively large quan­tities of aluminum to solid propellants significantly raised perfor­mance, together with the work of Aerojet chemists, led to successful propellants for both stages of Polaris A1. The addition of aluminum to Aerojet’s binder essentially solved the problem of performance for both Polaris (and, as it turned out, with a different binder, for Minuteman). Other key technical solutions relating to guidance and an appropriate warhead led to the directive on December 8, 1956, that formally began the Polaris program.85

Flight testing of Polaris at the air force’s Cape Canaveral (be­ginning in 1958 in a series designated AX) revealed a number of problems. Solutions required considerable interservice cooperation. On July 20, 1960, the USS George Washington launched the first functional Polaris missile. The fleet then deployed the missile on November 15, 1960.86

The navy quickly moved forward to Polaris A2. It increased the range of the fleet ballistic missile from 1,200 to 1,500 miles. Flight testing of the A2 missiles started in November 1960, with the first successful launch from a submerged submarine occurring on Octo­ber 23, 1961. The missile became operational less than a year later in June 1962. Polaris A3 was still more capable, with a range of 2,500 miles. It incorporated many other new technologies in both propulsion and guidance/control, becoming operational on Septem­ber 28, 1964. All three versions of Polaris made significant contri­butions to launch-vehicle technology, such as the Altair II motor, produced by the Hercules Powder Company under sponsorship of the Bureau of Naval Weapons and NASA and used as a fourth stage for the Scout launch vehicle.87

While Polaris was still in development, the air force had officially begun work on Minuteman I. Its principal architect was Edward N. Hall, a heterogeneous engineer who helped begin the air force’s involvement with solid propellants as a major at Wright-Patterson AFB in the early 1950s. As Karl Klager, who worked on both Polaris and Minuteman, has stated, Hall “deserves most of the credit for maintaining interest in large solid rocket technology [during the mid-1950s] because of the greater simplicity of solid systems over liquid systems." Hall’s efforts “contributed substantially to the Polaris program," Klager added, further illustrating the extent to which (unintended) interservice cooperation and shared informa­tion contributed to the solid-propellant breakthrough. Hall moved to the WDD as the chief for propulsion development in the liq­uid-propellant Atlas, Titan, and Thor programs, but he continued his work on solids, aided by his former colleagues back at Wright – Patterson AFB.88

Despite this sort of preparatory work for Minuteman, the mis­sile could not begin its formal development until the air force se­cured final DoD approval in February 1958, more than a year later than Polaris. Hall and others at WDD had a difficult job convincing Schriever in particular to convert to solids. Without their heteroge­neous engineering, the shift to solids might never have happened. They were aided, however, by development of Polaris because it provided what Harvey Sapolsky has dubbed “competitive pressure" for the air force to develop its own solid-propellant missile.89

Soon after program approval, Hall left the Ballistic Missile Divi­sion. From August 1959 to 1963, the program director was Col. (soon promoted to Brig. Gen.) Samuel C. Phillips. Hall and his coworkers deserve much credit for the design of Minuteman and its support by the air force, whereas Phillips brought the missile to completion.

Facing many technical hurdles, Phillips succeeded as brilliantly as had Levering Smith with Polaris in providing technical manage­ment of a complex and innovative missile. Often using trial-and – error engineering, his team working on the three-stage Minuteman I overcame problems with materials for nozzle throats in the lower stages, with firing the missile from a silo, and with a new binder for the first stage called polybutadiene-acrylic acid-acrylonitrile (PBAN), developed by the contractor, Thiokol Chemical Corpora­tion. Incorporating substantial new technology as well as some bor­rowed from Polaris, the first Minuteman I wing became operational in October 1962.90

Minuteman II included a new propellant in stage two, known as carboxy-terminated polybutadiene and an improved guidance/con – trol system. The new propellant yielded a higher specific impulse, and other changes (including increased length and diameter) made Minuteman II a more capable and accurate missile than Minute – man I. The newer version gradually replaced its predecessor in mis­sile silos after December 1966.91

In Minuteman III, stages one and two did not change from Min – uteman II, but stage three became larger. Aerojet replaced Hercules as the contractor for the new third stage. With the larger size and a different propellant, the third stage more than doubled its total impulse. These and other modifications allowed Minuteman IIIs to achieve their initial operational capability in June 1970. As a result of the improvements, the range of the missile increased from about 6,000 miles for Minuteman I to 7,021 for Minuteman II, and 8,083 for Minuteman III.92

