BIOMEDICAL RESULTS FROM SKYLAB

SECTION  I - INTRODUCTION

CHAPTER 1

Skylab Medical Program Overview

RICHARD S. JOHNSTON

History is filled with examples of man's desire to explore new frontiers. Having sensed the thrill of discovery, man has pressed on to scale new heights not weighing the cost or personal risk, but mindful only of his destiny to conquer the unknown. Under adverse conditions, he has crossed the seas and the wastes of the arctics until there were no longer any new seas to cross, mountains to climb, or arctic poles to visit. Thus has he explored his Earth.

Exploration has always been a risky undertaking and opportunity for it is largely dependent upon the advancement of technologies in transportation and life support. With the development of chemical propellants and the application of some fundamental laws of physics, high velocity rocket propulsion became a reality; this is all man needs to kindle his imagination to reach beyond his Earth and to start the exploration of his universe. Although preservation of life and health is essential to the successful conquest of the unknown, few explorers have conducted studies on themselves or documented their responses to new environments. A notable exception was the work conducted during the 1935 International High Altitude Expedition to the Chilean Andes when the members of that team conducted self-studies to record for medical science the effects of exposure to the hypoxic environment of high altitudes.Since then some of these data have been used by every student of space medicine.

Utilizing the Saturn V launch system, man has successfully completed an epoch-making lunar exploration program. Through the use of this same propulsion system, the United States has launched its first long-term space station and has acquired giant advancements in knowledge concerning the physiological effects of increasingly extended periods of exposure to the space flight environment and in determining how well man can function while performing tasks in space.

Space medicine studies using experimental animals were initiated prior to 1959. Limited medical studies and observations on men in space were initiated in the United States with the Project Mercury Program. This project (ref. 1) served to dispel many basic concerns regarding the frailties of the human space explorer. It was shown that man could operate effectively during the acceleration periods of launch and entry, and that he could adapt to the weightless environment and perform useful tasks. Medical measurements made during these early flights showed that normal body functions were not adversely altered. The few changes which occurred were moderate but reversible. For example, postural hypotension was observed when the astronauts returned to the Earth's gravity field.

The first series of medical studies during weightless flights was provided by the Gemini Program (refs. 2, 3). One objective of these flights was to evaluate the performance of men living in the space environment for 14 days to assure an effective lunar scientific excursion. The results of the Gemini flights further demonstrated that man could adapt to the weightless environment, could perform useful tasks, and could enter the Earth atmosphere and readapt to Earth gravity.

The Apollo Program originally included the conduct of a series of medical studies for the early orbital missions. After the tragic Apollo 204 accident, the decision was made to delete the medical studies and to dedicate all resources to the complex lunar landing program. Consequently, medical studies were primarily conducted with the Apollo crewmen before and after each flight.

Skylab, at its inception called the Apollo Applications Program, was a natural and necessary follow-on to the Gemini and Apollo Programs. The tested and proven spacecraft and launch vehicles from the Apollo missions were used in the design and flights of the Skylab Program. Development of medical experiments, initiated in the mid 1960's, included a decision to design the experimental program along classical lines of medical and physiological research; namely, to group related studies together according to their possible contribution to the understanding of the functioning of a major body system. Of course the results from the Gemini and Apollo flights influenced the planning and placement of emphasis for the new program. The experiment protocols developed to study the cardiovasular, cardiovascular, musculoskeletal, hematologic, vestibular, metabolic, and endocrine systems in the body, with few exceptions, remained unchanged throughout the Skylab Program. This chapter will provide an introduction and overview to the Skylab medical program. The chapters which follow will present the significant results from the three manned Skylab missions.

Operational Equipment

Several major medical subsystems were provided in the Skylab Orbital Workshop to sustain the crew and to protect their health.

