1.3    From Sputnik to Skylab, 1957-1973

American attitudes toward rocketry and space travel changed dramatically after October 4, 1957, when the Soviet Union used an intercontinental ballistic missile to place Sputnik I, the first man-made satellite, into Earth orbit.  U.S. government spending on aerospace research and development had surged during World War II and again during the Korean War, but official interest in rocketry had been limited primarily to military uses of ballistic missiles.  The discovery of German research plans and the enlistment of von Braun had led to some military and scientific interest in satellites and space stations, but this took a back seat to more immediate concerns.

Exactly three years earlier, on October 4, 1954, the Special Committee for the International Geophysical Year recommended the launching of scientific satellites [30].  In July 1955, both the United States and the Soviet Union announced their intentions to do so.  Yet the U.S. was stunned when the Soviets succeeded first.  Senate Majority Leader Lyndon B. Johnson compared Sputnik to Pearl Harbor.  McDougall cites many reasons for the failure of the U.S. to launch first, among them: uncertainty about the freedom of international space and the legality of satellite overflight; and a desire to separate the development of the civilian satellite from that of the military rocket.  By being first, the Soviet Union set a precedent in international law and established the freedom of space.  The launch of Sputnik II on November 3, 1957, reaffirmed it.  The United States' first satellite, Explorer I, was launched on January 31, 1958, by the Army Ballistic Missile Agency.  It's second satellite, Vanguard I, was launched on March 17 by the Naval Research Laboratory.  The U.S. then quickly proceeded to develop the reconnaissance satellites that it had been planning for several years [31]: "However much their lull in rocket research forced the Americans to play 'catch up' in space technology, their advanced thinking on the applications of spaceflight meant that the American space program, when it came, would be better and more quickly adapted to national needs."

Suddenly, space became a national priority.  It was a psychological front in the "total cold war" between the United States and the Soviet Union.  The two nations entered into a space race, the purpose of which was not merely military advantage but national prestige, to prove the superiority of a politco-socio-economic way of life.  As Lyndon Johnson put it [32]: "One can predict with confidence that failure to master space means being second-best in the crucial arena of our Cold War world.  In the eyes of the world, first in space means first, period; second in space is second in everything."  The United States transformed its National Advisory Committee for Aeronautics (NACA) into the more powerful National Aeronautics and Space Administration (NASA) on October 1, 1958.

On April 20, 1960, the Manned Space Stations Symposium convened in Los Angeles, sponsored by the Institute of the Aeronautical Sciences, with the cooperation of NASA and the RAND Corporation.  Manned space flight actually began one year later, on April 12, 1961, when the Soviet Union launched Yuri Alekseyevich Gagarin into orbit aboard Vostok I.  Three weeks later, on May 5, the United States sent Alan B. Shepard on a suborbital flight aboard a Mercury spacecraft.

On May 25, 1961, John F. Kennedy, in a speech before a joint session of Congress, proposed that the United States "should commit itself to achieving the goal, before this decade is out, of landing a man on the Moon and returning him safely to Earth."  Thus were opened the fiscal floodgates for project Apollo and its requisite Saturn launch vehicle.  The Lunar mission drew support from many quarters, for reasons that often had little to do with space exploration.  For example, Secretary of Defense Robert McNamara may have seen the swelling NASA budget as a safety net for the aerospace industry while he worked to reform defense department spending [33].  A manned Lunar landing was a vastly more difficult problem than Shepard's fifteen-minute up-and-down flight atop a ballistic missile, but of all the issues Kennedy would face as President, he "probably knew and understood least about space" [34].  As McDougall writes [35]:

Of all those who contributed to the Moon decision, the ones farthest in the background were the engineers of Langley and Goddard and Marshall, many of whom devoted their lives to spaceflight, designing dreams ...  What Constantine's conversion did to the Christian church, Apollo did to spaceflight: it linked it to Caesar.

After Sputnik, space station design ceased to be a hobby for "space cadets", and became a big business for large aerospace corporations.  Individual vision gave way to collaborative calculation.  In the race to be first, the grandeur of the earlier concepts was rolled back to meet the rapidly developing technology halfway.  What the new concepts lacked in scale and magnificence, they made up for in technical detail.  They also became inextricably tied to the national budget, and were greatly influenced by the ebb and flow of political support for NASA.

The Manned Space Stations Symposium of 1960 convened a year before anyone had actually flown in space, and a year before Kennedy launched the U.S. on a course for the Moon.  In 1960, the wisdom of the previous decade was still accepted: travel to the Moon and planets would require the prior establishment of a permanent Earth-orbiting space station.  It is ironic that the Moon project - what should have provided the "reason to be" for the space station - ultimately came into competition with it.  The Moon landing assumed such a high priority that the space station was bypassed entirely.  That this would occur was not immediately obvious, and space station research continued in earnest during the early 60's, with artificial gravity as a major consideration.

