SP-4208 LIVING AND WORKING IN SPACE: A HISTORY OF SKYLAB

 

18

RESULTS
 
Medical Findings.
Solar Observation.
Earth Observations.
NASA's Own Experiments.
Comet Observations and Student Experiment.
Skylab Science: An Assessment.

 

 

[339] As Schneider had said, the missions were only the first phase of Skylab's science program. Principal investigators immediately began processing the staggering amount of material the crews had collected (table 2). From the five solar telescopes, astronomers had almost 103 000 photographs and spectra (plus 68 000 from the H-alpha cameras); the earth-resource instruments had yielded piles of photographs and kilometers of magnetic tape, dense in detail. Medical investigators had 18 000 blood-pressure measurements, 200 hours of electrocardiograms, and extensive food, urine, and fecal samples for biochemical analysis.1

Only a small fraction of this information was available during the missions, most of it medical. Houston's medical directorate had significant operational responsibilities, apart from simply monitoring their experiments. Physicians assessed crew health and health trends daily, using telemetered data, the crew medical conferences, and channel B reports, and continuously advised program managers as to the physical condition of the astronauts. Any unfavorable trends or sudden changes could have curtailed a mission.2

The rest of the experimenters had to wait for each crew to return with film, tape, and samples. After each of the first two missions, quicklook" assessments suggested changes or additions to experiment plans for the next flight. Then the long and tedious evaluations began, to continue for years. Even during the later flights, however, preliminary results were presented to scientific meetings, and by the end of 1974 several major symposia had been conducted summarizing Skylab's results.

 

MEDICAL FINDINGS

 

In late August, medical investigators spent three days in Houston discussing the data from all the missions. In the entire program, these were the most important investigations for manned spaceflight; its future depended on man's ability to adapt to zero gravity, to remain healthy....

 

[340] Table 2. Science Accomplishments

Experiment Group

Planned

Actual

Deviation (%)

.

Solar physics (manhours)

880

941

7

Film (frames)

.

127000

.

Life science (investigations)

701

922

32

Engineering & technology (investigations)

264

245

-3

Astrophysics (investigations)

168

345

105

Student (investigations)

44

52

18

Materials science & manufacturing (investigations)

10

32

220

Earth observation (passes)

62

99

60

Film (frames)

.

46000

.

Magnetic tape, various experiment groups (meters)

.

73000

.

SOURCE: MSFC Skylab Mission Report-Saturn Workshop, NASA TM X-64814, 1974, p.3-39.

 

 

....while in space, and to return without suffering long-term after-effects. On the whole, findings presented at this life sciences symposium showed that few serious problems remained.

One that was still troublesome was motion sickness in orbit. Of the nine Skylab crewmen, five became ill in the early stages of flight, only the first crew, plus Ed Gibson on the last, showed no symptoms of motion sickness. (Joe Kerwin, however, was seasick in the command module while awaiting recovery of the spacecraft.) The workshop had carried an experiment to determine sensitivity to motion sickness, a chair in which the subject could be rotated while making rapid up-and-down and side-to-side head motions. On each flight, crewmen were tested periodically Al though on the ground all the astronauts could be brought to the verge of nausea on this device, in flight none could be taken to the same level of malaise.3

Motion sickness was so intimately involved with operational considerations that the experimental results were not clear-cut. They seemed to indicate that space malaise was a highly individualistic problem, still unpredictable in any particular case. The drugs used during the program reduced the severity of symptoms, but did not prevent them. All the crewmen, however, adapted within the first week, and illness did not recur for the rest of the mission. Motion sickness was obviously complicated, and Skylab did not provide enough information to understand it thoroughly. 4

In other areas, investigators were somewhat better served by their experiments. The mineral balance study, while imperfect, showed a clear trend. In space, all crewmen excreted more calcium in their urine, aIong with a high level of hydroxyproline, an amino acid whose loss is associated [341] with metabolic turnover of bone. This confirmed what had been found during Gemini and indicated a loss of structural material in weight-bearing bones that are subjected to compressive loads in normal gravity. Pre- and postflight x-rays of heel and wrist bones corroborated the mineral balance study. In spite of the third crew's increased exercise, loss of calcium and nitrogen-the latter indicating a loss of muscle mass- continued throughout the mission. The actual amount of bone mineral lost, even after 84 days, was not serious; but that depletion continued unabated implied that longer missions entailed risk. Comparison of the Skylab results with studies on bedridden patients-the nearest one-g analog-indicated the possibility of irreversible damage to leg bones on missions lasting a year or more. Another hazard was kidney stones formed as a result of high concentrations of calcium in the urine.5