   Food System.--The Skylab food system (fig.1-1)(ref. 4) was developed to provide a balanced and palatable diet which also met the necessary requirements for calories, electrolytes, and other constituents for the metabolic balance experiment (ch. 18). Seventy foods were available from which the crew could select their in-flight diets. Food types included frozen, thermostablized, and freeze-dried foods. Menus were planned for 6-day turnaround cycles. Each crewman was required to consume his individually planned diet for 21 days preflight, throughout the flight, and for 18 days postflight. Approximately one ton of food was stowed in the Orbital Workshop at launch to provide approximately 400 man-days of food. The ambient foods were packaged in 6-day supply increments and stowed; these were moved by the crewmen to the galley area for direct stowage, preparation, and eating. The galley area contained a freezer, a food chiller, and a pedestal which provided hot and cold water outlets, attachment points for three food trays, and body restraints which afforded each crewman the opportunity to sit down to eat. Each food tray contained seven recessed openings to hold cans or other containers, three of which had heaters for warming the food. The food cans were constructed with membranes or other designed devices which restrained the food within the container when in zero-gravity and allowed the crew to eat with conventional tableware. Drinks in a powdered form were packaged into individual bellows-like containers constructed with a drinking valve. Water, when needed, was added from the hot or cold water outlets located on the pedestal. The crewmen drank from the container by collapsing the bellows.

The variety of foods provided and the general design of the food system were acceptable to the Skylab crewmen. At the suggestion of  the returned Skylab 2 crew, more and varied spices were included in the later missions to improve the taste of the food.

The extension of the Skylab 4 mission for an additional 28 days required 250 pounds of additional Skylab food to be launched in the Command Module. This extra weight and the resulting stowage volume were excessive, therefore, a high density, high-caloric type food bar was stowed in the Command Module to provide the caloric requirements for the mission extension. The crewmen's in-flight menus were modified to include approximately 800-1000 calories of the food bars every third day. For Skylab 4, in addition to the 50 pounds of high-caloric type food bars, approximately 100 pounds of other Skylab-type food and drinks were launched in the Command Module.

   Waste Management System.--The Skylab Waste Management System included equipment for the collection, measurement, and processing of all urine and feces and for the management of trash such as equipment wrappers, food residues, et cetera (fig. 1-2).

   Waste Management.--Equipment used by the crew for the collection of urine and feces, and in addition, equipment used for personal hygiene were stowed and used in the waste management compartment. Feces were individually collected into a bag attached under a form-fitted commode seat seat. The bag was permeable to air and impermeable to liquids. An electric blower, actuated by the crewman during use, provided a positive airflow round the anal area to carry the feces into the collection bag. After each defecation, the crewman weighed the bagged stool on a mass measuring device, and then labeled and placed it into a vacuum drying processor. After 16 to 20 hours of drying, the bag of fecal residue was removed from the processor and stowed for return to Earth for postmission analysis.

Each crewman's urine was collected in an individual 24-hour pooling bag. A centrifugal fluid/gas separator was actuated at the start of urination to create a positive airflow to carry the urine into the equipment where urine was separated from the gas and was then collected into the pooling bag. A measured quantity of lithium chloride, added to each pooling bag prior to flight, permitted urine volumes to be calculated during analysis postflight. In addition, the crew used a gage to measure the filled pooling bag thickness to give a real-time estimate of daily urine output. Once every 24 hours each crewman collected a 120 milliliters urine aliquot from his pooled urine bag and placed this sample in a freezer for return and postflight analysis. The used pooling bag was discarded and a new bag was installed for use each day.

Trash accumulated from food wrappers, used equipment bags, used towels, et cetera, were discarded through an airlock into a large volume tank in the Orbital Workshop dome.

The Waste Management System and trash airlock operated satisfactorily throughout the Skylab missions and the crews reported complete satisfaction with the design of this equipment.

   Personal Hygiene.--Provisions were included in the Orbital Workshop for daily personal hygiene. Such items as wet wipes, towels, toothbrushes, razors and deodorants, were provided to maintain body cleanliness. In addition a shower contained in a collapsible cylindrical cloth bag (fig. 1-3) was provided to permit full body bathing. Warm water and a liquid soap were available in limited quantity for one shower per week for each man. The Skylab crewmen reported satisfaction with the shower and other personal hygiene equipment; however, the crewmen did indicate that an excessive amount of time was required to vacuum the collected water and dry out the shower after use. Microbiological studies conducted on the Skylab crewmen indicated that the personal hygiene techniques used were completely adequate.