The space station was initially seen as the next logical step after simple Earth-orbital flights and before Lunar landings; then as the next logical step after Lunar landings; then as the next logical step after the Shuttle [36].  As manned space flights increased in both number and duration, mission planners and medical experts gained confidence in astronauts' abilities to function in a weightless environment.  Ultimately, access to a weightless or micro-gravity environment for its own sake became a prime objective in space station planning, and artificial gravity was de-emphasized.

By the time of the first Moon landing, on July 20, 1969, NASA had become a target for federal budget cutters, and manned space flight had begun to compete with unmanned robotic missions - a technology unforeseen by the early proponents of space travel.  The last three Moon landings were canceled, and NASA program planners looked for other applications of Apollo technology.  The mission of a large space station had become uncertain.  By the time Skylab was launched, on May 14, 1973, NASA had settled on an interim "orbital workshop" fashioned from a remodeled upper stage of a leftover Saturn.  Development of a real space station would have to await the deployment of the Shuttle.

Douglas Aircraft Company

In 1959, the Douglas Aircraft Company developed a full-scale mock-up of a space station for exhibit at the London Home Show, sponsored by the London Daily Mail with the theme "A Home in Space."  The station was designed to function as an astronomical observatory with a crew of 4.  It was to be fashioned from the spent second stage of a two-stage launch vehicle.  Upon reaching orbit, the propellant tanks were to be flushed, repressurized with a breathable atmosphere, and equipped for living and working in a weightless environment.  This study is notable for developing many zero-gravity concepts that were used again in later designs, though artificial gravity concepts continued to dominate for much of the next decade [37].

Lockheed Aircraft Corporation

Saunders B. Kramer and Richard A. Byers, of the Lockheed Aircraft Corporation, published "A Modular Concept for a Multi-Manned Space Station" in the Proceedings of the Manned Space Stations Symposium of 1960.  This paper describes all aspects of the space station, including: the station itself (configuration, materials, structural details, mass estimates, power, communications); the micro-ecology (biochemical, psychological, external); station dynamics (guidance and control, rendezvous techniques, changes of orbit); the "astrotug" and "astrocommuter" vehicles (configuration, power and mass estimates); and a development plan with cost estimates for the entire program.  It was evidently the most thoroughly developed space station proposal of its time.  The authors acknowledge the contributions of twenty other Lockheed personnel in preparing it [38].

Figure 1.8

Figure 1.8:  Lockheed (Kramer and Byers), 1960.  Perspective.

Figure 1.9

Figure 1.9:  Lockheed (Kramer and Byers), 1960.  Schematic.

The main part of the station was to be assembled from ten cylindrical modules, 30 feet long and 10 feet in diameter, and six spherical modules, 18 feet in diameter.  Six of the cylindrical modules would be assembled into three pairs, forming three parallel coplanar 60-foot cylinders.  A spherical module would be attached to each of the six ends.  The remaining four cylindrical modules would act as spokes, connecting both side assemblies to the center.  The entire configuration would rotate around the center assembly to provide artificial gravity.  The radius of rotation (measured to the floor of the side assemblies) would be approximately 49 feet.  Other elements of the station, such as the docking port, observatory, and nuclear power plant, would extend from both ends of the station's center assembly.  Bearings would separate the rotating and non-rotating sections.  At some future time, the station could be expanded, first by adding another pair of assemblies on spokes perpendicular to the original, then by duplicating the entire arrangement along the axis.

This configuration differs from most artificial gravity designs in that the habitation modules are oriented parallel to the axis of rotation, rather than perpendicular to it (as in a torus).  This has the advantage of reducing the Coriolis acceleration of a person moving through the habitat.  The disadvantage is that these eccentric movements parallel to the axis can lead to significant disturbances in the station's inertia and rotation.  It is not clear whether such considerations had any bearing on the choice of configuration.

Given the station configuration, the Coriolis acceleration was a prime consideration in choosing the angular velocity and gravity level.  The authors reasoned that the absolute magnitude of the Coriolis acceleration was less important than its proportional magnitude as compared to the centripetal acceleration.  (The centripetal acceleration is the "design gravity"; the Coriolis acceleration is a "distortion" to be minimized.)  Coriolis acceleration increases with angular velocity, while centripetal acceleration increases with angular velocity squared.  Therefore, the greater the angular velocity, the smaller the ratio of Coriolis to centripetal acceleration.  The authors concluded that, given a floor radius of approximately 49 feet, one full g should be provided, requiring an angular velocity of more than 7.5 rotations per minute [39]:

It has often been suggested that the gravitational state on a large vehicle should be less than one g, and possibly as small as 1/10 g, but, in view of the Coriolis effects, this is considered impractical ...  A vehicle radius of approximately 49 feet (to the cabin floor) has been adopted as an acceptable radius for a vehicle to be spun up at one g.  No smaller spin radius has been considered, because of increasingly intolerable Coriolis components and gravity gradients.

