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Project Apollo: The Beginnings
| Mission Planning
| Landing Site Selection
| Earthbound Support Systems
Astronaut Selection and Training | The Saturn V | The Saturn 1B | The Apollo Spacecraft | Guidance and Navigation
Command and Service Modules | The Lunar Module | Assembling and Launching | Pathfinders | The Early Missions
Apollo 11, The First Landing | The Intermediate Missions | Apollo 15 Exploration | Apollo 16 Exploration
Apollo 17 Exploration | Skylab and Apollo-Soyuz | Conclusion
The cancellation of Apollo 15 as a 'H' type mission made one of the original Saturn V launch vehicles, which were already under construction, available for the launch of the United States first earth orbiting space station, Skylab. NASA's official designation of the Skylab missions were Skylab 1, the launch of the unmanned space station, and Skylab 2, 3, and 4, which were to be manned missions. The three manned missions became better known unofficially as Skylab I, II, and III. Once in orbit, Skylab would be visited by successive crews using Apollo Command and Service Modules launched on the less powerful Saturn S-1B booster.
Skylab was a converted S-IVB booster, of the type previously used on the Apollo moon missions as the third stage of the Saturn V launch vehicle. Devoid of its engine the fuel tanks were fitted out with living quarters and environmental systems to provide accommodation for three astronauts for extended stays of up to three months in earth orbit. Its purpose was to allow investigation of the effects on human health of working and living for extended periods in space. It would also provide an observatory for solar and stellar astronomy free of the earth's atmosphere. The astronauts would be able to conduct experiments in zero gravity and carry out earth resource observations.
Skylab's internal living space of 7,500 cubic feet was divided into two floors. One floor was used for storage, conducting experiments and exercise equipment, including a static bicycle and treadmill. The second floor provided living quarters, including shower and dining facilities and a work area. Each floor had its own airlock on opposing sides of the craft for EVA's to retrieve external camera film and experiments. Access to Skylab from the Apollo Command and Service Module was via a docking hatch at the end of the station, where the CSM remained docked throughout the mission. Power to the station was to be supplied by two, double solar panel arrays, one pair for the station and the second for the station's largest piece of equipment the Apollo Telescope Mount (ATM), which was to be used for solar and astronomical observation.
The last Saturn V to be launched lifted off from pad 39A at Kennedy Space Centre on 14 May, 1973, carrying the unmanned, 100 ton Skylab as payload. 63 seconds into the flight, Skylab's micro-meteorite/sunshield deployed inadvertently and ripped loose from the craft, damaging one of the solar panels, which partly deployed. As the Saturn staged, the retro rockets exhaust, which pushed the expended first stage booster clear, caught and destroyed the partially extended solar panel. The second panel was trapped by debris from the sunshield and would not deploy when signalled to do so.
Skylab had, however, achieved its intended orbit of 270 miles above the Earth; but, without power from the solar array or protection from the sunshield, temperatures inside the station were building to over 125 degrees Fahrenheit. The launch of the first crew, who were to occupy Skylab the following day, was postponed, while mission scientists placed Skylab in a holding attitude to minimize overheating and considered their options.
The crew of Skylab 2, Commander Charles 'Pete' Conrad, Paul J Weitz, and Joseph P Kerwin, launched ten days later on 25 May, 1973, atop a Saturn S-1B booster, carrying along with them a parasol heat shield to replace the one lost during Skylab's launch. On their first approach to the stricken space station they manoeuvred their CSM around the station and closed in to assess the damage. After a rest period they vented their spacecraft's atmosphere, opened the command module's hatch and Weitz leaned out with Kerwin holding his legs. Using a pole with a metal cutter on the end Weitz tried to pry some of the debris free and allow the solar panel to deploy, but was unsuccessful.
