EP-107 Skylab: A Guidebook

 

Chapter IV: Skylab Design and Operation

 

[61] Historically, the design of Skylab and the concept of its functions have evolved through several phases of increasing complexity. From the beginning, however, Skylab was to be a laboratory in orbit where men could live and work for extended periods. Man was to contribute to the accomplishments of Skylab in four major ways: as a scientific observer, as an experimenter, as an operator, and as the object of biomedical studies. The Skylab Project will offer its crew members the opportunity of intimate involvement in these four areas of activity.

It will form the basis from which many of the future space systems for science, technology, Earth observations, applications, and exploration will evolve.

The following sections describe details of the design and the functions of the major Skylab system components, and of the subsystems needed for Skylab operation.

 

1. SKYLAB COMPONENTS

The Skylab cluster, first U.S. space station, will be the largest manned spacecraft ever placed in Earth orbit. With the Command and Service Module docked to it, the Skylab cluster will be approximately 35 meters (117 ft.) long; it will have a mass of 90,606 kilograms (199,750 Ibs.) and contain a habitable volume of about 354 cubic meters (12,700 cubic. ft. (Fig. 69). Major Skylab cluster elements include the following:

The Orbital Workshop (OWS) houses the crew quarters, most of the stored expendables, and a large experiment area. It supports the large solar arrays, and it contains the cold gas tanks and thrusters for secondary attitude control.

The Airlock Module (AM) has an airlock for extravehicular activities, the main systems for communication and data transmittal, environmental and thermal control systems, and the electric. power control system.

The Multiple Docking Adapter (MDA) provides the docking ports for the Command and Service Module (CSM); it houses the control console for the Apollo Telescope Mount (ATM), controls and sensors for Earth resources viewing, and a number of other experimental facilities.

The Apollo Telescope Mount carries the solar telescopes, the control moment gyros (CMG) for primary attitude control, and four solar array wings.

 


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Figure 69. Skylab cluster in orbit, showing major components and interior equipment. [small picture- it's a link to a larger picture on a separate page]

Figure 69. Skylab cluster in orbit, showing major components and interior equipment.

 

The modified Command and Service Module functions as the manned logistics vehicle for the missions and also provides certain communication functions to the Workshop.

Each major Skylab cluster element is described in detail in the following section. Fig. 70 depicts the individual elements of the cluster.

 

a. Orbital Workshop (OWS)

From the outside, the Orbital Workshop looks in size and shape like the S IVB stage which served as the second propulsion stage of the Saturn IB launch vehicle and as the third propulsion stage of the Saturn V-Apollo launch vehicle (Fig. 71). Attached to the outside wall are two large, wing like solar arrays. The interior of this stage, which originally consisted mainly of two tanks for liquid hydrogen and liquid oxygen, underwent . thorough conversion; the larger hydrogen tank became a living and working facility (the Workshop) for three astronauts, and the smaller oxygen tank became a container for waste products accumulating during the mission (Fig. 72). The Workshop measures 6.7 m (22 ft) in diameter, and 14.6 m (48 ft) in length. Its habitable volume is 275 m3 (9550 ft3), it weight 38,380 kg (78,000 Ibs). The solar arrays extend 9 m (30 ft) or opposite sides for a total tip-to-tip wing span of about 27 m (90 ft).

 


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Figure 70. Major parts of Skylab cluster. [small picture- it's a link to a larger picture on a separate page]

Figure 70. Major parts of Skylab cluster.

 

To protect the Workshop against penetration by meteoroids, a thin metal shield envelops the Workshop wall at a distance of 0.15 meter (6 inches) from the outer surface. Meteroid particles hitting this shield will suffer an energy reduction, and they will be broken up into a shower of numerous smaller particles, none of which will be able to penetrate the Workshop wall. During launch, the meteoroid shield will be packed tighty against the wall; after orbit insertion, the shield is swung out into position by torsion bars.

 


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Figure 71. Basic elements of Orbital Workshop (OWS). [small picture- it's a link to a larger picture on a separate page]

Figure 71. Basic elements of Orbital Workshop (OWS).

 

Serving as living quarters and as a laboratory for the astronauts, the Workshop consists of two compartments, separated by a perforated wall or "floor." The rearward compartment contains the wardroom for food preparation and eating, the sleep section, the waste management section (toilet), and the experiment work area. Biomedical experiments will be performed in this work area (Fig. 73). The forward compartment is devoted primarily to experiments requiring relatively large volumes or designed to utilize one of the two scientific airlocks for external viewing or exposure (Fig. 74).

Storage facilities, containers for food, water, and clothing, and a number of subsystems occupy part of the room available in the two compartments.

Circulation of the air will be achieved by fans and by ducts between the Workshop wall and a partial inner wall which will permit the air to flow in one direction between the walls and in the other direction through the room.

A number of handles, grips, and foot restraints, mounted at appropriate places throughout the two compartments, will enable the crew members to move through the Workshop and to station themselves at desired locations while floating weightlessly (Fig. 75).

 


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Figure 72. Arrangement and major components of interior installations of Orbital Workshop, showing the two floors of the living area. [small picture- it's a link to a larger picture on a separate page]

Figure 72. Arrangement and major components of interior installations of Orbital Workshop, showing the two floors of the living area.

 

A window in the wardroom will allow the astronauts to look out in a direction away from the Sun. Depending on Skylab's location in orbit, they will be able to look down at the Earth or out into space.

Two scientific airlocks are provided in the Workshop wall of the forward compartment, one directed toward the Sun, the other facing in the opposite direction (solar and antisolar airlock) (Fig. 76). Each of the scientific airlocks will permit deployment of sensors and instruments such as Experiments No. 5019, T027, and 5073 (see Chapter V). An articulated mirror system and a universal extension mechanism can be used with the scientific airlocks for certain experiments (Figs. 77, 78).

A considerable array of tools, supplies, and support equipment will be available to the astronauts on Skylab, including repair kits, films, hand-tools, tapes, clamps, fasteners, scissors, thermometers, photographic lights, and still and movie cameras.

 


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Figure 73. First (lower) floor of Orbital Workshop, showing crew quarters and medical experiment work area. [small picture- it's a link to a larger picture on a separate page]

Figure 73. First (lower) floor of Orbital Workshop, showing crew quarters and medical experiment work area.


Figure 74. Second (upper) floor of Orbital Workshop, showing equipment for space technology experiments. [small picture- it's a link to a larger picture on a separate page]

Figure 74. Second (upper) floor of Orbital Workshop, showing equipment for space technology experiments.


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Figure 75. Second (upper) floor of Orbital Workshop, showing scientific airlock, had rails, and other installations. [small picture- it's a link to a larger picture on a separate page]

Figure 75. Second (upper) floor of Orbital Workshop, showing scientific airlock, had rails, and other installations.


Figure 76. Inside door of scientific airlock. [small picture- it's a link to a larger picture on a separate page]

Figure 76. Inside door of scientific airlock.