Results of the several experiments dealing with the cardiovascular system were complex but encouraging. The bicycle ergometer and metabolic analyzer showed that the body's tolerance for exercise did not decrease during flight. Postflight tests, however, showed that adaptation to weightlessness had occurred; astronauts could no longer perform at their preflight levels of physiological efficiency. Readjustment was slowest with the first crew; those astronauts took nearly three weeks to return to their preflight exercise capacity. The others required less than a week.6

The lower-body negative-pressure experiment, designed to measure changes in the heart's effectiveness during long exposure to weightlessness, turned out to be more stressful in orbit than on the ground. Results from the first mission had been discouraging; on two occasions Joe Kerwin had been forced to stop his test prematurely. Even after 28 days, crew adaptation seemed minimal. Cardiovascular experts assessed the results and advised continuation of the standard procedure for the next two missions. This decision proved sound. The longer flights showed that after the first 30 to 50 days, astronauts gradually built up a tolerance to the inflight testing. And while the first crew required nearly three weeks to return to their preflight responses, subsequent crews readapted more quickly .7

Many of the medical investigations contributed to a picture of what happens to the human body during weightlessness: measurement of leg volume (part of the lower-body negative-pressure experiment), stereophotographs (which enabled calculation of changes in body volume), hormonal and hematological studies, and the infrared photographs and limb measurements that cost the third crew so much time. Before Skylab, aerospace medical researchers had constructed a working hypothesis to account for the physiological changes observed in spaceflight. On entry into weightlessness, body fluids, no longer pulled down by the force of gravity, shifted toward the upper body, producing the distended veins, puffy eyelids, and feelings of nasal congestion experienced by all orbiting [342] astronauts. The body's sensors interpreted this as an increase in blood volume and reacted by altering the hormone balance to stimulate loss of fluid. This triggered a complex set of physiological interactions leading to a new equilibrium (adaptation); among other things, the blood contained fewer red cells, less plasma, and a lower concentration of potassium.8 Skylab's medical data were not completely consistent with this hypothesis. Blood analyses showed hormone levels lower than expected, along with anomalous levels of electrolytes. More experimental work would be necessary before even a qualitative description of adaptation to weightlessness could be constructed. No physiological changes had been observed that would preclude weightless flights lasting up to nine months, but it was not possible to extend that duration without limit. Much still had to be learned, especially about motion sickness and bone deterioration, before manned missions lasting up to a year could be contemplated.9

In a panel discussion that concluded the three-day medical symposium, several outside experts speculated about the meaning of the Skylab results. Most agreed that Skylab had settled some of the major questions about man's survival in orbit and satisfactory readaptation on re urn. All had ideas for new research or new techniques to be used in future investigations. Imagining a second generation of space laboratories in which only a few occupants would need to be astronauts in the classical sense, one investigator suggested sending up "professional 'subjects' " or laboratory testing. These would be normal individuals who would have no responsibility for managing the spacecraft, so their systems could be allowed to deteriorate in order to test compensatory (preventive or therapeutic) measures. Another, speculating on ways to avoid the consequences of bone loss, believed that the physical qualifications for astronauts might well be changed. Recognizing the need for crewmen to function both in zero g and during reentry, he postulated that "individuals already adapted to something closer to zero g" might have certain physical advantages-"sedentary, skinny, small individuals." This same expert thought that serious consideration should be given to selecting legless amputees as astronauts, since many of the medical problems were associated with legs. 10

On one point all were agreed: Skylab's medical investigations had raised as many questions as they had answered-always the hallmark of good research. For more answers, the only place to go was back to space Among all the investigations, only one could effectively be simulated on earth-the mineral balance studies, for which prolonged bed rest seemed to model the space environment adequately.

 

SOLAR OBSERVATIONS

 

Astronomers had, if anything, more data than the medical investigators. Cataloging, classifying, and calibrating the thousands of [343] photographs and spectra would take months, and interpretation still longer. Even before the second mission, astronomers began publishing preliminary results; only a month after the first crew returned, researchers at American Science and Engineering submitted a brief description of their x-ray data to a professional journal. Other investigators soon followed.11 Though the astronomers did not conduct an all-inclusive seminar, as had the medical investigators, assessments of the solar physics programs were made at several professional meetings.

