An earth-orbiting station, equipped to study the sun, the stars, and the earth, is a concept found in the earliest speculation about space travel. During the formative years of the United States space program, space stations were among many projects considered. But after the national decision in 1961 to send men to the moon, space stations were relegated to the background.
Project Apollo was a firm commitment for the 1960s, but beyond that the prospects for space exploration were not clear. As the first half of the decade ended, new social and political forces raised serious questions about the nation's priorities and brought the space program under pressure. At the same time, those responsible for America's space capability saw the need to look beyond Apollo for projects that would preserve the country's leadership in space. The time was not propitious for such a search, for the national mood that had sustained the space program was changing.
In the summer of 1965, the office that became the Skylab program office was established in NASA Headquarters, and the project that evolved into Skylab was formally chartered as a conceptual design study. During the years 1965-1969 the form of the spacecraft and the content of the program were worked out. As long as the Apollo goal remained to be achieved, Skylab was a stepchild of manned spaceflight, achieving status only with the first lunar landing. When it became clear that America's space program could not continue at the level of urgency and priority that Apollo had enjoyed, Skylab became the means of sustaining manned spaceflight while the next generation of hardware and missions developed.
The first five chapters of this book trace the origins of the Skylab concept from its emergence in the period 1962-1965 through its evolution into final form in 1969.
Directions for Manned Spaceflight. Space Stations after 1962. Sizing Up a Space Station. Air Force Seeks Role in Space. President Calls for NASA's Plans. Mueller Opens Apollo Applications Program Office.
 The summer of 1965 was an eventful one for the thousands of people involved in the American space program. In its seventh year, the National Aeronautics and Space Administration (NASA) was hard at work on the Gemini program, its second series of earth-orbiting manned missions. Mercury had concluded on 16 May 1963. For 22 months after that, while the two-man Gemini spacecraft was brought to flight readiness, no American went into space. Two unmanned test flights preceded the first manned Gemini mission, launched on 23 March 1965.1
Mercury had been used to learn the fundamentals of manned spaceflight. Even before the first Mercury astronaut orbited the earth, President John F. Kennedy had set NASA its major task: to send a man to the moon and bring him back safely by 1970. Much had to be learned before that could be done-not to mention the rockets, ground support facilities, and launch complexes that had to be built and tested-and Gemini was part of the training program. Rendezvous-bringing two spacecraft together in orbit-was a part of that program; another was a determination of man's ability to survive and function in the weightlessness of spaceflight.
That summer the American public was getting acquainted, by way of network television, with the site where most of the Gemini action was taking place-the Manned Spacecraft Center (MSC). Located on the flat Texas coastal plain 30 kilometers southeast of downtown Houston- close enough to be claimed by that city and given to it by the media-MSC was NASA's newest field center, and Gemini was the first program managed there. Mercury had been planned and conducted by the Space Task Group, located at Langley Research Center, Hampton, Virginia. Creation of the new Manned Spacecraft Center, to be staffed initially by members of the Space Task Group, was announced in 1961; by the middle of 1962 its personnel had been moved to temporary quarters in Houston; and in 1964 it occupied its new home. The 4.1-square-kilometer center provided facilities for spacecraft design and testing, crew training, and  flight operations or mission control. By 1965 nearly 5000 civil servants and about twice that many aerospace-contractor employees were working at the Texas site.2
Heading this second largest of NASA's manned spaceflight centers was the man who had formed its predecessor group in 1958, Robert R. Gilruth. Gilruth had joined the staff at Langley in 1937 when it was a center for aeronautics research of NASA's precursor, the National Advisory Committee for Aeronautics (NACA). He soon demonstrated his ability in Langley's Flight Research Division, working with test pilots in quantifying the characteristics that make a satisfactory airplane. Progressing to transonic and supersonic flight research, Gilruth came naturally to the problems of guided missiles. In 1945 he was put in charge of the Pilotless Aircraft Research Division at Wallops Island, Virginia, where one problem to be solved was that of bringing a missile back through the atmosphere intact. When the decision was made in 1958 to give the new national space agency the job of putting a man into earth orbit, Gilruth and several of his Wallops Island colleagues moved to the Space Task Group, a new organization charged with designing the spacecraft to do that job.3
The Space Task Group had, in fact, already claimed that task for itself, and it went at the problem in typical NACA fashion. NACA had been a design, research, and testing organization, accustomed to working with aircraft builders but doing no fabrication work itself. The same mode characterized MSC. The Mercury and Gemini spacecraft owed their basic design to Gilruth's engineers, who supervised construction by the McDonnell Aircraft Company of St. Louis and helped test the finished hardware.4
In the summer of 1965 the Manned Spacecraft Center was up to its ears in work. By the middle of June two manned Gemini missions had been flown and a third was in preparation. Thirty-three astronauts, including the first six selected as scientist-astronauts,i were in various stages of training and preparation for flight. Reflecting the general bullishness of the manned space program, NASA announced plans in September to recruit still more flight crews.5
Houston's design engineers, meanwhile, were hard at work on the spacecraft for the Apollo program. The important choice of mission mode-rendezvous in lunar orbit-had been made in 1962; it dictated two vehicles, whose construction MSC was supervising. North American Aviation, Inc., of Downey, California, was building the command ship consisting of a command module and a supporting service module- collectively called the command and service module-which carried the crew to lunar orbit and back to earth. A continent away in Bethpage  Long Island, Grumman Aircraft Engineering Corporation was working on the lunar module, a spidery-looking spacecraft that would set two men down on the moon's surface and return them to the command module, waiting in lunar orbit, for the trip home to earth. Houston engineers had established the basic design of both spacecraft and were working closely with the contractors in building and testing them. All of the important subsystems-guidance and navigation, propulsion and attitude control, life-support and environmental control-were MSC responsibilities; and beginning with Gemini 4, control of all missions passed to Houston once the booster had cleared the launch pad.6
Since the drama of spaceflight was inherent in the risks taken by the men in the spacecraft, public attention was most often directed at the Houston operation. This superficial and news-conscious view, though true enough during flight and recovery, paid scant attention to the launch vehicles and to the complex operations at the launch site, without which the comparatively small spacecraft could never have gone anywhere, let alone to the moon.