 

[68] Skylab's atmosphere Will be a mixture of 25,000 Nm-2 ( Newtons per square meter) (0.25 atm. or 3.7 psi) partial pressure oxygen and 9,000 Nm-2 (0.09 atm. or 1.3 psi) partial pressure nitrogen. Relative humidity will be controlled to about 26% at 29° C (85° F); room temperature can vary between 13° C and 32° C (55° F and 90° F) (See Chap. IV-2-b).

The workshop is connected with the rest of the Skylab cluster through the instrument Unit, as illustrated in Fig. 79.

 

b. Instrument Unit (IU)

Control of the Saturn V launch vehicle during launch and powered flight will be accomplished by guidance and control systems located in the Instrument Unit (Figs. 79, 80). This function will be maintained by the IU throughout Skylab orbit insertion and deployment. Equipment in the IU will first guide the launch vehicle from the moment of liftoff through the separation of Skylab from the second stage of the Saturn V booster. After separation, the IU will provide commands to various Skylab systems which m turn will rotate the Skylab by 180°, turn on refrigeration systems, jettison the payload shroud, roll the Skylab until the Apollo Telescope Mount points toward the Sun, deploy the meteoroid shield that envelops the Workshop, and pressurize all the compartments with oxygen (Skylab will be filled only with nitrogen during launch). The solar arrays on ATM and on OWS will be deployed upon command from the IU or by command from the ground. All these functions will be completed about 7.5 hours after orbit insertion. The batteries energizing the IU will be depleted soon after this time. From then on, the Instrument Unit will be passive.

 


Figure 77. Expanded view of scientific airlock, showing photometer deployment. [small picture- it's a link to a larger picture on a separate page]

Figure 77. Expanded view of scientific airlock, showing photometer deployment.


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Figure 78. Movable mirror outside the airlock, as needed for certain scientific observations. [small picture- it's a link to a larger picture on a separate page]

Figure 78. Movable mirror outside the airlock, as needed for certain scientific observations.

 

c. Airlock Module (AM)

The Airlock Module, as a connecting link between OWS and Multiple Docking; Adapter, serves a threefold purpose: as a major structural element of the Skylab cluster; as a module containing the port through which an astronaut can leave the interior of Skylab in order to perform extravehicular activities (EVA); and as the electrical, environmental, and communications control center for Skylab. In addition, many of the high pressure containers for oxygen and nitrogen which provide Skylab's atmosphere are mounted on the trusses between the inner and outer walls of the AM.

The Airlock Module consists of two concentric cylinders (Fig. 8). Matching the OWS in diameter, the outer cylinder or Fixed Airlock Shroud carries the Payload Shroud during the launch, and it serves as mounting base for the structure that supports the Apollo Telescope Mount. The inner cylinder, or tunnel, represents the airlock (Figs. 81, 82) it forms the passageway through which crew members can move between the Workshop and the Multiple Docking Adapter. Hatches at both ends of the tunnel can be closed for depressurization (Figs. 83, 84), and a third hatch in the side wall can be opened for the egress of a crew member (Fig. 85). After return of the crew member, the egress hatch is closed, the tunnel is pressurized, and the forward and rear hatches are reopened.

The Airlock Module also contains the automatic Skylab malfunction alarm system, and the manual controls for Skylab pressurization and air purification, and for electric power and communications.

Many of the supplies, and most of the control systems for Skylab are located in the Airlock Module; this module could well be called the "utility center" of the Skylab cluster.

 


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Figure 79. Instrument Unit, showing guidance, control, and power systems equipment. [small picture- it's a link to a larger picture on a separate page]

Figure 79. Instrument Unit, showing guidance, control, and power systems equipment.

 

d. Multiple Docking Adapter (MDA)

Like other major components of Skylab, the Multiple Docking Adapter will serve several purposes. It is equipped with docking ports for the manned Command and Service Modules that will carry astronauts to and from Skylab. It houses the control units for ATM, for the Earth Resources Experiment Package (EREP), and for the M512 (zero-gravity materials processing facility); and it is used for storage of films, experiment components, and electric and television equipment (Fig. 86).

Two docking ports are provided on the MDA. The primary port, located at the forward end for axial docking of a CSM, will be used under all normal conditions. The side port will be used in contingency cases only.

EREP equipment, consisting of sensors and cameras for Earth viewing and of control and display units to be operated by the astronauts, is mounted in the MDA. These Earth-observing instruments will be looking in the antisolar direction (Figs. 87, 88).

 


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Figure 80. Instrument Unit during assembly. [small picture- it's a link to a larger picture on a separate page]

Figure 80. Instrument Unit during assembly.


Figure 81. Airlock Module with hatch for extra-vehicular activities. [small picture- it's a link to a larger picture on a separate page]

Figure 81. Airlock Module with hatch for extra-vehicular activities.


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Figure 82. Inside view of Airlock Module with open door leading to Workshop. [small picture- it's a link to a larger picture on a separate page]

Figure 82. Inside view of Airlock Module with open door leading to Workshop.

 

Astronaut operation of the Apollo Telescope Mount and the Skylab attitude control will be performed at the ATM Control and Display Console in the MDA. This console contains several TV screens. and other visual indicators which will enable the astronauts to follow ATM activities closely and to actively participate in target selection, telescope orientation, experimental procedures, and interpretation of instrumental and visual observations.

The television system for Skylab is housed in the MDA. Several remote stations are located in the other Skylab modules. A video tape recorder is included in this system.

Crew members will spend a significant portion of their orbital time in the Multiple Docking Adapter, at the ATM and EREP consoles and the M512 zero-gravity materials processing and manufacturing facility.

 


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Figure 83. Airlock Module, showing major components and installations. [small picture- it's a link to a larger picture on a separate page]

Figure 83. Airlock Module, showing major components and installations.

 

e. Apollo Telescope Mount (ATM)

During launch and ascent, the Apollo Telescope Mount unit is positioned axially with the rest of Skylab and the launch vehicle (Fig. 11). After insertion into orbit and jettisoning of the shroud (Fig. 89), the ATM support structure will rotate the ATM by 90° from its axial position into a radial position (Fig. 90). This operation will clear the primary docking hatch, and it will enable the ATM telescopes and the ATM solar arrays to face the Sun. The ATM solar panels will be deployed after this 90° rotation.

ATM consists of two major parts, the outer structure or rack and the inner part or canister with the solar telescopes (Fig. 91). The rack, an octagonal truss structure of 3.3 m (11 ft) diameter and 3.6 m (12 ft) length, connects ATM with the rest of Skylab. It carries the four solar-electric power arrays and electric batteries. The rack also contains electrical and mechanical (gyro) components of the Skylab primary attitude control system and the ATM communications system.

Attitude control of Skylab must be achieved with a system which operates for a long period of time, while producing as little environmental contamination as possible because of the sensitivity of the solar, stellar, and Earth-looking telescopes to condensed vapors and particulate matter in the vicinity of the spacecraft. For these reasons, control moment gyroscopes (CMG) were chosen to produce the major portion of required control torques. The three control moment gyros are mounted on the rack (Fig. 92). The rack and the rest of Skylab, being rigidly connected to each other, will act as one unit as far as primary attitude control is concerned.

