Abstract and Keywords
This introductory chapter sets out the purposes of the book, which is to address the question: How could the United States have advanced so rapidly from the relatively primitive rocket technology available on a small scale in the mid-1950s to the almost routine access to space available by the 1980s? It also traces the convoluted technological trajectory from Robert H. Goddard's imaginative but problem-prone early rockets to the huge Saturn V and the complex space shuttle, among other launch vehicles. An overview of the subsequent chapters is also presented.
Note: As these pages reprise the introduction to Goddard Rockets to Minute-man III: Preludes to U.S. Space-Launch Vehicle Technology, readers of theprevious volume may wish to skip to the concluding two paragraphs.
Although black-powder rockets had been around for centuries, it was not until 1962 that American physicist and rocket developer Robert H. Goddard launched the first known liquid-propellant rocket. Despite this auspicious beginning, not until the mid-1950s did the United States begin to invest significant resources in rocket development. Already by the end of January, the United States had launched its first satellite, and within a generation it had developed a series of missiles and launch vehicles of enormous power and sophistication. The Atlas, Titan, Scout, Delta, Saturn, and space shuttle launched a huge number of satellites and other spacecraft that revolutionized our understanding of the universe, including our own planet, and brought events and reporting from all parts of the world into the American living room with unprecedented speed. How could the United States have advanced so rapidly from the relatively primitive rocket technology available on a small scale in the mid-1950s to the almost routine access to space available by the 1980s?
This book and the preceding volume, Preludes to U.S. Space-Launch Vehicle Technology: Goddard Rockets to Minuteman III, attempt to answer thatquestion and to trace the convoluted technological trajectory from Goddard's imaginative but problem-prone early rockets to the huge Saturn V and the complex space shuttle, among other launch vehicles. The history of these vehicles has been punctuated by failures on the path to overall success. But on the whole, the achievements have been remarkable.
Perhaps most remarkable have been the unique features of the space shuttles. As the United States approaches the end of shuttle flights in 2010, (p.2) it is appropriate to reflect that in some ways this astonishing but troubled launch vehicle and spacecraft was the culmination of the development process discussed in these two volumes. It represented a bold dream of converting previously expendable missile and launch vehicle technologies into a reusable source of routine access to and return from space, analogous to airliners and large cargo aircraft for the nearer skies. In one sense the effort was a failure, since the Air Force continues to rely on expendable launch vehicles and NASA is retreating, under budgetary and safety pressures, from reusability to a concept akin to the Saturn launch vehicles of the Apollo era.
In another sense, however, the crew and cargo launch vehicles Ares I and V (discussed in the final chapter of this book) are themselves a legacy of the shuttles since they will use shuttle experience and technology as part of the basis upon which to build a more affordable and safer way to return to the Moon and even go to Mars.
It is also worthwhile to recognize that many of the achievements of the space shuttles would have been extraordinarily difficult to accomplish without the unique features built into the shuttles. To give but one example, after space shuttle Discovery launched the Hubble Space Telescope in April 1990, it quickly became apparent that the enormous promise of this astronomical instrument was marred by a small but critical flaw in its primary mirror. Following a partial correction by computer enhancement, a planned routine repair mission turned into a rescue mission in December 1993 in which the huge telescope was recaptured in the payload bay of space shuttle Endeavour, outfitted with a corrective mechanism for the optics of the primary mirror, and serviced in other ways to allow the scientific instrument to continue to function as originally envisioned. Some 1,200 women and men were involved in orchestrating, designing, practicing for, and carrying out this delicate and complex resuscitation effort, which could hardly have been performed by an expendable launch vehicle coupled with any other existing spacecraft. Endeavour's astronauts used five spacewalks to install the device using additional mirrors to correct Hubble's optics as well as to replace failed gyroscopes and the wide field/planetary camera. They then installed equipment to improve the telescope's failing computer memory, among other things. Although Hubble had been providing important new scientific data even before the rescue mission, afterwards it began to live up to and even exceed the performance that astronomers had expected from it, including provision of the first solid evidence for the presence in space of black holes (regions of intense gravitational force) and of spectacular images (p.3) that graced the pages of newspapers and even appeared on a cover of Newsweek.