On 3 December 1973, when the third crew had been in orbit only three weeks, Leo Goldberg discussed the significance of some of the early ATM data at the 141st meeting of the American Astronomical Society, where he gave the Henry Norris Russell lecture, entitled "Research with Solar Satellites." Goldberg, director of the Kitt Peak National Observatory in Arizona, had been the original principal investigator for the Harvard solar instrument. In AAP's early days he had clashed with NASA officials over management of the Apollo telescope mount (p. 103) and had been pessimistic about the use of man as an observer in space. Having looked at the early results, however, Goldberg was full of praise for NASA. As things had turned out, the delay in launching Skylab (and the improvements delay made possible) had transformed "a mere exercise in manned space flight into one of the most important events in the history of solar physics." The stability of the orbital cluster to 2.S seconds of arc was "one of the outstanding engineering achievements embodied in Skylab." The spatial resolution obtained was certain to bring about a complete revision of solar theories. And as far as the role of man in space astronomy was concerned, Goldberg was a convert. Having doubted that man had any use in orbit beyond adjustment and repair of equipment, he acknowledged that Skylab had proved otherwise. 12

Goldberg's enthusiasm for the quality of the Skylab results was shared by all the solar research groups. In Los Angeles on 22 August 1974, E. M. Reeves of Harvard College Observatory summarized the accomplishments of the ATM project at the annual meeting of the American Astronautical Society. Reeves noted that all the instruments had equaled or exceeded their expected performance. The photographs from the coronagraph were of a quality and quantity never obtained before. Above all, Reeves was impressed by the flexibility and responsiveness of the experiment management system-that is, operations. One of the remarkable accomplishments of that system during the missions had been a study of the planet Mercury during its transit across the face of the sun on 10 November 1973. The remote-control capability built into the Harvard instrument, together with the rapid transmission of data from remote stations in the communications network, had produced data that would permit an estimate of the density of Mercury's atmosphere.13

No investigators were more satisfied with their results than the team at the High Altitude Observatory in Colorado. Their white-light [344] coronagraph had shown that the solar corona was far more dynamic than had previously been surmised. Changes in its form and structure were apparent, not only from one day to the next, but over much shorter intervals. During 227 days of observation, the coronagraph (which, like the Harvard instrument, could be operated during unmanned periods), recorded approximately 100 events called "coronal transients." Taking place in a period of minutes, these events sometimes involved the ejection of large amounts of matter and energy into the corona. Roughly half the transients were associated with flares or eruptive prominences. 14

Everyone who participated was impressed with the intensity and variety of solar activity during a "quiet" period. Although program delays had forced abandonment of plans to observe the sun during its maximum activity in 1969-1970 (p. 103), eight solar flares had been photographed during the three missions. The last, which the astronomers called the "Gibson flare," was recorded from its inception, after Garriott and Gibson had deduced a pattern of solar x-ray activity that preceded major eruptions. Simultaneous use of all the ATM instruments thoroughly documented the evolution of these flares and their relation to events in the corona.15

By the end of 1974, solar astronomers were sure that they had the best observations ever obtained from space. Correlation of the x-ray, ultraviolet, and coronagraph observations and interpretation in terms of processes on the sun would take years. Looking back at development problems and ahead to the task of interpretation, Richard Tousey, principal investigator for the Naval Research Laboratory, asked whether it was worth the great effort:

That it was, would be denied by very few. The solar observations made by the ATM experiments were extraordinarily valuable, perfect, and complete. In spite of innumerable problems, far more than ever imagined possible was accomplished. The solar observations retrieved are staggering in quantity and quality. Best estimates made by each [principal investigator] are that no less than five years of work by competent and sizeable teams are required to reduce and interpret the data, and ten years may well be needed.

Tousey, whose space research started with instruments carried aloft on V-2s in the 1940s, was convinced that unmanned spacecraft could never have come near producing the ATM results. "Skylab has vindicated the use of man in space to perform scientific experimentation, notwithstanding opinions still voiced to the contrary." And after the interpretations, then what? Much would be left to do in solar research, Tousey said another solar maximum would soon come around, and it would be very worthwhile to fly the backup solar observatory. All but ready to fly, it constituted "a valuable resource that should not be allowed to go to....

 


[
345]

A huge solar eruption recorded by the extreme-ultraviolet spectroheliograph S082A; helium has been ejected more than 800 000 km.

A huge solar eruption recorded by the extreme-ultraviolet spectroheliograph S082A; helium has been ejected more than 800 000 km. For comparison, the earth is not much larger than the black dot near the rim of the sun and beneath the arch of helium. The instrument was constructed by the U.S. Naval Research Laboratory and Ball Brothers Research Corp. S-74-15562.