The deployment of Minuteman I in 1961 marked the completion of the solid-propellant breakthrough in terms of its basic technol­ogy, though innovations and improvements continued to occur. But the gradual phaseout of liquid-propellant missiles followed almost inexorably from the appearance on the scene of the first Minuteman. The breakthrough in solid-rocket technology required the extensive cooperation of a great many firms, government laboratories, and uni­versities, only some of which could be mentioned here. It occurred on many fronts, ranging from materials science and metallurgy through chemistry to the physics of internal ballistics and the mathematics and physics of guidance and control, among many other disciplines. It was partially spurred by interservice rivalries for roles and mis­sions. Less well known, however, was the contribution of interser­vice cooperation. Necessary funding for advances in and the sharing of technology came from all three services, the Advanced Research Projects Agency, and NASA. Technologies such as aluminum fuel,

methods of thrust vector control, and improved guidance and con­trol transferred from one service’s missiles to another. Also crucial were the roles of heterogeneous engineers like Raborn, Schriever, and Hall. But a great many people with more purely technical skills, such as Levering Smith and Sam Phillips, ARC, Thiokol, and Aerojet engineers made vital contributions.

The solid-propellant breakthrough that these people and many others achieved had important implications for launch vehicles as well as missiles. The propellants for the large solid-rocket boosters on the Titan III, Titan IVA, and the Space Shuttles were derived from the one used on Minuteman, stage one. Without ARC’s dis­covery of aluminum as a fuel and Thiokol’s development of PBAN as a binder, it is not clear that the huge Titan and shuttle boosters would have been possible. Many other solid-propellant formula­tions also used aluminum and other ingredients of the Polaris and Minuteman motors. Although some or all of them might have been developed even if there had been no urgent national need for solid – propellant missiles, it seems highly unlikely that their development would have occurred as quickly as it did without the impetus of the cold-war missile programs and their generous funding.

There were other developments relating to kerosene-based engines for Thor and Delta, among other vehicles, but the huge Saturn en­gines marked the most important step forward in the use of RP-1 for launch-vehicle propulsion. The H-1 engine for the Saturn I’s first stage resulted from the work of the Rocketdyne Experimental Engines Group on the X-1. Under a contract to the Army Ballistic

H-1 engines, which were used in a cluster of eight to power the first stage of both the Saturn I and the Saturn IB. (Photo courtesy of NASA)

passed its preliminary flight-rating tests, leading to the first flight test on October 27, 1961.47

Meanwhile, Rocketdyne had begun uprating the H-1 to 188,000 pounds of thrust, apparently by adjusting the injectors and increas­ing the fuel and oxidizer flow rates. Although the uprated engine was ready for its preliminary flight-rating tests on September 28, 1962, its uprating created problems with combustion instability that en­gineers had not solved by that time but did fix without detriment to the schedule. The first launch of a Saturn I with the 188,000-pound engine took place successfully on January 29, 1964.48

Development had not been unproblematic. Testing for combus­tion instability (induced by setting off small bombs in the combus­tion chamber beginning in 1963) showed that the injectors inher­ited from the Thor and Atlas could not recover and restore stable combustion once an instability occurred. So Rocketdyne engineers rearranged the injector orifices and added baffles to the injector face. These modifications solved the problem. Cracks in liquid-oxygen domes and splits in regenerative-cooling tubes also required rede­sign. Embrittlement by sulfur from the RP-1 in the hotter environ­ment of the 188,000-pound engine required a change of materials in the tubular walls of the combustion chamber from nickel alloy to stainless steel. There were other problems, but the Saturn person­nel resolved them in the course of the launches of Saturn I and IB from late 1961 to early 1968.49

Because the H-1s would be clustered in two groups of four each for the Saturn I first stage, there were two types of engines. H-1Cs used for the four inboard engines were incapable of gimballing to steer the first stage. The four outboard H-1D engines did the gim – 132 balling. Both versions used bell-shaped nozzles, but the outboard Chapter 3 H-1Ds used a collector or aspirator to channel the turbopump exhaust gases, which were rich in unburned RP-1 fuel, and deposit them in the exhaust plume from the engines to prevent the still-combustible materials from collecting in the first stage’s boat tail.50

The first successful launch of Saturn I did not mean that devel­opers had solved all problems with the H-1 powerplant. On May 28, 1964, Saturn I flight SA-6 unexpectedly confirmed that the first stage of the launch vehicle could perform its function with an en­gine out, a capability already demonstrated intentionally on flight SA-4 exactly 14 months earlier. An H-1 engine on SA-6 ceased to function 117.3 seconds into the 149-second stage-one burn. Telem­etry showed that the turbopump had ceased to supply propellants. Analysis of the data suggested that the problem was stripped gears in the turbopump gearbox. Previous ground testing had revealed to

