Skylab was the first manned effort specifically designed to develop applied space technology for improving life on Earth. Although some Skylab instruments functioned automatically, most were operated by astronauts.
The Skylab Program had several objectives:
* To enrich scientific knowledge of the Earth, the Sun, the stars, and cosmic space.
* To study the effects of weightlessness on living organisms, including the astronauts.
* To develop new and valuable processing and manufacturing techniques in zero gravity.
* To devise and test new methods of gathering information about the Earth's surface.
Comparable in volume to a modest three-bedroom home, Skylab carried at launch 2,100 pounds (953 kilograms) of food; 6,000 pounds (2722 kilograms) of water; and nitrogen, oxygen, and other life-sustaining essentials. The three three-man crews, who occupied the station for 28, 59, and 84 days, respectively, used 54 items of experimental hardware to conduct 270 scientific and engineering investigations, many of several months duration.
Skylab orbited Earth once every 93 minutes, at an altitude of 268 miles (431 kilometers). The orbital trajectory swept an area covering 75 percent of the Earth's surface, 80 percent of its food-producing regions, and 90 percent of its population. Almost 40,000 pictures were taken by Skylab's cameras.
The Skylab program began early in the 1960s, when some NASA scientists were considering how vehicles and spacecraft might be used in other projects.
On Aug. 6, 1965, NASA established the Apollo Applications Office to formulate a program that included long-duration orbital missions, during which astronauts would conduct scientific and technical experiments. The program name was changed to Skylab on Feb. 24, 1970.
As the program matured, the major elements of the station became:
* The orbital workshop, which housed the crew, most of the expendable supplies, a major experiments area, and cold gas storage and thrusters for the attitude control system. It also provided structural support for the larger solar array which would derive energy from sunlight.
* A multiple docking adapter, containing docking ports for a modified Apollo command/service module (which would transport the crew to and from Skylab), the control panel for the telescope, a window for filming Earth's surface features, and other experiments.
* An Apollo Telescope mount, containing the solar experiments, control moment gyros, and its own separate solar array.
* An airlock module for extravehicular experiments, communications and data transmission equipment, the environmental-thermal system and electrical power controls.
Marshall Space Flight Center directed the major contractual efforts, engaging McDonnelI Douglas to build the workshop and airlock module, and Martin Marietta the multiple docking adapter. The telescope, photographic equipment, and food were procured by Johnson Space Center.
Two mobile launchers were modified for the Skylab vehicles. A steel pedestal 127 feet (39 meters) tall was placed on one launcher to adapt it to the Saturn IB, which was much shorter than the Apollo-Saturn Vs previously boosted from the same launcher. The second one was adapted to fit the somewhat shorter Skylab atop the Saturn V second stage.
Stages of the Skylab 1 and Skylab 2 launch vehicles began arriving at KSC during late summer 1972. For the initial launch, the Saturn V would consist of two stages plus the instrument unit. The Skylab-orbital workshop replaced the third stage.
The crew was made up of Navy Capt. Charles Conrad, the commander, a veteran of two Gemini flights and the Apollo 12 lunar landing mission; Navy Cmdr. Joseph Kerwin, a physician, and Navy Cmdr. Paul Weitz, both entering space for the first time.
The complete Skylab space station assembly was 118.5 feet (36.1 meters) long, 27 feet (8.2 meters) in diameter at the widest point, and weighed 100 tons (91 metric tons). A payload shroud provided cover for the telescope mount, airlock, and docking adapter during the boost phase. The workshop itself contained 10,426 cubic feet (295 cubic meters) of space and weighed 78,000 pounds (35,380 kilograms). Except for attitude control thrusters, there was no propulsion system. Within the tank, aluminum open-grid floors and ceilings were installed to divide the two-story space cabin. Crew quarters in the aft end were divided by solid partitions into sleep, waste management, and experiments compartments. The thermal control and ventilation system was designed to maintain temperatures ranging from 60 to 90 degrees Fahrenheit (16 to 32 degrees Celsius), while the nitrogen-oxygen atmosphere was constant at five pounds per square inch (0.352kg/cm2) pressure. Outside the workshop shell was a meteoroid shield to provide thermal control and decrease the possibility of hazardous punctures. Once in orbit, the shield was to be deployed and held five inches (12.2 centimeters) from the workshop shell.
