Skylab 4
From The Space Library
November 16-February 8, 1974: The Skylab 4 Apollo spacecraft carrying a three-man crew was launched into near-earth orbit and rendezvoused and docked with the Skylab 1 Orbital Workshop (launched May 14) for the third and final manned mission in the Skylab program. Despite persistent problems with the spacecraft's onboard control moment gyroscopes, the crew proceeded successfully, making four space walks and setting new manned flight records. The astronauts collected significant data in medical experiments, astronomy (including 121 observations of Comet Kohoutek), and earth resources surveys for 84 days before undocking for a safe return to earth Feb. 8, 1974.
November 16-21: Skylab 4 (SL-4) lifted off on time at 9:01 am EST from Kennedy Space Center's Launch Complex 39, Pad B, on the two-stage Saturn IB-208 launch vehicle. The Apollo command and service module (CSM-118) and its crew-Gerald P. Carr, Dr. Edward G. Gibson, and William R. Pogue-roared into a clear blue sky. Traveling at 1600 km per hr (1000 mph) the spacecraft successfully endured maximum dynamic pressure at 72 sec after liftoff, proving the reliability of the Saturn IB launch vehicle and relieving the tense atmosphere in Mission Control at KSC. During the prelaunch period cracks discovered in the fins and body of the launch vehicle had twice postponed the launch date for replacement of the Saturn TB's eight stabilizing fins [see Nov. 6, 12, and 13]. Director of Launch Operations Walter J. Kapryan said he "personally sweated out those first 72 seconds through max q." The CSM/S-IVB combination was placed in a phasing orbit with a 222.3-km (138.1-mi) apogee and 148.2-km (92.1-mi) perigee 9 min 45 sec after launch. Eight minutes later the CSM separated from the stage. The S-IVB/IU deorbit maneuver was commanded on the third orbit and the stage impacted in the Pacific Ocean at 3:00 pm EST. After five rocket maneuvers the CSM rendezvoused with the Orbital Workshop during the fifth orbit. Docking was achieved at 5:02 pm EST after two unsuccessful attempts. Carr radioed down to Mission Control, "Great to be home."
During rendezvous and docking Pogue suffered from motion sickness and vomited. Later, in a conversation unintentionally taped by the astronauts and transmitted to the ground the astronauts decided not to report the incident to ground controllers. Capsule communicator Alan B. Shepard later told the crew, "We think you made a fairly serious error in judgment" in the attempt to cover up Pogue's condition. Carr agreed, "It was a dumb decision." Pogue recovered by late evening, Carr suffered only minor motion sickness problems, and Gibson remained in good health. Carr, Gibson, and Pogue entered the multiple docking adapter at 9:32 am EST Nov. 17 (Mission Day 2) and began Workshop activation. They found a welcoming note on the teleprinter: "Jerry, Ed and Bill, welcome aboard the space station Skylab. Hope you enjoy your stay. We're looking forward to several months of interesting and productive work. Signed, Flight Control." In addition they found three dummies dressed in tan flight suits left by Skylab 3 Astronauts Alan L. Bean, Dr. Owen K. Garriott, and Jack R. Lousma. Pogue replenished the fluid in the Workshop's primary cooling system, which had developed a leak during the Skylab 3 mission [see July 28-Sept 25]. The 51/2-hr task required Pogue to punch a hole into the plumbing lines to inject the fluid. Spacecraft activation was completed Nov. 21.
November 22-February 4: The first extravehicular activity (EVA-1) began at 12:44 pm EST Nov. 22. Pogue and Gibson moved through space to install film cassettes in the Apollo Telescope Mount (ATM) cameras, deploy experimental hardware, and repair the control system for an earth-scanning antenna that had jammed during the Skylab 3 mission.
Gibson, anchored in a portable foot restraint on the bottom of the spacecraft, held onto Pogue while Pogue rewired the instrument, bypassing a short circuit and restoring the antenna to 80% of its original capacity. Gibson and Pogue reentered the Workshop and began pressurization at 6:19 pm EST. The 6-hr 35-min EVA surpassed the 6-hr 31-min record set Aug. 6 by Skylab 3 Astronauts Garriott and Lousma. At 3:45 am EST Nov. 23 one of three moment gyros which controlled the spacecraft overheated and was ordered shut down by Flight Controller Philip C. Shaffer. Shaffer told the press at Johnson Space Center that a near-normal mission could still be flown but it would take more time and fuel to make maneuvers. Pogue began extensive photographic study of Comet Kohoutek.
