The Habitability and Crew Quarters experiment was established to evaluate the effectiveness of the habitability provisions of Skylab. It was not an experiment in the classical sense. The experiment was more a demonstration of how well technology could reduce habitability to an activity entirely incidental to the space flight mission itself. Within the limits of programmatic resources, Skylab was configured to reflect the best understanding of the requirements for habitability. The experiment sought to evaluate the suitability of those requirements, not the technical excellence of their engineering implementation.
Measurements were conducted in the following areas:
Twenty Functional Objectives (FOs) were scheduled for Skylab-2.
1. Assessment of the design and operation of habitability equipment
2. Assessment of the habitability aspects of the living compartments
3. Assessment of the frequency of use of habitability features
4. Roundtable discussion by all crewmembers during early mission activities
5. Roundtable discussion by all crewmembers during middle mission activities
6. Roundtable discussion by all crewmembers during late mission activities
7. Measure sound pressure levels and center band frequency spectrum
8. Measure the air velocity, ambient, surface and air temperatures, push/pull forces, and distance
9. Photograph crew performing routine living activities early in the mission
10. Photograph crew performing routine living activities midway in the mission
11. Photograph crew performing routine living activities late in the mission
12. Photograph crew performing housekeeping activities early in the mission
13. Photograph crew performing housekeeping activities midway in the mission
14. Photograph crew performing housekeeping activities late in the mission
15. Photograph crew performing maintenance tasks early in the mission
16. Photograph crew performing maintenance tasks midway in the mission
17. Photograph crew performing maintenance tasks late in the mission
18. Additional photography for support of experiment M516, Crew Activities/ Maintenance Study
19. Photographic demonstrations of Waste Management Compartment (WMC) methods
20. Photograph off-duty and hygiene activities
Functional objectives 9 through 18 were expected to demonstrate the efficacy of the habitability equipment and to reveal any difference in the utilization of the equipment by the crew as the mission progressed.
Functional Objective 19 was a demonstration of the preferred methods for mounting and dismounting the fecal/urine collector, use of all restraints including lap strap, and the methods used for various personal hygiene and grooming techniques such as shaving, hair combing, using the hand washer, washcloth squeezer, and mirror and associated restraints.
Eighteen FOs were scheduled for the Skylab-3 mission. Experience gained during the Skylab-2 mission led to several changes in the FOs proposed. The following are the changes.
Nineteen FOs were scheduled for the Skylab-4 mission.
Data Acquisition: Objective and subjective data were acquired from real-time television and video tapes, 16mm film returned with the crews, operational conversations, subjective reports by the crew during the missions, and postflight debriefings.
Data acquisition techniques were intended to be unobtrusive in the sense that staged demonstrations were avoided; however, time was required to set up cameras, use environmental measuring instruments, and tape inflight debriefings.
Subjective evaluation data - Two types of subjective evaluation data were solicited from the crew. Questions were asked of the crew concerning general aspects of living and working in 0-G, and rating scale evaluations of specific equipment items and compartment architectural arrangements. Questionnaire forms were furnished as part of the M487 data package. All subjective evaluations were voice recorded and transmitted to the ground.
Along with scheduled inflight evaluations, ad hoc crew commentary was requested as the mission progressed. As the experiment support team gained experience with this method of data collection, certain changes in format were deemed appropriate.
Debriefing questionnaires: A series of general questions were formulated concerning the various aspects of living and working in 0-G. The questions were varied, so more specific questions were used during the early-mission evaluation and general questions were used during middle- and late-mission evaluations. The questions were intended to stimulate discussion between crews about the various habitability parameters but only the Skylab 2 crew used them in this manner. The other crews chose to answer the questions individually as a matter of timeline and scheduling convenience.
Equipment items and compartment evaluations: The crew individually evaluated the various spacecraft equipment items and architectural parameters of each spacecraft compartment. A 5 point rating scale was designed specifically for use with the evaluation forms, but the prime data return was expected to be the crews' comments and suggestions in support of their specific individual evaluations.