The authors apparently gave no consideration to the effects of cross-coupled rotations that would occur, for example, when a crew member turned his head from side to side.  Research into motion sickness - some of it published in the same 1960 symposium proceedings - has indicated that angular velocity should be considerably less than the 7.5 rotations per minute proposed for this station.  (This is discussed further in Chapter 2.)

Given the minuteness of some of the specifications, one glaring omission is any mention of the presumed crew size.  Nevertheless, the article does specify that the crew's personal quarters were to be divided between two of the 30-foot modules, one on each side of the rotation axis.

The station was to be assembled at an altitude of 318 statute miles, on an orbit inclined 50 degrees to the equator.  This orbit was chosen to stay below the inner Van Allen radiation zone and away from the Winkler radiation areas above the geomagnetic poles.  Given the planar configuration of the station and its particular inertial properties, orientation of the rotation axis normal to the orbital plane was found (mathematically) to be unstable, and susceptible to large deviations caused by gravitational torque.  For maximum dynamic stability, the axis of rotation was to be inertially fixed within the orbital plane.  "It thus acts like a gyroscope, and tends to remain in this attitude.  Resultant oscillations due to gravitational coupling, and to personnel motion aboard, render effects in pitch, roll, and yaw smaller than those found on an ocean liner like the Queen Elizabeth riding in a glassy calm sea" [40].  It is not clear whether this last assertion is based on engineering analysis or merely wishful thinking.

Besides gravitational torque and crew motion, other potentially destabilizing influences noted by the authors were: rotating machinery; interaction with the Earth's electromagnetic field; and micrometeoroid impacts.  The stabilization system would consist of a pumped fluid - "possibly mercury because of its high density", and inertia wheels of "substantial mass".

North American Aviation

Fred A. Payne, of North American Aviation, published "Work and Living Space Requirements for Manned Space Stations" in the 1960 symposium proceedings.  Unlike the paper by Kramer and Byers (Lockheed), this paper is brief, apparently the work of one individual, focusing not on the technical details of a specific design but rather on principles of human living requirements that should guide the design process.  Payne began with a question:  "What are the probable standards of comfort and convenience necessary to entice crews into Space Station Service?"  - restated:  "How can we get people into space after the romance has worn off?"  He proceeded to identify several key aspects of space station design, including: spatial requirements; spatial arrangement; protocol; environmental interest and decor; and artificial gravity [41].

He offered few specifics.  On the subject of artificial gravity, he assumed that the head-to-foot gravity gradient should not exceed 15 percent, which means that, for a six-foot person, the radius of rotation measured to the floor should be at least 40 feet.  In contrast to Kramer and Byers, Payne believed that the knowledge of artificial gravity in 1960 could not support more than schematic design: "If one recognizes the fact that the necessary information on g level does not exist to the point where actual station designs may be made but admits that artificial g is desirable, a schematic representation of a space station may be made."  He proposed the following guidelines for any artificial gravity station:

The advice against outside viewing seems misguided.  The major source of disorientation would be from vestibular disturbances associated with motion within the rotating habitat.  These would occur whether or not outside viewing was possible.  From the standpoint of environmental design, it would be preferable to provide the option of outside viewing to all living quarters.  Any individual who found it disorienting could simply close the blinds.

Figure 1.10

Figure 1.10:  North American (Payne), 1960.

The schematic design offered by Payne shows three separate spherical nodes of differing diameters for the control center, equipment maintenance area, and off-duty quarters.  The control center is located on the station's axis of rotation.  Three spokes extend away from the axis, and connect the control center to the equipment maintenance area, the off-duty quarters, and a counterweight.  The counterweight is intended to compensate for the differing sizes and masses of the nodes, as well as the redistribution of mass (personnel and equipment) among them.  A non-rotating cylinder extends from the control center along the station axis, and supports an air lock and a variety of antennas and tracking devices.

NASA Langley Research Center and North American Aviation

Scientists from NASA Langley Research Center published a series of articles in the September 1962 issue of Astronautics, describing space station studies conducted by Langley and North American Aviation (under contract) that led to the design of an "automatically erectable modular torus" (AEMT).  The lead article by Paul R. Hill and Emanuel Schnitzer, "Rotating Manned Space Stations", outlines the presumed mission of the station and the parameters that guided its design [42].  Rene A. Berglund's article "AEMT Space-Station Design" describes the evolution of the station's configuration [43].  Peter R. Kurzhals and James J. Adams wrote "Dynamics and Stabilization of the Rotating Space Station", which describes theoretical and experimental investigations into the sources and magnitudes of instability, and the design of compensating systems [44].  Other articles in the series discuss materials and structures, temperature control, and life support.