The Saturn launch vehicles were the responsibility of NASA's largest field center, the George C. Marshall Space Flight Center, 10 kilometers southwest of Huntsville in northern Alabama. Marshall had been built around the most famous cadre in rocketry-Wernher von Braun and his associates from Peenemunde, Germany's center for rocket research during World War II. Driven since his schoolboy days by the dream of spaceflight, von Braun in 1965 was well on the way to seeing that dream realized, for the NASA center of which he was director was supervising the development of the Saturn V, the monster three-stage rocket that would power the moon mission.7
Marshall Space Flight Center was shaped by experiences quite unlike those that molded the Manned Spacecraft Center. The rocket research and development that von Braun and his colleagues began in Germany in the 1930s had been supported by the German army, and their postwar work continued under the supervision of the U.S. army. In 1950 the group moved to Redstone Arsenal outside Huntsville, where it functioned much as an army arsenal does, not only designing launch vehicles but building them as well. From von Braun all the way down, Huntsville's rocket builders were dirty-hands engineers, and they had produced many Redstone and Jupiter missiles. In 1962 von Braun remarked in an article written for a management magazine, "we can still carry an idea for a space vehicle . . . from the concept through the entire development cycle of design, development, fabrication, and testing." That was the way he felt his organization should operate, and so it did; of 10 first stages built for the Saturn I, 8 were turned out at Marshall.8
The sheer size of the Apollo task required a division of responsibility, and the MSC and Marshall shares were sometimes characterized as  "above and below the instrument unit." ii To be sure, the booster and its payload were not completely independent, and the two centers cooperated whenever necessary. But on the whole, as Robert Gilruth said of their roles, "They built a damned good rocket and we built a damned good spacecraft." Von Braun, however, whose thinking had never been restricted to launch vehicles alone, aspired to a larger role for Marshall: manned operations, construction of stations in earth orbit, and all phases of a complete space program-which would eventually encroach on Houston's responsibilities.9
But as long as Marshall was occupied with Saturn, that aspiration was far from realization. Saturn development was proceeding well in 1965. The last test flights of the Saturn I were run off that year and preparations were under way for a series of Saturn IB shots. iii In August each of the three stages of the Saturn V was successfully static-fired at full thrust and duration. Not only that, but the third stage was fired, shut down, and restarted, successfully simulating its role of injecting the Apollo spacecraft into its lunar trajectory. Flight testing remained to be done, but Saturn V had taken a long stride.10
Confident though they were of ultimate success, Marshall's 7300 employees could have felt apprehensive about their future that summer. After Saturn V there was nothing on the drawing boards. Apollo still had a long way to go, but most of the remaining work would take place in Houston. Von Braun could hardly be optimistic when he summarized Marshall's prospects in a mid-August memo. Noting the trend of spaceflight programs, especially booster development, and reminding his coworkers that 200 positions were to be transferred from Huntsville to Houston, von Braun remarked that it was time "to turn our attention to the future role of Marshall in the nation's space program." As a headquarters official would later characterize it, Marshall in 1965 was "a tremendous solution looking for a problem." Sooner than the other centers, Marshall was seriously wondering, "What do we do after Apollo ?" 11
Some 960 kilometers southeast of Huntsville, halfway down the Atlantic coast of Florida, the third of the manned spaceflight centers had no time for worry about the future. The John F. Kennedy Space Center, usually referred to as "the Cape" from its location adjacent to Cape Canaveral' was in rapid expansion. What had started as the Launch Operations Directorate of Marshall Space Flight Center was, by 1965, a busy center with a total work force (including contractor employees) of 20 000 people. In April construction teams topped off the huge Vehicle  Assembly Building, where the 110-meter Saturn V could be assembled indoors. Two months later road tests began for the mammoth crawler-transporter that would move the rocket, complete and upright, to one of two launch pads. Twelve kilometers eastward on the Cape, NASA launch teams were winding up Saturn I flights and working Gemini missions with the Air Force.12
Under the directorship of Kurt Debus, who had come from Germany with von Braun in 1945, KSC's responsibilities included much more than launching rockets. At KSC all of the booster stages and spacecraft first came together, and though they were thoroughly checked and tested by their manufacturers, engineers at the Cape had to make sure they worked when put together. One of KSC's largest tasks was the complete checkout of every system in the completed vehicle, verifying that NASA's elaborate system of "interface control" actually worked. If two vehicle components, manufactured by different contractors in different states, did not function together as intended, it was KSC's job to find out why and see that they were fixed. Checkout responsibility brought KSC into close contact not only with the two other NASA centers but with all of the major contractors.13
Responsibility for orchestrating the operations of the field centers and their contractors lay with the Office of Manned Space Flight (OMSF) at NASA Headquarters in Washington. One of three program offices, OMSF reported to NASA's third-ranking official, Associate Administrator Robert C. Seamans, Jr. Ever since the Apollo commitment in 1961, OMSF had overshadowed the other program offices (the Office of Space Science and Applications and the Office of Advanced Research and Technology) not only in its share of public attention but in its share of the agency's budget.
