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| Home > Saturn/Apollo > MSFC Propulsion Center of Excellence is Built on Solid Foundation |
MSFC Propulsion Center of Excellence is Built on Solid FoundationMike Wright Note: The following article originally appeared in "Technology for the Stars: Extending our Reach," the Marshall Space Flight Center 1995 Annual Research and Technology Report. MSFC's propulsion expertise continued in 1995, as the launch of STS-70 in 1995 marked the first flight of an upgraded version of the space shuttle main engine. Managed by MSFC, the new Block 1 engine featured such improvements as a new liquid-oxidizer turbopump built by Pratt & Whitney. Many of the turbopump parts were produced through a casting process designed to eliminate all but six of the more than 300 welds that had existed in the previously used turbopump. "The engine performed just as expected," said Otto Goetz, deputy manager of the Space Shuttle Main Engine Project. <1> The successful flight of the new engine was in keeping with MSFC's historic role as NASA's primary propulsion development center. 1995 marked MSFC's 35th anniversary, but the roots of its propulsion expertise run to the latter half of the 1940's and to the New Mexico desert. There, members of a German V-2 rocket team, originally assembled by Wernher von Braun in Germany, reassembled to work on missile and rocket developments under contract to the U.S. Army. In 1950, the Army transferred the Von Braun team to Huntsville and expanded its membership. Throughout the 1950's, engineers and scientists on Redstone Arsenal made new strides in rocket and missile development for the Army. On September 8, 1960, President Eisenhower came to Huntsville to dedicate the new George C. Marshall Space Flight Center, where hundreds of those same engineers and scientists who had worked for the Army formed the nucleus of the new NASA center. The V-2 Rocket Motor The V-2 rocket motor has been called "the immediate ancestor of many of the American rockets to follow." <2> The 46-foot V-2 rocket could carry a 1,650-pound warhead 225 miles. During World War II, an estimated 1,115 V-2 rockets were successfully fired against England and 1,675 against continental targets.<3> After World War II, more than 100 V-2 missiles were launched at White Sands, where they provided invaluable data in the beginning of America's missile program. The engine for the V-2 used a 5,000-revolutions-per- minute turbine to develop 504 kilowatts (675 horsepower). The rocket produced a thrust of 59,500 pounds at sea level and 70,000 pounds at altitudes above 25 miles. According to rocket and space historian Willy Ley, the fuel for the V-2 "was ordinary ethyl alcohol-in this case made from potatoes-to which enough water had been added to bring its strength down to 75 percent by volume." Liquid oxygen was used as the oxidizer. For the first time a turbopump was incorporated, powered by an 80-percent hydrogen-peroxide steam generator.<4> In the late 1940's and throughout the 1950's, V-2 rocket motor technology directly influenced plans for the development of missiles and rockets in the United States. Engine Proposals for Hermes C After World War II, American rocket experts at White Sands were anxious to exploit German V-2 rocket motor technology. For example, they initiated the Hermes program, actually a conglomeration of different projects and proposals. For a while, engineers proposed building a three-stage Hermes C rocket using six rocket motors in clusters of two in its first stage. These motors would be designed to develop a total of 600,000 pounds of thrust during a burning time of 1 minute. After jettisoning the first stage, the second-stage motors would provide an additional 100,000 pounds of thrust during a 1-minute burning time. A winged third stage would have given Hermes C a range of about 2,000 miles. Hermes C, and an even smaller version known as Hermes C-2, turned out to be too ambitious, and the project was scaled back. <5> Nevertheless, Hermes research conducted by General Electric contributed to the advancing state of the art in rocket motor design, especially for the Redstone. "The Hermes C-1 study was handed to our team, and the design and development of the new rocket with a 500-mile range was given a very high priority by the Chief of Ordnance in the fall of 1950," Von Braun said.