Hill and Schnitzer began by describing six potential uses of manned space stations:

The first three, in particular, would support subsequent long-duration Lunar and interplanetary missions.  The last three would support general scientific inquiry.  (Notably absent from the list is any distinctly military application.  NASA was created to promote civilian uses of space; military applications were left to the Air Force.)

Although gravity research was only one of several potential applications for the space station, the requirements of artificial gravity and its attendant rotation completely dominated the station's development, despite its incompatibility with activities such as Earth and astronomical observation.  Hill and Schnitzer justified this by stating [45]:

This list of potential space-station uses shows that few applications involve a requirement for artificial gravity.  That requirement comes from man himself ...  If there develops a reason why an entire space laboratory should be operated without gravity or without rotation, the most desirable shape for a rotating station also proves excellent for a nonrotating one with a solar power plant, because out-of-plane disturbances which would affect solar pointing are small.

The Langley scientists began by studying the inertial characteristics, dynamic stability, and spatial organization of a variety of elementary configurations: a cross formed from two cylinders; a simple torus; a torus with spokes; a single cylinder rotating end-over-end; cylinders parallel to the axis of rotation (similar to the Lockheed design of 1960); cylinders perpendicular to the axis and tangent to the rotation.  Their criteria were: the moment of inertia about the axis of rotation should be substantially different than the moments about the other two axes, which should be equal; and the radius of rotation should be at least 75 feet.  On this basis, the tangent cylinder configuration was selected for continued development.  It evolved into a hexagonal "torus" formed from six rigid cylinders, with mechanical joints at the vertices that allowed them to be folded side-by-side.  The station would be constructed almost entirely on the ground, folded up, packed aboard a Saturn launch vehicle, sent into an orbit of approximately 300 nautical miles, and "automatically erected" in space.  Three telescoping spokes would connect the torus to a hub that would accommodate a non-rotating docking port and zero-gravity laboratory.  Power would be obtained from solar cells mounted on the torus, implying that its rotation axis would need to be directed toward the sun, and would need to precess approximately one degree each day (similar to von Braun's station).

Figure 1.11

Figure 1.11:  NASA Langley and North American, "AEMT", 1962.  Deployment.

Figure 1.12

Figure 1.12:  NASA Langley and North American, "AEMT", 1962.  Perspective.

Based on then-current knowledge of the comfort zone for rotation, a radius of 75 feet was considered to be near the minimum acceptable; 50 feet was unacceptable.  Taking 75 feet as the minimum floor radius at the midpoint of each cylinder, this determined the cylinder length to be approximately 90 feet; the cylinder diameter was approximately 10 feet.  The upper limit for angular velocity was taken to be 4 rotations per minute, limiting the gravity level to not more than approximately 0.4 g.

Because the apparent gravity would always be aligned radially, a hexagonal floor would be unacceptable.  (Only the midpoint of each side is normal to the radius.)  Therefore, a curved floor was to be built within the straight cylinders.  Because the cylinders were too narrow to accommodate a continuous sixty-degree curve, the floor would be divided into steps of concentric arcs, with the highest steps (shortest radii) at the midpoint of each cylinder and the lowest steps (longest radii) at the vertices.

Figure 1.13

Figure 1.13:  NASA Langley and North American, "AEMT", 1962.  Section.

The station was to provide a shirt-sleeve environment for a nominal crew of 21, for a tour of duty of at least 6 weeks.  No details were given for the living and working accommodations within the torus.

NASA Langley Research Center and Douglas Aircraft Company

From 1963 to 1966, the Douglas Aircraft Company, under contract with Langley, developed concepts for a Manned Orbital Research Laboratory (MORL).  Douglas began by establishing technical design concepts first, then determining "utilization potential" by comparing the initial design to various mission requirements.  When the initial design was found to be inadequate, it was revised to support the requirements of the missions that offered the highest utilization potential.  The MORL was essentially a zero-gravity station, but it did include a centrifuge, situated between the living and working areas, for conducting research in gravity and acceleration and for physical therapy in the event that long exposure to zero gravity was debilitating to the crew members.  Douglas also considered artificial gravity experiments in which the MORL would be tethered to the upper stage of a Saturn launch vehicle and the configuration rotated to produce 1/3 g in the laboratory [46].

Figure 1.14

Figure 1.14:  NASA Langley and Douglas, "MORL", 1966.