   Inflight Medical Support System.--In-flight Medical Support System (IMSS) (app. A., sec. II.a.) was designed to provide for the conduct of selected in-flight medical evaluation experiments and, as required, first level medical diagnosis and treatment for an ill or injured crewman (fig. 1-4). The equipment was stowed in the wardroom and included: diagnostic, minor surgery, dental, catheterization, and bandage kits. Sixty-two medications for the three missions were stowed in modules to insure an adequate and fresh supply. Prior to flight, drug-sensitivity testing was conducted on mission-designated Skylab crewmen. In addition, microbiological equipment and slide-staining capabilities were provided. Petri dishes, an incubator, microscope, and slide stainer were available for use by the crew. The microbiological equipment was used to collect airborne and surface microbial samples in flight. As part of his mission preparation, each Skylab crewman underwent 80 hours of paramedical training in the use of the In-flight Medical Support System for diagnosis and in treatment of injury or illness.

   Cardiovascular Counterpressure Garment.—Cardiovascular counterpressure garments (fig. 1-5) were launched in the orbital workshop for all three missions. These garments were designed to provide mechanical counterpressure to the lower extremities to reduce the postural hypotension effects following landing and operations under one-gravity conditions. The garment has a built-in capstan in the length of each leg. Inflation of the capstan by a pressure bulb provided a pressure gradient of 85 to 90 millimeters of mercury (mmHg) pressure at the ankles to 10 mm Hg pressure at the waist. A garment was donned by each crewman prior to entry and it was sometimes inflated during descent and always following landing. Subsequent chapters (chs. 5, 29) will discuss the physiological protection afforded by these garments.

Life Sciences Experiments

The Skylab medical experiments listed in table 1-I were designed to provide an indepth study of individual body systems and at the same time provide an overlap to give comprehensive understanding of man's reaction to long-term weightless flight. Added special in-flight tests are shown in table 1-II to indicate other type studies which were completed in the three missions. The inclusion of major in-flight medical experiments provided the capability to study physiological responses during exposure to weightless flight as opposed to the pre- and postflight studies as carried out in the Apollo and Gemini Programs. Results of these studies are the subject of this book.

The Skylab medical experiments equipment was located in and occupied about one-third of the floor area of the crew living level of the two-storied Orbital Workshop. Figure 1-6, a photograph taken during the Skylab 3 mission, shows this medical experiment area. On the right is the collapsed shower previously described. The two consoles against the workshop wall contain the medical experiment electronic equipment. This figure also shows photographs of equipment for two of the major medical experiments: M172 and M092.

The M171 ergometer and metabolic analyzer (app. A., sec. I.f. and app.A,sec.I.g) shown at the upper left of figure 1-7 are being used by the Skylab 2 Pilot. the metabolic analyzer contains a mass spectrometer for measuring oxygen, carbon dioxide, nitrogen, and water vapor. In addition, spirometers were provided to measure respiratory volumes. The bicycle ergometer was used to provide a quantitative stress level for investigation of physiological response and it was also used as the prime off-duty crew exercise device. Blood pressure, vectorcardiograms, and body temperature measurements were also made as a part of the M171 Metabolic Activity experiment.

The M092 Lower Body Negative Pressure Device is shown on the upper right of figure 1-7 as it was used in Skylab 2; this experiment was monitored at all times by a second crewman. The leg volume measuring bands (app. A., sec. I.b.) used with the Lower Body Negative Pressure Device are shown also. The electronic center for these experiments, labeled on figure 1-7 as Experiment Support System (app. A., sec. I.k.), contains the displays and experiment controls.

In the upper left-hand corner of  figure 1-8, the Skylab 2 Scientist Pilot is shown wearing the M133 electroencephalographic sleep cap (app. A., sec. I.i). One crewman, i.e., the Scientist Pilot, performed this experiment in each mission. The Body Mass Measuring Device and Specimen Mass Measuring Devices (ch. 19) were evaluated as experiments to establish the method and accuracy of determining mass in the weightless environment. In addition, these devices were used to provide daily body weights and the mass of food residues and fecal specimens. The M131 rotating litter chair (app. A., sec., I.j.) was used to study vestibular functions and susceptibility to motion sickness.