Inside the rack, the cylindrical canister is mounted in such a way that it can be rotated around its cylindrical axis upon a manual signal. This roll ring mount (Fig. 93) provides the ± 120° roll capability which is required for polarization studies of the solar radiations, and also for the exchange of some of the film cassettes. The astronaut, in order to retrieve the cassettes,...

 


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Figure 84. Airlock Module with details of service and control panels. [small picture- it's a link to a larger picture on a separate page]

Figure 84. Airlock Module with details of service and control panels.


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Figure 85. Wall of Airlock Module, showing EVA hatch for exit and entrance during extra-vehicular activities. [small picture- it's a link to a larger picture on a separate page]

Figure 85. Wall of Airlock Module, showing EVA hatch for exit and entrance during extra-vehicular activities.

 

....will roll the canister by manually controlled switches until one of the cassette doors faces his EVA work station at the ATM rack (Fig. 94).

The telescope-bearing canister is not attached directly to the roll ring. Another concentric ring (gimbal ring), mounted between roll ring and canister and connected to the canister and to the roll ring in the fashion of a universal joint, will permit the canister axis to move relative to the rack axis around two perpendicular axes in order to achieve fine pointing and attitude stabilization of the telescopes. These angular motions need not be large because the Skylab cluster as a whole will always achieve coarse pointing. Maximum canister axis deflections relative to the rack axis will be ±2°. The bearings allowing these angular motions consist of flexure pivots (Fig. 95) which provide small angular deviations by flexing metal bands rather than by moving parts. Rotational motion of the canister around the two "universal joint" axes will be accomplished by electric torquers (Fig. 95) upon manual or automated signals.

 


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Figure 86. Multiple Docking Adapter (MDA) with major components and installations. [small picture- it's a link to a larger picture on a separate page]

Figure 86. Multiple Docking Adapter (MDA) with major components and installations.

 

A cylindrical shroud covers the experiment canister for protection against contamination and for thermal control purposes. The canister, 3 m ( 10 ft) long and 2.1 m (7 ft) in diameter, will maintain a steady temperature of 21° C (70° F) by means of an active cooling system which employs cooling pipes and a mixture of methanol and water to exchange heat between the canister wall and radiation cooling panels.

All eight solar telescopes, the fine Sun sensors, and some auxiliary systems are mounted on the "spar," a cruciform light-weight mountings panel which divides the canister lengthwise into four equal compartments (Fig. 96). The spar is designed for high rigidity it serves as an optical bench for the solar telescopes. However, three of the experiments (S052, S055, and S082B) are built to apply additional individual fine corrections to their pointing directions. Each of the four compartments carries two of the solar telescopes (Fig. 97). The front end of the canister is covered by a sunshield with openings for telescopes and Sun sensors (Fig. 98). During ground storage and launch, these openings remain closed by individual doors for protection.

Operation of the solar telescopes and their auxiliary equipment will be monitored and controlled from the Control and Display Panel inside the Multiple Docking Adapter (Fig. 99). Experiment controls are located in the center of the panel, thermal control and lighting control readouts and switches are on the left, pointing control system displays and switches are...

 


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Figure 87. Inside view of Multiple Docking Adapter with major components. [small picture- it's a link to a larger picture on a separate page]

Figure 87. Inside view of Multiple Docking Adapter with major components.


Figure 88. Multiple Docking Adapter, arrangement of experiments and structural elements. [small picture- it's a link to a larger picture on a separate page]

Figure 88. Multiple Docking Adapter, arrangement of experiments and structural elements.


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Figure 89. Skylab Shroud during separation in orbit. [small picture- it's a link to a larger picture on a separate page]

Figure 89. Skylab Shroud during separation in orbit.


Figure 90. Deployment of Apollo Telescope Mount (ATM) by rotation through 90 degrees. [small picture- it's a link to a larger picture on a separate page]

Figure 90. Deployment of Apollo Telescope Mount (ATM) by rotation through 90 degrees.

 

...on the upper right, power controls on the lower right and alert indicators above the center panels. Two TV screens on the panel will show selectively images from five different viewing instruments; they will enable the astronauts to select targets, to correct for pointing errors or drifts, to follow visually the development of active areas on the Sun, and to compare findings with observers on the ground by voice link.

 


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Figure 91. Apollo Telescope Mount showing external rack with control moment gyroscopes and solar panels, and internal canister with telescopes. [small picture- it's a link to a larger picture on a separate page]

Figure 91. Apollo Telescope Mount showing external rack with control moment gyroscopes and solar panels, and internal canister with telescopes.


Figure 92. Control moment gyroscopes, needed to provide fine attitude control for the Skylab cluster. [small picture- it's a link to a larger picture on a separate page]

Figure 92. Control moment gyroscopes, needed to provide fine attitude control for the Skylab cluster.


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Figure 93. Apollo Telescope Mount (ATM) during assembly, showing telescopes, roll ring, and inner gimbal system. [small picture- it's a link to a larger picture on a separate page]

Figure 93. Apollo Telescope Mount (ATM) during assembly, showing telescopes, roll ring, and inner gimbal system.

 

During launch and ascent, the Skylab cluster will be covered by the Payload Shroud (Fig. 100).

 

f. Command and Service Module (CSM)

The astronauts will be transported from the ground to Skylab, and back to the ground, by the Apollo Command and Service Module (Fig. 101). Basically, the CSMs for Skylab are identical with the CSMs used on the Apollo flights; the differences concern the capabilities of power and life support systems ( Fig. 102 ) . While the CSM on an Apollo mission had to be capable of sustaining its operation over a period of 14 days, the Skylab CSMs need to support their operations only for the short periods of ascent....

 


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Figure 94. Apollo Telescope Mount (rack) with opening, showing canister inside the rack with a hatch to exchange film cassettes. [small picture- it's a link to a larger picture on a separate page]

Figure 94. Apollo Telescope Mount (rack) with opening, showing canister inside the rack with a hatch to exchange film cassettes.

 

...and descent. During the time of docking in orbit. CSM systems, which include data and communications systems, will be supported by the Skylab supply sources.

The Command Module, 4m (13ft) in diameter and 3.6m (12ft) high, contains a crew compartment for three astronauts, a docking tunnel to the top of the cone-shaped module, and a hatch that can be opened from the inside after docking with the Multiple Docking Adapter. Twelve latches at the outside of the tunnel end will attach the Command Module firmly to the port of the MDA before crew transfer can begin (Fig. 103) .

 


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Figure 95. Flexure pivot bearings of the ATM canister, permitting fine attitude control. [small picture- it's a link to a larger picture on a separate page]

Figure 95. Flexure pivot bearings of the ATM canister, permitting fine attitude control.