Cole and Cox

In 1964, Dandridge M. Cole and Donald W. Cox published Islands in Space: The Challenge of the Planetoids [47].  Cole was a space program analyst for General Electric's Missile and Space Division; Cox was a free-lance lecturer and writer formerly associated with NASA in space science education.  Though General Electric provided assistance in producing the book, it was primarily an individual effort independent of any corporate or governmental program.  As such, it stands out from its contemporaries, in scope as well as parentage.

The main point of the book is that near-Earth asteroids or planetoids could be valuable intermediate destinations, filling the gap between Lunar landings and interplanetary missions to Venus or Mars.  By virtue of their low surface gravity and relative proximity to Earth's orbit about the sun, they could serve as strategic way stations and resource quarries.

A chapter titled "Inside-Out Worlds" describes the formation of rotating space colonies from planetoid resources.  An elongated iron planetoid - one mile in diameter and two miles long - would be selected for the raw material.  A large parabolic mirror - several miles in diameter - would focus intense sunlight to bore through to the planetoid's core.  The bore holes would be charged with tanks of water, acquired perhaps from other near-Earth asteroids or comet debris.  The planetoid would then be set spinning under the heat of the mirror, until it became a molten mass of iron.  Under the combined effects of inertial and cohesive forces, the iron would assume a roughly cylindrical shape.  When the heat finally penetrated through to the water tanks at its axis, the water would vaporize and the expanding steam would inflate an iron bubble - ten miles in diameter and twenty miles long.  The colony would have an inside surface area of 628 square miles - over half the size of the state of Rhode Island - and could "very comfortably" accommodate 100,000 people.  The authors' utopian visions are unabashed:  "There may still be some who dream of a physical paradise and for them, and for all the dreamers of the past, the hollow planetoid would be heaven."

Figure 1.15

Figure 1.15:  Cole and Cox, 1964.  (Illustration by Roy Scarfo.)

Cole and Cox suggested 9 rotations per hour (0.15 rotations per minute) to provide 1/5 gravity at a radius of 5 miles.  The large parabolic mirror would be attached to one end of the iron cylinder to collect sunlight and direct it down the axis, forming an internal linear sun.  While concentrating sunlight at the axis, the mirror would also shade most of the end area, allowing it to cool to below freezing.  Thus, within the colony, ice caps would form near the poles.  Under the influence of artificial gravity, the ice would slowly slide away from the pole, down toward the cylinder wall and out of the shade, where it would melt.  The melt water would collect in an equatorial lake, evaporate, recondense at the poles, and repeat the cycle.  The colonists would have complete control over the weather and all other aspects of their environment.  But, as the authors note, complete control implies complete responsibility.

Grumman Aerospace and Warner Burns Toan and Lunde

In September 1967, the architectural firm of Warner Burns Toan and Lunde (WBTL) was commissioned by Grumman Aerospace to assist in developing space station design concepts [48].  The architects focused their attention on issues of volumetric requirements, functional layout, comfort, and efficiency.  Initially, their work was aimed at a zero-gravity station to support a crew of six to twelve men on tours of duty lasting three to six months.  The station was to be constructed from a stack of cylindrical modules, 7.5 feet long and 15 to 33 feet in diameter.  The architects preferred the 33-foot diameter - the largest that could be launched by a Saturn V rocket - but worked with the 15-foot diameter, presumably at the insistence of NASA or Grumman.  They explored various schemes for subdividing the volume, sometimes varying the up-down orientation from one chamber to another.  Progressive Architecture commented [49]:

Even though the scheme could not be used in a continued artificial gravity situation, its clear expression of the properties of space, of life in space, of the body freedom, are appealing to the imagination.  Where is the fun, after all, if the Earth environment is too closely duplicated?  Taken to extremes, it could mean lace curtains and French provincial in light-weight plastic.

Early in 1969, NASA announced that work should commence on a 50-man space base.  (See "Other NASA and DOD Studies" below.)  The WBTL architects drew on studies of urban ecology and concepts of "communitability" in developing preliminary designs for a large artificial-gravity station.  They rejected schemes that tended to be isolative in the manner of disjoint suburbs or urban high-rise buildings.  An early design sketch shows a closed circular arrangement of twenty-four cylindrical modules.  Four of the modules are connected by elevator shafts to a cylindrical hub.  Each of the modules is 22 feet in diameter, yielding a rim radius (measured to module center points) of approximately 84 feet.  In the sketch, the modules are oriented parallel to the plane of rotation, such that they are circular in elevation.  A full-scale mock-up of one module was turned perpendicular to the plane of rotation.  An interior photograph shows a circular plan divided into sectors and furnished with light-weight plastic tables and inflatable lounge chairs.

Figure 1.16

Figure 1.16:  Grumman, and Warner Burns Toan and Lunde, 1969.  Concept sketch for 50-man space base.

Figure 1.17

Figure 1.17:  Grumman, and Warner Burns Toan and Lunde, 1969.  Full-scale mock-up of space base module interior.