Environmental measurements: Several environmental instruments were used for measuring various aspects of the Skylab environment. The data were used to supplement the crews' subjective impressions. The instruments included the following:
1. A velometer to measure air velocity
2. Digital and ambient thermometers to measure surface and ambient temperatures
3. A force gage to determine push/pull forces
4. A sound meter to monitor the sound pressure levels
5. A frequency analyzer for measuring the acoustic spectrum
6. A measuring tape to gather quantitative data on dimensions and arrangement of the orbital assembly (OA) architecture
Photographic coverage: Besides the scheduled photography, scheduled and unscheduled television transmission provided real-time and videotaped visual records of many crew activities.
Inflight Objectives: All functional objectives were accomplished for three missions, except the photographic requirements of FOs 10 and 20. However, it was evident as the mission progressed that the intent of those FOs was being achieved by television coverage and by photography for other purposes. Also, as the missions progressed, the formalities of real-time communication between the experiment support team and the crew relaxed to the point where pertinent questions could be discussed more readily while the circumstances of the issues were fresh in the mind of everyone. Taken together, enough voice comments, taped evaluations, and televised images were transmitted and enough film was brought back by the crews to satisfy essentially all data acquisition objectives of the experiment.
Of the data sources, video tapes and the 16 mm film provided the most useful objective data. The periodic reports by the crewmen during the mission provided the most useful subjective data, especially after group reporting was abandoned in favor of individual reporting and more meaningful questions were asked of the crewmen. Although televised activities tended to be somewhat staged, careful review of activities incidental to the main subject often would reveal nominal performance. Subjective reports by all nine crewmembers did not always agree, but the disparities were not of the degree or nature that would refute the consensus.
Postflight Debriefings: A series of debriefings of the flight crews by several management and technical levels of NASA took place after the crew returned to Houston and had an opportunity to rest. The debriefings provided another valuable source of data, not so much because additional facts were brought out, but because earlier comments were clarified. In some instances, the crews were able to explain objective data that otherwise would have been misunderstood. There were three formal debriefings and a number of unscheduled discussions with individual crew.
Management debriefings: When practical after their return, each of the crews briefed upper levels of NASA management on the highlights of the mission. Aspects of the current mission important to the upcoming mission were emphasized. However, the debriefings were mostly summaries and not especially pertinent to experiment data collection.
Technical crew debriefings: A few days after a management debriefing, the crewmembers recounted their recollection of all aspects of their mission. To bring out as much information as possible, they compared notes and impressions, which enhanced their individual recollections of the entire mission. They generally followed an outline of subject matter prepared for them as a guide, but were free to digress. Since the technical debriefings were taped without an audience and the transcripts were intended for very limited distribution, the comments were candid.
Systems and experiments debriefings: Debriefings were conducted for technical specialists representing spacecraft systems, operations, and experiments. Debriefings lasted several days and were arranged according to subject matter. Pertinent portions of transcripts of the technical debriefing were furnished to the technical specialist beforehand, so that the specialists could avoid repetitious questions and could seek clarification of a possibly misunderstood point. Although many pertinent comments were brought out by the question-and-answer type debriefings, some questions tended to become leading and the crew became both weary and wary.
Informal debriefings: The support team for experiment M487 was located at Johnson Space Center (JSC) and was able to consult with the returned crew on a frequent and informal basis. These informal consultations were especially useful for pursuing an obscure point or explaining an apparent contradiction of data. And, in return, a crew or crewmember used the experiment team and data bank to refresh their memory of how things went during a particular phase of a mission.