 

...waste."16 There was virtually no hope of that, however, since a second Skylab had long since been ruled out (pp. 116-18).

 

EARTH OBSERVATIONS

 

Skylab's earth-resource experiments differed in several ways from the medical and solar experiments. Given the wider variety of instruments, the larger number of investigators, and the diversity of objectives, no clear assessment of the value of the earth-sensing experiments could emerge quickly. Early reports by investigators focused narrowly on individual projects. In the independent but related visual observations program, however-an exercise conducted largely by the third crew-it was possible to assess the value of man as an observer of earth s surface features.

At the Skylab Results Symposium in Los Angeles in August 1974, four teams of investigators indicated the breadth of the earth-resources program and something of the value of the results. A group at the University of Kansas found that the microwave instruments showed promise for measuring soil moisture from orbit. Geologists at the University of Wyoming evaluated the earth-terrain and multispectral photographs for mapping geological and agricultural features. They concluded that the Skylab instruments were, for some purposes, better than those on the Landsat satellite-chiefly because of the better resolution afforded by photographs-but that both had to be supplemented by high-altitude photography from aircraft.17

Of more interest were the data returned from the multispectral scanner, which covered 13 wavelength bands in the visible and infrared [346] regions of the spectrum. Investigators at Purdue University used these and the multispectral photographs from S190A in a computerized program of land-use determination; their project aimed at automatic classification of land into nine categories ranging from residential and commercial to grass, farmland, and woodland. By isolating the characteristic spectra of each of these uses, particularly using two or more spectral bands, they could classify land with high accuracy. Skylab's data were roughly as good as those from Landsat's multispectral scanner, which sensed only four wavebands. Similar results were reported by researchers with the U.S. Geological Survey, studying swampland in Florida, and General Electric, looking at geologic features in New Mexico.18

Later in the year, similar reports for the other sensors were presented to a conference at Huntsville. Again the multispectral scanner received much of the attention, but geophysicists also reported encouraging results from the radar altimeter. This instrument proved to be able to measure the shape of the earth's surface-more particularly, the ocean's surface-with reasonable accuracy. Perhaps the most impressive result was the detection of local variations in sea level, such as a 20-meter depression near Puerto Rico, probably caused by a local gravity anomaly. The instrument also responded to subsurface geologic features; altimeter data showed clear correlations with the profile of the continental shelf off the coast of Georgia and Florida.19

While preliminary results indicated that Skylab's earth sensors had performed as expected and that the investigators had found them useful, wider use of the data was slow in coming. Users seemed content to rely on Landsat, which had been launched in July 1972, possibly because of familiarity with it, but also because Landsat viewed the same ground track every 18 days at the same local time. This repetitive coverage was not available from Skylab. In mid-1975 a NASA-sponsored earth-resources symposium heard 166 reports, only 29 dealing with Skylab results.20

The earth-resource experiments did little to establish the value of man in space. Added to the program late, the instruments could not be optimized for man's participation. Apart from tracking assigned sites with the viewfinder on the infrared spectrometer, the operator's main job during a data-gathering pass consisted of punching buttons and recording times and operational sequences on channel B. Judgment as to alternative sites or modes of operation did not enter. On the other hand, astronauts could replace components and do routine maintenance-something the astronomers had felt was absolutely essential, but which their instruments were not designed for. Apart from the major repair job on the microwave antenna carried out by Pogue and Gibson, the crews cleaned tape recorder heads, replaced one tape recorder, and installed an improved detector on one of the infrared instruments during flight. 21

[347] The value of an intelligent observer for earth observations from orbit was, however, clearly established by the special program developed for the third crew. A team of 19 scientists put together a plan for visual and photographic observations of surface features. This program was only minimally structured; scientists briefed the crew in the most general terms as to the major areas of interest (ocean currents, geology, African drought regions, plus a dozen others) and prepared a book summarizing what the astronauts should look for and what they might expect to see. Some observations were formally scheduled, but much of the program depended on the crew's ability to locate and describe (or photograph) features of interest. During the mission, weekly conferences allowed for modifications and additions to the schedule.22

Gazing out the window was a prime recreational activity for the astronauts, and when it acquired a scientific value they enjoyed it even more. With two cameras and an assortment of lenses and film, plus 10-power binoculars, they spent many hours at the wardroom window looking at assigned sites or simply keeping an eye open for something interesting. If the results were not quantifiable, they nonetheless proved what all man-in-space enthusiasts intuitively knew. Man's ability to discriminate, to select the important features of a wide vista, and to respond effectively to unexpected events constituted his greatest contribution to orbital investigations. Following and describing ocean currents for distances up to 3500 km, recognizing upwelling eddies of cold water in warm currents and then discovering the same phenomenon in unexpected localities, waiting for the precise moment to take a photograph-such achievements could not have been programmed into completely automatic sensors.23