Directing OMSF in 1965 was George E. Mueller (pronounced "Miller"), an electrical engineer with a doctorate in physics and 23 years' experience in academic and industrial research. Before taking the reins as associate administrator for manned spaceflight in 1963, Mueller had been vice president of Space Technology Laboratories, Inc., in Los Angeles, where he was deeply involved in the Air Force's Minuteman missile program. He had spent his first year in Washington reorganizing OMSF and gradually acclimatizing the field centers to his way of doing business. Considering centralized control to be the prime requisite for achieving the Apollo goal, Mueller established an administrative organization that gave Headquarters the principal responsibility for policy-making while delegating as much authority as possible to the centers.14
 Mueller had to pick his path carefully, for the centers had what might be called a "States'-rights attitude" toward direction from Headquarters and had enjoyed considerable autonomy. Early in his tenure, convinced that Apollo was not going to make it by the end of the decade, Mueller went against center judgment to institute "all-up" testing for the Saturn V. This called for complete vehicles to be test-flown with all stages functioning the first time-a radical departure from the stage-by-stage testing NASA and NACA had previously done, but a procedure that had worked for Minuteman. It would save time and money-if it worked- but would put a substantial burden on reliability and quality control. Getting the centers to accept all-up testing was no small feat; when it succeeded, Mueller's stock went up. Besides putting Apollo back on schedule, this practice increased the possibility that some of the vehicles ordered for Apollo might become surplus and thus available for other uses.15
In an important sense the decision to shoot for the moon shortcircuited conventional schemes of space exploration. From the earliest days of serious speculation on exploration of the universe, the Europeans who had done most of it assumed that the first step would be a permanent station orbiting the earth. Pioneers such as Konstantin Eduardovich Tsiolkowskiy and Hermann Oberth conceived such a station to be useful, not only for its vantage point over the earth below, but as a staging area for expeditions outward. Wernher von Braun, raised in the European school, championed the earth-orbiting space station in the early 1950s in a widely circulated national magazine article.16
There were sound technical reasons for setting up an orbiting waystation en route to distant space destinations. Rocket technology was a limiting factor; building a station in orbit by launching its components on many small rockets seemed easier than developing the huge ones required to leave the earth in one jump. Too, a permanent station would provide a place to study many of the unknowns in manned flight, man's adaptability to weightlessness being an important one. There was, as well, a wealth of scientific investigation that could be done in orbit. The space station was, to many, the best way to get into space exploration; all else followed from that.17
The sense of urgency pervading the United States in the year following Sputnik was reflected in the common metaphor, "the space race." It was a race Congress wanted very much to win, even if the location of the finish line was uncertain. In late 1958 the House Select Committee on Space began interviewing leading scientists, engineers, corporate executives, and government officials, seeking to establish goals beyond Mercury. The committee's report, The Next Ten Years in Space, concluded that a space station was the next logical step. Wernher von Braun and his staff at the Army Ballistic Missile Agency presented a similar view in briefings for NASA. Both a space station and a manned lunar landing  were included in a list of goals given to Congress by NASA Deputy Administrator Hugh Dryden in February 1959.18
Later that year NASA created a Research Steering Committee on Manned Space Flight to study possibilities for post-Mercury programs. That committee is usually identified as the progenitor of Apollo; but at its first meeting members placed a space station ahead of the lunar landing in a list of logical steps for a long-term space program. Subsequent meetings debated the research value of a station versus a moon landing, advocated as a true "end objective" requiring no justification in terms of some larger goal to which it contributed. Both the space station and the lunar mission had strong advocates, and Administrator T. Keith Glennan declined to commit NASA either way. Early in 1960, however, he did agree that after Mercury the moon should be the end objective of manned spaceflight.19
Still, there remained strong justification for the manned orbital station and plenty of doubt that rocket development could make the lunar voyage possible at any early date. Robert Gilruth told a symposium on manned space stations in the spring of 1960 that NASA's flight missions were a compromise between what space officials would like to do and what they could do. Looking at all the factors involved, Gilruth said, "It appears that the multi-man earth satellites are achievable . . ., while such programs as manned lunar landing and return should not be directly pursued at this time. " Heinz H. Koelle, chief of the Future Projects Office at Marshall Space Flight Center, offered the opinion that a small laboratory was the next logical step in earth-orbital operations, with a larger (up to 18 metric tons) and more complex one coming along when rocket payloads could be increased.20 This was the Marshall viewpoint, frequently expressed up until 1962.
During 1960, however, manned flight to the moon gained ascendancy. In the fiscal 1961 budget hearings, very little was said about space stations; the budget proposal, unlike the previous year's, sought no funds for preliminary studies. The agency's long-range plan of January 1961 dropped the goal of a permanent station by 1969; rather, the Space Task Group was considering a much smaller laboratory-one that could fit into the adapter section that supported the proposed Apollo spacecraft on its launch vehicle.21
Then, in May 1961, President John F. Kennedy all but sealed the space station's fate with his proclamation of the moon landing as America's goal in space. It was the kind of challenge American technology could most readily accept: concise, definite, and measurable. Success or failure would be self-evident. It meant, however, that all of the efforts of NASA and much of aerospace industry would have to be narrowly focused. Given a commitment for a 20-year program of methodical space development, von Braun's 1952 concept might have been accepted as the best way  to go. With only 8 1/2 years it was out of the question. The United States was going to pull off its biggest act first, and there would be little time to think about what might follow.