The astronauts flew their jets into Patrick Air Force Base on May 12 to undergo final medical checks, then stood by awaiting launch. The plan was to place Skylab in Earth orbit, confirm that its systems were operating normally, then launch the first crew a day later for rendezvous and docking with the workshop.
The countdown proceeded without interruption, and liftoff occurred on time at 1:30 p.m. EDT on May 14.
But, after Earth orbit was achieved, there was no confirmation that the solar arrays of the workshop had deployed. Radio signals from Earth, dispatched two hours as a backup attempt, failed to move them. By that time the telemetry data had been examined, revealing an unexplained malfunction had occurred 63 seconds after liftoff as the vehicle reached maximum dynamic pressure. As a result, the arrays had opened. Also, the meteoroid shield had been torn away. NASA's manned space flight managers, evaluating the alternatives, decided to delay the Skylab 2 launch until May 20, to allow time to appraise the situation.
The scope of the problem became more clear over the next several days:
* Electrical power generating capacity had been cut in half.
* Skin temperatures of the Sun side of the workshop ranged up to 295 degrees Fahrenheit (146 degrees Celsius).
* Internal temperatures hovered between 70 degrees Fahrenheit (21 degrees Celsius) on the cool side and 120 degrees Fahrenheit (49 degrees Celsius) on the wall towards the Sun.
Johnson flight controllers, in consultation with Marshall engineers, struggled to reduce the heat by changing Skylab's attitude. This required delicate maneuvering. When the workshop was tilted to minimize solar exposure, the electrical supply dropped. But if the solar wings were tilted toward the Sun, the workshop became hotter.
By May 17, Skylab was stabilized at an angle of about 50 degrees to the Sun. Temperatures in the workshop fell to about 90 degrees Fahrenheit (32 degrees Celsius). Astronauts Conrad and Kerwin of the Skylab 2 prime crew were at Marshall, rehearsing space walk procedures to install a sunscreen to replace the missing meteoroid shield.
The manned launch was further delayed until May 25, to allow time to develop a shield and the means to deploy it. Additional cryogenics were loaded into the service module tanks, to extend the normal life of the fuel cells so that they could supplement Skylab's electrical budget.
Within hours of launch, Johnson delivered a parasol device fashioned from aluminized Mylar-nylon laminate. It could be deployed through the scientific airlock like an umbrella, opened up in space, and pulled down into position.
The countdown clock for Skylab 2 had been stopped at T minus 59 hours. It was resumed at 8:30 p.m. EDT, May 22. The Saturn IB roared off from Pad 8 at 9 a.m. EDT, May 25, and Conrad steered his ship to the rendezvous point in space. Late in the afternoon the crew approached Skylab and turned on television equipment so engineers on Earth could visually assess the situation. Most of the micrometeoroid shield had disappeared, but some remnants were jammed against the remaining solar wing, preventing its deployment. The other wing had completely vanished.
Conrad guided the ship to a soft dock with the laboratory, and the crew attempted unsuccessfully to free the solar wing.
They abandoned the attempt, then sought to hard dock with Skylab, only to encounter a problem with the latching mechanism. After several unsuccessful attempts, they removed the drogue-working outside the command module and trimmed up the latch system, finally locking the spacecraft firmly with Skylab.
Entering the workshop next day they found the interior hot but otherwise shipshape and proceeded to install the parasol device. Within hours the temperature began to drop; by May 29 it had reached 83 degrees Fahrenheit (28 degrees Celsius). The crew turned on experiments, began recording solar phenomena with the telescope, and filming Earth as planned. Subsequently, Conrad and Kerwin performed another work-in-space task and this time freed the jammed solar wing.
The crew completed the planned 28 days in space and accomplished the objectives required by 48 experiments. The astronauts also filmed a hurricane in the Pacific Ocean, and a solar flare. They disengaged from their temporary home in space and landed in the Pacific, southwest of California.