International Academy of Astronautics

In October 1968, the International Academy of Astronautics organized a symposium titled "Manned Laboratories in Space" [50].  S. Fred Singer, the program chairman and proceedings editor, commissioned nine papers - eight from the United States and one from the Soviet Union.  Two of the papers focused on the design of the orbital laboratory itself; the other seven focused on applications: for Earth observation, for astronomical observation, and as "stepping stones" to manned interplanetary flight.

Robert R. Gilruth, the Director of the NASA Manned Spacecraft Center, presented an overview of the rationale and characteristics of manned space stations [51].  He stated that "the characteristics of artificial gravity are important objectives for a near-term Earth orbital activity."  Artificial gravity would:

Gilruth regretted that the initial orbital workshop (later known as Skylab) would not provide artificial gravity, and described two concepts for providing it in future missions.

Figure 1.18

Figure 1.18:  Gilruth, 1968.  Artificial-Gravity Research Environment.

To provide an initial research environment, an Apollo spacecraft with an attached experiment module would be tethered to a spent booster stage that would serve as a counterweight for rotation.  The tether length would be adjustable; the rotational radius to the experiment module would be at least 50 feet.  Previous experiments with ground-based centrifuges and parabolic flights had indicated that the comfort zone for artificial gravity had a lower bound of 0.3 g and an upper bound of 4 rotations per minute.  Nevertheless, there was considerable uncertainty in these results, particularly with regard to the effect of the Earth's 1-g field in ground-based tests.  The tethered Apollo would provide a space-based environment for verifying the earlier results, as well as for experimenting with higher gravity levels (up to 1 g) and lower rotational rates.

Figure 1.19

Figure 1.19:  Gilruth, 1968.  50-man space station.

The first operational space station would be launched in three parts by three Saturn V rockets, assembled in orbit to form a slender linear structure, and rotated end-over-end.  A non-rotating hub extending from one side would accommodate a zero-gravity laboratory, a docking port, and a hangar for satellite maintenance.  In its initial configuration, the station would accommodate at least 50 crew members; with additional construction, it could grow to accommodate at least 100.  The habitable areas would be arranged as a cylindrical tower extending 240 feet from one side of the hub; the power section and counterweight would hang from a truss extending as much as 375 feet from the opposite side.  The station would rotate 3.5 times per minute to provide 1 g in the lowest level of the habitat.

Theodore J. Gordon and Robert L. Gervais, of the McDonnell-Douglas Astronautics Company, described the critical engineering problems of space station design [52].  They acknowledged the "maladaptation of critical body functions to prolonged zero-g exposure," and stated that "one of the major purposes of first-generation space stations will be to investigate this problem in greater depth and over longer periods of time."  They were less concerned with providing an Earth-like environment per se than with maintaining the effectiveness of the crew.  Rotating the entire station to provide artificial gravity might disturb many mission tasks; providing a non-rotating or detached zero-gravity module would complicate the overall design.  As an alternative, they suggested periodic use of an on-board centrifuge and exercise:

It is anticipated that a routine centrifuge schedule can be developed which will require no more than a half-hour per man per day.  A variety of active and passive exercise techniques will also abate physiological deterioration ...  However, it may prove more desirable to rotate the entire station than to experience loss of crew effectiveness in long-term zero-g operation.

Walter M. Hollister, of the Massachusetts Institute of Technology, presented a development program leading to interplanetary flight [53].  An interplanetary spacecraft would be a solar-orbital laboratory, performing essentially the same functions as Earth-orbital laboratories.  Hollister stated that one of the most important unresolved issues was the level of artificial gravity required.  He cited Earth-based studies indicating a lower bound of 0.2 g and an upper bound of 6 rotations per minute, but argued that orbital studies were required in order to determine the medically and operationally acceptable levels.  Compared to zero-gravity spacecraft, he anticipated a 50% increase in spacecraft mass per g of artificial gravity provided.

Kubrick and Clarke

Despite NASA's dominance of serious space station planning, independent thinkers continued to flourish during this period, expressing their visions of the future through the genre of science fiction.  One work from this period is particularly notable for its vivid portrayal of rotating space stations and space travel, and for its broad public appeal: the film 2001: A Space Odyssey.  Stanley Kubrick and Arthur C. Clarke wrote the screenplay.  Kubrick directed the film; Clarke wrote a novella based on the screenplay [54].  The film and book were produced in 1968 - the year that men first orbited the Moon.  Considering the remarkable achievements of the previous eight years, and the extraordinary special effects of the film, it seemed that the space culture and technology portrayed in 2001 were just around the corner.