 

Inside the Command Module are the guidance and control system, electric batteries, oxygen containers, control and display panels for the combined CSM, couches for the three crew members, stowage for the consumables needed during ascent and descent, and provisions for the stowage of equipment to be transported to or from Skylab. A heat shield, coated with ablative material, will protect the Command Module against the heat produced during reentry (Fig. 104). Except for the last half hour during reentry, the Service Module will remain firmly attached to the Command Module. It contains....

 


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Figure 96. ATM canister, showing gimbal rings and the internal spar which carries the telescopes. [small picture- it's a link to a larger picture on a separate page]

Figure 96. ATM canister, showing gimbal rings and the internal spar which carries the telescopes.

 

....service systems and supplies that do not require access by crew members during flight, such as the main propulsion system, a maneuvering system, fuel cells for electric power, part of the oxygen for breathing, and radiators for cooling. After separation from the Command Module shortly before reentry, the Service Module will heat up in the atmosphere and burn completely; only ashes will reach the ground.

 


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Figure 97. Cross section through ATM canister, showing the cruciform spar and the telescopes. [small picture- it's a link to a larger picture on a separate page]

Figure 97. Cross section through ATM canister, showing the cruciform spar and the telescopes.

 

g. Integration, Testing, and Quality Assurance

All the elements of Skylab components produced at many different plants and places were subjected to elaborate procedures of component testing and integration. Tests had to be performed on individual elements, on subassemblies of elements, and finally on the completed assemblies. Some tests were performed at the manufacturing sites; others were performed at assembly sites. Fig. 105 illustrates how the major elements of Skylab flight components flowed together in the testing and integration operations.

The Orbital Workshop was assembled with experiments, thruster attitude control system, and habitability support systems at Huntington Beach, California. It was then shipped to Kennedy Space Center (KSC) for test, checkout, and assembly together with other Skylab elements in the Vertical Assembly Building (VAB). Before being transported to the launch pad, it underwent an integrated systems test with all of the other modules except the CSM.

The Apollo Telescope Mount experiments were assembled in the ATM canister at MSFC. After vibration testing, the assembly was first shipped to JSC for a thermal vacuum test, and from there to KSC for systems test and....

 


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Figure 98. Apollo Telescope Mount front end at the moment of film retrieval by astronaut. Telescope orifices are closed. [small picture- it's a link to a larger picture on a separate page]

Figure 98. Apollo Telescope Mount front end at the moment of film retrieval by astronaut. Telescope orifices are closed.

 

....checkout. It was then assembled with other Skylab elements, tested as a major component of the total system, and transported to the launch pad.

The Payload Shroud was manufactured on the west coast, and then shipped to KSC for assembly, integrated systems test, and launch.

The Airlock Module was built and fitted with experiments in St. Louis, Missouri.

The Multiple. Docking Adapter shell was built at MSFC, shipped to Denver, Colorado, where it was outfitted and tested, and then sent to St. Louis for assembly with the Airlock Module. The AM-MDA assembly then underwent systems tests, altitude chamber tests, and checkout before it was shipped to KSC for integration with the CSM and testing.

The AM-MDA was then moved to the VAB, assembled with the other payload modules, tested as part of an integrated systems test on top of the launch vehicle, and transported to the launch pad for final checkout and launch.

 


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Figure 99. Console for monitoring and controlling the telescopes in ATM. [small picture- it's a link to a larger picture on a separate page]

Figure 99. Console for monitoring and controlling the telescopes in ATM.

 

From the beginning of Skylab, the desire for a high probability of success has made it necessary that careful attention be given to all aspects of reliability and quality assurance. Experience gained in many previous space projects formed the basis for a comprehensive reliability program established specifically for Skylab. Quality and reliability requirements were carefully documented in numerous plans which controlled all phases of the Skylab from I design through production, test, launching, and operation in space. These reliability requirements were imposed uniformly upon all contractors and suppliers who participated in Project Skylab.

 


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Figure 100. Payload shroud, needed to protect the front part of Skylab during ascent. [small picture- it's a link to a larger picture on a separate page]

Figure 100. Payload shroud, needed to protect the front part of Skylab during ascent.

 

The specific quality and reliability program requirements generated for the Skylab project required that only such parts could be used for Skylab which either had been flight proven or had undergone elaborate and rigorous testing. Likewise, only such vendors were accepted who either had records of successful performance on previous flights or had been found acceptable after very careful screening. An attempt was made to use for Skylab as many components of previous successful flight projects as possible; if new components had to be developed, they were subjected to extensive testing. The principle of high reliability was made a basic feature of design from the very beginning of Skylab program work. A thorough failure-mode analysis had....

 


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Figure 101. Command and Service Module (CSM) launch configuration. [small picture- it's a link to a larger picture on a separate page]

Figure 101. Command and Service Module (CSM) launch configuration.

 

...to be made of every functional part of the complex Skylab system. If it was found that failure of a single component or system could jeopardize the mission, the design had to be changed, or redundancy 1 had to be incorporated; if neither was feasible, a specific effort was made in the manufacturing and testing of that component or system to assure the highest reasonable degree of reliability. As part of the test program, an elaborate failure reporting system was established. If a failure occurred, its cause was traced back to its origin, and the likelihood of a recurrence of a similar failure was eliminated by proper actions.

Experience has shown that a major step toward high quality can be accomplished by proper "procurement control." Drawings and specification lists must reflect the quality requirements to the extent that the vendor knows exactly what he is expected to deliver, and acceptance testing must be sufficiently rigorous to eliminate all weak parts and components.

 

2. SKYLAB OPERATIONAL SYSTEMS

Astronauts and experiments on Skylab are supported by a number of auxiliary or "housekeeping" systems for all those functions which are necessary to make Skylab a self-contained, well-functioning, and efficient laboratory. These operational systems include attitude control, environmental control, communications, data management, crew accommodations, and electric power generation.

Details of these systems are described in the following sections.

 


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Figure 102. Service Module showing major components and equipment. (MMH is monomethyl hydrazine, N2O4 is nitrogen tetroxide, UDMH is unsymmetrical dimethylhydrazine, He is helium). [small picture- it's a link to a larger picture on a separate page]

Figure 102. Service Module showing major components and equipment. (MMH is monomethyl hydrazine, N2O4 is nitrogen tetroxide, UDMH is unsymmetrical dimethylhydrazine, He is helium).

 

a. Attitude and Pointing Control System

Skylab experiments will view three basic targets; the Sun, the Earth, and celestial space. Instruments for these experiments are located at places which will provide proper viewing directions with a minimum of maneuvering (Fig. 106). Active and continuous control of Skylab attitude will assure that instruments are pointed in their desired directions during the periods of their operation.

The solar power arrays on the Workshop and the Apollo Telescope Mount will require orientation toward, or at least nearly toward, the Sun for as much time as possible.

Pointing accuracy requirements of the ATM solar telescopes around the three axes of Skylab, illustrated in Fig. 107, are listed below.

 


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Figure 103. Command Module with major components and installations. [small picture- it's a link to a larger picture on a separate page]

Figure 103. Command Module with major components and installations.