Rocketdyne and Marshall technicians that there was need for rede­sign of the gear’s teeth to increase their width. Already programmed to fly on SA-7, the redesigned gearbox did not delay flight testing, and there were no further problems with H-1 engines in flight.51

None of the sources for this history explain exactly how Rock­etdyne increased the thrust of each of the eight H-1 engines from 188,000 to 200,000 pounds for the first five Saturn IBs (SA-201 through SA-205) and then to 205,000 pounds for the remaining ve­hicles. It would appear, as with the uprated Saturn I engines, that the key lay in the flow rates of the propellants into the combustion chambers, resulting in increased chamber pressure. After increasing with the shift from the 165,000- to the 188,000-pound H-1s, these flow rates increased again for the 200,000-pound and once more for the 205,000-pound H-1s.52

LAUNCH VEHICLE ENGINES

H-l ON SATURN IB FIRST STAGE

F-l ON SATURN V FIRST STAGE

J-2 ON SATURN IB

SECOND STAGE

J-2 ON SATURN V SECOND STAGE

* ALSO SATURN V THIRD STAGE

FIG. 3.10 Diagram of the engines used on the Saturn IB and Saturn V. The Saturn IB used eight H-1s on its first stage and a single J-2 on its second stage; the Saturn V relied on five F-1 engines for thrust in its first stage, with five J-2s in the second and one J-2 in the third stage. (Photo courtesy of NASA)

For the Saturn V that launched the astronauts and their spacecraft into their trajectory toward the Moon for the six Apollo Moon land­ings, the first-stage engines had to provide much more thrust than the eight clustered H-1s could supply. Development of the larger F-1 engine by Rocketdyne originated with an air force request in 1955. NASA inherited the reports and other data from the early de – 134 velopment, and when Rocketdyne won the NASA contract to build Chapter 3 the engine in 1959, it was, “in effect, a follow-on" effort. Since this agreement preceded a clear conception of the vehicle into which the F-1 would fit and the precise mission it would perform, designers had to operate in a bit of a cognitive vacuum. They had to make early assumptions, followed by reengineering to fit the engines into the actual first stage of the Saturn V, which itself still lacked a firm configuration in December 1961 when NASA selected Boeing to build the S-IC (the Saturn V first stage). Another factor in the design of the F-1 resulted from a decision “made early in the program. . . [to make] the fullest possible use of components and techniques proven in the Saturn I program."

In 1955, the goal had been an engine with a million pounds of thrust, and by 1957 Rocketdyne was well along in developing it. That year and the next, the division of NAA had even test-fired

SATURN IB LAUNCH VEHICLE

PROPOSED MISSIONS

CHARACTERISTICS

• APOLLO SPACECRAFT DEVELOP­MENT AND ORBITAL MANEUVERS • APOLLO CREW TRAINING IN LM RENDEZVOUS AND DOCKING •ADVANCE LARGE BOOSTER TECHNOLOGY •ORBIT LARGE SCIENTIFIC PAYLOADS

MS’C-M-INO HAM

such an engine, with much of the testing done at Edwards AFB’s rocket site, where full-scale testing continued while Rocketdyne did the basic research, development, and production at its plant in Canoga Park. It conducted tests of components at nearby Santa Su – sana Field Laboratory. At Edwards the future air force Rocket Pro­pulsion Laboratory (so named in 1963) had three test stands (1-A, 1-B, and 2-A) set aside for the huge engine. The 1959 contract with NASA called for 1.5 million pounds of thrust, and by April 6, 1961, Rocketdyne was able to static-fire a prototype engine at Edwards whose thrust peaked at 1.64 million pounds.53

Burning RP-1 as its fuel with liquid oxygen as the oxidizer, the F-1 did not break new ground in its basic technology. But its huge thrust level required so much scaling up that, as an MSFC publica­tion said, “An enlargement of this magnitude is in itself an inno­vation." For instance, the very size of the combustion chamber— 40 inches in diameter (20.56 inches for the H-1) with a chamber area almost 4 times that of the H-1 (1,257 to 332 square inches)—required new techniques to braze together the regenerative cooling tubes. Also because of the engine’s size, Rocketdyne adopted a gas-cooled, removable nozzle extension to make the F-1 easier to transport.54

The engine was bell shaped and had an expansion ratio of 16:1 with the nozzle extension attached. Its turbopump consisted of a single, axial-flow turbine mounted directly on the thrust chamber with separate centrifugal pumps for the oxidizer and fuel that were driven at the same speed by the turbine shaft. This eliminated the

The huge first stage of the Saturn V launch vehicle being hoisted by crane from a barge onto the B-2 test stand at the Mississippi Test Facility (later the Stennis Space Center) on January 1, 1967. Nozzles for the F-1 engines show at the bottom of the stage. (Photo courtesy of NASA)