The decision to go for the moon did not in itself rule out a space station; it made a large or complex one improbable, simply because there would be neither time nor money for it. At Marshall, von Braun's group argued during the next year for reaching the moon by earth-orbit rendezvous-the mission mode whereby a moon-bound vehicle would be fueled from "tankers" put into orbit near the earth. Compared to the other two modes being considered-direct flight and lunar-orbit rendezvousiv-this seemed both safer and more practical, and Marshall was solidly committed to it. In studies done in 1962 and 1963, Marshall proposed a permanent station capable of checking out and launching lunar vehicles. In June 1962, however, NASA chose lunar-orbit rendezvous for Apollo, closing off prospects for extensive earth-orbital operations as a prerequisite for the lunar landing.22
From mid-1962, therefore, space stations were proper subjects for advanced studies-exercises to identify the needs of the space program and pinpoint areas where research and development were required. Much of this future-studies work went to aerospace contractors, since NASA was heavily engaged with Apollo. The door of the space age had just opened, and it was an era when, as one future projects official put it, "the sky was not the limit" to imaginative thinking. Congress was generous, too; between 1962 and 1965 it appropriated $70 million for future studies. A dozen firms received over 140 contracts to study earth-orbital, lunar, and planetary missions and the spacecraft to carry them out. There were good reasons for this intensive planning. As a NASA official told a congressional committee, millions of dollars in development costs could be saved by determining what not to try.23
Langley Research Center took the lead in space-station studies in the early 1960s. After developing a concept for a modest station in the summer of 1959-one that foreshadowed most of Skylab's purposes and even considered the use of a spent rocket stage-Langley's planners went on to  consider much bigger stations. Artificial gravity, to be produced by rotating the station, was one of their principal interests from the start. Having established an optimum rate and radius of rotation (4 revolutions per minute and 25 meters), they studied a number of configurations, settling finally on a hexagonal wheel with spokes radiating from a central control module. Enclosing nearly 1400 cubic meters of work space and accommodating 24 to 36 crewmen, the station would weigh 77 metric tons at launch.24
Getting something of this size into orbit was another problem. Designers anticipated severe problems if the station were launched piecemeal and assembled in orbit-a scheme von Braun had advocated 10 years earlier-and began to consider inflatable structures. Although tests were run on an 8-meter prototype, the concept was finally rejected, partly on the grounds that such a structure would be too vulnerable to meteoroids. As an alternative Langley suggested a collapsible structure that could be erected, more or less umbrella-fashion, in orbit and awarded North American Aviation a contract to study it.25
Langley's first efforts were summarized in a symposium in July 1962. Papers dealt with virtually all of the problems of a large rotating station, including life support, environmental control, and waste management. Langley engineers felt they had made considerable progress toward defining these problems; they were somewhat concerned, however, that their proposals might be too large for NASA's immediate needs.26
Similar studies were under way in Houston, where early in 1962 MSC began planning a large rotating station to be launched on the Saturn V. As with Langley's proposed stations, Houston's objectives were to assess the problems of living in space and to conduct scientific and technological research. Resupply modules and relief crews would be sent to the station with the smaller Saturn IB and an Apollo spacecraft modified to carry six men, twice its normal complement. MSC's study proposed to put the station in orbit within four years.27
By the fall of 1962 the immediate demands of Apollo had eased somewhat, allowing Headquarters to give more attention to future programs. In late September Headquarters officials urged the centers to go ahead with their technical studies even though no one could foresee when a station might fly. Furthermore, it had begun to look as though rising costs in Apollo would reduce the money available for future programs. Responses from both MSC and Langley recognized the need for simplicity and fiscal restraint; but the centers differed as to the station's mission. Langley emphasized a laboratory for advanced technology. Accordingly, NASA's offices of space science and advanced technology should play important roles in planning. MSC considered the station's major purpose to be a base for manned flights to Mars.28
 The following month Joseph Shea, deputy director for systems in the Office of Manned Space Flight, sought help in formulating future objectives for manned spaceflight. In a letter to the field centers and Headquarters program offices, Shea listed several options being considered by OMSF, including an orbiting laboratory. Such a station was thought to be feasible, he said, but it required adequate justification to gain approval. He asked for recommendations concerning purposes, configurations' and specific scientific and engineering requirements for the space station, with two points defining the context: the importance of a space station program to science, technology, or national goals; and the unique characteristics of such a station and why such a program could not be accomplished by using Mercury, Gemini, Apollo, or unmanned spacecraft.29 Public statements and internal correspondence during the next six months stressed the agency's intention to design a space station that would serve national needs.30
By mid-1963, NASA had a definite rationale for an earth-orbiting laboratory. The primary mission on early flights would be to determine whether man could live and work effectively in space for long periods. The weightlessness of space was a peculiar condition that could not be simulated on earth-at least not for more than 30 seconds in an airplane. No one could predict either the long-term effects of weightlessness or the results of a sudden return to normal gravity. These biomedical concerns, though interesting in themselves, were part of a larger goal: to use space stations as bases for interplanetary flight. A first-generation laboratory would provide facilities to develop and qualify the various systems, structures, and operational techniques needed for an orbital launch facility or a larger space station. Finally, a manned laboratory had obvious uses in the conduct of scientific research in astronomy, physics, and biology.
Although mission objectives and space-station configuration were related, the experiments did not necessarily dictate a specific design.