<6> Navaho Booster Engines The development of the propulsion system for Redstone was also directly linked to an Air Force project, i.e., Navaho, which had roots in the V-2 engine. Before the Air Force became convinced that ballistic missiles represented the most effective approach to unmanned strategic long-range weapons, it developed early air-breathing cruise missiles. Even though it used a ramjet engine for sustained flight to the target, the Navaho was boosted into the air by three liquid-propellant rocket engines originally designed with 75,000 pounds of thrust. <7> MSFC engineers Alex McCool and Keith B. Chandler traced the development trends of early liquid-propellant engines and noted that while early V-2 concepts were incorporated in these engines, many new design features and improvements were also brought in for the Navaho. A new thrust-chamber design provided better cooling for the higher heat-transfer rate and an improved single injector replaced 18 separate injectors. <8> Eventually the engine was updated to 135,000 pounds of thrust. The Redstone NAA 75-110 The Navaho production contract was later canceled, but its research and development effort directly influenced future rocket engines, including the engine for the Redstone. The Navaho XLR43- NA-1 engine, basically a redesigned version of the V-2, came nearer than any other engine did to meeting the special requirements for the Redstone. "We decided to adapt to our purpose the liquid-propulsion system then used in the Navaho test missile-a North American Aviation engine," Von Braun wrote.<9> The Redstone engine was designated " NAA 75-110 " and rated at 75,000 pounds thrust at sea level, with a thrust-burning time of 110 seconds. <10> Improvements in the performance features and components of the engine yielded seven different engine types, A-1 through A-7. The A-7 engine was the power plant for the Mercury-Redstone launch vehicles. Basically, it was the same power plant used in the latest tactical Redstone ballistic missiles with modifications to improve overall efficiency and safety. The engine generated 78,000 pounds of thrust at sea level. <11> In May 1961, a Mercury-Redstone designed by the Von Braun team in Huntsville and managed by the new Marshall Center launched Alan B. Shepard, the first American astronaut, into space.<12> Jupiter S-3D Engine On May 31, 1957, an Army Jupiter Intermediate-Range Ballistic Missile was fired to an altitude of 250 to 350 miles and to a range of 1,500 miles, marking the limit of its design capability and the first successful flight of such a missile. <13> The success was tied to Huntsville where members of the Von Braun team at Redstone Arsenal had modified existing engine hardware to meet new requirements. Like the Redstone, the Jupiter missile drew power from a V-2 engine originally adapted for the Navaho. <14> For the Jupiter, however, the engine was scaled up to a thrust of 150,000 pounds. The engine was also designed to operate on liquid oxygen and kerosene (RP-1) instead of the liquid oxygen and ethyl alcohol used in the Redstone, resulting in about a 7-percent gain in propellant performance. The engine also utilized a tubular-wall, regeneratively cooled thrust chamber that provided a major reduction in weight, cost, and fabrication, as compared to previous double-walled chambers. <15> The Rocketdyne Division of North American Aviation supplied the S-3D engine. The Jupiter space flight that probably attracted more public attention than any other came on May 28, 1959, when two primates, Able and Baker, rode in a capsule aboard a nose cone and survived the flight in spite of reentry temperatures of approximately 5,000 °F. <16> Jupiter C Engine Other launch vehicles, including the Jupiter C, developed by the Army missile team in Huntsville also received their inheritance from the experience the team had acquired on the V-2, the Hermes, and the Redstone. On August 7, 1957, an Army Jupiter C, developed by the Von Braun team in Huntsville, fired a one-third-scale model nose cone 1,200 miles down range from a Florida launch site. The nose cone reached a summit altitude of 600 miles and was recovered the next day. On November 7, the nose cone was shown on television by President Eisenhower as evidence that the United States had marked another milestone in the missile and space race. <17> Engineers at Redstone Arsenal had solved the reentry heating problem for the Jupiter missile. They had also modified the Redstone and designed it to serve as the first stage for the Jupiter C. Two clustered stages of solid-propellant motors developed by the Jet Propulsion Laboratory in California served as the second and third stages for the vehicle. Changes to the Jupiter C stage included increasing the tankage so that it could