Literally millions of people had watched as the shuttle astronauts performed their repairs, and the entire team responsible for the mission received the 1993 Robert J. Collier Trophy from the National Aeronautic Association “for outstanding leadership, intrepidity, and the renewal of public faith in America's space program by the successful orbital recovery and repair of the Hubble Space Telescope.” This and other almost equally astonishing achievements showed the unique value of the space shuttle as the fruition of a comparatively short but intense period of development of space launch capabilities.1
Although the focus of these two books is on technology used by launch vehicles, which permitted space exploration such as that carried out by Hubble, Preludes to U.S. Space-Launch Vehicle Technology is mostly about missiles and can be read by itself as a history of missile technology. Viking to Space Shuttle, likewise, can serve as a self-standing history of launch vehicletechnology, although most readers may also want to read Preludes to U.S. Space-Launch Vehicle Technology for the technology upon which that forlaunch vehicles was significantly based. Missiles follow trajectories aimed at places on Earth instead of the heavens; they carry warheads instead of satellites or spacecraft. But especially in the area of propulsion, they use much the same technology as launch vehicles. In fact, many launch vehicles have been converted missiles. Others have borrowed stages from missiles.
One major irony stands out in this process. While the complexity and sophistication of missiles and launch vehicles gave birth to the expression “rocket science,” careful study of the vehicles' development reveals many instances in which the designers and operators encountered problems they did not fully understand. They frequently had to resort to trial-and-error fixes to make their rockets perform as intended. Although data about and understanding of the advancing technologies continually increased, each large jump in scale and performance introduced new difficulties. Rocketry was, and is, as much an art as a science, fitting the description of engineering—as distinguished from science—provided by Edwin Layton, Walter Vincenti, and Eugene Ferguson, among others. (Besides engineering as art, these scholars also emphasized engineering's focus on doing rather than knowing, on design of artifacts rather than understanding the universe, and on making technological decisions in the absence of clear understanding—all features that distinguish engineering from science in their view.)2
This is not to say that science and scientists did not contribute to rocket (p.4) technology. For example, Ronald L. Simmons earned a B.A. in chemistry at the University of Kansas in 1952 and went on to work for thirty-three years as a propulsion and explosives chemist with the Hercules Powder Company, a year with Rocketdyne, and thirteen years with the U.S. Navy at Indian Head, Maryland. Among other projects, he worked on upper stages for Polaris, Minuteman, Poseidon, and Trident.
In he wrote, “I consider myself to be a chemist … even though my work experience has been a lot of engineering. I really believe the titles are arbitrary, though I consider myself a scientist rather than an engineer.” He added in relation to the issue of rocket engineering versus rocket science, “’Tis amazing how much we don't know or understand, yet we launch large rockets routinely … and successfully … that is when we pay attention to details and don't let the schedule be the driving factor. … By and large, I believe that we understand enuff to be successful … yet may not understand why.” Although he spent much of his career working with double-base propellants—primarily those using nitrocellulose (NC) and nitroglycerin—he admitted, “There is much no one understands about nitrocellulose (and black powder for that matter) in spite of the fact that NC has been known since and black powder since before 1300!”3
Chronologically, the two books follow the development of American rocket technology through the end of the cold war in 1989–91. Chapter 2 of Preludes to U.S. Space-Launch Vehicle Technology covers the German V-2 because it became one of the foundation stones for U.S. rocket technology. Many of the V-2's developers immigrated to the United States after the end of World War II. They became the nucleus of the later NASA Marshall Space Flight Center. Under the leadership of Wernher von Braun, many of these Germans (along with hundreds of Americans) oversaw the development of the Saturn launch vehicles that lifted twelve astronauts on their journey to the Moon in the Apollo program.
The present book ends about 1990–91 with the close of the cold war because, after that, launch vehicle development began a new chapter. Funding became more spartan, and the United States began borrowing technology from the Russians, who had competed with American missile and launch-vehicle technology during the Soviet era.