By the end of the mission Comet Kohoutek had been observed and recorded 121 times as it approached, looped around, and retreated from the sun. The first full day of scientific research was scheduled for Nov. 27. While photographing a barium cloud-created by the launch of a Black Brant IVA sounding rocket from Poker Flats, Alaska-the space-craft's thruster attitude-control system used three times the amount of nitrogen gas fuel anticipated. The extra fuel use, in addition to poor weather conditions, forced postponement of the first earth resources experiment package (EREP) pass while ground teams designed improved techniques for managing attitude control and fuel consumption. For the first time Carr pointed the space station's six large solar telescopes at an unusually active region of the sun.
The first EREP pass was made Nov. 29 during a 23-min 8850-km (5500-mi) sweep from the southwestern U.S. to South America. In a Johnson Space Center press conference Skylab Program Director William C. Schneider said that the ground team had concluded that the Nov. 28 problem had been caused by an incorrect input of initial conditions into the fuel management program. Restrictions on maneuvers were eliminated and, with proper fuel management, the mission could "continue essentially as planned." On Dec. 1 the astronauts photographed a laser beam pointed at them by Goddard Space Flight Center scientists who were testing the lasers as a reference point for possible use in spacecraft navigation and communications. Earlier attempts to spot the flashing green laser had failed.
In a Dec. 13 Mission Day 28 Review of the first third of the mission Program Director Schneider said the Skylab 4 crew had accomplished 84 hrs of ATM solar viewing, 45 separate observations of Comet Kohoutek, 80 earth observation experiments, and 12 EREP passes, although a significant portion of the data from 9 passes had been lost because of wrong camera filters. Schneider said that the crew was in good physical and mental health and that their performance had been outstanding, but flight planners had needed to adjust work schedules to the pace of the crew.
A spectacular limb prominence on the sun, estimated to be the largest observed in 25 yrs, was recorded by the crew Dec. 18-19. Astronauts Carr and Pogue opened the hatch for EVA-2 at 11:55 am EST Dec. 25, Christmas Day. Pogue mounted three special cameras to photograph the sun and Comet Kohoutek before it passed behind the sun. Photographs were taken of the comet's tail and coma. Carr replaced film cassettes in the ATM and repaired a jammed filter on an ATM camera. The constant movement of Carr and Pogue outside the spacecraft disrupted Gibson's efforts to aim the laboratory cameras at Kohoutek and the thruster attitude control system used more fuel than planned. Carr and Pogue reentered the Workshop and closed the hatch at 6:56 pm EST after a 7-hr 1-min spacewalk that surpassed Gib-son and Pogue 's Nov, 22 record.
The Dec. 28 perihelion passage of Comet Kohoutek was marked with a live ground-to-air televised conference between Dr. Lubos Kohoutek, discoverer of the comet (1973F), and the Skylab 4 crew. Gibson said that the comet, as seen on the white-light coronagraph, was growing dramatically. The tail fanned out 20° from the central axis and could be seen back to a distance three times the diameter of the coma. Dr. Kohoutek congratulated the "first human beings studying a comet from outer space" and wished them a flawless splashdown in February.
The crew began EVA-3 at 12:29 pm EST Dec. 29. Carr and Gibson moved outside to photograph the sun and Comet Kohoutek as it began its trajectory away from the sun. Gibson said the comet had a spike and a tail. "That spike is very evident. It is not 180 degrees out from the tail, but more like 160 degrees. It is yellow and orange . . . just like a flame. It seems to be the same distance out as the tail, and there is a diffuse amount of material which goes out and joins up with the tail." The astronauts recorded other astronomical phenomena, retrieved samples from the magnetospheric particle collector, and retrieved the comet observation camera. At 3:58 pm EST Carr and Gibson moved back in-side the Workshop and closed the hatch after 3 hrs 29 min.
On Jan. 10 the mission was given a go-ahead for a seven-day extension, with weekly reviews through the end of a tentative 84-day total mission. In the 56-day mission review at JSC, Skylab Program Director Schneider said the crew was "in good spirits and excellent physical condition and the spacecraft is in good shape to continue." On Jan. 13 and 14 the Skylab 4 crew photographed a solar flare from beginning to end-the first opportunity for scientists to study the complete life cycle of a solar flare. At 10:10 pm EDT Jan. 14 Carr, Gibson, and Pogue had been in orbit 59 days 11 hrs 9 min, surpassing the record manned flight time in space on a single flight set by Skylab 3 Astronauts Bean, Garriott, and Lousma during their July 28-Sept. 25 mission. Mission controllers struggled with gyroscope problems with increasing frequency throughout the mission. On Jana 22 the second control moment gyro was in the distress position for six hours, causing Skylab officials to order the recovery force into port at San Diego three days earlier than planned. EREP passes were limited and other maneuvers reduced to conserve fuel and reduce stress. Despite nearly three dozen gyro 2 stress periods, gyros 2 and 3 held up for the rest of the mission.