hold more fuel and oxidizer, thus extending engine burning time. The engine itself was also modified to burn a more powerful fuel, Hydyne (unsymmetrical dimethylhydrazine and diethylene triamine), boosting the first-stage thrust to 83,000 pounds. <18> On January 31, 1958, the engineers from Huntsville used the Jupiter C to tackle the biggest test of all: they used the Jupiter C rocket to launch Explorer I, the first U.S. satellite, into orbit. <19> H-1 Engines for Saturn I and Saturn IB As the United States planned for the decade of the 1960's, its missile and space experts reviewed their existing inventory of launch vehicles. The review demonstrated the clear need to develop a large-scale engine that could be arranged in a cluster in the first stage to launch communications satellites and other scientific payloads, including weather satellites and instrumented probes. <20> The engine would eventually boost the Saturn launch vehicle. The history of the Saturn program began in the Spring of 1957; Wernher von Braun recalled, "Our preliminary designers were studying a large, clustered-engine, first-stage arrangement. In the late summer of 1958, we were authorized to proceed with the design and development of a 1.5-million-pound thrust stage based on this bunching concept." The H-1 engine based on the Jupiter S-3D engine was selected for the new booster that would eventually be known as Saturn I. <21> The S-I stage for the Saturn I became the S-IB first stage for the Saturn IB. The design used Von Braun's clustering concept. This involved using former Redstone and Jupiter tanks, which were lengthened to carry added propellant, while the basic diameter of the 70-inch Redstone and the 105-inch Jupiter tanks were retained. The tank arrangement gave an alternate pattern of the four fuel and four oxidizer tanks, clustered around the 105-inch center oxidizer tank. Rocketdyne was selected as the contractor to modify the S-3D design for the H-1, which would use liquid oxygen and RP-1. <22> "The H-1 also shed a number of accessories carried over from the Jupiter engine system," wrote Saturn historian Roger Bilstein. "Early versions of the H-1 relied on the Jupiter's lubrication system, which featured a 73-liter (20-gallon) oil tank. The H-1 designers arranged for the vehicle's own fuel, RP-1 (along with some additives), to do the same job. This arrangement eliminated not only the oil tankage, but also a potential source of contamination." <23> Rocketdyne's Edward E. Straub also reviewed the modifications made to the H-1. Two ground start tanks (with complex accessories) for the Jupiter engine were replaced on the H-1 by a simple solid-propellant cartridge starter. In addition, a complex thrust-level control system for the Jupiter engine was modified for the H-1.<24> Initial versions of the Saturn I vehicle, called "Block I," had eight H-1 engines-each producing 165,000 pounds of thrust. H-1 engines were also used in a Block II design that increased thrust to 188,000 pounds each. By the time the tenth and last Saturn I vehicle lifted off on July 30, 1965, the United States had clearly committed itself to President Kennedy's challenge to land a man on the Moon by the end of the decade. The final Saturn I flight climaxed with what MSFC officials termed as a "program which started the U.S. on the road to the Moon with 10 straight successes."<25> RL-10 Upper-Stage Engines During the 1960's, many MSFC efforts were directed toward advanced engine technology and higher energy propellants. Fuel-efficiency assessments pointed to liquefied gases as the promising new propellants for advanced missions, and to liquid hydrogen, in particular, for the Saturn upper stages.<26> Liquid hydrogen, however, introduced even more risk and danger into missile and space research. Joel E. Tucker, who has traced the history of Pratt & Whitney's RL-10 upper-stage rocket engine, has noted that the company's key engineers and researchers were introduced to hydrogen-fueled projects in 1956, with a sketch of the Hindenburg's last fateful moments and a report on an explosion of a hydrogen lab. <27> Undaunted, but cautious, industry and government rocket experts were drawn by what Saturn historian Roger Bilstein has called the "lure of liquid hydrogen." Studies showed that "compared to an RP-1- fueled engine of similar size, liquid-hydrogen fuel could increase the specific impulse of an engine by 40 percent," Bilstein noted. <28> The RL-10 engine was rooted in liquid-hydrogen engine research. Pratt & Whitney had explored liquid hydrogen for the Air Force for