Equipment also was developed and flown to collect, process, and preserve in-flight blood samples (fig. 1-9) (app. A., sec. I.e.). The crewmen acquired approximately 11 milliliter blood samples with a conventional syringe and then transferred the whole blood into a pre-evacuated sample processor.  The sample processor was then placed into a centrifuge to separate the plasma from the cells and to transfer the plasma into a separate collection vial for preservation. This transfer operation had to be automatically accomplished while the blood was being centrifuged due to problems associated with weightless operations and fluid dynamics.

The cross section drawing of the sample processor shown in Figure 1-10 illustrates how the equipment functioned. Whole blood was transferred from the syringe through a septum into the processor. A spring-loaded piston was attached to the bottom of the sample processor and the unit was placed in the centrifuge. Following initial centrifugation, the cells and plasma were separated. At this point, the centrifuge speed was increased to force the piston to drive the plasma vial septum past a needle and allow the plasma to flow into the vial. Following this separation process, the blood was placed in a freezer and preserved for postflight analysis. The medical experiment equipment functioned without problems throughout the three flights. Medical data of high quality were obtained for all experiments. Vast quantities of medical data available for reduction and analysis were processed in an orderly fashion. This could not have been accomplished in a timely manner without computer processing. The quantity of information obtained from the medical studies conducted with the Skylab crewmen over a relatively short period of time is perhaps unique in medical research Over 600,000 biochemical analyses were made on food, blood, urine, and fecal samples. In completing two of the major medical experiments, more than 18,000 blood pressure determinations were made and over 12,000 minutes of vectorcardiographic data were obtained.

Skylab Medical Operations

The medical operational planning for Skylab was much more complex than any other U.S. manned space mission. The logistics planning required for crew feeding, sample collection, base line experiment data acquisition, crew medical examinations, crew health care, data processing, and flight management into an integrated plan that meshed with program milestones required a major medical team effort.

The Skylab medical operations program was initiated in June 1972 with a 56-day altitude chamber test (ref. 5) and was completed in April 1974 with the last postflight Skylab 4 crewmen evaluation tests.

The first launch (Skylab 1) was to place the Skylab Orbital Workshop in correct orbit; it was unmanned. The compressed schedule of the subsequent manned Skylab launches and the extension of mission duration after the first manned launch, Skylab 2, created an extremely heavy burden on the Skylab medical team. The medical experiment program was unique in that it not only provided scientific data, but, in turn, the data were used as the basis for operational decisions for commitment to longer duration flights. This meant that at the end of each of the first two manned missions, the medical team had to make a recommendation for the extension of the next successive mission. From figure 1-11 it can be seen that the preflight phase of Skylab 3 started before the completion of the Skylab 2 postflight phase and after baseline data collection for Skylab 4 had begun. Skylab 3 was launched only 2 weeks after the Skylab 2 postflight studies were completed. Skylab 4 was launched only 5 weeks after completion of the Skylab 3 postflight medical studies. This quick turnaround required careful planning, establishing Priorities for samples and data processing, and the dedication and tireless effort of all members of the medical team.

   Skylab Medical Experiment Altitude Test.—The Skylab medical experiment altitude chamber test was a 56-day mission simulation conducted in a 6.1 meter (20 ft) diameter vacuum chamber. The interior of the chamber was configured closely to the Orbital Workshop crew quarters level which consisted of the medical experiments area, wardroom, waste management compartment, sleeping quarters, and recreational area. The atmosphere in the chamber was maintained at a composition identical to that of the Orbital Workshop, with 70 percent oxygen, 30 percent nitrogen mixture at a pressure of 34 X 10[3] Pa (5 Ib/in ). Carbon dioxide levels were controlled at a nominal level of 16.9 kP (5 in. Hg) pressure.

The prime objectives of the test were to acquire background dataand to exercise the data management and processing techniques for selected medical experiments. Other test objectives included the evaluation of medical experiment and operational equipment, the evaluation of operational procedures and the training of support personnel under simulated mission conditions.

Like a flight mission, the test consisted of a 21-day prechamber phase, a 56-day chamber test, and an 18-day postchamber test period. All preflight and postflight medical protocols were performed with astronaut crewmen. The inchamber test portion of the program was carried out using full mission simulation procedures, and included: crew checklist, real-time mission planning, and data management. The communications with the crewmen were limited to a spacecraft communicator, as programmed to be carried out in the mission. Simulated network communications were followed to evaluate the problems of lost communication between flight crew and mission control center, as they would be experienced in actual flight. A remote console was used by the medical team to evaluate the problems of  lost communications and procedures for flight. This test program was successful; the required baseline data were obtained and the encountered equipment failures and problems were corrected prior to flight. The ground support personnel became an effective team ready to carry out the complex flight program.