Having carefully reviewed Skylab's status following the mission, Program Director William C. Schneider announced that the second mission, was planned to extend for 56 days, thus doubling the astronauts' exposure time. NASA's physicians would check the crew's health daily. At the end of 28 days, the doctors would thereafter decide on a weekly basis if the crew could continue.
Navy Capt. Alan Bean, veteran of Apollo 12, commanded the Skylab crew. The science pilot was Dr. Owen Garriott, a specialist in ionospheric physics, having been trained by NASA as a jet pilot. Maj. Jack Lousma, U.S. Marine Corps, completed the crew.
Preparations for the mission were in progress at KSC when NASA decided to attempt a full-duration mission.
Skylab's problems prompted Schneider to announce on June 6 that the Skylab 3 launch would be advanced from Aug. 8 to July 28 to get the astronauts into the space station at the earliest possible time. Accordingly, KSC Launch Director Walter Kapryan tightened the work schedules.
Numerous thundershowers occurred the afternoon of July 27. Extensive fog reduced visibility to three miles (4.8 kilometers)-the distance between the pad and the Launch Control Center, with ground fog at 600 feet (183 meters) in spots. Still, the terminal countdown began at 7 a.m. EDT on July 25, and liftoff came at 7:11 a.m. EDT, July 28.
Skylab 3 vanished in the fog shortly after launch. Five hours later the crew steered to a firm docking with Skylab and moved in to occupy the workshop, In retrospect, NASA physicians thought the relatively quick transfer caused the motion sickness which disabled all three astronauts soon after they took over Skylab. The Skylab 2 crew possibly escaped the problem because they slept in the command module the first night and carried out a more gradual transition into the space station.
By the fourth day, the astronauts' recovery from the motion sickness was complete, and they started up the experiments and carried out the planned routines. On Aug. 6, Garriott and Lousma installed a new sail, replacing the parasol. The internal temperature was soon stabilized.
For their second task performed outside the station, Lousma installed and connected six rate gyroscopes carried aloft in the Skylab 3 spacecraft. The gyros replaced those which had malfunctioned in the months following Skylab's launch, possibly because they were baked by temporary high temperatures after the loss of the meteoroid shield.
From time to time during the mission, television viewers on Earth saw the astronauts go about their duties. From the 29th day on, new records for time-in-space were established daily.
Garriott took special delight in operating the telescopes which filmed solar phenomena, since the Sun continued very active in a period of supposed quiet. More than 100 solar flares were observed. Dr. Neil R. Sheeley of the Naval Research Laboratory reported that Garriott witnessed magnetic field phenomena, never seen by observers using Earth telescopes.
After tidying up their space home at, the end of their visit, the crew undocked on Sept. 25 and splashed down in the Pacific 0cean at 6:19 p.m. EDT, in rough seas.
Skylab experimenters were enthusiastic about the quality of Skylab data, and were busy evaluating the information in terms of its potential applications.
Skylab's third crew was unusual in that all three astronauts were making their first trip into space. Gerald Carr, the commander, was a Marine Corps lieutenant colonel. Dr. Edward Gibson, science pilot, had joined NASA in 1965. The agency gave him pilot training. Lt. Col. William Pogue, U.S. Air Force, rounded out the crew in the pilot's berth.
A leaking coolant loop in Skylab was causing 'concern. Marshall engineers foresaw the possibility of the system running out of coolant by about Nov. 20, unless repair and replenishment fixed the problem. So there was some urgency attached to the prospective launch date of Nov, 10. A repair kit would be carried aboard Skylab 4.
The flight readiness review considered a matter of new concern, stress corrosion in the forged aluminum "E" beams of the first stages of the Skylab 4 vehicle and the standby Skylab rescue vehicle. The beams were load-bearing and supported the structure. The cracks formed by fatigue, corrosion, and load carrying were repaired by removing metal on either side and welding new metal in the opening.