NASA could test man's reaction to weightlessness in a series of gradually extended flights beginning with Gemini hardware, a low-cost approach particularly attractive to Washington. An alternate plan would measure astronauts' reaction to varying levels of artificial gravity within a large rotating station. Joseph Shea pondered the choices at a conference in August 1963:
Is a minimal Apollo-type MOL [Manned Orbiting Laboratory] sufficient for the performance of a significant biomedical experiment? Or perhaps the benefits of a truly multi-purpose MOL are so overwhelming . . that one should not spend unnecessary time and  effort . . . building small stations, but, rather, proceed immediately with the development of a large laboratory in space.31
Whatever choice NASA made, it could select from a wide range of spacestation concepts generated since 1958 by the research centers and aerospace contractors. The possibilities fit into three categories: small, medium, and large.
The minimum vehicle, emphasizing the use of developed hardware, offered the shortest development time and lowest cost. Most often mentioned in this category was Apollo, the spacecraft NASA was developing for the lunar landings. There were three basic parts to Apollo: command, service, and lunar modules. The conical command module carried the crew from launch to lunar orbit and back to reentry and recovery, supported by systems and supplies in the cylindrical service module to which it was attached until just before reentry. Designed to support three men, the CM was roomy by Gemini standards, even though its interior was no larger than a small elevator. Stowage space was at a premium, and not much of its instrumentation could be removed for operations in earth orbit. One part of the service module was left empty to accommodate experiments, but it was unpressurized and could only be reached by extravehicular activity. The lunar module was an even more specialized and less spacious craft. It was in two parts: a pressurized ascent stage containing the life-support and control systems, and a descent stage, considerably larger but unpressurized. The descent stage could be fitted with a fair amount of experiments; but like the service module, it was accessible only by extravehicular activity.32
The shortage of accessible space was an obvious difficulty in using Apollo hardware for a space station. Proposals had been made to add a pressurized module that would fit into the adapter area, between the launch vehicle and the spacecraft, but this tended to offset the advantages of using existing hardware. Still, in July 1963, with the idea of an Apollo laboratory gaining favor, Headquarters asked Houston to supervise a North American Aviation study of an Extended Apollo mission.33
North American, MSC's prime Apollo contractor, had briefly considered the Space Task Group's proposal for an Apollo laboratory two years earlier. Now company officials revived the idea of the module in the adapter area, which had grown considerably during the evolution of the Saturn design. Though the study's primary objective was to identify the modifications required to support a 120-day flight, North American also examined the possibility of a one-year mission sustained by periodic resupply of expendables. Three possible configurations were studied: an Apollo command module with enlarged subsystems; Apollo with an attached module supported by the command module; and Apollo plus a new, selfsupporting laboratory module. A crew of two was postulated for the first concept; the others allowed a third astronaut.34
 Changing the spacecraft's mission would entail extensive modifications but no basic structural changes. Solar cells would replace the standard hydrogen-oxygen fuel cells, which imposed too great a weight penalty. In view of the adverse effects of breathing pure oxygen for extended periods, North American recommended a nitrogen-oxygen atmosphere, and instead of the bulky lithium hydroxide canister to absorb carbon dioxide, the study proposed to use more compact and regenerable molecular sieves.v Drawing from earlier studies, the study group prepared a list of essential medical experiments and established their approximate weights and volumes, as well as the power, time, and workspace required to conduct them. It turned out that the command module was too small to support more than a bare minimum of these experiments, and even with the additional module and a third crewman there would not be enough time to perform all of the desired tests.35
North American's study concluded that all three concepts were technically sound and could perform the required mission. The command module alone was the least costly, but reliance on a two-man crew created operational liabilities. Adding a laboratory module, though obviously advantageous, increased costs by 15-30% and posed a weight problem. Adding the dependent module brought the payload very near the Saturn IB's weight-lifting limit, while the independent module exceeded it. Since NASA expected to increase the Saturn's thrust by 1967, this was no reason to reject the concept; however, it represented a problem that would persist until 1969: payloads that exceeded the available thrust. North American recommended that any follow-up study be limited to the Apollo plus a dependent module, since this had the greatest applicability to all three mission proposals. The findings were welcomed at Headquarters, where the funding picture for post-Apollo programs remained unclear. The company was asked to continue its investigation in 1964, concentrating on the technical problems of extending the life of Apollo subsystems.36
Several schemes called for a larger manned orbiting laboratory that would support four to six men for a year with ample room for experiments Like the minimum vehicle, the medium-sized laboratory was usually a zero-gravity station that could be adapted to provide artificial gravity Langley's Manned Orbiting Research Laboratory, a study begun in late 1962, was probably the best-known example of this type: a four-man canister 4 meters in diameter and 7 meters long containing its own life-support systems. Although the laboratory itself would have to be  developed, launch vehicles and ferry craft were proven hardware. A Saturn IB or the Air Force's Titan III could launch the laboratory, and Gemini spacecraft would carry the crews. Another advantage was simplicity: the module would be launched in its final configuration, with no requirement for assembly or deployment in orbit. Use of the Gemini spacecraft meant there would be no new operational problems to solve. Even so, the initial cost was unfavorable and Headquarters considered the complicated program of crew rotation a disadvantage.37
Large station concepts, like MSC's Project Olympus, generally required a Saturn V booster and separately launched crew-ferry and logistics spacecraft. Crew size would vary from 12 to 24, and the station would have a five-year life span. Proposed large laboratories ranged from 46 to 61 meters in diameter, and typically contained 1400 cubic meters of space. Most provided for continuous rotation to create artificial gravity, with non-rotating central hubs for docking and zero-gravity work. Such concepts represented a space station in the traditional sense of the term, but entailed quite an increase in cost and development time.38
Despite the interest in Apollo as an interim laboratory, Houston was more enthusiastic about a large space station. In June 1963, MSC contracted for two studies, one by Douglas Aircraft Company for a zerogravity station and one with Lockheed for a rotating station. Study specifications called for a Saturn V booster, a hangar to enclose a 12-man ferry craft, and a 24-man crew. Douglas produced a cylindrical design 31 meters long with pressurized compartments for living quarters and recreation, a command center, a laboratory that included a one-man centrifuge to simulate gravity for short periods, and a hangar large enough to service four Apollos. The concept, submitted in February 1964, was judged to be within projected future capabilities, but the work was discontinued because there was no justification for a station of that size.39
Lockheed's concept stood a better chance of eventual adoption, since it provided artificial gravity-favored by MSC engineers, not simply for physiological reasons but for its greater efficiency. As one of them said, "For long periods of time [such as a trip to Mars], it might just be easier and more comfortable for man to live in an environment where he knew where the floor was, and where his pencil was going to be, and that sort of thing." Lockheed's station was a Y-shaped module with a central hub providing a zero-gravity station and a hangar for ferry and logistics spacecraft. Out along the radial arms, 48 men could live in varying levels of artificial gravity.40
While studies of medium and large stations continued, NASA began plans in 1964 to fly Extended Apollo as its first space laboratory. George Mueller's all-up testing decision in November 1963 increased the likelihood of surplus hardware by reducing the number of launches required in the moon program. Officials refused to predict how many flights might be eliminated, but 1964 plans assumed 10 or more excess Saturns.