Habitability Evaluation: Habitability or whatever one chooses to call the quality of daily living is, at best, a nebulous concept. To lend some semblance of order when reporting on the subject, habitability is presumed to comprise the following nine elements:
1. Environment: Composition, temperature, and movement of the respirable atmosphere; acoustic and lighting levels.
2. Spacecraft Architecture: Geometric arrangements of compartments and interior appointments.
3. Mobility and restraint: Locomotion and restraint of the crewman and mechanical aids.
4. Food and drink: Stowage, preparation, serving, and eating.
5. Garments: Shirt-sleeve clothing.
6. Personal hygiene: Facilities for waste collection, washing, and grooming.
7. Housekeeping: Housecleaning, refuse disposal, and stowage.
8. Communication: Intravehicular only.
9. Off-duty activity equipment: Music, books, games, and other entertainment.
The respirable atmosphere in the Skylab was 70 percent oxygen and 30 percent nitrogen, and was maintained at an absolute pressure of approximately 260 torr. Air leaving the conditioning apparatus was ducted to the aft end of the workshop and worked its way through the living quarters and experiment area to collectors in the forward dome area. Local flow in the crew quarters could be regulated by adjustable anemostats.
Portable fans were sometimes necessary because of apparent lack of gravity-induced air convection. Combinations of air and wall temperature, humidity, and general circulation were such that the crew would not be expected to become overheated. However, there were instances when the crew felt that they were submerged in a stagnant bubble of hot air. A good example was when a crewmember was exercising on the ergometer. The lack of circulation due to lack of convection undoubtedly accounted for the tendency of the crew to overheat.
Airflow from foot to head in the sleeping compartments was undesirable. One of the crewmembers reversed his sleeping bag so his head would be next to the air inlet.
Background noise was low, probably because of the low density of the air. Background noise was so low in the sleep compartments that very slight noises which propagated through the metallic structure disturbed the crew during sleep.
Local lighting was marginally adequate. In several areas, illumination levels were so low that portable lights were necessary. In some instances, switches were located so inconveniently that the crew "sufficed" without proper light rather than take the time to go to the switch panel. Lack of control of lighting sometimes interfered with scheduled activities. When an experiment was conducted that required the operator and experiment station to be in darkness, the entire experiment area and living area had to be darkened. Lighting and compartmentation did not allow sufficient localized control of light.
2. Spacecraft Architecture
Skylab consisted of five major compartments, none of which bore any architectural resemblance to each other. The Multiple Docking Adapter (MDA) was a 3-meter diameter cylinder with interior equipment arranged more or less to fit the cylindrical walls. The Airlock Module was little more than a passageway between the MDA and forward dome compartment of the Orbital Workshop (OWS). The dome area was approximately 6.5 meters in diameter and 6.5 meters long. Equipment was arrayed about the periphery, leaving a large open area in the center.
Architecturally, the dome area exhibited a sort of "up-and-down" arrangement. The lights were around the dome, there was a "floor" opposite the dome, and legends on lockers and equipment read as though one were perpendicular to the floor.
The crew quarters definitely exhibited the up-and-down convention. There was a definite floor, walls, and a ceiling. All equipment was mounted as though Skylab were in a gravity environment.
The architectural adherence to the up-and-down convention proved to be more of a convenience than a constraint. Although more efficient use could have been made of volume and wall areas in the spacecraft by eliminating the conventional floor plane, the visual cues afforded by up-and-down architecture enabled the crew immediately and unconsciously to sense their positions relative to equipment position, and, at least in small compartments, to move from one duty station to another without much change in body attitude. Furthermore, the gravity oriented architecture was a great convenience during pre-launch activities.
Volumetric efficiency of small manned compartments was very similar to compartments on Earth. It was reasoned before flight that freedom of crewmembers to move about in three dimensions in 0-G would increase the effective size of a given compartment. This was not true in certain compartments in Skylab. For example, the Wardroom was crowded when occupied by all three crewmembers, yet the crew seemed reluctant to use the space above the table to relieve the congestion. There seemed to be a natural reluctance to occupy or to pass through a space normally not used for such purposes on Earth.