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need for a gearbox, which had been a problematic feature of many earlier engines. A fuel-rich gas generator burning the engine pro­pellants powered the turbine. The initial F-1 had the prescribed 1.5 million pounds of thrust, but starting with vehicle 504, Rock – etdyne uprated the engine to 1.522 million pounds. It did so by in­creasing the chamber pressure through greater output from the tur­bine, which in turn required strengthening components (at some expense in engine weight). There were five F-1s clustered in the S-IC stage, four outboard and one in the center. All but the center engine gimballed to provide steering. As with the H-1, there was a hypergolic ignition system.55

Perhaps the most intricate design feature of the F-1 was the in­jection system. As two Rocketdyne engineers wrote in 1989, the

injector “might well be considered the heart of a rocket engine, since virtually no other single component has such a major impact on overall engine performance." The injector not only inserted the propellants into the combustion chamber but mixed them in a pro­portion designed to produce optimal thrust and performance. “As is the case with the design of nearly all complex, high technology hardware," the two engineers added, “the design of a liquid rocket injector is not an exact science, although it is becoming more so as analytical tools are continuously improved. This is because the basic physics associated with all of the complex, combustion pro­cesses that are affected by the design of the injector are only partly known." A portion of the problem lay with the atomization of the propellants and the distribution of the fine droplets to ensure proper mixing. Even as late as 1989, “the atomization process [wa]s one of the most complex and least understood phenomena, and reli­able information [wa]s difficult to obtain." One result of less-than – optimal injector design was combustion instability, whose causes and mechanisms still in 1989 were “at best, only poorly known and understood." Even in 2006, “a clear set of generalized validated design rules for preventing combustion instabilities in new TCs [thrust chambers] ha[d] not yet been identified. Also a good uni­versal mathematical three-dimensional simulation of the complex nonlinear combustion process ha[d] not yet been developed."56

This was still more the case in the early 1960s, and it caused huge problems for development of the F-1 injector. Designers at Rocket – dyne knew from experience with the H-1 and earlier engines that injector design and combustion instability would be problems. They began with three injector designs, all based essentially on that for the H-1. Water-flow tests provided information on the spacing and shape of orifices in the injector, followed by hot-fire tests in 1960 and early 1961. But as Leonard Bostwick, the F-1 engine manager at Marshall, reported, “None of the F-1 injectors exhibited dynamic stability." Designers tried a variety of flat-faced and baffled injec­tors without success, leading to the conclusion that it would not be possible simply to scale up the H-1 injector to the size needed for the F-1. Engineers working on the program did borrow from the H-1 effort the use of bombs to initiate combustion instability, saving a lot of testing to await its spontaneous appearance. But on June 28, 1962, during an F-1 hot-engine test in one of the test stands built for the purpose at the rocket site on Edwards AFB, combustion instabil­ity caused the engine to melt.57

Marshall appointed Jerry Thomson, chief of the MSFC Liquid Fuel Engines Systems Branch, to chair an ad hoc committee to ana-

lyze the problem. Thomson had earned a degree in mechanical en­gineering at Auburn University following service in World War II. Turning over the running of his branch to his deputy, he moved to Canoga Park where respected propulsion engineer Paul Castenholz and a mechanical engineer named Dan Klute, who also “had a spe­cial talent for the half-science, half-art of combustion chamber de­sign," joined him on the committee from positions as Rocketdyne managers. Although Marshall’s committee was not that large, at Rocketdyne there were some 50 engineers and technicians assigned to a combustion devices team, supplemented by people from uni­versities, NASA, and the air force. Using essentially cut-and-try methods, they initially had little success. The instability showed no consistency and set in “for reasons we never quite understood," as Thomson confessed.58

Using high-speed instrumentation and trying perhaps 40-50 de­sign modifications, eventually the engineers found a combination of baffles, enlarged fuel-injection orifices, and changed impinge­ment angles that worked. By late 1964, even following explosions of the bombs, the combustion chamber regained its stability. The en­gineers (always wondering if the problem would recur) rated the F-1 injector as flight-ready in January 1965. However, there were other problems with the injector. Testing revealed difficulties with fuel and oxidizer rings containing multiple orifices for the propellants. Steel rings called lands held copper rings through which the propel­lants flowed. Brazed joints held the copper rings in the lands, and these joints were failing. Engineers gold-plated the lands to create a better bonding surface. Developed and tested only in mid-1965, the new injector rings required retrofitting in engines Rocketdyne had already delivered.59

Overall, from October 1962 to September 1966, there were 1,332 full-scale tests with 108 injectors during the preliminary, the flight­rating, and flight-qualification testing of the F-1 to qualify the en­gine for use. According to one expert, this was “probably the most intensive (and expensive) program ever devoted primarily to solving a problem of combustion instabilities."60