   Premission Support.--The premission support for the first manned mission started in December 1972 with acquisition of the first baseline data for the Lower Body Negative Pressure (M092, ch.29) and Metabolic Activity (M171, ch. 36) experiments. Additional baseline tests were conducted in support of the medical experiments at designated periods up to approximately 1 week before the launch of Skylab 2. These baseline data were primarily obtained in an Orbital Workshop one-gravity trainer. This full scale trainer contained fully functional medical experiments and other operational hardware. Combined crew training and baseline data collection were conducted with both the prime and backup crewmen. A remote medical console and data recording system was used to monitor the crewmen during training sessions and to train members of the medical team in control procedures and in the reduction of flight data. This combination of training and medical baseline data acquisition was excellent for both the crewmen and medical experimenter. A comprehensive medical examination of both the prime and backup crews was given 30 days before scheduled launch and additional baseline data were obtained for the experiments.

Twenty-one days before launch, the crew was placed in semi-isolation (fig. 1-12) to meet the requirements of the Skylab Crew Health Stabilization Program (ch. 7). The objective of this program was to protect the in-residence flight crew from illnesses which might cause them to be removed from flight status and to preclude exposure to infectious disease which could develop in flight. All personnel who were required to work with the flight crews were designated as primary contacts. To protect the crewmen, these personnel underwent periodic extensive medical examinations and immunizations, were required to wear a surgical mask while in contact with the crew, and were required to report all personal and family illnesses.

Isolated crew quarters were established and personnel access Into designated primary work areas was rigidly controlled. The Skylab Crew Health Stabilization Program was effective and no major problems were encountered.

During this period of isolation, the crew consumed foods identical to those provided from pre-planned in-flight menus (ref. 4). Daily collections of urine and fecal samples were initiated. Medical examinations, microbiological and blood sampling, and experiment baseline testing were continued at the Johnson Space Center up to 3 days before launch when the prime and backup crews were moved to the Kennedy Space Center for the launch.

  In-flight Operational Support.--The management of the in-flight medical operations support and the necessary interactions with program management personnel, personnel representing the scientific disciplines, and the Flight Control Team were accomplished through a medical management group. The medical group met each morning of the mission to review crew health status, to evaluate the current state of the medical studies, to discuss equipment or other operational problems, and to establish changes in experiment priorities. Health trend charts were plotted each day (fig. 1-13) to provide experimental data which were useful in understanding crew health status. These charts included: crew weight, caloric intake, quantity of sleep, heart rate and blood pressure under dynamic stress, urine volume output, and other pertinent information. The chairman of the Medical Management Group reported to a Flight Management Team on all medical matters and participated in operational decisions such as changing crew timelines, adjusting science requirements to insure maximum utilization of the crew and the current science opportunities, and to provide advice on major operational policy changes. This management scheme was extremely effective and was a key factor in the success of the Skylab Program.

The in-flight activities of Skylab 2, illustrated in figure 1-14, shows the medical activities for a typical Skylab mission. The first 2 to 3 days of each mission were spent in the activation of the Orbital Workshop. These activities included such tasks as system checkouts and activation, transfer of equipment from the command module to the Orbital Workshop, changing air filters, et cetera.

In-flight medical monitoring of the crewmen started at launch through the use of the Operational Bioinstrumentation System (app. A, sec.II.d). The bioinstrumentation system was used to monitor the crew during all extravehicular activities. The frequency of in-flight medical experiments and tests for the Skylab 2 crewmen is also indicated in figure 1-14. Throughout all Skylab missions, the Lower Body Negative Pressure (M092) and Metabolic Activity (M171) experiments were accomplished approximately every fourth day. Blood samples were collected weekly during the missions and biosampling was accomplished daily.