 Dollar signs, however, had become more important than surplus hardware Following two years of generous support, Congress reduced NASA's budget for fiscal 1964 from $5.7 to $5.1 billion. The usually Optimistic von Braun told Heinz Koelle in August 1963, "I'm convinced that in view of NASA's overall funding situation, this space station thing will not get into high gear in the next few years. Minimum C-IB approach [Saturn IB and Extended Apollo] is the only thing we can afford at this time." The same uncertainty shaped NASA's planning the following year. In April 1964, Koelle told von Braun that Administrator James Webb had instructed NASA planners to provide management with "various alternative objectives and missions and their associated costs and consequences rather than detailed definition of a single specific long term program." Von Braun's wry response summed up NASA's dilemma: "Yes, that's the new line at Hq., so they can switch the tack as the Congressional winds change."41
At the FY 1965 budget hearings in February 1964, testimony concerning advanced manned missions spoke of gradual evolution from Apollo-Saturn hardware to more advanced spacecraft. NASA had not made up its mind about a post-Apollo space station. Two months later, however, Michael Yarymovych, director for earth-orbital-mission studies, spelled out the agency's plans to the First Space Congress meeting at Cocoa Beach, Florida. Extended Apollo, he said, would be an essential element of an expanding earth-orbital program, first as a laboratory and later as a logistics system. Some time in the future, NASA would select a more sophisticated space station from among the medium and large concepts under consideration. Mueller gave credence to his remarks the following month by placing Yarymovych on special assignment to increase Apollo system capabilities.42 Meanwhile, a project had appeared that was to become Skylab's chief competitor for the next five years: an Air Force orbiting laboratory.
For a decade after Sputnik, the U.S. Air Force and NASA vied for roles in space. The initial advantage lay with the civilian agency, for the Space Act of 1958 declared that "activities in space should be devoted to peaceful purposes." In Line with this policy, the civilian Mercury project was chosen over the Air Force's "Man in Space Soonest" as America's first manned space program.43 But the Space Act also gave DoD responsibility for military operations and development of weapon systems; Consequently the Air Force sponsored studies over the next three years to define space bombers, manned spy-satellites, interceptors, and a command and control center. In congressional briefings after the 1960 elections, USAF spokesmen stressed the theme that "military space, defined as space out to 10 Earth diameters, is the battleground of the future."44
 For all its efforts, however, the Air Force could not convince its civilian superiors that space was the next battleground. When Congress added $86 million to the Air Force budget for its manned space glider, Dyna-Soar, Secretary of Defense Robert S. McNamara refused to spend the money. DoD's director of defense research and development testified to a congressional committee, "there is no definable need at this time, or military requirement at this time" for a manned military space program. It was wise to advance American space technology, since military uses might appear; but "NASA can develop much of it or even most of it." Budget requests in 1962 reflected the Air Force's loss of position. NASA's $3.7 billion authorization was three times what the Air Force got for space activities; three years earlier the two had been almost equal.45
Throughout the Cold War, Russian advances proved the most effective stimuli for American actions; so again in August 1962 a Soviet space spectacular strengthened the Air Force argument for a space role. Russia placed two spacecraft into similar orbits for the first time. Vostok 3 and 4 closed to within 6 1/2 kilometers, and some American reports spoke of a rendezvous and docking. Air Force supporters saw military implications in the Soviet feat, prompting McNamara to reexamine Air Force plans. Critics questioned the effectiveness of NASA-USAF communication on technical and managerial problems. In response, James Webb created a new NASA post, deputy associate administrator for defense affairs, and named Adm. Walter F. Boone (USN, ret.) to it in November 1962. In the meantime, congressional demands for a crash program had subsided, partly because successful NASA launchesvi bolstered confidence in America's civilian programs.46
The Cuban missile crisis occupied the Pentagon's attention through much of the fall, but when space roles were again considered, McNamara showed a surprising change of attitude. Early in 1962 Air Force officials had begun talking about a "Blue Gemini" program, a plan to use NASA's Gemini hardware in early training missions for rendezvous and support of a military space station. Some NASA officials welcomed the idea as a way to enlarge the Gemini program and secure DoD funds. But when Webb and Seamans sought to expand the Air Force's participation in December 1962, McNamara proposed that his department assume responsibility for all America's manned spaceflight programs. NASA officials successfully rebuffed this bid for control, but did agree, at McNamara's insistence, that neither agency would start a new manned program in near-earth orbit without the other's approval.47 The issue remained alive for months. At one point the Air Force attempted to gain control over  NASA's long-range planning. An agreement was finally reached in September protecting NASA's right to conduct advanced space-station studies but also providing for better liaison through the Aeronautics and Astronautics Coordinating Board (the principal means for formal liaison between the two agencies). The preamble to the agreement expressed the view that, as far as practicable, the two agencies should combine their requirements in a common space-station.48
McNamara's efforts for a joint space-station were prompted in part by Air Force unhappiness with Gemini. Talk of a "Blue Gemini" faded in 1963 and Dyna-Soar lost much of its appeal. If NASA held to its schedules, Gemini would fly two years before the space glider could make its first solo flight On 10 December Secretary McNamara terminated the Dyna-soar project, transferring a part of its funds to a new project, a Manned Orbiting Laboratory (MOL).49