The resultant injector contained 6,300 holes—3,700 for RP-1 and 2,600 for liquid oxygen. Radial and circumferential baffles divided the flat-faced portion of the injector face into 13 compartments, with the holes or orifices arranged so that most of them were in groups of five. Two of the five injected the RP-1 so that the two streams impinged to produce atomization, while the other three in­serted liquid oxygen, which formed a fan-shaped spray that mixed with the RP-1 to combust evenly and smoothly. Driven by the

52,900-horsepower turbine, the propellant pumps delivered 15,471 gallons of RP-1 and 24,811 gallons of liquid oxygen per minute to the combustion chamber via the injector.61

Despite all the effort that went into the injector design, the turbo­pump required even more design effort and time. Engineers experi­enced 11 failures of the system during development. Two of these involved the liquid-oxygen pump’s impeller, which required use of stronger components. The other 9 failures involved explosions. Causes varied. The high acceleration of the shaft on the turbopump constituted one problem. Others included friction between mov­ing parts and metal fatigue. All 11 failures necessitated redesign or change in procedures. For instance, Rocketdyne made the turbine manifold out of a nickel-based alloy manufactured by GE, Rene 41, which had only recently joined the materials used for rocket en­gines. Unfamiliarity with its welding techniques led to cracking near the welds. It required time-consuming research and training to teach welders proper procedures for using the alloy, which could withstand not only high temperatures but the large temperature dif­ferential resulting from burning the cryogenic liquid oxygen. The final version of this turbopump provided the speed and high vol­umes needed for a 1.5-million-pound-thrust engine and did so with minimal parts and high ultimate reliability.62

Once designed and delivered, the F-1 engines required further testing at Marshall and NASA’s Mississippi Test Facility. At the lat­ter, contractors had built an S-IC stand after 1961 on the mud of a swamp along the Pearl River near the Louisiana border and the Gulf of Mexico. Mosquito ridden and snake infested, this area served as home to wild pigs, alligators, and panthers. Construction workers faced 110 bites a minute from salt marsh mosquitoes, against which nets, gloves, repellent, and long-sleeved shirts afforded little protec­tion. Spraying special chemicals from two C-123 aircraft did reduce the number of bites to 10 per minute, but working conditions re­mained challenging. Nevertheless, the stand was ready for use in March 1967, more than a year after the first static test at Marshall. But thereafter, the 410-foot S-IC stand, the tallest structure in Mis­sissippi, became the focus of testing for the first-stage engines.63

Despite static testing, the real proof of successful design came only in actual flight. For AS-501, the first Saturn V vehicle, the flight on November 9, 1967, largely succeeded. The giant launch vehicle lifted the instrument unit, command and service modules, and a boilerplate lunar module to a peak altitude of 11,240 miles. The third stage then separated and the service module’s propulsion sys­tem accelerated the command module to a speed of 36,537 feet per second (about 24,628 miles per hour), comparable to lunar reentry speed. It landed in the Pacific Ocean 9 miles from its aiming point, where the USS Bennington recovered it. The first-stage engines did experience longitudinal oscillations (known as the pogo effect), but these were comparatively minor.64

Euphoria from this success dissipated, however, on April 4, 1968, when AS-502 (Apollo 6) launched. As with AS-501, this vehicle did 140 not carry astronauts onboard, but it was considered “an all-important Chapter 3 dress rehearsal for the first manned flight" planned for AS-503. The initial launch went well, but toward the end of the first-stage burn the pogo effect became much more severe than on AS-501, reaching five cycles per second, which exceeded the spacecraft’s design speci­fications. Despite the oscillations, the vehicle continued its upward course. Stage-two separation occurred, and all five of the engines ignited. Two of them subsequently shut down, but the instrument unit compensated with longer-than-planned burns for the remain­ing three engines and the third-stage propulsion unit, only to have the latter fail to restart in orbit, constituting a technical failure of the mission, although some sources count it a success.65

As Apollo Program Director Samuel Phillips told the Senate Aero­nautical and Space Sciences Committee on April 22, 1968, 18 days

after the flight, pogo was not a new phenomenon, having occurred in the Titan II and come “into general attention in the early days of the Gemini program." Aware of pogo, von Braun’s engineers had tested and analyzed the Saturn V before the AS-501 flight and found “an acceptable margin of stability to indicate" it would not de­velop. The AS-501 flight “tended to confirm these analyses." Each of the five F-1 engines had “small pulsations," but each engine ex­perienced them “at slightly different points in time." Thus, they did not create a problem. But on AS-502, the five 1.5-million-pound engines “came into a phase relationship" so that “the engine pulsa­tion was additive."66