Stress corrosion popped up again Nov. 6. This time hairline cracks appeared in eight large tail fins of the first stage. Fourteen cracks were discovered. The fins helped stabilize the rocket in flight and also supported its weight on the pad.
The corrosion may have resulted from increased salt concentration in the air at the oceanfront launch pad. Kapryan recommended delaying the launch until Nov. 16, allowing time to bring in spare fins from Michoud, La. Contractor crews worked around the clock applying doublers on the new fins to strengthen their attachment to the stage.
Two days before launch, shallow, almost indistinct cracks were found in aluminum beams within the second stage. Experts in metallurgy and fracture mechanics concluded that the cracks would not adversely affect the beams. The Manned Flight Management Council accepted the findings that the stage was safe for flight.
The Management Council also approved the proposal to consider Skylab 4 a 59day mission, which could be extended week by week to a maximum of 84 days. This involved loading more food in the Apollo spacecraft, including an enriched foodstuff to stretch out the primary food supply. Since the Skylab 4 crew would exercise more, physicians concluded there would be no lasting ill effects from spending virtually three months in zero gravity.
On Nov. 16, 1973, Skylab 4 lifted off the mobile launcher at Pad B at 9:01 a.m. EST. The Saturn IB performed flawlessly, and rendezvous with Skylab was accomplished on the fifth revolution. The crew encountered some difficulty in docking but made the hard connection on the third attempt.
As soon as they adjusted to the Skylab environment, the crew went to work, repairing and servicing the coolant systems of the airlock module. They settled into a full routine of tending experiments, exercising, eating and discussing schedules and notable sightings with Mission Control.
By early December, the crew's productive routine included photographing solar phenomena and comet Kohoutek, and measuring Earth resources. Infrared cameras and heat-seeking sensors probed the Earth from 275 miles (443 kilometers) in space, looking for evidence of oil deposits and seeking natural steam wells which might be harnessed to yield power in areas of California, Arizona, New Mexico, Central America, and Mexico.
The astronauts completed their first month in space on Dec. 14, surpassing the time of the stay of the Skylab 2 crew.
Christmas Day was a busy time for the astronauts, who spent seven hours photographing comet Kohoutek and performing other experiments outside the workshop.
During early January, they continued to observe Kohoutek, conducted Earth resources studies, filmed solar phenomena and managed a wide range of other experiments.
On Jan. 14 the three astronauts broke the Skylab 3 record of 59 days, 11 hours, and 9 minutes in space. On Jan. 25 all three crewmen broke Alan Bean's record of 69 days in space-exchanging congratulations with Bean, who sat in Mission Control. Program Director Schneider warned that an ailing gyroscope might cease to function at any time. However, it might be possible to complete the mission by using the gas thrusters and the Apollo thruster system to stabilize Skylab. As a precaution, NASA ordered the USS New Orleans, the recovery ship, into the recovery area three days early.
Near the end of their stay, the astronauts packed gear in Apollo and put the space station in order for a possible visit by astronauts in the future. On Feb. 8, they undocked the Apollo spacecraft, said their goodbyes to Skylab, and headed for splashdown. They had traveled some 34 million miles in their space station. The recovery went without a hitch.
Carr, Pogue, and Gibson met the press on Feb. 22, showed films which sampled their voluminous coverage of Earth terrain features, and talked of the highlights of observations of the Sun and comet Kohoutek.
There were many honors for the Skylab crews and for the men and women who designed and built Skylab, who prepared the vehicles and spacecraft for launch, and who managed the mission so effectively.
The Skylab space station, many of its systems still operating, remained in orbit for another 5 1/2 years. At 12:39 p.m. EDT, July 11, 1979, it re-entered Earth's atmosphere and disintegrated, raining debris harmlessly along a path extending over the southern Indian Ocean and sparsely populated areas of western Australia. Concern over the huge spacecraft's impact point was one of the most talked-about events of the young space age, but in the end, it proved groundless. The Skylab mission began with major problems and ended with much speculation about its return to Earth, but in fact the program established an unparalleled record for scientific return on the investment. Skylab paved the way for the Spacelab, the major scientific payload of the Space Shuttle.
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