Most readers of this book will have watched launches of the space shuttle or other launch vehicles on television. For those less familiar with the fundamentals of rocketry, this may help: Missiles and other rockets lift off from Earth through the thrust created by the burning of propellants (fuel and oxidizer).4 This combustion creates expanding exhaust products, mostly (p.5) gaseous, that pass through a nozzle at the back of the rocket. The nozzle contains a narrow throat and an exit cone that cause the gases to accelerate, thereby increasing thrust. The ideal angle for the exit cone depends on the altitude and pressure at which it will operate, with different angles needed at sea level than at higher altitudes where the atmosphere is thinner and the outside (ambient) pressure is lower.
Rockets in the period covered by this book typically used multiple stages to accelerate the vehicle all the way to its designed speed. When the propellants from one stage became exhausted, that stage would drop off the stack, so that as succeeding stages took over, there was less weight to be propelled to higher speeds. Multiple stages also permitted using exit cones of varying angles for optimal acceleration at different altitudes.
Most propellants required an ignition device to begin combustion, but hypergolic fuels and oxidizers ignited upon contact, dispensing with the need for an igniter. These types of propellants typically had less propulsive power than the extremely cold (cryogenic) liquid oxygen and liquid hydrogen, but they required less special handling than their cryogenic counterparts. Liquid oxygen and liquid hydrogen would boil off if not loaded just before launch, so they needed a lot more preparation time before a launch could occur. Hypergolic propellants, by contrast, could be stored in propellant tanks for comparatively long periods, allowing almost instant launch upon command. This was an especial advantage for missiles, and for spacecraft launches that had narrow “windows” of time, when the desired trajectory was lined up with the launch location only for a short period as Earth rotated and circled the Sun.
Solid-propellant missiles and rockets also enjoyed rapid-launch capabilities. They were much simpler and usually less heavy than liquid-propellant rockets because the fuel and oxidizer filled the combustion chamber without a need for propellant tanks, high pressure or pumps to force the propellant into the chamber, extensive plumbing, and other complications. Typically, technicians loaded a solid propellant into a combustion chamber with thin metal or a composite structure as the case, insulation between the case and the propellant, and a cavity in the middle where an igniter started combustion. Engineers designed the internal cavity to provide optimal thrust, with more exposed propellant surface providing more instant thrust and a smaller amount of surface providing less initial thrust. The propellant burned from the inside toward the case, with the insulation protecting the case as the propellant burned outward. The disadvantage of solids was the difficulty of stopping and restarting combustion, which could be done with valves in the (p.6) case of liquids. Thus, for launch vehicles, solids usually appeared as initial stages, called stage, to provide maximum thrust for the initial escape from Earth's gravitational field or as upper stages (although the Scout remained a fully solid-propellant, multistage launch vehicle from 1960 to 1994).
Liquid propellants found more frequent use for the core stages, usually stage and often stage 2, of launch vehicles such as the Atlas, Titan, Delta, and space shuttle. They also served in upper stages that needed to be stopped and restarted in orbit for insertion of satellites and spacecraft into particular orbits or trajectories. But the process of injecting fuels and oxidizers into the combustion chamber proved to be fraught with problems. For reasons that have been difficult for engineers to understand, mixing the two types of propellants in the needed proportions frequently resulted in oscillations that could destroy the combustion chamber. Known as combustion instability, this severe problem only gradually yielded to solutions—each scaling up of a particular type of engine usually causing new problems that required their own specific solutions.
Solid propellants also experienced combustion instability. Problems with solids were somewhat different from those with liquids. But as with liquids, the solutions required much research and, often, trial and error before they could be solved, or at least ameliorated.5
Besides propulsion systems, rockets required structures that would withstand the high heats of combustion, intense dynamic pressures as the vehicles accelerated through the atmosphere, shock waves as they passed through the speed of sound (referred to as Mach 1), and aerothermodynamic heating from friction while traveling at high speeds through the atmosphere. Because weight slowed acceleration to orbital speeds and altitudes, structural issues required much research to find lighter materials that would still withstand the rigors of launch. Engineers gradually found new materials that were strong, heat resistant, light, and, if possible, affordable.