the super-secret high-altitude reconnaissance aircraft known later as the "SR71 Blackbird." The Air Force was also interested in a liquid-hydrogen engine that would enable it to launch heavier payloads, such as communications satellites. <29> NASA eventually inherited responsibility for the RL-10 engine under development by Pratt & Whitney-and destined for use in the Saturn I upper stages. The first flight of the engine occurred in 1964 after engineers at MSFC and Pratt & Whitney logged hours of engine testing in Huntsville and at other sites. The tests helped score hundreds of innovative design breakthroughs in cryogenic pumps, the thrust chamber, the injector face, and the lubrication system. <30> J-2 Engines for Saturn IB and Saturn V The selected configuration for the Saturn I second stage, the S-IV stage, was a cluster of six RL-10 engines, each having 15,000 pounds of thrust. But as NASA looked beyond Saturn I to large launch vehicles for future missions, clustering the RL-10 was not enough. Beginning in 1960, development of the J-2 engine, a single-chamber hydrogen/oxygen engine of 200,000 pounds thrust was underway. <31> By late 1960, the first experimental components for the J-2 were being fabricated and assembled by a research and development team. Like the RL-10, the development of the J-2 engine was dependent on innovation and design simplicity. For example, engineers had to design a system for forming some 600 uniform posts on the face of the J-2 injector, and they had to tackle new problems of insulation, metals embitterment, and sealing. In addition, engineers had to develop a new method of brazing high-strength stainless-steel tubing to form the J-2's regeneratively cooled thrust chamber. <32> These huge engines, built by Rocketdyne for MSFC, became the powerhouse for Saturn IB and Saturn V upper stages. A single J-2 was used in the Saturn IB second stage and Saturn V third stage. Five J-2 engines were clustered in the Saturn V second stage for a million pounds of thrust. Saturn V F-1 Engine The origins of the Saturn launch vehicle concept are rooted in the research conducted within the Army Ballistic Missile Agency in the late 1950's. However, interest in the program moved well beyond the borders of Redstone Arsenal after President Kennedy's challenge in 1961 to land a man on the Moon before the end of the decade. In reality, the Von Braun team had recognized early on that a rocket engine of tremendous capabilities would be needed if man ever embarked on lunar journeys or sent probes into deep space. As a result, development started in the 1950's on the 1.5-million-pound-thrust F-1 engine even before a vehicle was designed for it. The F-1 would burn the familiar liquid oxygen and RP-1, and had roots in the Air Force Navaho program. The F-1 was based on an initial concept for a 360,000-pound-thrust E-1 engine that would burn liquid oxygen and RP-1. <33> Rocketdyne was selected as the contractor for the F-1, and-for a brief while-NASA considered using the F-1 on a vehicle of tremendous size, the Nova, which would be capable of direct flights to the Moon. The Nova never materialized, but the F- 1 did and would eventually be used in the first stage (S-IC) of the vehicle that would launch men on their way to the Moon. Five F-1 engines would provide a total thrust of 7.5 million pounds in the Saturn V S-IC stage. Rocketdyne's Bob Biggs has pointed out that although the giant F-1 engine was simple, it was not developed without problems. "Its very 'bigness' created a brand-new territory for technical problems." According to Biggs, the most significant problem was also the one most expected and the most difficult to solve- combustion instability. The engine was designed to the man-rated safety concept, which required that it be dynamically stable. If any engine system was disturbed from any source, the system was required to automatically overcome the disturbance and return to stable operations. <34> Saturn historian Roger Bilstein has recounted the efforts that Rocketdyne and MSFC engineers used to solve the stiff challenge of combustion instability. "The most bizarre aspect of F-1 testing (like the H-1) involved the use of small bombs to upset the thrust exhaust pattern to measure the engine's ability to recover from disturbance."<35> Biggs has termed the F-1 as "the No-Frills Giant." <36> NASA and Rocketdyne news releases often tried to put the size and power of the engine in perspective by pointing out, for example, that "the fuel pump of the Rocketdyne F-1 pushes fuel with the force of 30 diesel locomotives," or that the five engines generated "double the amount of potential hydroelectric power that would be available at any given moment if all the moving waters of North America were channeled through turbines."