 

NASA'S OWN EXPERIMENTS

 

Surveying the results of the habitability experiment, Caldwell Johnson had reason to be pleased with what his group had done for the workshop. Inflight evaluations by each crewman, movies and videotapes made during the missions, and postflight debriefings indicated that no serious mistakes had been made. Still, many aspects of habitability were still to be optimized, and a great many small irritations remained.

Skylab clearly showed that it was feasible to live for extended periods in orbit without becoming disoriented or encountering major problems with the lack of a gravity field. It was simply another work environment, one to which all the crewmen adjusted more or less rapidly. Indeed, they all enjoyed it. Some tasks were actually easier without gravity; moving massive objects, for example, was not hard at all, provided there were adequate handholds to control them. Small objects were more troublesome; hand tools, screws, and other small parts would not stay put. [348] Crews quickly learned, however, that there was little danger of losing something of this kind, because air currents in the workshop would sooner or later carry small objects to the screen covering the intake of the ventilation system.24

None of the nine astronauts expressed any strong preference for a uniform architectural arrangement such as that designed into the wardroom and experiment area of the workshop. Although that layout-with a clearly recognizable "floor" and "ceiling"-was an advantage for assembly and testing before flight, once in orbit a uniform up-and-down orientation was superfluous. What was essential was a reference axis at each work station, with all related instruments keyed to a single direction. In the multiple docking adapter, where circumstances had forced a more or less random arrangement of equipment, all the crewmen found they could work easily with any of it. Shifting from one work station to another meant changing the orientation, but this produced no confusion and required only a simple readjustment. Ed Gibson, in fact, gave the docking adapter high marks because it used all the available space with great efficiency, while the workshop wasted wall and ceiling space.25

One odd sensation was experienced in the docking adapter by both Jerry Carr and Ed Gibson. Carr noticed that when he entered the compartment from the command module feet first, he had the feeling that he was very high and had to be careful lest he fall all the way "down" to the workshop. Gibson felt the same way when he used one particular foot restraint, which poised him above the airlock hatch. It was the only place in the cluster where he had a sensation of height.26

One area in which much work clearly remained to be done was mobility and restraint in zero g. Not surprisingly, this was the area in which exhaustive simulations could not be done before flight; only a few experiments had been simulated in the zero-g aircraft. Mobility was superb and caused no problems, except for the difficulty of controlling the feet when passing through a narrow space, such as the hatch into the airlock or docking adapter. Feet tended to bump into the sides of the passageway, occasionally tripping a switch that was poorly located or inadequately protected. Restraint was the problem; the triangular metal gridwork used as flooring throughout the workshop worked well enough, and the triangular cleats attached to the crewmen's shoes provided good security when locked into it. But in the waste management compartment, where smooth surfaces had been provided for ease in cleaning, it was very hard to hold position. Straps on the floor, under which the feet could be slipped, proved useless.27

Many small deficiencies had, of course, shown up in the workshop during flight. Every crew remarked on the need for a workbench where maintenance and small repairs could be conducted. Forced to improvise, they used the ventilation screen in the forward dome, where the air.....

 


[
349]

Crystal-growing in space. The left crystal was grown during the third crew's tenure on Skylab, the middle crystal during the second. All crystals grown on the second mission showed a ring-shaped groove, probably caused by a spacecraft maneuver during the cool-down period. From H. U. Walter, Seeded, Containerless Solidification of Indium Antimonide, Proceedings of 3d Space Processing Symposium-Skylab Results, vol. 1 (NASA, 1974). The Skylab product on the right, a 20-mm crystal of germanium selenide, was the largest grown on earth or in space as of 1974. S-74-19677.

.

Crystal-growing in space. The left crystal was grown during the third crew's tenure on Skylab, the middle crystal during the second. All crystals grown on the second mission showed a ring-shaped groove, probably caused by a spacecraft maneuver during the cool-down period. From H. U. Walter, Seeded, Containerless Solidification of Indium Antimonide, Proceedings of 3d Space Processing Symposium-Skylab Results, vol. 1 (NASA, 1974). The Skylab product on the right, a 20-mm crystal of germanium selenide, was the largest grown on earth or in space as of 1974. S-74-19677. Below, NASA Administrator James C. Fletcher explains the process to President Gerald Ford. At the right is Howard Johnson, chairman of MIT. 74-H-1017.