Spacecraft sleep stations require more space than tier bunks on Earth. Because Earth gravity presses a sleeping person against a mattress and limits the extent to which he flails his arms and legs, very little space is required between the person and bunk above. In 0-G, he is not so forcibly biased to one side of the compartment and requires little unconscious effort to bump his arms and feet against the far wall and disturb his sleep. The station should be at least 0.7 meters from back to front. Additionally, men increase 30 to 40 millimeters in height after a period of time in 0-G. That difference must be considered in the design of the sleep station. "Vertical" sleep stations were acceptable. One crewmember initially experienced some difficulty in sleeping against the "wall" of his compartment but the difficulty soon passed.
There was some concern with the airlock separating the living and work areas from the reentry spacecraft. For future space stations the living/sleeping facilities should be closer to the reentry spacecraft.
Crewmembers had mixed emotions concerning the Waste Management Compartment (WMC). Most felt that it was adequately arranged for one-man use and had few complaints. However, it was considered a bottleneck. If one man was using the washing equipment, a second man had difficulty getting past to use the waste collection equipment. There were times when two men needed to use the WMC simultaneously.
The design "eye" position and "reach" envelopes in 0-G are different from those in Earth gravity. A crewmember assumes a crouch position when working at console stations; he neither sits down nor stands fully erect. Consequently, his normal eye position is approximately 0.3 meters higher than at his normal seated position, and can reach approximately 0.4 meters beyond his normal seated reach. The best writing surface probably should be 0.90 to 0.95 meters above the foot restraints.
The lack of an "office" was apparent. There was no central location in the spacecraft for keeping daily bulletins, orders, checklists, etc. Consequently, considerable time was lost in searching for misplaced printed information.
Instances of poor cabinet design were especially aggravating. Cabinet doors that hinged the wrong way or required a 180 degree opening for removal of contents, and latches that drifted back to the latched position after opening, or broke or failed to latch when doors were slammed shut, are minor annoyances on Earth, but are troublesome in a spacecraft.
One general complaint concerning the Orbital Workstation (OWS) was the electrical power system arrangement. Crewmembers voiced a need to have more high power outlets located in the areas where they were to be used. Apparently, many power cables or extension cords were strung about the spacecraft and were somewhat confusing, a big nuisance to move from one point to another, and cluttered the interior volume of the spacecraft in some areas.
3. Mobility and Restraint of Crewmen
Mobility modes varied according to the architecture and free space of the compartment to be traversed. When in the relatively confined gravity-oriented crew quarters, the crewmembers moved about more or less perpendicular to the floor by using their hands and toes to propel and guide themselves. The so called compression mode of walking was not adopted and little use was made of the overhead handrails. When in the relatively open dome area, crewmembers usually crossed the open space headfirst and did not always reach their destination with the most desirable body attitude. The fireman's pole that ran the full length of the dome area along the centerline was used to some extent as a mobility aid by the first and third crews, but not by the second.
During traverse, control of the legs and feet was often poor to the point where the crewmember changed direction or passed through an opening. When using the hands to maneuver the upper body, the crewmember often was unable to manage his lower legs and would inadvertently bump his feet against equipment or structures alongside the route. In many instances, switches on control panels alongside a busy route were inadvertently and unknowingly actuated by a crewmember's foot.
When proper restraints were available, manual tasks were performed almost as well in 0-G as in Earth gravity. Properly designed foot restraints provided sufficient restraint for tasks not requiring strenuous work with the arms. Many types of foot restraints were located in Skylab. The shoes with the triangular cleats that could be locked into the grid floor were a nuisance to put on and take off but they offered the best all around restraint. Flimsy instep straps such as those in front of the urinal were useless.
Chairs were not useful. In a weightless environment, sitting is not a natural body position, is tiring to maintain without lap straps, and serves no useful purpose. The semi-chair designed for use at the Apollo telescope mount console was used to some extent in the first mission but was later discarded. The thigh restraints at the wardroom table were effective only when the feet were also restrained.