All engines developed a simultaneous vibration of 5.5 hertz (cy­cles per second). The entire vehicle itself developed a bending fre­quency that increased (as it consumed propellants) to 5.25 hertz about 125 seconds into the flight. The engine vibrations traveled longitudinally up the vehicle structure with their peak occurring at the top where the spacecraft was (and the astronauts would be on a flight carrying them). Alone, the vibrations would not have been a problem, but they coupled with the vehicle’s bending frequency, which moved in a lateral direction. When they intersected (with both at about the same frequency), their effects combined and mul­tiplied. In the draft of an article he wrote for the New York Times, Phillips characterized the “complicated coupling" as “analogous to the annoying feedback squeal you encounter when the microphone and loud speaker of a public address system. . . coupled." This cou­pling was significant enough that it might interfere with astronauts’ performance of their duties.67

NASA formed a pogo task force including people from Marshall, other NASA organizations, contractors, and universities. The task force recommended detuning the five engines, changing the fre­quencies of at least two so that they would no longer produce vi­brations at the same time. Engineers did this by inserting liquid helium into a cavity formed in a liquid-oxygen prevalve with a cast­ing that bulged out and encased an oxidizer feed pipe. The bulging portion was only half filled with the liquid oxygen during engine operation. The helium absorbed pressure surges in oxidizer flow and reduced the frequency of the oscillations to 2 hertz, lower than the frequency of the structural oscillations. Engineers eventually applied the solution to all four outboard engines. Technical people contributing to this solution came from Marshall, Boeing, Martin, TRW, Aerospace Corporation, and North American’s Rocketdyne Division.68 This incidence of pogo showed how difficult it was for

FIG. 3.14

Launch of the giant Saturn V on the Apollo 11 mission (July 16, 1969) that carried Neil Armstrong, Edwin Aldrin, and Michael Collins on a trajectory to lunar orbit from which Armstrong and Aldrin descended to walk on the Moon’s surface. (Photo courtesy of NASA)

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rocket designers to predict when and how such a phenomenon might occur, even while aware of and actively testing for it. The episode also illustrated the cooperation of large numbers of people from a variety of organizations needed to solve such problems.

The redesign worked. On the next Saturn V mission, Apollo 8 (AS-503, December 21, 1968), the five F-1s performed their mission without pogo (or other) problems. On Christmas Eve the three astro­nauts aboard the spacecraft went into lunar orbit. They completed 10 circuits around the Moon, followed by a burn on Christmas Day to return to Earth, splashing into the Pacific on December 27. For the first time, humans had escaped the confines of Earth’s imme­diate environs and returned from orbiting the Moon. There were no further significant problems with the F-1s on Apollo missions.69

The development of the huge engines had been difficult and unpre­dictable but ultimately successful.

The next major development in double-base propellants was a method for casting (rather than extruding) the grain. The company that produced the first known rocket motor using this procedure was the Hercules Powder Company, which had operated the govern­ment-owned Allegany Ballistics Laboratory since the end of World War II. The firm came into existence in 1912 when an antitrust suit

against its parent company, E. I. du Pont de Nemours & Company, forced du Pont to divest some of its holdings. Hercules began as an explosives firm that produced more than 50,000 tons of smokeless powder during World War I. It then began to diversify into other uses of nitrocellulose. During World War II, the firm supplied large quantities of extruded double-base propellants for tactical rockets. After the war, it began casting double-based propellants by beginning with a casting powder consisting of nitrocellulose, nitroglycerin, and a stabilizer. Chemists poured this into a mold and added a cast­ing solvent of nitroglycerin plus a diluent and the stabilizer. With heat and the passage of time, this yielded a much larger grain than could be produced by extrusion alone.

Wartime research by John F. Kincaid and Henry M. Shuey at the National Defense Research Committee’s Explosives Research Laboratory at Bruceton, Pennsylvania (operated by the Bureau of Mines and the Carnegie Institute of Technology), had yielded this process. Kincaid and Shuey, as well as other propellant chemists, had developed it further after transferring to ABL, and under Hercu­les management, ABL continued work on cast double-base propel­lants. This led to the flight testing of a JATO using this propellant in 1947. The process allowed Hercules to produce a propellant grain that was as large as the castable, composite propellants that Aero­jet, Thiokol, and Grand Central were developing in this period but with a slightly higher specific impulse (also with a greater danger of exploding rather than burning and releasing the exhaust gases at a controlled rate).24