Figure 104. Command Module with parachutes shortly before splashdown. [small picture- it's a link to a larger picture on a separate page]

Figure 104. Command Module with parachutes shortly before splashdown.


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Figure 105. Flow of Skylab components from manufacturing to testing, integration, and launch. [small picture- it's a link to a larger picture on a separate page]

Figure 105. Flow of Skylab components from manufacturing to testing, integration, and launch.

 


TABLE 5. Pointing Accuracy of ATM Solar Telescope Canister.

System axis

Pointing Accuracy

Stability

.

X

± 2.5 arc sec.

± 2.5 arc sec/15 min

Y

± 2.5 arc sec.

± 2.5 arc sec/15 min

Z

± 10 arc sec.

± 7.5 arc sec/15 min

 

These pointing accuracies for the telescopes can be accomplished because of the gimbal mounting of the ATM experiment canister within the ATM rack, Pointing accuracies to which the entire Skylab cluster can be held in various observational modes are listed below.

 


TABLE 6. Pointing Accuracy of Entire Skylab Cluster.

OBSERVATION MODE

.

System axis

Solar

Earth or sky

During docking maneuvers

.

X

± 6 arc min.

± 2 degree

± 6 degree.

Y

± 6 arc min.

± 2 degree

± 12 degree.

Z

± 10 arc min.

± 2 degree

± 6 degree.


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Figure 106. Viewing ports on Skylab. [small picture- it's a link to a larger picture on a separate page]

Figure 106. Viewing ports on Skylab.

 

Controlling the attitude of Skylab will be the task of the Attitude and Pointing Control System. This function will include rotating the Skylab cluster to the desired orientation, holding this orientation as long as necessary, and providing the high precision pointing control for the Apollo Telescope Mount. In order to execute these actions, the Attitude and Pointing...

 


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Figure 107. Principal axes of Skylab cluster. [small picture- it's a link to a larger picture on a separate page]

Figure 107. Principal axes of Skylab cluster.

 

....Control System uses sensors to read out the existing attitude with respect to reference directions and a mechanism to change the attitude in a controlled fashion.

Skylab will use rate gyroscopes as basic sensing elements for its attitude control system. Rate gyroscopes measure the rate of angular rotation of Skylab around each of the three principal axes. By integrating these angular rates over a given time, the angular changes during this period will be obtained. Reference directions from which angular changes can be counted will be provided by Sun and star seekers (Figs. 110, 111). The Sun seeker which monitors the solar reference direction will aim at the center of the solar disc. The star seeker will aim at one of three stars, preferably at Canopus in the southern constellation Argus.

 


[
94]

Figure 110. Sun seeker (acquisition sensor) for angular guidance. [small picture- it's a link to a larger picture on a separate page]

Figure 110. Sun seeker (acquisition sensor) for angular guidance.

 

Changes in Skylab attitude can be accomplished by either one of two operational control systems, the Control Moment Gyro System (CMG) or the Nitrogen Thruster Attitude Control System (TACS). The CMC control system, consisting of three large gyroscopes with mutually perpendicular axes represents the prime method of Skylab control (Fig. 112). The TACS system can also control Skylab in a manner characteristic of conventional cold gas thruster control systems (Fig. 113). In these systems, jets of gas are released through rocket-type nozzles, thus producing small amounts of thrust.

Each of the three CMGs in the Skylab control system weighs 181 kg (400 lbs.); it consists of a rotor of 0.55 m (22 in.) diameter, spinning at 9,000 RPM, and an inner and an outer gimbal ring. The outer gimbal ring permits Skylab to rotate around the gimbal axis of each CMG. However, an electric torque motor attached to Skylab and acting upon the outer gimbal ring can produce a torque between Skylab and that CMG, resulting in a tilting motion (precession) of the CMG rotor axis around the inner gimbal ring axis by virtue of the characteristic property of a spinning gyroscope to respond to torques around one axis with a tilting motion ( precession ) around the other axis. The reactive force of the torque motor then causes Skylab to change its angular position while the rotor axis moves (precesses). Operation of the torque motor is controlled by commands received from the Skylab digital control computer. During an attitude control procedure, the torque motors of all three CMGs will normally receive control commands,...

 


[
95]

Figure 111. Star seeker for angular guidance. [small picture- it's a link to a larger picture on a separate page]

Figure 111. Star seeker for angular guidance.

 

...and each CMG rotor axis will slowly tilt. Should the control torque persist long enough, the tilting motions would continue until the rotor axis of each gyro eventually would be parallel with the axis of the control torque. From that moment on, none of the CMGs could continue to react to the control torque of the torque motor by further precession. If all three CMG rotor axes should be parallel with their torque axes, the CMG system would be "saturated" and would no longer be capable of controlling the attitude of Skylab. In order to avoid this saturation, a desaturation procedure is provided which utilizes the gravity field of the Earth as generator of a counteracting torque.

 


[
96]

Figure 112. Control scheme of three control moment gyroscopes. [small picture- it's a link to a larger picture on a separate page]

Figure 112. Control scheme of three control moment gyroscopes.

 

On an orbiting spacecraft, gravitational forces are exactly balanced by centrifugal forces at every point on a line representing the orbital trajectory of the center of gravity of the spacecraft. Points below this line experience an excess of gravitational forces; points above this line, an excess of centrifugal forces. The amount of each of these forces at a given point on the spacecraft is a function of the distance between the point and the center-of gravity line. In general, the integrated effect of these two forces represents a force couple, or a torque, called gravity gradient torque. Its magnitude depends, among other factors, on the shape and the attitude of the spacecraft. On Skylab, this gravity gradient torque is used as desaturating torque for the CMGs. For this purpose, a computer routine is incorporated in the Attitude and Pointing Control System which continuously calculates the amount of desaturation required. On the night side of each orbit when the....

 


[
97]

Figure 113. Reaction nozzles for angular control, using compressed nitrogen parallel and series valves for each nozzle increase reliability through redundancy. [small picture- it's a link to a larger picture on a separate page]

Figure 113. Reaction nozzles for angular control, using compressed nitrogen parallel and series valves for each nozzle increase reliability through redundancy.

 

....Sun is not visible, proper signals are generated for the CMGs which turn the Skylab cluster into an attitude that produces an appropriate gravity gradient torque. The Attitude and Pointing Control System, in an effort to maintain this attitude, generates control torques against the gravity gradient torque in such a manner that the precession axes of the CMGs tilt until their previously accumulated precession angles are completely used up. This desaturation maneuver normally will suffice to restore the capability of the CMGs to fully control Skylab. Should the amounts of accumulated precession angles exceed the amounts that can be neutralized by the gravity gradient torque, the TACS will be energized to neutralize the difference.

It is anticipated, though, that desaturation of the CMGs by TACS operation will occur very rarely. This Will help keep the external environment of Skylab reasonably free from gases and other contaminants.