With MOL the Air Force hoped to establish a military role for man in space; but since the program met no specific defense needs, it had to be accomplished at minimum cost. Accordingly, the Air Force planned to use proven hardware: the Titan IIIC launch vehicle, originally developed for the Dyna-Soar, and a modified Gemini spacecraft. Only the system's third major component, the laboratory, and its test equipment would be new. The Titan could lift 5700 kilograms in addition to the spacecraft; about two-thirds of this would go to the laboratory, the rest to test equipment. Initial plans provided 30 cubic meters of space in the laboratory, roughly the volume of a medium-sized house trailer. Laboratory and spacecraft were to be launched together; when the payload reached orbit, two crewmen would move from the Gemini into the laboratory for a month's occupancy. Air Force officials projected a cost of $1.5 billion for four flights, the first in 1968.50
The MOL decision raised immediate questions about the NASA-DoD pact on cooperative development of an orbital station. Although some outsiders considered the Pentagon's decision a repudiation of the Webb-McNamara agreement, both NASA and DoD described MOL as a single military project rather than a broad space program. They agreed not to construe it as the National Space Station, a separate program then under joint study; and when NASA and DoD established a National Space Station Planning Subpanel in March 1964 (as an adjunct of the Aeronautics and Astronautics Coordinating Board), its task was to recommend a station that would follow MOL. Air Force press releases implied that McNamara's approval gave primary responsibility for space stations to the military, while NASA officials insisted that the military program complemented its own post-Apollo plans. Nevertheless, concern that the two programs might appear too similar prompted engineers at Langley and MSC to rework their designs to look less like MOL.51
Actually, McNamara's announcement did not constitute program  approval, and for the next 20 months MOL struggled for recognition and adequate funding. Planning went ahead in 1964 and some contracts were let, but the deliberate approach to MOL reflected political realities. In September Congressman Olin Teague (Dem., Tex.), chairman of the House Subcommittee on Manned Space Flight and of the Subcommittee on NASA Oversight, recommended that DoD adapt Apollo to its needs. Shortly after the 1964 election, Senate space committee chairman Clinton Anderson (Dem., N.M.) told the president that he opposed MOL; he believed the government could save more than a billion dollars in the next five years by canceling the Air Force project and applying its funds to an Extended Apollo station. Despite rumors of MOL's impending cancellation, the FY 1966 budget proposal included a tentative commitment of $ 150 million.52
The Bureau of the Budget, reluctant to approve two programs that seemed likely to overlap, allocated funds to MOL in December with the understanding that McNamara would hold the money pending further studies and another review in May. DoD would continue to define military experiments, while NASA identified Apollo configurations that might satisfy military requirements. A joint study would consider MOL's utility for non-military missions. A NASA-DoD news release on 25 January 1965 said that overlapping programs must be avoided. For the next few years both agencies would use hardware and facilities "already available or now under active development" for their manned spaceflight programs-at least "to the maximum degree possible."53
In February a NASA committee undertook a three-month study to determine Apollo's potential as an earth-orbiting laboratory and define key scientific experiments for a post-Apollo earth-orbital flight program. Although the group had worked closely with an Air Force team, the committee's recommendations apparently had little effect on MOL, the basic concept for which was unaltered by the review. More important, the study helped NASA clarify its own post-Apollo plans.54
Since late 1964, advocates of a military space program had increased their support for MOL, the House Military Operations Subcommittee recommending in June that DoD begin full-scale development without further delay. Two weeks later a member of the House Committee on Science and Astronautics urged a crash program to launch the first MOL within 18 months. Russian and American advances with the Voskhod and Gemini flights-multi-manned missions and space walks-made a military role more plausible. On 25 August 1965, MOL finally received President Johnson's blessing.55 Asked if the Air Force had clearly established a role for man in space, a Pentagon spokesman indicated that the chances seemed good enough to warrant evaluating man's ability "much more thoroughly than we're able to do on the ground." NASA could not provide the answers because the Gemini spacecraft was too cramped. One  newsman wanted to know why the Air Force had abandoned Apollo; the reply was that Apollo's lunar capabilities were in many ways much more than MOL needed. If hindsight suggests that parochial interests were factor, the Air Force nevertheless had good reasons to shun Apollo. The lunar landing remained America's chief commitment in space. Until the goal was accomplished, an Air Force program using would surely take second place.56
In early 1964 NASA undertook yet another detailed examination of its plans, this time at the request of the White House. Lyndon Johnson had played an important role in the U.S. space program since his days as the Senate majority leader. Noting that post-Apollo programs were likely to prove costly and complex, the president requested a statement of future space objectives and the research and development programs that supported them.57