Fixed equipment was used for mobility and restraint, although it may have not been designed for such a purpose. When dedicated restraint was not available, any solid appearing object within reach was used, especially when necessary to arrest motion. Sometimes this action resulted in minor damage to equipment. For instance, the latches holding the food trays to the table were sprung by the crew when they used the food tray as a mobility aid.
4. Food and Drink
The Skylab food system was entirely different from those used for previous space flights. The system development was based on three considerations that were not dominant in earlier programs: a medical requirement to account for all food and beverage intake, a requirement for approximately 1 year of stowage at ambient pressures ranging from 0 to 26 psia, and a requirement for greater crew acceptance.
The onboard preparation of food was improved by using a higher percentage of ready-to-eat foods, programmable heating devices, and a dedicated galley. Food presentation was improved by using open dishes, conventional silverware, and a tray to retain several dishes, silverware, condiments, and napkins. Certain foods had been eaten in Apollo spacecraft with spoons from open plastic pouches, but the Skylab crew demonstrated the practicality of eating almost all ordinary foods from open dishes with ordinary silverware. Occasionally, portions of the less viscous soups and gravies were lost, but usually only when opening the containers.
Palatability was improved by the addition of frozen and chilled foods and a higher percentage or thermostabilized wet foods. Inflight preparation of rehydrated foods were not performed as readily and conveniently as had been expected. The plastic pouches required for the rehydration process were unattractive and, in many respects, defeated the benefits of open dish eating.
All crewmembers commented on the apparent blandness of the food although the control food on the ground tasted adequately seasoned. The crew's subjective opinion of the taste of the food in flight has no generally accepted explanation.
Astronaut clothing for early space flight missions was designed principally to meet the requirements of biomedical instrumentation, pressure-suit operations, communications equipment, nonflammability, and null gravity. The influence of aircraft flight garments was noticeable in the preference for one-piece garments, location of pockets, and insignia. Little attention was given to styling. For Skylab, comfort and overall appearance received increased consideration. However, the garments were compromised by flammability constraints. The wardrobe was expanded to include a nonflammable jacket, a knit shirt, trousers, conventional cotton T-shirts, undershorts, and socks.
The conventional pants/shirt/jacket combination proved to be convenient for the same reasons that the combination is convenient on Earth: easy adjustment to different temperatures, ease in donning and doffing, less sensitivity to fit, and waste management convenience.
Knitted or elastic cuffs inside the sleeves and pant legs were intended to prevent the sleeves and pant legs from riding up. Several crewmembers removed the cuffs and noted that only occasionally was it necessary to shake their sleeves or pant legs back into place. However, other crewmembers seemed to prefer the cuffs.
Clothing became soiled mostly from the wearer's body, not from the spacecraft. The outer garments could be worn much longer than anticipated and the converse was true of the underwear. Too many outer garments were provided but not enough underwear and socks were included in the clothing budget.
The outer shirt was knitted of a nonflammable synthetic fiber called Durette. When it was worn without a T-shirt underneath, it quickly developed a particularly offensive odor.
There was no requirement for protective headgear. Lightly padded, soft, bump hats were furnished but not used.
Pockets were especially useful in Skylab. Pockets provided one of the few places to temporarily stow and carry small articles. Skylab experience indicates that pockets deserve more engineering attention than they usually receive. The location and nature of pockets for use in space flight should be somewhat different than on Earth. The pockets should be deep enough to close over items and the pocket should close simply and naturally. Pockets on the lower part of the pant legs are not readily accessible. Additional bulk on the lower legs compounds the mobility problem.
6. Personal Hygiene
The Skylab provisions for personal hygiene, particularly body-waste collection, were luxurious compared to those provided for Mercury, Gemini, and Apollo crews. However, convenient use of the waste collection system was compromised by the requirement of medical experiments to process and return urine and fecal samples. The integrated fecal/urine collector in Skylab did not always work perfectly but the problems encountered were mechanical in nature and amenable to engineering solutions.