During the first 7.5 hours after orbit insertion, Skylab Will carry out several directional maneuvers (Fig. 20). Gyro platform and digital computers in the instrument Unit (see Chapter IV-I-b) will generate the necessary control signals, and the thruster attitude control system will execute the maneuvers. After this initial period, the instrument Unit will transfer the control authority to the ATM digital computer which will use the Control Moment Gyros as the prime system for attitude control and the thruster system only when needed for CMG desaturation. This combined system will suffice for the accuracy requirements of Skylab as listed in Table 6. Higher accuracies as required by the solar telescope canister in ATM (Table 5), will be provided by the Experiment Pointing Control Loop which consists of the canister flexure pivots and associated torque motors. Signals for the [98] attitude control of the ATM canister are derived from fine Sun sensors and rate gyros on the canister and processed in the Experiment Pointing Electronic Assembly. By overriding these signals, the astronauts can move the ATM canister to a specific target on the Sun with a hand controller from the ATM Control Console in the MDA (Fig. 99). At any selected position, the Experiment Pointing Control Loop system will keep the pointing accuracy and stability within the necessary limits.

 

b. Environmental Control System

Environmental control within Skylab will be achieved by an open-cycle life support system in which the consumables are not reclaimed for reuse. Before each crew arrives, Skylab will be pressurized to 34,000 Nm-2 (one-third of an atmosphere or 5 psi) of a mixture of oxygen and nitrogen (approximately 74 percent oxygen and 26 percent nitrogen). This mixture will assure that the astronauts will breathe the same amount of oxygen as they would on Earth. The Airlock Module, serving as a nerve center for the total Skylab cluster, among other functions Will also control the internal atmosphere and temperature. The atmospheric gases will be stored in gaseous form in bottles mounted on the Airlock Module (Fig. 8). Flow regulator valves will ensure that correct pressure and gas mixture are maintained.

Relative humidity will be controlled to about 26 percent at 30° C (86° F). The carbon dioxide concentration will be held below a maximum pressure level of 700 Nm-2 (7 millibars). Temperature in the habitation areas Will be controlled between 13° and 32° C (55° and 90° F).

Life support and atmospheric consumables will include 2,700 kg (6,000 Ibs ) of water, 670 kg (1,470 Ibs ) of food, 2,240 kg (4,930 Ibs ) of oxygen, and 600 kg (1,320 Ibs) of nitrogen. Environmental operating limits are shown in Table 7.

Skylab systems have been designed to ensure that at any given time the overall sound pressure level will not exceed 72.5 db above the normal human hearing threshold 2 when the individual sound pressure levels from all sources are added together.

Atmospheric purification and humidity control will be achieved by passing the cabin gases through carbon dioxide removal equipment and through water removal condensers. Odors Will be removed by passing the gases through charcoal filters (activated coconut shell charcoal).

The Skylab CO2 removal equipment consists of two units, each containing two beds of zeolite for absorption of carbon dioxide (Fig. 115). The beds will operate on a reversible cycle. After absorbing CO2 for 15 minutes, a bed will undergo a process that extracts most of the CO2 and expels it overboard; during this purging time, the other bed will be switched to the absorbing mode.

The thermal effects of solar irradiation on the daylight side and lack of any heat source on the dark side have been almost eliminated as influences on the temperature inside Skylab through insulation and thermal coatings around the Workshop, the Airlock Module, and the Multiple Docking Adapter.

 

 


[
99] Table 7. Environmental Conditions in Crew Quarters.

Temperature

Relative Humidity

Pressure1

Gas

°C

°F

%

Nm-2

psi

Atm.

.

.

Prelaunch nonoperational

-18 to 71

0 to 160

30 to 45...

1.2 x 105 to 1.8 x 105

16.8 to 26.5

1.2 to 1.8

Air

.

Prelaunch operational

5 to 27

40 to 80

0 to 40...

105 to 1.8 x 105

14.7 to 26.5

1 to 1.8
20 to 0% O2
80 to 100% N2

.

Launch and ascent

5 to 43

40 to 110

.... do ....

1.6 x 105 to 1.8 x 105

23.5 to 26.5

1.6 to 1.8

100% N2

.

Orbit Operational

13 to 32

55 to 90

25 to 85..

0.33 x 105 to 0.35 x 105

4.8 to 5.2

0.33 to 0.35
74% O2
26% N2

.

Orbit Storage

5 to 30

40 to 85

25 to 100

0.03 x 105 to 0.4 x 105

0.45 to 6

0.03 to 0.4
74% O2
26% N2

1 Nm-2 = Newtons per square meter.
psi = poumds per square inch.
Atm = atmospbere.

 

To control temperatures and humidity during manned and unmanned periods, an active thermal control system for OWS, AM, and MDA has been provided. Located in the Airlock Module, this system will cool and purify the atmosphere. A combination of air duct heaters and wall heaters, located in other areas of the Skylab, will provide heating as required. The heaters will prevent condensation from forming and damaging instruments and equipment, and they will maintain a comfortable environment for the crews. Some heat-producing components that require cooling are mounted on cold plates which will be temperature-controlled by a liquid coolant system m the AM. Excess heat from the AM cooling system will be radiated to space through radiators on the MDA and on the forward AM.

Thermal control of the Apollo Telescope Mount will be provided by a system of passive control measures, radiant heaters, and a liquid coolant system with cold plates and space radiators. A Sun shield will protect much of the ATM equipment from direct sunlight (Fig. 98).

 

c. Data and Communications Systems

A space system as above and complex as Skylab produces a huge amount of data which must be sent to Earth for evaluation and use. Basically, there are two types of data; first, physical data including film, tapes, emulsion plates, surface samples, biomedical specimens, log books, and notes; and...

 


[
100]

Figure 115. Carbon dioxide removal system, using reusable zeolite beds. [small picture- it's a link to a larger picture on a separate page]

Figure 115. Carbon dioxide removal system, using reusable zeolite beds.

 

...second, data in the form of signals such as audio, telemetry, and video signals. Physical data will be brought back from Skylab on the Command Module. Transmittable data will be sent from Skylab to Earth, and also from the Earth to Skylab, through a system of transmitters and receivers on Skylab and in the Spacecraft Tracking and Data Network (STDN).

Fig. 116 shows the locations and the approximate ranges of 13 STDN stations, 11 of them fixed, one ship-borne, and one air-borne. The Skylab communications system, whose characteristics are listed in Table 8, provides the links between Skylab and the STDN. In addition to real-time telemetry, which Will be available during about one-fourth of the time with an average contact time of 6.5 minutes per station, delayed time data and voice will be recorded on board for playback while Skylab is over a ground station. The playback system has the capability to dump two hours of stored data in 5.45 minutes. Periodic television transmission for the five ATM cameras and for the portable TV cameras will be achieved through the frequency-modulated S-band link on the Command and Service Module. A video tape recorder system will be available in the Multiple Docking Adapter. The portable color cameras, either hand-held or bracket-mounted (Fig. 118), have 525 scan lines at 30 frames per second. They can operate within a wide range of illumination.