The navy had contracted with Hercules for a motor to be used as an alternative third stage on Vanguard (designated JATO X241 A1). The propellant that Hercules’ ABL initially used for the motor was a cast double-base formulation with insulation material between it and the case. This yielded a specific impulse of about 250 lbf-sec/ lbm, higher both than Grand Central’s propellant for its Vanguard third-stage motor and the specification of 245 lbf-sec/lbm for both motors. A key feature of the motor was its case and nozzle, made of laminated fiberglass. ABL had subcontracted work on the case and nozzle to Young Development Laboratories, which developed a method during 1956 of wrapping threads of fiberglass soaked in epoxy resin around a liner made of phenolic asbestos. (A phenol is a compound used in making resins to provide laminated coatings or form adhesives.) Following curing, this process yielded a strong, rigid Spiralloy (fiberglass) shell with a strength-to-weight ratio 20 percent higher than the stainless steel Aerojet was using for its propellant tanks on stage two of Vanguard.25

In 1958, while its third-stage motor was still under development, Hercules acquired this fiberglass-winding firm. Richard E. Young, a test pilot who had worked for the M. W. Kellogg Company on the Manhattan Project, had founded it. In 1947, Kellogg had designed a winding machine under navy contract, leading to a laboratory in New Jersey that built a fiberglass nozzle. It moved to Rocky Hill, New Jersey, in 1948. There, Young set up the development labora­tories under his own name and sought to develop lighter materials for rocket motors. He and the firm evolved from nozzles to cases, seeking to improve a rocket’s mass fraction (the mass of the propel­lant divided by the total mass of a stage or rocket), which was as important as specific impulse in achieving high velocities. In the mid-1950s, ABL succeeded in testing small rockets and missiles us – 236 ing cases made with Young’s Spiralloy material.26

Chapter 6 This combination of a cast double-base propellant and the fiber­glass case and nozzle created a lot of problems for Hercules engi­neers. By February 1957, ABL had performed static tests on about 20 motors, 15 of which resulted in failures of insulation or joints. Combustion instability became a problem on about a third of the tests. Attempting to reduce the instability, Hercules installed a plastic paddle in the combustion zone to interrupt the acoustic pat­terns (resonance) that caused the problem. This did not work as well as hoped, so the engineers developed a suppressor of thicker plastic. They also improved the bond between insulator and case, then cast the propellant in the case instead of just sliding it in as a single piece. Nine cases still failed during hydrostatic tests or static firings. The culprits were high stress at joints and “severe combus­tion instability."27

In February 1958, ABL began developing a follow-on third-stage motor designated X248 A2 in addition to X241. Perhaps it did so in part to reduce combustion instability, because 3 percent of the propellant in the new motor consisted of aluminum, which burned in the motor and produced particles in the combustion gases that suppressed (damped) high-frequency instabilities. But another moti­vation was increased thrust. The new motor was the one that actu­ally flew on the final Vanguard mission, September 18, 1959. As of August 1958, ABL had developed a modification of this motor, X248 A3, for use as the upper stage in a Thor-Able lunar probe. By this time, ABL was testing the motors in an altitude chamber at the air force’s Arnold Engineering Development Center and was experienc­ing problems with ignition and with burnthroughs of the case the last few seconds of the static tests.28

The X248 solid-rocket motor consisted of an epoxy-fiberglass case filled with the case-bonded propellant. The nozzle was still made of epoxy fiberglass, but with a coating of "ceramo-asbestos." By November 11, 1958, wind-tunnel static tests had shown that the X248 A2 filament-wound exit cone was adequate. By this time also, the motor had a sea-level theoretical specific impulse of about 235, which extrapolated to an impulse at altitude of some 255 lbf-sec/ lbm, and designers had overcome the other problems with the mo­tor. The X248 offered a "considerable improvement in reliability and performance over the X241 contracted for originally," according to Kurt Stehling. He also said the ABL version of the third stage suc­cessfully launched the Vanguard III satellite weighing 50 pounds, whereas Grand Central Rocket’s third stage could orbit only about 30 pounds.29

Simultaneously with the development of Polaris and then Minute – man, the air force continued work on two liquid-propellant missiles, the Titans I and II. The Titan II introduced storable propellants into the missile inventory and laid the groundwork for the core portion of the Titans III and IV space-launch vehicles. Titan I began as es­sentially insurance for Atlas in case the earlier missile’s technology proved unworkable. The major new feature of the first of the Titans was demonstration of the ability to start a large second-stage engine at a high altitude.93 The WAC Corporal had proved the viability of the basic process involved, and Vanguard would develop it further (after Titan I was started). But in 1955, using a full second stage on a ballistic missile and igniting it only after the first-stage engines had exhausted their propellants seemed risky.