<37> Of course, those who watched the launch of Apollo 11 on July 15, 1969, understood the power of the Saturn V vehicle that Wernher von Braun called the "Giant." <38> Space Shuttle Main Engine The last Saturn F-1's that NASA employed helped lift Skylab into orbit in 1973. By then, NASA engineers were already deep into the design for the space shuttle main engine, a concept that broke with the past, according to shuttle historian Dennis R. Jenkins. The challenge, Jenkins said, was "not to build a larger, more powerful engine, but to build a small, compact engine that could be throttled during ascent to provide some measure of control over the maximum dynamic pressure and speed of the vehicle." <39> MSFC engineers who have traced the technology projects leading to the development of the space shuttle main engine have pointed to an "aggressive technology program in high-pressure tubomachinery initiated in the 1960's." They point out that much of the work was done by Pratt & Whitney under MSFC's sponsorship, with outgrowth known in-house as the concept for the HG-3, a 350,000-pound-thrust engine named after Hans G. Paul, the long-time chief of the Propulsion Division. In essence, the HG-3 concept eventually became the space shuttle main engine.<40> The main engines would become the most advanced cryogenic liquid-fueled rocket engines ever built. To get very high performance from an engine compact enough that it could not encumber the orbiter or diminish its desired payload capability, MSFC worked closely with its prime contractor, the Rocketdyne Division of Rockwell International. The greatest problem was to develop the combustion devices and complex tubomachinery-the pumps, turbines, seals, and bearings-that could contain and deliver propellants to the engines at pressures several times greater than in the Saturn engines. The shuttle main engine was also designed as the first propulsion system with a computer mounted directly on the engine to control operation and automatically make corrective adjustments or shut down the engine safely. For improved fuel efficiency, engineers developed an ingenious, staged combustion cycle never before used in rocket engines. <41> Rocketdyne's Bob Biggs has reported on the first 10 years of the shuttle main engine and has traced the technical hurdles and challenges that engineers at Rocketdyne and MSFC faced during the development period. These included predicting the transient behavior of the propellants and engine hardware during start and shutdown. Rocketdyne engineers and officials, such as Rocketdyne Vice President Matt Eck, also sought solutions to concerns with high-pressure fuel turbopump bearing instability problems, explosions, and blade failures. On various occasions during different tests, engineers confronted a fire that started in the engine's main oxidizer valve, a major fracture in the housing for the main fuel valve, the rupture of a nozzle fuel coolant feedline, and a fire that burned through the engine's fuel preburner. Solutions were also sought to heat-exchanger failures, weld cracks in the main combustion chamber, and problems with the main injector posts. A major portion of the problems were answered by conducting ground test after ground test. In fact, a goal of 65,000 seconds of total ground testing was reached during an engine test on March 24, 1980-a little more than a year before the first space shuttle was launched on April 12, 1981. <42> It is possible to draw charts and diagrams that trace the origins of MSFC's expertise in liquid-propulsion systems all the way back to the days of the V-2 or the Navaho missile. Unfortunately, charts and diagrams do not adequately convey the thousands of hours engineers at MSFC and its contractor sites have spent year after year, studying, designing, analyzing, testing, and dissecting pumps, bearings, valves, insulation, fuel mixtures, nozzles, feedlines, and thousands of other rocket engine components. Better evidence of that expertise came in 1995 when NASA launched the first flight of the upgraded space shuttle main engine and marked more than 200 main engine flights overall. References 1. July 19, l995. STS-70 Sees First Use of New Space Shuttle Main Engine: Inertial Upper Stage Deploys Last Tracking and Data Relay Satellite System. Marshall Star.
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