Some of the scientific data, such as solar ultraviolet spectral measurements of Experiment S055, will be recorded on tape and transmitted to ground when Skylab is in line of sight for one of the receiving stations. Measurements taken by the numerous control instruments on Skylab, including housekeeping information on temperature, pressure, and humidity, and biomedical data from sensors worn by the astronauts, will be processed by...

 


[
101]

Figure 116. Network of ground stations around the Earth for communications to and from Skylab. [small picture- it's a link to a larger picture on a separate page]

Figure 116. Network of ground stations around the Earth for communications to and from Skylab.

 

...onboard instrumentation systems and either transmitted directly to Earth or recorded on tape for transmission when ground contact exists.

Commands can be sent to Skylab from Mission Control Center in Houston to perform onboard functions, and to supply data to the onboard computers and the crew. An onboard teleprinter is available to produce paper copies of information for the crew, along with daily schedules of

Skylab activities. Voice communication between Skylab and Mission Control at the Lyndon B. Johnson Space Center in Houston will be handled through the Command and Service Module docked at Skylab while astronauts are in orbit. Internal communications between astronauts anywhere in the Skylab cluster or on extravehicular activities will be possible through a number of communications panels and loudspeakers.

Principal Investigators (PIs) will have the opportunity of communicating with crew members through the Mission Control Flight Director.

Flow and distribution of Skylab data are illustrated in Fig. 119. All the signals received at STDN stations will first be passed on to the Goddard Space Flight Center, and from there to the Mission Control Center in Houston. The Principal Investigators will receive their data through Mission Control either in the form of tapes of processed and printed data, and of photographs as obtained from transmitted signals, or as films, samples, specimens, notes, and log books brought back in the Command Modules. After the Principal Investigators have analyzed the data and had an opportunity to publish the results, NASA will make the experiment data available to other qualified investigators upon request.

 

[102] TABLE 8. Skylab External Communications

Frequency Mhz

Mode 1

Modulation

Use

.

230.4

T

FM/PCM

Launch telemetry.

230.4

T

FM/PCM

Telemetry, voice, data.

235.0

T

FM/PCM

Telemetry, voice, data.

246.3

T

FM/PCM

Telemetry, voice, data.

450.0

R

FM

Ground Command teleprinter.

296.8

T

AM

CSM ranging.

259.7

R

Tones

CSM ranging.

231.9

T

FM/PCM

ATM telemetry.

237.0

T

FM/PCM

ATM telemetry.

450.0

R

FM

ATM ground command.

243.0

T

ICW

Recovery beacon.

259.7

T

AM

Ranging to Skylab.

259.7

R

AM

Ranging to Skylab.

296.8

T

AM

Voice, range, data.

296.8

R

AM

Voice, range, data.

2106.4

T

PM/PCM

Telemetry.

2287.5

T

PM/PCM

Telemetry.

2272.5

T

FM

TV, telemetry.

1 T = Transmitter, R = Receiver.

 


Figure 118. Handheld TV camera for use on Skylab. [small picture- it's a link to a larger picture on a separate page]

Figure 118. Handheld TV camera for use on Skylab.

 

[103] The supply of photographic films for the complete Skylab mission includes about 280 cassettes, most of them with 400 ft-reels of 16 mm film; 64 magazines with 16 mm, 35 mm, or 70 mm film; and a number of packs and rolls with films of special sizes and varying lengths.

Weights of films, tapes, specimens, and other physical data expected to be brought back from Skylab in the three Command Modules are listed in Table 9.

 

d. Crew Accommodations

As a manned space vehicle, Skylab provides a habitable environment with living quarters, crew provisions, and facilities for food preparation and waste disposal to support a three-man crew for three missions (one for 28 days, and two for 56 days each). The center of activity is the Workshop shown in Fig. 72. The main "floor" of the Workshop contains the wardroom or food management subsystem, individual sleeping compartments, an experiment work area, and the waste management subsystem (toilet) with hygiene facilities (Fig. 121).

The Food Management Subsystem consists of equipment and supplies required for the storage, preparation, and consumption of the daily meals by the astronaut crew. The astronauts, provided with a 140-day supply of food and beverages, will use the wardroom as kitchen and dining room. Food is stored in food boxes, galley trays, food freezers, and a food chiller. A galley, the food table, food trays, and eating utensils are provided for the preparation and consumption of the meals.

For the first manned space flights during the early 1960's, meals were prepared and packaged specifically for the zero-gravity environment with the result that they barely resembled normal Earth food. Real progress in astronaut eating was achieved on Christmas Day, 1968, when Frank Borman, James Lovell, and William Anders, circling the Moon on board Apollo 8, opened a surprise food package. It contained natural pieces of turkey with brown gravy, bright red cranberry applesauce, and a normal spoon. That meal proved that it was possible to serve tasty, familiar food, and to eat it with normal utensils, under zero gravity. Loose food and liquids could be controlled easily; even the gravy stayed where it belonged. A further step toward more normal food has been taken for Skylab. The Skylab crew will have a wide variety of frozen and dehydrated food to prepare menus ranging from cold cereals to potato salad, shrimp cocktail, and filet mignon. Foods that will adhere to a fork or knife, such as steak, mashed potatoes, or pie, will be eaten with normal utensils; liquids, including coffee, tea, instant breakfast, grape and orange drink, cocoa, and lemonade, will be served in squeezable plastic containers and sipped through tubes.

The galley in the wardroom will provide the daily supply of food; galley-located equipment will be used for preparation and disposal of food. Meal preparation and consumption equipment is shown in Fig. 122; trash disposal in Fig. 123.

The food table will permit three crewmen to simultaneously heat their food and to eat their meals in an efficient and comfortable manner, using...

 


[
104]

Figure 119. Flow and distribution of data returned from Skylab. [small picture- it's a link to a larger picture on a separate page]

Figure 119. Flow and distribution of data returned from Skylab.

 

TABLE 9. Weights of Data and Material to Be Returned On Board Command Modules

Type of material

Mission

I

II

III

kg

lbs

kg

lbs

kg

lbs

.

Biomedical Specimem

36

79

48

106

46

101

Solar Astronomy Films

84

185

168

370

84

185

Science Films and Samples

34

73

16

33

5.3

12

Earth Resources Films and Tapes

33

77

33

77

40

88

Technology Films and Samples

30

66

2

4

....

....

Operations Films

24

53

28

62

13

27

 

....normal utensils and food trays. The table also supports components of the water system, including the water chiller and the wardroom water heater. The water chiller provides cold water for cold reconstitution of dehydrated foods and beverages and also for drinking purposes. The wardroom water heater provides hot water for hot reconstitution of dehydrated....

 


[
105]

Figure 121. Main floor of Skylab, showing hatch for waste disposal (formerly oxygen tank) in foreground, and waste management subsystem (toilet) in rear center. [small picture- it's a link to a larger picture on a separate page]

Figure 121. Main floor of Skylab, showing hatch for waste disposal (formerly oxygen tank) in foreground, and waste management subsystem (toilet) in rear center.