Another field of research was aerodynamics. Missiles and launch vehicles needed to have as little drag (friction from the atmosphere that slowed flight and increased temperatures) as possible. They also had to be steerable by means of vanes, canards, moveable fins, vernier (auxiliary) and attitude-control rockets, fluids injected into the exhaust stream, and/or gimballed (rotated) engines or nozzles.
Associated with these types of control devices were various guidance and control systems incorporating computers programmed to adjust steering and keep the missile or launch vehicle on course. Such systems varied greatly in design and weight. They involved increasingly sophisticated programming (p.7) of the computers. But they were essential to the success of both missiles and launch vehicles.6
Chapter 1 of Preludes to U.S. Space-Launch Vehicle Technology: Viking to Space Shuttle introduces the two rocket pioneers who had the greatest influence on American missiles and launch vehicles, the American physicist and rocket experimenter Robert H. Goddard and the Romanian-German rocket theorist Hermann Oberth. Both were fascinating characters with highly inventive minds. Although Goddard's innovations foreshadowed many later rocket technologies, his failure to publish many details of his research and development during his lifetime limited his influence. Oberth published his more theoretical conceptions in greater detail and had real influence on Wernher von Braun and other Germans who developed the V-2 missile before and during World War II and then immigrated to the United States. Through them, Oberth arguably had greater influence on U.S. missile and launch-vehicle development than did Goddard. But it can also be argued that they had a synergistic effect, with Goddard providing an example of how to develop rockets, at least to a point, while Oberth provided more theoretical details about rocket development in sources that he published early enough for them to be consulted by early rocket developers.
Although the V-2 was only one of many influences on American rocket technology, it was important, if sometimes overrated. Chapter 2 of Preludes to U.S. Space-Launch Vehicle Technology discusses the development of thismissile and provides the technical information needed for later analysis of ways in which the V-2 was and was not a stepping-stone for American rocketry. Chapter 3 covers rocket development in the United States before, during, and shortly after World War II at what became the Jet Propulsion Laboratory (JPL) near Pasadena, California. Chapter 4 discusses other American rocket efforts from 1930 to 1954, culminating in a joining of German and JPL rocket technologies in the Bumper WAC project. Meanwhile, other efforts during and after World War II yielded important solid-propellant innovations that paralleled those at JPL, which had worked on both liquid and solid propellants. These developments at JPL and elsewhere form the subject of chapter 5.
Chapter 6 of Preludes to U.S. Space-Launch Vehicle Technology covers the Redstone missile and its modification into the first stage of the Juno I launch vehicle that placed the first U.S. satellite in orbit on January 31, 1958. The upper stages of the Juno I employed JPL technology, which again blended with that of Wernher von Braun's team in Alabama as they had on the Bumper WAC. The Redstone itself combined German and American contributions (p.8) to rocketry, including some from the Air Force's Navaho missile. Chapters 7 through 9 cover the Atlas, Thor, Jupiter, Titan I and II, Polaris, and Minuteman missiles that produced still other technologies and separate stages used on later launch vehicles. Without the cold war and the developments it prompted, these contributions to launch vehicle technology would have evolved far more slowly they did.
Chapter 1 of Viking to Space Shuttle covers the Viking and Vanguard programs, separate American rocket efforts that contributed importantly to missile and launch vehicle technology, including the use of gimbals for steering. Chapters 2 through 7 of this book then discuss the uses of missile technology in development of the Delta, Atlas, Scout, Saturn, Titan, and space shuttle launch vehicles. Development of these vehicles, and of the missiles that preceded or were contemporaneous with them, was by no means problem-free. Besides cold-war threats and resultant funding, factors in the evolution of rocket technology in the United States included the efforts of both technical rocket engineers and others who were often less intimately involved with technical matters than with engineering the social aspects of missile and launch-vehicle development by promoting that cause in Congress, the Pentagon, and the media (as, previously, the V-2 was advocated to the Nazi regime in Germany). Without the promotional efforts of these so-called heterogeneous engineers, even the cold war might not have been enough to overcome the inertia that stood in the way of complex and expensive development, punctuated by many well-publicized failures in the early years.