Because "common knowledge" of artificial gravity has been so strongly influenced by this work, it is worth examining in detail to see how realistic it is.  Although the specifics of space station design are not important to the plot, Kubrick provides flattering images of the hardware, and Clarke manages to work a few specifics into his text.  The book is illustrated with scenes from the film, and trivia buffs may be interested to know that the accompanying captions do not always agree with the main text.

Clarke describes "Space Station One" as a polished metal disk, three-hundred yards in diameter, rotating once per minute to produce "an artificial gravity equal to the Moon's".  A non-rotating docking port extends from the central axis of the station.  After docking, people exit the transport ship and move through an air lock into a large, padded, circular chamber, which is gradually spun up to match the rotation of the station.  They then descend along a "curving stair" from the axis to the rim.  Given that the radius of the station is one-hundred-fifty yards, the stair descends nearly forty stories - a rather unfriendly entrance, especially when one considers the Coriolis acceleration that results from radial motion.  At the bottom of the stair, in the rim of the station, is a passenger lounge with seating area, restaurant, post office, barber shop, drug store, movie theater, and souvenir shop.  The station is apparently an international operation, with U.S. and Soviet sections requiring passports and visas.

Figure 1.20

Figure 1.20:  Kubrick and Clarke, "Space Station V", 1968.

In the film, the station is depicted as a pair of toroidal "cart wheels", each connected to a common "axle" by four spokes.  There is no non-rotating docking port.  Instead, an approaching ship must align itself and rotate to match the rotation of the station.  This looks poetic on film, but is considered impracticable in real life.  In the caption that accompanies this scene, it is identified as "Space Station V".  It is one-thousand feet in diameter, and revolves to give its occupants "a feeling of normal gravity".  But Earth-force gravity would require 2.4 rotations per minute, which would not feel "normal".

Clarke describes the spaceship "Discovery" as an "arrow-shaped structure more than a hundred yards long".  At its head is a pressure sphere that comprises the habitable area.  The equatorial region of the sphere contains a drum, thirty-five feet in diameter, rotating nearly six times per minute to produce "an artificial gravity equal to that of the Moon".  In reality, this small radius and large angular velocity are seriously beyond the estimated comfort zone for rotation.  Within this drum are the kitchen, dining, washing, and toilet facilities, personal cubicles for each of the five astronauts, and "hibernaculums".  The rotation of the drum can be stopped if necessary, by transferring its angular momentum to a flywheel.  Passage in to and out of the rotating drum is accomplished by crawling hand-over-hand along a pole at its axis.

Figure 1.21

Figure 1.21:  Kubrick and Clarke, "Spaceship Discovery", 1968.

The film shows a tube, rather than a pole, at the axis of the drum.  The astronauts climb between the floor of the drum and the central axis on a ladder built into the side wall, coplanar with the rotation.  In this orientation, Coriolis acceleration would tend to pull the astronauts sideways off of the ladder as they climb.  The caption in the book states that the rotation produces "a sensation of normal weight".  But Earth-force gravity would require nearly 13 rotations per minute, well beyond any semblance of normalcy.

Other NASA and DOD Studies

NASA, the Department of Defense, and several contractors carried other space station studies to various levels of refinement during the 1960's and -70's.  Their significance to this chapter is primarily as indicators of trends in space station planning.  It seems that the more technical the studies became, the less they revealed significant individual architectural concepts.  The information in this section is extracted primarily from Logsdon and Butler:

In 1962, the NASA Manned Spacecraft Center initiated Project Olympus, to develop concepts for the largest rotating space station possible to be launched into orbit by a two-stage Saturn V and to include both zero-gravity and artificial-gravity sections.  The projected crew size was 24.  A variety of configurations were examined for both Earth-orbital and interplanetary missions.

The NASA Marshall Space Flight Center concentrated on developing a space station from a Saturn IV-B upper stage, which could be launched either "wet" (as an active rocket stage participating in the launch) by a three-stage Saturn I-B (I-B, II, IV-B), or "dry" (as dead weight) by a two-stage Saturn V (V, II).  The habitable areas would be fashioned from the empty fuel tanks of the Saturn IV-B.  The "wet" scenario is reminiscent of the Douglas Aircraft proposal of 1959; the "dry" scenario was eventually carried out in the creation and launch of Skylab in 1973.

In 1963, in view of the independent and uncoordinated studies being conducted by several NASA centers, the Department of Defense, and various contractors, NASA Associate Administrator Robert Seamans called for an agency-wide, four-to-six-week, high-priority study of an Earth Orbital Laboratory (EOL).  The study had little impact, due to tight budgets, rising costs, and the high priority of the Lunar landing program.