.

Below, NASA Administrator James C. Fletcher explains the process to President Gerald Ford. At the right is Howard Johnson, chairman of MIT. 74-H-1017.

 

[350] ....current kept small parts in place, but a properly designed workbench incorporating that feature would have been a great help. Similarly, they found that they needed an office, or at least a desk where they could do their paper work. Stowage also needed considerable improvement. Bill Pogue's bitterest complaints were reserved for the locker numbering system and for the poor latches on lockers and film vaults.28

On the whole, however, Skylab proved to be well designed for living and working in space; few habitability features were so poorly conceived as to hamper the missions. There had been frustrations, but most of the astronauts learned to work around the workshop's faults. And, as all good experiments are supposed to do, the habitability experiment had shown spacecraft designers the limits of their expertise; it pinpointed the areas where they needed new ideas.

NASA had another major experiment on board, exploring means for controlled maneuvering by a man outside a spacecraft. Apart from one or two tests during the Gemini program, engineers had not experimented with maneuvering aids, and with the approach of the Shuttle era they felt a need to try out some concepts. The workshop's upper dome, 6.5 meters in diameter and about the same in height, was an ideal space in which to conduct tests, and this had been one of the first experiments suggested for the wet workshop in 1965 (p. 27). Skylab tested three concepts for an astronaut maneuvering unit: a large backpack, a small, hand-held gas pistol similar to that used by Ed White on Gemini 4, and a foot-controlled unit designed to leave the hands free for work.

The backpack, though bulky, was far more sophisticated than the other two. Fourteen cold-gas thrusters gave the astronaut control over motion along three axes and rotation about three, using a hand controller. Gyroscope stabilization of attitude was available, and small control gyros could be used for rotation. During the second and third missions, five crewmen tested the unit, flying it for nearly 14 hours to give the engineers data on all modes of operation. Owen Garriott determined that operation of the unit was easily learned; having no preflight experience with it, he picked up the techniques of operation in less than an hour. Several potentially useful tasks were performed with the experimental unit. Besides simple point-to-point flying and station-keeping, the astronauts simulated inspection of a spacecraft by flying the unit in a semicircle concentric with the workshop wall and about half a meter away from the upper stowage lockers. Then, after a second crewman had suspended a large object in the upper dome, giving it a slow spin in the process, the operator approached the spinning object, gave himself a rate of spin synchronous with it, grasped it, and used the maneuvering unit to reduce the spin to zero. The technique could be useful in recovering tumbling objects in space.29

The two other units, though much simpler, were also less versatile....

 


[
351]

Carrying the astronaut maneuvering equipment of experiment M509 in the forward (upper) compartment of the workshop.

Carrying the astronaut maneuvering equipment of experiment M509 in the forward (upper) compartment of the workshop. Two distinct models are involved: the small hand-held unit in Carr's right hand and the large backpack, the controls for which are in the arm rests. Neither proved completely satisfactory. The hatch to the airlock module is behind Carr. S-74-17305.

 

....and therefore less promising for orbital use. The hand-held unit proved too difficult to control accurately; it was hard to produce translational motion without also causing some rotation. While the astronauts felt that it might be useful for short point-to-point movements, it was much less attractive for complex maneuvers. The same was true of the foot-controlled unit. Its thrusters, located alongside the astronaut's feet, could not produce simple linear motion except vertically, and it too tended to cause unwanted rotation. Although the tests on Skylab indicated some success with this unit and gave its designers some data, it was clearly inferior to the backpack unit.30

 

COMET OBSERVATIONS AND STUDENT EXPERIMENTS

 

Among the scores of other experiments carried by Skylab, two sets received extensive public notice: the observations of comet Kohoutek and the student projects. Four months after the third crew returned with data on Kohoutek, NASA hosted a symposium at Marshall Space Flight Center to examine these and other results. The Skylab observations had been merely a small part of NASA's extensive program to observe this comet. Ground-based observatories, airborne telescopes, and satellites had all [352] been brought to bear, most of them using instruments better designed for the purpose than those Skylab carried. While Skylab's instruments produced several useful observations, their contribution was minor compared to the data gathered by the others. The most successful experiments of the Skylab group were the far-ultraviolet electronographic camera, which detected a cloud of hydrogen surrounding the comet, and the photometric camera, whose periodic exposures showed that Kohoutek dimmed appreciably after passing perihelion. Sketches and visual observations were among the most interesting data provided from the Skylab program.31