Other factors in the rapid development of U.S. rocketry included both rivalry between military services (and the rocket firms that supported them) and, at the same time, a high degree of cooperation and sharing of knowledge by the competitors. A wide range of disciplines was required to design and develop rockets, calling for unselfish collaboration among competitors in solving problems that occurred during tests and operational launches. Universities also played a role in this process, as did a growing technical literature. Relatedly, the movement of personnel between firms (carrying technical knowledge from one project to another), professional networks, and federal intellectual property arrangements all helped promote and transfer innovation, leading to increasingly powerful and sophisticated launch vehicles that placed satellites in orbit and sent spacecraft on missions to explore our solar system and beyond.
A final contributing factor to the rapid and ultimately successful development of launch vehicle technology was a variety of management systems (p.9) that helped to integrate efforts on the many systems in missiles and rockets, to keep them on schedule, and to promote configuration and cost control. All of these factors and others are discussed in these two books.
Both books are organized essentially by project. As the dates in the chapter titles will suggest, there was a great deal of overlapping in time between projects. Since these projects borrowed technologies from one another, there is an inherent problem with presenting technical materials in such a way that readers not highly familiar with the history of rocket technology can easily follow the story. The problem is compounded by the fact that different systems on a given missile or rocket were developed simultaneously. Thus it is impossible to follow a strictly chronological path in the narrative. Even if that could be done, the result would hardly be comprehensible. To assist the reader, I have included in the present book an appendix of Notable Technological Achievements for both missiles and launch vehicles and a glossary of technical terms and acronyms. The roughly chronological list of achievements may provide background for those who have not read Preludes to U.S. Space-launch vehicle Technology, and it can serve as a refresherif earlier events are imperfectly remembered during the reading of this volume.
Let me conclude by saying that although I have spent many years delving in dusty archives and poring over highly technical literature to gather the materials for both books, I am acutely aware that my narrative does not and cannot represent the final word on the subject. Practitioners of rocket design and development are extremely numerous. I could interview or locate interviews of only a small fraction of them, and many sources exist in scattered places I could not locate. My experience suggests that many rocket engineers know only small parts of the story I have told and that their memories do not always coincide with those of colleagues in other firms or military services. I hope that the material I have been able to assemble will stimulate others to build on or correct what I have contributed.
(1.) Tatarewicz, “Telescope Servicing Mission” (quotations,392, 365); Bilstein, Testing Aircraft, Exploring Space, 156–57; Crouch, Aiming for the Stars, 278–79; Launius, NASA, 126.
(2.) See Layton, “Mirror-Image Twins,” 562–63,565, 575–76,578,580; Layton, “Technology as Knowledge,”40; Layton, “Presidential Address,”602,605; Vincenti, What Engineers Know,4,6–7,161; Ferguson, Mind's Eye, xi,1,3,9,12,194. Of course, there aremany ways in which science and engineering overlap, as emphasized in Latour, Science in Action,107,130–31,174, and by Layton himself as quoted in Bijker, Hughes, and Pinch, Social Construction of Technological Systems,20.
(3.) Simmons, résumé, n.d., and e-mail messages, July 15,2002 (quotations), UP. Actually, black powder has probably been known since before 1100.
(4.) Even people who know better often refer to liquid- or solid-fuel rockets. But the liquids or solids in question include not just fuel but an oxidizer. This is what distinguishes rockets from jet engines; jets use oxygen from the atmosphere to combine with their fuel and permit combustion, while rockets carry their own oxidizer. Hence, the proper terminology is liquid- or solid-propellant rockets.
(5.) Incidentally, the proper technical designation of liquid-propellant combustion systems is engines, while their solid-propellant counterparts are called motors.
(6.) This section is based on far too many sources to cite here. One source that covers much the same material in language comprehensible to nonexperts is NASA Education Division, Rockets, 12–18. Guidance involves selection of a maneuvering sequence to move a rocket from a particular location and direction along its trajectory to the place and attitude needed to carry it to its destination; control executes the maneuvers dictated by the guidance function. See Haeussermann, “Guidance and Control,”225.