In December 1963, Secretary of Defense Robert McNamara announced the cancellation of a much-beloved Air Force project known as DynaSoar.  It was to be replaced by a project to develop a manned orbital laboratory, as a "trailer" to be orbited behind a modified Gemini capsule (Gemini X).  In January 1964, the Air Force awarded contracts for Orbital Space Station Studies (OSSS).  In August 1966, Douglas Aircraft was awarded a contract to develop a Manned Orbital Laboratory (MOL) for the Department of Defense.  This is not to be confused with the MORL studies that Douglas had just completed for NASA Langley Research Center (described above).  The MOL was to be a small space station, launched on a Titan III, to support two men in a shirt-sleeve environment for thirty days.  It was canceled in June 1969 due to budget cutbacks and the lack of a defined Air Force requirement for an orbital laboratory.

In 1965, NASA initiated the Apollo Applications Program to develop uses for Apollo technology beyond the initial series of Lunar landings.  This program led eventually to the Orbital Workshop concept (OWS) that became Skylab.

In 1966, with Apollo development nearing completion, NASA administrators called for another agency-wide effort to update their space station studies.  The new study was divided into two parts: one to focus on system design; the other to focus on the need for, the requirements of, and the constraints on a space station intended to support activities in:

The study charter allowed that a permanent space station might not be the best means of supporting these activities, and that the study itself was "in no way an indication of an agency decision to proceed with or propose a manned space station; it is very important that this point be clearly understood by all concerned with the study and by those with whom it is discussed" [55].

The requirements portion of the 1966 study found that "the most difficult problem to resolve is the matter of artificial gravity.  If artificial gravity becomes a firm requirement for crew comfort, its implementation can have a very large impact on space station design, [since] zero gravity is mandatory for major portions of the experiment programs" [56].

In December 1968, Apollo 8 carried men into Lunar orbit.

In February 1969, in the euphoria following Apollo 8, Aviation Week and Space Technology reported that NASA was rejecting earlier space station plans as "too conservative in size, scope, and potential accomplishments when compared with the funding required."  Earlier studies had called for a station with an orbital lifetime of two years, supporting a crew of six to nine people.  NASA now felt that a relatively modest increase would permit a large permanent space base.  The new schedule under consideration called for a 100-man modular station to be completed by 1980.  The first module, supporting as many as twelve men, would be launched by 1975 [57].  NASA refined its concept of the space station program to include:

Figure 1.22

Figure 1.22:  Space station concept, 1970.

The initial station would be fashioned from a cylinder, 33 feet in diameter and 52 feet long, divided into four decks joined by a 10-foot-diameter central tunnel.  It would be carried into orbit by a Saturn V.  It would support a crew of twelve, with resupply every 45 days and crew change every 90 days.  It would normally be a zero-gravity environment, but artificial-gravity experiments would be conducted early in its mission by tethering it to a counterweight and rotating the configuration.  Later that year (1969), another requirement was added: the space station module would also serve as the core of a spacecraft for a manned mission to Mars.

The NASA Office of Manned Space Flight conducted an "Artificial Gravity Experiment Definition Study" to outline the experiments that would be required in designing an artificial-gravity space station.  The goal was "to provide living conditions which approach the contemporary terrestrial situation as closely as possible during off-duty hours ...  Overall, ease of habituation to artificial gravity conditions may be the most important issue in providing such environments, with determination of their convenience or nuisance the single most important aspect" [58].  But at the same time, "many interesting innovations can be derived which exploit the artificial gravity environment" [59].  The habitability section stressed a need for research in furniture and equipment arrangement, gravity levels, and Coriolis effects, as they related to food preparation and eating, garment design (shoe traction), laundry, housekeeping, personal hygiene, sleeping facilities, off-duty activities, waste management, stowage, environmental parameters (convection, gas-fluid-solid separation), and control panels.

On July 20, 1969, Apollo 11 landed men on the Moon.

On July 29, 1970, Congress discontinued funding for the Saturn V.  Since nothing else existed that could carry a 33-foot-diameter cylinder into orbit, work commenced to redefine the space station in terms of modules that would fit within the planned 15-foot cargo bay of the shuttle.  By 1972, the space station was finally reduced to a single small module (the Spacelab, developed later by the European Space Agency), and the Shuttle itself became the top priority development program.

On April 19, 1971, the Soviet Union placed the Salyut 1 space station in orbit.

On December 19, 1972, Apollo 17 - the last Lunar mission - returned to Earth.

On May 14, 1973, the last launch of a Saturn V sent Skylab into orbit.  Subsequently, three crews of three inhabited Skylab for 28-, 59-, and 84-day missions, which exceeded the combined total man-hours of all previous U.S. and Soviet space flights.  Skylab proved that artificial gravity is not a "firm requirement for crew comfort" for missions of up to 84 days.  Despite lingering concerns over the deleterious effects of prolonged exposure to weightlessness, artificial gravity was no longer an important factor in near-term space station design.