In view of their late entry into the program, it was to be expected that the student experiments would produce mixed results. Several were unsuccessful on account of equipment failure, some could not be conducted for operational reasons, and others yielded usable information. A planned observation of Jupiter with the x-ray telescopes had to be canceled because power limitations did not allow the necessary maneuvering. When a substitute observation of an x-ray source in the Veil Nebula was proposed, Skylab s instruments proved to lack the required sensitivity and pointing accuracy. Similar problems foiled two other student investigators: detection of ultraviolet radiation from pulsars and a study of x-rays from stars of different spectral types.32

Experiments with living organisms had better luck. Students found differences in bacterial colonies grown in Skylab, compared to controls on earth; and rice seedlings exhibited curious anomalies during development. Probably the most widely noticed student project used the webspinning ability of the common cross spider (Areaneus diadematus ) to test for adaptation to weightlessness. After dismal failures on their first tries, two spiders taken along by the second crew soon produced nearly normal webs. Owen Garriott wanted to extend this experiment a few more days, but both spiders died shortly after the initial observations-either from starvation or dehydration.33

No one would claim that the student experiments produced real advances in science, although their ideas were original and often sophisticated. This was scarcely the point. The project's real effect was on the students and their high school teachers, who were greatly stimulated by NASA's interest in their ideas. The contact with "real world" scientific investigations was an enlightening experience, not only for the winners in the competition, but for all of the competitors. Those who saw their experiments flown sometimes learned that failure is also a possible result of research. For its part, NASA learned that simple experiments, developed at low cost and flown in a short time, can be effective. The poor results of some experiments can be attributed to the lack of adequate training for crewmen and operations personnel, the result of the very busy training schedule.34

 

[353] SKYLAB SCIENCE: AN ASSESSMENT

 

For all the vagaries of its early development, Skylab held to its primary purpose of putting man into orbit to perform scientific work, and in that aim it was indisputably successful. Some scientists even felt that a second Skylab would be justified, even if it did no more than continue the work of the first; but NASA, in a period of shrinking space budgets that forced hard choices, could not afford to plow that ground again. The three Skylab missions cleared the way for the agency to move ahead to the Shuttle. The backup hardware, a fully functional copy of the orbiting Skylab, was taken out of storage in 1976 and consigned to the National Air and Space Museum-surely one of the most striking museum exhibits in history.

Skylab's medical results broke down most remaining barriers to extended manned spaceflight by showing that man adapts rather well to the zero-gravity environment, retaining his ability to function effectively for many weeks. Given proper attention to the appropriate environmental factors, he can maintain his physical well-being and morale, then readapt to earth surface conditions with surprising speed. Long-term problems remain unsettled, but these will provide the next generation of research problems. Skylab showed that spacefarers need not be superbly conditioned physical specimens; normal healthy individuals can be taken on orbital missions without risk.

As for man's value as a scientific observer, the point doubtless can be debated whether the money spent on the systems required to sustain man could have been better spent for more sophisticated unmanned equipment. Scientists who participated in Skylab will argue for man. Astronomers who had for years worked with unmanned satellites were won over by the performance of the Skylab crews and ground support personnel. Their ability to react to unexpected occurrences on the sun was a prime factor in the success of the ATM experiments. The same could be said for the earth-observations program; a man in orbit, trained to look for objects of interest and alert for unfamiliar features, proved to be of great value to earth scientists in many disciplines.35

In retrospect it seems clear that Skylab's experiment program was just a little too ambitious and heterogeneous. The large number of widely different experiments created operational difficulties, crowded the training schedule, and occasionally led crewmen into errors. While the difficulties were successfully overcome and much valuable experience was gained in the process, individual experiments would probably have fared better had there been fewer of them. But the political atmosphere in which Skylab matured gave managers little choice. As the last manned program for many years, the first multipurpose space station, and the proving ground for man's usefulness in space, Skylab was forced to take on more experiments than was optimum. The earth-resources package [354] the student experiments are cases in point (chap. 10). The former was a well timed response to an expressed public demand, the latter a way of broadening public support for manned spaceflight, and both paid their way.

Although the specific results of many of Skylab's experiments will not be worked into the fabric of science for a number of years, Skylab clearly established that man has a place in space science. Had it failed, or even left a few key questions unanswered, the future of manned spaceflight would have been bleak indeed. Skylab's success assured that man would not be the limit to the American venture into space.