At 1:46 pm EDT Jan. 25 (MD-71) the crew passed the record cumulative time in space of 69 days 15 hrs 45 min set by Bean during the Skylab 3 mission. The hatch was opened for EVA-4 at 11:19 am EDT Feb. 3. Gibson and Carr measured the atmosphere surrounding the Skylab solar instruments to evaluate the light-scattering produced when photos of the sun were taken. The astronauts also photographed the sun with an x-ray sensitive camera, retrieved film from ATM cameras, and removed a plate and piece of rubberized material from the side of the spacecraft for a study of effects of nine-month exposure to the space environment. EVA operations ended at 4:38 pm EDT after 5 hrs 19 min.
February 5-8: Deactivation of the Workshop was begun Feb. 5 (MD-82). A three-minute firing of the steering rockets at 4:48 pm EDT Feb. 6 raised the Workshop's altitude to about 450 km (280 mi) to reduce atmospheric drag and extend the orbital lifetime to an estimated nine years, increasing chances for a future revisit to the laboratory, although it could not be inhabited again. The crew left behind samples of food, film, teleprinter paper, and electrical cables for possible inspection during the 1975 U.S.-U.S.S.R. Apollo Soyuz Test Project mission or during U.S. space shuttle flights planned to begin in 1979. The CSM undocked from the Workshop at 6:34 am EDT Feb. 8 (MD-85) and made a fly-around inspection of the Workshop. One of two redundant CSM rocket thruster systems developed a leak during re-entry preparation, forcing the astronauts to reenter without a. backup thruster system. Just before SM jettison at 10:45 am EDT, a procedural error caused circuit breakers to open, blocking the stabilization and control thrusters from firing. Carr quickly took manual control for re-entry.
The CM splashed down upside down at 11:17 am EDT Feb. 8, 282 km (175 mi) southwest of San Diego and 5 km (3 mi) from the recovery ship U.S.S. New Orleans-ending 1214 revolutions of the earth. The capsule was righted by flotation bags while the carrier maneuvered alongside, and the CM was raised by a crane to the hangar deck about 40 min after landing. Immediate medical examinations found the crew had no apparent severe effects from their long exposure to weightlessness. They had grown one to two inches taller from stretched spinal columns in space and had lost some muscle mass, with body fluids readjusted for zero gravity; but they lost most of the slim-trim look on return to the earth. They were back to normal in a few days. The astronauts would remain aboard ship in San Diego for medical examinations and, after a brief dockside ceremony Feb. 10, would fly to Houston. The men would be allowed to rejoin their families but contact with the general public would be restricted for one week. The Skylab 4 mission achieved its primary objectives of performing Saturn Workshop operations, reactivating the Skylab orbital assembly in earth orbit, obtaining medical data for use in extending the duration of manned space flights, and performing inflight experiments. All 58 planned scientific and technical experiments in biomedicine, solar astronomy, solar physics, and engineering were accomplished. EREP instruments were operated during 39 passes over the earth and the crew spent 338 hrs photographing the sun and Comet Kohoutek with ATM instruments. Skylab 4 was officially adjudged a success Mar. 29, 1974.
Major records set by the mission included the longest-duration manned space flight to date, 84 days 1 hr 16 min; the longest cumulative time in space for a man, 84 days each for Carr, Gibson, and Pogue; the longest orbital EVA, 7 hrs 1 min Dec. 25; the longest cumulative inflight EVA time for one mission, 22 hrs 24 min; and the longest distance in orbit for a manned mission, 55.5 million km (34.5 million mi). Skylab 4 was the third and final mission to man the Skylab Orbital Workshop. Skylab 2 astronauts had worked aboard the laboratory 28 days, May 15-June 22, conducting experiments as well as making repairs to the orbital assembly to salvage the Skylab program. The Skylab 3 crew collected data in medical experiments, solar astronomy, and earth resources surveys for 59 days, July 28-Sept. 25. There were no plans to send another crew to inhabit the Workshop, which would be g-dormant-lacking in power, air conditioning, and atmosphere-by Feb. 9. Skylab 1 was expected to remain in orbit for nine years before reentering the earth's atmosphere and burning up. (NASA prog off; JSC press briefing & communications transcripts, 11/16/73-2/2/74; JSC Skylab Off; JSC, NASA Facts; NASA Release 74-8; Wilford, NYT, 11/17/73, 1; UPI, W Star-News, 12/16/73, Fl; AP, B Sun, 12/27/73, A6 ; McElheny, NYT, 2/7-9/73)