During the flight phase, real-time monitoring of the medical experiments was accomplished only when the spacecraft was over a tracking station. This meant, in some instances, there was a complete loss of communications with the crew and the telemetered data during medical testing. To overcome this problem, all experiment data were recorded onboard and subsequently telemetered through the tracking stations to the Mission Control Center. The use of software programs permitted automatic computer reduction of the experiment data with a preliminary data printout to the experimeter within 24 hours after completion of the test. During the last few days of all three missions, work/rest cycles were changed to adjust the circadian rhythm of the crewmen to the required length of the pre-entry day and the time of spacecraft splashdown.

The inflight portion of the three Skylab missions totaled 168 days during a 8.5-month period. Throughout this long and arduous period, the interest, enthusiasm, and concern for the crew were maintained at the highest level by all members of the medical and program management teams.

   Postflight Activities.--The recovery procedure used for the Skylab crewmen was altered from the procedures used in the Apollo Program. Figure 1-15 illustrates how the Command Module and the crew were retrieved and lifted directly onboard the recovery aircraft carrier and how the crew egressed onto a platform on the hangar deck. Spacecraft and crew retrieval took approximately 35 minutes from time of splash.

Specialized mobile laboratories (fig. 1-16) were developed and equipped to acquire preflight and postflight medical experiments data. The laboratories were designed and constructed to be moved in a C-5A transport aircraft and thus permit the medical team to cover contingency splashdown in the event of an early mission abort. For a normal mission, the laboratories were flown to port and were lifted onboard the recovery carrier. Six laboratories made up the laboratory complex and those were equipped with backup support systems, i.e., electrical power, heating, cooling, et cetera. In addition, a data complex was included which permitted processing of medical data in a format compatible with the flight data. In use, the mobile laboratories proved to be useful facilities; they added to the convenience of the medical operations, they were operated without problems, and they provided high quality medical data.

Medical studies were initiated immediately after recovery operations. A summary of all postflight activities is shown in figure 1-17. The recovery day testing for Skylab 2 lasted for approximately 10 hours and included a comprehensive medical examination and the acquisition of data for all major medical studies listed in figure 1-18. In subsequent missions, the length of an over-long recovery day of medical studies was shortened to reduce crew stress and fatigue.

The health stabilization program was followed throughout the first week following recovery to provide protection for the crew from any infectious disease that might result from a depressed immune response after the long isolation period of the flights. In all Skylab missions postflight medical testing was continued until preflight control levels were reached.

Operational Experience

The Skylab Orbital Workshop was launched on May 20, 1973. The loss of the micrometeoroid shield exposed the skin of the workshop causing an increase in internal workshop temperatures and the partial deployment of the solar panels reduced the electrical power supply available for experiments and systems operation. The Orbital Workshop failure also caused a 10-day delay in the launch of Skylab 2 which impacted the medical program. This necessitated that the health stabilization, controlled feeding, and biosample collection be extended. The exposure of the skin of the workshop caused an elevation in both wall and spacecraft air temperature. The plot shown in Figure 1-19 illustrates the temperatures in the food stowage area exceeded 327.59 K (130 F). In the 10-day period before the launch of Skylab 2, a thermal screen was developed which the crew could deploy to shield and insulate the orbital workshop. In the intervening time period, however, the increase in temperature caused the following concerns to the medical team:

     Would the foods be spoiled or changed by the elevated temperatures?

     Would other medical equipment be damaged by the increased temperatures?

     Would the polyurethane walls of the workshop be heated to a point where carbon monoxide or toluene diisocyanate           would be emitted into the spacecraft atmosphere?

Immediate action was taken to conduct ground based test programs or to develop equipment which the crew could use to understand and/or solve the problems.

Food test programs were initiated to study the effects of the increased temperature on microbial growth, food quality, and other characteristics. Identical foods were placed in thermal chambers; the temperature data from the workshop were used for a thermal profile. Periodic food sampling was accomplished to determine biological and chemical composition changes, and the thermal effects on taste and palatability were evaluated. No significant food failures were encountered during these tests and the launch of Skylab 2 proceeded without major alterations to the food system. The food test program was, however, continued throughout the Skylab Program and selected food samples were returned from the three missions for analyses.