Because of the water budget and rag squeezer limitation, satisfactory rinsing of soap from a washrag was impractical. Skylab crewmembers found it almost impossible to satisfactorily rinse a soapy washrag. They discarded the soapy rag and rinsed successively with clean rags. The rag squeezer would have been more useful if it could have accommodated a towel.
The esthetic benefit of the shower was hardly worth its operational nuisance. Water management during showering was satisfactory but the collection of loose water afterwards was a tedious and time consuming task.
The personal hygiene equipment was adequate but most crewmembers would have liked more personalized equipment by selecting brands and types of articles. Performance of the windup shaver was not satisfactory; replacement heads had to be replaced more often than anticipated.
Housekeeping is an aspect of manned space flight that attracts little engineering attention, probably because that aspect of daily living on Earth is taken for granted. However, proper housekeeping in space flight was found to be as difficult and time consuming as on Earth. Fortunately, the Skylab crews appreciated the potential problems that could arise from sloppy housekeeping and disciplined themselves to run a tight ship.
Temporary trash receptacles were required at points of high trash production. Almost all articles used in flight arrived in some type of disposable package. As the articles were used, trash accumulated. In 0-G, trash cannot be left lying around awaiting periodic pickup. Each item of trash must be placed in a receptacle as it is discarded.
Pieces of tissue, loose washers, tape, and other debris eventually arrived at the air filters. Filters should be readily accessible for retrieval of lost articles and for frequent cleaning or replacement.
Small articles must be stowed with appreciation for the lack of gravity. Small articles were well packed for launch, but after they were unpacked in orbit were often no longer properly restrained when put back into stowage lockers. When a locker is opened to get an article, all the other small articles float out. Articles placed in drawers often float about haphazardly and jam the drawer.
Provisions to aid stowage location were necessary. Many stowage lockers were aboard Skylab and many of them looked alike. Because many lockers were switched around at the last minute, the identification numbers were out of sequence and location and gave little clue as to the contents. The ground technicians knew where everything was at launch but after the various flight crews had switched articles to more convenient locations, both the ground technicians and crewmembers lost track of many articles. A great deal of time was wasted looking for lost articles.
Sleep stations required provisions for "hanging" clothing at night. Crewmembers resorted to stuffing clothing taken off at night or not needed during the day into or under any handy piece of equipment in and around the sleep stations.
Skylab did not develop unpleasant odors despite the inevitable spills during food preparation and minor accidents during urine and feces processing. The low ambient humidity may have contributed to this condition by speeding the drying of spills, but the rigorous cleaning by the crews was probably the main reason.
Voice communication between crewmembers in Skylab was not entirely satisfactory, principally because of the poor impedance match of the human voice and ear in the low-density atmosphere. The crew soon gave up trying to converse when separated by more than several meters.
9. Off-Duty Activity Equipment
Books, tape decks and individual players, and several types of games were stowed aboard Skylab as recreational or entertainment equipment. Except for the tape players, few were used. The crew made little or no use of competitive type games. Whatever the explanation, there appears to be little reason to stock spacecraft with checkers, chess, or playing cards. The darts were aerodynamically unstable in the 5 psia atmosphere of Skylab.
The wardroom window provided one of the more important means of relaxation. Most of the time, the Earth was in view. The crew never seemed to tire of the view. On some occasions, the casual viewing of Earth by a crewmember was the means of serendipitous discovery.
The bicycle ergometer was not placed onboard Skylab in the interest of recreation, however, the crews found exercise provided a significant degree of relaxation.
In conclusion, except for the areas of mobility and restraint, habitability requirements for spacecraft are very similar to habitability requirements on Earth. The requirements of mobility and restraint in 0-G were not fully understood before the Skylab missions; few surprising conclusions were drawn from the Skylab experience. The Skylab experience, combined with the experiences of earlier manned missions, has provided an understanding of habitability requirements in spacecraft that will benefit the planning of habitability budgets for the next generation of spacecraft.