Figure 122. Galley equipment, including food table and food storage lockers. [small picture- it's a link to a larger picture on a separate page]

Figure 122. Galley equipment, including food table and food storage lockers.

 

[106] ....foods and beverages. Each eating station has a foot and thigh restraint to hold the crewman in a comfortable position while eating.

One portable food tray per crewman is used to heat frozen food in large food cans, and to serve the complete meal (Fig. 124). Magnets, dispersed about the surface of the food tray, retain the reusable utensils while they are not in use. One utensil set consisting of knife, spoon, and fork is allocated to each crewman. Disinfectant-moistened pads, obtained from a galley-located tissue dispenser, will be used to cleanse the utensils after each use.

The wardroom food preparation and serving table also provides support in other activities, such as writing and playing games, when body restraint and restraint for objects are needed A window in the wardroom, designed to accommodate several experiments which require exterior viewing, also affords a look to the ouside for the crew ( Fig. 125 ) .

The Waste Management Area (toilet) is shown in Fig. 126. Waste management facilities presented a unique challenge to spacecraft designers. In addition to collection of liquid and solid human wastes, there is a medical requirement to dry all solid human waste products and to return the residue to Earth for examination. Liquid human waste (urine) will be sampled and frozen for return to Earth. Total quantities of each astronaut's liquid and solid wastes will be precisely measured.

 


Figure 123. Hatch for disposal of waste in former oxygen tank. [small picture- it's a link to a larger picture on a separate page]

Figure 123. Hatch for disposal of waste in former oxygen tank.

 

[107] In the case of solid waste, a bag with a special filter is installed in the suction line of the toilet, allowing gases to pass through, and retaining only feces. Upon collection, the weight will be determined on a special spring-pendulum scale, and the bag will be placed in an electrically heated compartment where the contents are dried. The bag containing solid residue will then be stored for return to Earth.

Liquid waste will be processed with a centrifugal device installed in the suction line which imparts to the liquid sufficient force to actuate a precise liquid quantity meter. A constant volume (approximately 120 milliliters) of the liquid will then be separated and stabilized by freezing until it is returned to Earth.

Cabin air will be drawn into the toilet and over the waste products to generate a flow of the waste m the desired direction. The air will then be filtered for odor control and for antiseptic purposes prior to being discharged back into the cabin.

The washing facility is also illustrated in Figure 127. The crewman will wet a washcloth by placing it over the water discharge, apply soap to the cloth, and bathe and rinse as he would at home. The wet cloth will be discarded after use. A body shower will be taken by each crewman about once a week, the limit being set by the water storage capacity on Skylab (six pints per shower). Water will be discharged through a showerhead at the end of a flexible hose. Showers will be taken inside a cylindrical compartment (Fig. 127). The floating water droplets will be driven into a water collection system by air flow. Towels and tissues will be supplied as well as antiseptic cleaning agents.

Electric or safety razors may be used for shaving. A mirror is provided above the lavatory (Fig. 126).

Each crewman is assigned a small space for sleeping, as shown in Figure 128. Because of the absence of gravity, sleeping comfort can be achieved in any position relative to the spacecraft; body support is not necessary. Sleeping, therefore, can be accommodated quite comfortably in a bag which holds the body at a given place in Skylab and also encloses it m a manner which is psychologically and physically pleasing.

Finally, the main floor includes an experiment work area m addition to the wardroom and the waste management and sleeping areas described above. This work area is shown in Figures 129 and 130. Medical experiments will be conducted in this area (Chapter V-3).

 

e. Electric Power System

Solar energy is the prime source of electric power on Skylab. Two systems of solar-electric cell arrays, one on the Workshop and one on the Apollo Telescope Mount, will be deployed after the Skylab cluster has reached orbit. The OWS system consists of two wing-like structures which are folded and packed against the Workshop wall during ascent. The ATM system, folded in a similar way during ascent, deploys in the shape of a four-bladed windmill (Fig. 131).

 


[
108]

Figure 124. Food tray and eating utensils for Skylab crew. By contrast, Apollo astronauts had only the food packets shown in the foreground. [small picture- it's a link to a larger picture on a separate page]

Figure 124. Food tray and eating utensils for Skylab crew. By contrast, Apollo astronauts had only the food packets shown in the foreground.


Figure 125. Food table with leg restraints, and window to the outside. [small picture- it's a link to a larger picture on a separate page]

Figure 125. Food table with leg restraints, and window to the outside.

 

[109] Each system provides about 110 m2 (1180 ft2) of active silicon cell area. Under ideal conditions of solar irradiation, each array will produce almost 12 kw of electric power. During the dark portion of each orbit, solar energy is not received, and storage batteries must provide power. Battery chargers, voltage regulators, power conditioning units, and distribution....

 


Figure 126. Waste management (toilet) and sample storage. [small picture- it's a link to a larger picture on a separate page]

Figure 126. Waste management (toilet) and sample storage.

 

[110] ....components will consume a certain portion of power. Under the influence of all these factors, the OWS array will produce an average usable power of about 3.8 kw, and the ATM array an average usable power of about 3.7 kw.

The Airlock Module will serve as the power center for the Workshop, the MDA, and the AM. Power from the OWS array is routed to the AM where batteries and power conditioning components are located. The ATM power conditioning equipment is mounted on the ATM rack; it will be controlled from the ATM Control and Display Console located in....

 


Figure 127. Shower compartment within Workshop. [small picture- it's a link to a larger picture on a separate page]

Figure 127. Shower compartment within Workshop.

 

[111] .....the MDA. Although the two power systems are self-contained, they are interconnected in a parallel mode to allow maximum utilization of the available capacity. In addition to the permanently wired power-consuming systems, there are 28-volt utility outlets in the OWS, the AM, and the MDA for lights, tools, equipment, and even a vacuum cleaner.

Power for the Command and Service Module will be provided by hydrogen-oxygen fuel cells during ascent. After docking, the CSM power line will be connected to the Workshop network. On the return flight to Earth, the CSM will draw its electric power from batteries.

 


Figure 128. Sleep compartment with sleeping bag. [small picture- it's a link to a larger picture on a separate page]

Figure 128. Sleep compartment with sleeping bag.


[
112]

Figure 129. Work area with litter chair for rotation of an astronaut (mockup). [small picture- it's a link to a larger picture on a separate page]

Figure 129. Work area with litter chair for rotation of an astronaut (mockup).


Figure 130. Work area with medical experiments, including Lower Body Negative Pressure system and wheelless bicycle (Ergometer). [small picture- it's a link to a larger picture on a separate page]

Figure 130. Work area with medical experiments, including Lower Body Negative Pressure system and wheelless bicycle (Ergometer).


[
113]

Figure 131. Unfolding of solar arrays of Apollo Telescope Mount (ATM) in orbit. [small picture- it's a link to a larger picture on a separate page]

Figure 131. Unfolding of solar arrays of Apollo Telescope Mount (ATM) in orbit.


1 Redundancy: See Glossary for explanation.

2 A sound level of 72.5 db is approximately equal to that of a "noisy office."