The air force approved development of Titan I on May 2, 1955. Meanwhile, the Western Development Division had awarded a 44 contract on January 14, 1955, to Aerojet for engines burning liq – Chapter 1 uid oxygen and a hydrocarbon fuel for possible use on Atlas. These soon evolved into engines for the two-stage missile. Even though the Aerojet engines burned the same propellants as Atlas, there were problems with development, showing that rocket engineers

still did not have the process of design “down to a science." Despite the change in propellants, the Titan II used a highly similar design for its engines, making Aerojet’s development for that missile less problematic than it might otherwise have been (although still not without difficulties), with technology then carrying over into the Titans III and IV core launch vehicles. Meanwhile, the air force de­ployed the Titan Is in 1962. They quickly deactivated in 1965 with the deployment of Minuteman I and Titan II, but Titan I did provide an interim deterrent force.94

The history of the transition from Titan I to Titan II is compli­cated. One major factor stimulating the change was the 15 minutes or so it took to raise Titan I from its silo, load the propellants, and launch it. Another was the difficulty of handling Titan I’s extremely cold liquid oxygen used in Titan I inside a missile silo. One solution to the twin problems would have been conversion to solid propel­lants like those used in Polaris and Minuteman, but another was storable propellants. Under a navy contract in 1951, Aerojet had begun studying hydrazine as a rocket propellant. It had good perfor­mance but could detonate. Aerojet came up with a compromise so­lution, an equal mixture of hydrazine and unsymmetrical dimethyl hydrazine, which it called Aerozine 50. With nitrogen tetroxide as an oxidizer, this fuel mixture ignited hypergolically (upon contact with the oxidizer, without the need for an ignition device), offering a much quicker response time than for Titan I.95 As a result of this and other issues and developments, in November 1959 the Depart­ment of Defense authorized the air force to develop the Titan II. The new missile would use storable propellants, in-silo launch, and an all-inertial guidance system.96

On April 30, 1960, the Air Force Ballistic Missile Division’s de­velopment plan for Titan II called for it to be 103 feet long (compared to 97.4 feet for Titan I), have a uniform diameter of 10 feet (whereas Titan I’s second stage was only 8 feet across), and have increased thrust over its predecessor. This higher performance would increase the range with the Mark 4 reentry vehicle from about 5,500 nauti­cal miles for Titan I to 8,400. With the new Mark 6 reentry vehicle, which had about twice the weight and more than twice the yield of the Mark 4, the range would remain about 5,500 nautical miles. Because of the larger nuclear warhead it could carry, the Titan II served a different and complementary function to Minuteman I’s in the strategy of the air force, convincing Congress to fund them both. It was a credible counterforce weapon, whereas Minuteman I served primarily as a countercity missile, offering deterrence rather than the ability to destroy enemy weapons in silos.97

In May 1960, the air force signed a letter contract with the Mar­tin Company to develop, produce, and test the Titan II. It followed this with a contract to General Electric to design the Mark 6 reentry vehicle. In April 1959, AC Spark Plug had contracted to build an in­ertial guidance system for a Titan missile, although it was not clear at the time that this would be the Titan II.98

Although the Titan II engines were based on those for Titan I, the new propellants and the requirements in the April 30 plan necessi­tated considerable redesign. Because the new designs did not always work as anticipated, the engineers had to resort to empirical solu­tions until they found the combinations that provided the necessary performance. Even with other changes to the Titan I engine designs, the Titan II propulsion system had significantly fewer parts than its Titan I predecessor, reducing chances for failure during operation. Despite the greater simplicity, the engines had higher thrust and higher performance, as planned.99

Flight testing of the Titan II had its problems, complicated by plans to use the missile as a launch vehicle for NASA’s Project Gem­ini, leading to the Project Apollo Moon flights. However, the last 13 flights in the research-and-development series were successful, giving the air force the confidence to declare the missile fully opera­tional on the final day of 1963. Between October and December 1963, the Strategic Air Command deployed six squadrons of nine Titan IIs apiece. They remained a part of the strategic defense of the United States until deactivated between 1984 and 1987. By that time, fleet ballistic missiles and smaller land-based, solid-propellant ballistic missiles could deliver (admittedly smaller) warheads much more accurately than could the Titan IIs. Deactivation left the former operational Titan II missiles available for refurbishment as space – launch vehicles.100

Development of Titan I and Titan II did not require a lot of new technology. Instead, it adapted technologies developed either ear­lier or simultaneously for other missile or launch-vehicle programs. Nevertheless, the process of adaptation for the designs of the two Titan missiles generated problems requiring engineers to use their fund of knowledge to find solutions. These did work, and Titan II became the nation’s longest-lasting liquid-propellant missile with the greatest throw weight of any vehicle in the U. S. inventory.