Similar thermal testing was accomplished for many miscellaneousmedical items such as electrode sensors, sealed containers, et cetera. From these tests, it was determined that resupply of certain medications would be carried by the Skylab 3 crewmen. Additional procedures and equipment were developed which allowed the crew to reconstitute the Electroencephalographic electrodes on the sleep study caps.

The potential toxicity problems associated with the overheating of the workshop polyurethane wall insulation also was studied through thermal testing. It was determined that toluene diisocyanate and carbon monoxide could be present in the tmosphere. Therefore, special sampling tubes and adapters were built in the 10-day period between the launches of the Orbital Workshop and Skylab 2. The equipment developed permitted the crew to withdraw an atmospheric sample from the airlock and then the workshop before opening the hatch into these areas. In addition, special masks were provided to allow the crew to move into the orbital workshop if the toluene diisocyanate and/or carbon monoxide levels so dictated. The Skylab 2 crew found no toluene diisocyanate and the carbon monoxide concentration was less than five parts per million. The toxicological aspects of the Skylab Program are covered in more detail in chapter 10.

The Skylab crew deployed the first thermal screen on the second day of their mission and immediately the Orbital Workshop wall temperatures started to decrease. Within the next several days, the ambient gas temperature had dropped below 26.6 C (80 F). The elevated temperature in the workshop did delay the start of some medical experiments and, no doubt, influenced the results of the first medical studies. However, through the efforts of the Skylab 2 crewmen, the mission and the workshop were saved from what appeared to be an obvious total failure. Subsequently, the Skylab 3 crew deployed an additional thermal screen to further protect the Orbital Workshop against excessive heat changes for that mission and for Skylab 4.

Throughout the Skylab Flight Program, alterations in equipment and procedures were made for each succeeding mission to capitalize on the flight experience of the previous mission. The Skylab 2 crew recommended that the personal in-flight exercise program be extended in both duration and type. To meet this recommendation, the exercise period for the Skylab 3 crew was expanded from one-half hour to 1 hour daily and an additional exercise device was launched with the crew of Skylab 3.

On Skylab 4, the duration of crew exercise was further expanded to one and a half hours daily and a unique treadmill device was used by the crew. In addition to these equipment-associated changes, additional scientific studies were added to the programs for Skylab 3 and 4. These additional studies demonstrate the flexibility afforded the medical team and the support given to this team by program management and the flight crews.

Conclusions

Skylab 2, the first manned Skylab mission, was launched on May 25, 1973, with a crew of three: Charles P. Conrad, Commander; Joseph P. Kerwin, Scientist Pilot, and Paul J. Weitz, Pilot. After 672 hours, 49 minutes, and 49 seconds in flight, they splashed down on June 22,1973. The crew on Skylab 3 consisted of Alan L. Bean, Commander; Owen K. Garriott, Scientist Pilot, and Jack R.Lousma, Pilot. This second manned mission began with launch on July 28, lasted 1427 hours, 9 minutes, and 4 seconds and ended with splashdown on September 25, 1973. The third and last manned mission, Skylab 4, was launched November 16, 1973. The crew, Gerald P. Carr, Commander, Edward Gibson, Scientist Pilot, and William Pogue, Pilot, spent 2017 hours, 15 minutes, and 32 seconds in flight before splashing down on February 8, 1974.

The Skylab medical program met or exceeded all of the planned Objectives. The medical operations were conducted without any major problems and the medical equipment functioned flawlessly. The medical data received from the crew were of excellent quality and the quantity of information available from these three missions is staggering when viewed in its entirety. Skylab represents a significant milestone in the development of space medical knowledge. From the information presented, we feel confident that man can fly longer missions as required for future space exploration. The Skylab crewmen have demonstrated the versatility and ingenuity of man to make repairs, to carry out observations, and to conduct scientific studies.

References

1. Space Medicine in Project Mercury. NASA SP-4003, 1965.

2. Gemini Midprogram Conference, Including Experiment Results, February 23-25, 1966. Manned Spacecraft Center, Houston, Texas, NASA SP-121, 1966.

3. Gemini Summary Conference, February 1-2, 1967, Manned Spacecraft Center, Houston, Texas, NASA SP-138. 967.

4. Skylab Food System. NASA TM X-58139, October 1974.

5. Skylab Medical Experiments Altitude Test (SMEAT). NASA TM X-8115, October 1973

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