Webb handed the assignment to an ad hoc Future Programs Task Group. After five months of work, the group made no startling proposals. Their report recognized that Gemini and Apollo were making heavy demands on financial and human resources and urged NASA to concentrate on those programs while deferring "large new mission commitments for further study and analysis." By capitalizing on the "size, versatility, and efficiency" of the Saturn and Apollo, the U.S. should be able to maintain space preeminence well into the 1970s. Early definition of an intermediate set of missions using proven hardware was recommended. Then, a relatively small commitment of funds within the next year would enable NASA to fly worthwhile Extended Apollo missions by 1968. Finally, long-range planning should be continued for space stations and manned flights to Mars in the 1970s.58
The report apparently satisfied Webb, who used it extensively in subsequent congressional hearings. It should also have pleased Robert Seamans, since he was anxious to extend the Apollo capability beyond the lunar landing. Others in and outside of NASA found fault with the document. The Senate space committee described the report as "somewhat obsolete," containing "less information than expected in terms of future planning." Committee members faulted its omission of essential details and recommended a 50% cut in Extended Apollo funding, arguing that enough studies had already been conducted. Elsewhere on Capitol Hill, NASA supporters called for specific recommendations. Within the space agency, some officials had hoped for a more ambitious declaration, perhaps a recommendation for a Mars landing as the next manned project. At Huntsville, a future projects official concluded that the plan  offered no real challenge to NASA (and particularly to Marshall) once Apollo was accomplished.59
In thinking of future missions, NASA officials were aware of how little experience had been gained in manned flight. The longest Mercury mission had lasted less than 35 hours. Webb and Seamans insisted before congressional committees that the results of the longer Gemini flights might affect future planning, and a decision on any major new program should, in any event, be delayed until after the lunar landing. The matter of funding weighed even more heavily against starting a new program. NASA budgets had reached a plateau at $5.2 billion in fiscal 1964, an amount just sufficient for Gemini and Apollo. Barring an increase in available money, new manned programs would have to wait for the downturn in Apollo spending after 1966. There was little support in the Johnson administration or Congress to increase NASA's budget; indeed, Great Society programs and the Vietnam war were pushing in the opposite direction. The Air Force's space program was another problem, since some members of Congress and the Budget Bureau favored MOL as the country's first space laboratory.60
Equally compelling reasons favored an early start of Extended Apollo. A follow-on program, even one using Saturn and Apollo hardware, would require three to four years' lead time. Unless a new program started in 1965 or early 1966, the hiatus between the lunar landing program and its successor would adversely affect the 400 000-member Apollo team. Already, skilled design engineers were nearing the end of their tasks. The problem was particularly worrisome to Marshall, for Saturn IB-Apollo flights would end early in 1968. In the fall of 1964, a Future Projects Group appointed by von Braun began biweekly meetings to consider Marshall's future. In Washington, George Mueller pondered ways of keeping the Apollo team intact. By 1968 or 1969, when the U.S. Ianded on the moon, the nation's aerospace establishment would be able to produce and fly 8 Apollos and 12 Saturns per year; but Mueller faced a cruel paradox: the buildup of the Apollo industrial base left him no money to employ it effectively after the lunar landing.61
Until mid-1965 Extended Apollo was classified as advanced study planning; that summer Mueller moved it into the second phase of project development, project definition. A Saturn-Apollo Applications Program Office was established alongside the Gemini and Apollo offices at NASA Headquarters. Maj. Gen. David Jones, an Air Force officer on temporary duty with NASA, headed the new office; John H. Disher became deputy director, a post he would fill for the next eight years.62 Little fanfare attended the opening on 6 August 1965. Apollo and Gemini held the  spotlight, but establishment of the program office was a significant milestone nonetheless. Behind lay six years of space-station studies and three years of post-Apollo planning. Ahead loomed several large problems: winning fiscal support from the Johnson administration and Congress, defining new relationships between NASA centers, and coordinating Apollo Applications with Apollo. Mueller had advanced the new program's cause in spite of these uncertainties, confident in the worth of Extended Apollo studies and motivated by the needs of his Apollo team. In the trying years ahead, the Apollo Applications Program (AAP) would need all the confidence and motivation it could muster.
i All three of the Skylab scientist-astronauts were in this first group, selected on 27 June 1965.
ii The instrument unit was the electronic nerve center of inflight rocket control and was located between the booster's uppermost stage and the spacecraft.
iii The Saturn IB or "uprated Saturn 1" was a two-stage rocket like its predecessor but with an improved and enlarged second stage.
iv In direct flight the vehicle travels from the earth to the moon by the shortest route, brakes, and lands; it returns the same way. This requires taking off with all the stages and fuel needed for the round trip, dictating a very large booster. In lunar-orbit rendezvous two spacecraft are sent to the moon: a landing vehicle and an earth-return vehicle. While the former lands, the latter stays in orbit awaiting the lander's return; when they have rejoined, the lander is discarded and the crew comes home in the return ship. Von Braun and his group adopted earth-orbit rendezvous as doctrine.
v Molecular sieves contain a highly absorbent mineral usually a zeolite (a potassium aluminosilicate), whose structure is a 3-dimensional lattice with regularly spaced channels of molecular dimensions; the channels comprise up to half the volume of the material. Molecules (such as carbon dioxide) small enough to enter these channels are absorbed, and can later be driven off by heating regenerating the zeolite for further use.
vi Mariner 2 was launched toward Venus on 27 August 1962; in October came two Explorer launches and the Mercury flight of Walter M. Schirra, on 16 November NASA conducted its third successful Saturn I test flight.