 


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Skylab 4's view of its starting point, taken with the earth-terrain camera on color infrared film.

Skylab 4's view of its starting point, taken with the earth-terrain camera on color infrared film. Launch complexes 39B and 39A, upper left, are connected by crawlerways to the Vehicle Assembly Building. Lining Cape Canaveral itself are older Saturn and Titan complexes. Cocoa Beach is just to the right of the Cape; Patrick Air Force Base runways are visible farther down the coast. SL4-93-167.


A spectacular solar flare photographed by the third crew 19 December 1973 in the light of ionized helium, using the extreme-ultraviolet spectroheliograph of the U.S. Naval Research Laboratory.

A spectacular solar flare photographed by the third crew 19 December 1973 in the light of ionized helium, using the extreme-ultraviolet spectroheliograph of the U.S. Naval Research Laboratory. The twisted sheet of gas spans 588 000 km and seems to be unwinding itself. The darker areas at the top and bottom are the solar poles. 74-HC-260.


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X-ray photograph of the solar corona, 28 May 1973.

X-ray photograph of the solar corona, 28 May 1973. The corona is the thin outer portion of the sun's atmosphere. Areas hotter than one million degrees can be observed in x-rays. The loops and arches are produced by the interaction of the sun's magnetic field and the ionized gas of the corona. S-73-31696.


The sun photographed at a wavelength of 625.3 angstroms through Harvard College's spectroheliometer.

The sun photographed at a wavelength of 625.3 angstroms through Harvard College's spectroheliometer. The black areas are the surface of the sun, the reds yellows, and whites are the corona some 70 000 km above the surface. The picture is one of a set studying active regions. S-74-21923.


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This image of the sun in the extreme ultraviolet was transmitted from Skylab to Houston, where computer reduction added the color contours and gave it a needlepoint character.

This image of the sun in the extreme ultraviolet was transmitted from Skylab to Houston, where computer reduction added the color contours and gave it a needlepoint character. The black area starting at the north pole and extending well into south latitudes is a large coronal hole, an area where temperature and density are unusually low. Data collected with Skylab instruments established, beyond doubt, that coronal holes are the source of the high-speed streams of particles (the solar wind ) that buffet the earth's upper atmosphere, disrupt the magnetic field, and cause other effects in the lower atmosphere. S-73-32884.


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S190B photograph of the Black Hills (lower left) and Badlands (lower right) area of southwestern South Dakota.

S190B photograph of the Black Hills (lower left) and Badlands (lower right) area of southwestern South Dakota. The Cheyenne River meanders across the right side. Rapid City and Ellsworth Air Force Base are adjacent to the Black Hills. The rectangular patterns are caused by the practice of dry-lands strip farming. The light areas produced crops-mostly wheat-the previous year; the dark areas are the current year's growing crops. SL2-81-159.


Remarkably detailed photograph of the Grand Canyon area of northern Arizona.

Remarkably detailed photograph of the Grand Canyon area of northern Arizona. The high sun angle, light snow cover, and excellent visibility combined to give a picture of unusual value to the geologist. Only a few of the abundant lineations which indicate faulting, joining, and monoclinal flexing, were shown on contemporary geologic maps of the area. SL4-142-4436.


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Plankton bloom (upper right) in the South Atlantic, 25 December 1973.

Plankton bloom (upper right) in the South Atlantic, 25 December 1973. Off the east coast of South America, the south-flowing Brazil Current meets the north-flowing Falkland Current near 40° south latitude, where both turn eastward. The light area across the middle of the photo is the boundary between the two. Skylab crewmen followed the boundary visually more than 3500 km. The pink formation in the lower left is clouds. SL4- 137-3721.


Two smoke plumes stretch some 140 km across the Gulf of Mexico from the central Louisiana coast, 7 December 1973.

Two smoke plumes stretch some 140 km across the Gulf of Mexico from the central Louisiana coast, 7 December 1973. The value of such photographs in studying diffusion of pollutants is obvious. SL4-136-3475.


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Marshes of Dorchester County, Maryland, photographed in color-infrared by S190A in June 1973.

Marshes of Dorchester County, Maryland, photographed in color-infrared by S190A in June 1973. Land-use maps can be compiled and the relative salinity of bodies of water can be determined from such imagery. SL2-15-174.


Birthplace of Western civilization, as seen from one of its highest technological achievements.

Birthplace of Western civilization, as seen from one of its highest technological achievements. The photograph was taken with a 70-mm Hasselblad camera, 100-mm lens, and medium-speed Ektachrome film. SL3-121-2385.


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