After docking, the crew lived in the Apollo Command Module, until they were able to erect the replacement parasol sunshield and bring Skylab's internal temperatures down to a manageable 75 degrees. Two weeks into the flight, Conrad and Kerwin went outside for a second time and removed the debris still trapping the remaining solar panel, attached a rope and physically pulled the panel free allowing it to extend fully and provide power. Conrad quipped: 'Y'know how hard it is to get an electrician here in this neighbourhood?'
The crew spent the remainder of the mission working up Skylab to operational status and conducting experiments. Conrad regarded his Skylab mission as the outstanding point of his career, more satisfying than his moon landing in Apollo 12 and being the third man to walk on the moon. He was subsequently awarded the newly inaugurated Space Medal of Honour for his retrieval of Skylab's working capability.
With Skylab now functioning, the crew remained to complete their mission, carrying out the planned range of experiments and observations including three EVA's. On 25 May 1973, the crew undocked their CSM and returned to Earth, having set a new endurance record for living in space of 28 days, 50 minutes.
Just over a month after Conrad's crew returned, Skylab 3's crew lifted off to take up residence. The crew were Commander, Alan L Bean, Jack R Lousma, and Owen K Garriott. One of their first tasks was to erect another more substantial sunshield, during an EVA lasting six and a half hours. Two further EVA's tested an Astronaut Manoeuvering Unit, (AMU), a reaction power unit to propel and manoeuvre the astronauts in space that had not been tried since an aborted test on an earlier Gemini mission. The prodigious work output of Skylab 3's crew exceeded their planned schedule, as they completed scientific and medical experiments, which included one inspired by school students to observe spiders to see how they weaved their webs under weightless conditions.
The crew finally returned to Earth on 25 September, 1973, after doubling Conrad's endurance record to 59 days, 11 hours.
Skylab 4's crew, Commander Gerald P Carr, William R Pogue, and Edward G Gibson took off for the final Skylab mission on 16 November, 1973. The start of their mission was marred by all the crew members suffering from nausea in the first few days, a fact that they initially tried to keep from the mission controllers, which resulted in a dressing down for Carr as the crew's commander. Further friction followed throughout the mission between the crew and mission control. Following Skylab 3's prodigious work rate the ground based experimenters began to add extra work to the current crew's workload under the expectation that it would be easily assimilated. Eventually this lead to a showdown when the crew complained that they were being unjustifiably overloaded.
The routine of scientific and medical experiments occupied the crew for the longest duration flight by American astronauts at 84 days 1 hour 15 minutes. They far exceeded the original planned work schedule and completed four space walks, including one on Christmas day to photograph the flyby of Comet Kohoutek.
The Skylab 4 crew returned to Earth on 8 February, 1974, and Skylab was subsequently shut down to be left in a stable orbit, where it was expected to remain for a further ten years. In 1977, however, it was discovered that its orbit was beginning to decay prematurely due to increased solar activity causing an expansion of the earth's atmosphere. This resulted in increased friction when it extended into Skylab's orbital plane slowing its velocity. NASA's inability to predict an exact time and, more alarmingly, a point of re-entry brought much speculation in the worlds press for the following nine months. Skylab finally plunged into the atmosphere on 11 July 1979, and broke up over the Indian Ocean, some parts were also scattered over Western Australia's outback.
The Apollo Soyuz Test Project (ASTP)
Occasionally referred to as Apollo 18, the final chapter in the Apollo series of space flights was the Apollo Soyuz Test Project, (ASTP). The intention was to bring together and dock Apollo and Soyuz spacecraft in Earth orbit. Conceived as a joint venture with the Soviet Union in the early 1970s, it was intended to test the compatibility of the docking mechanisms and environmental systems of the two spacecraft and pave the way for future co-operation and joint missions between the USA and the USSR.
Differences in the Apollo and Soyuz environmental and docking mechanisms required the design of a separate docking module that would have to be interspaced between the two craft. It would be launched with the Apollo craft in the bay previously reserved for a lunar module. It would also require the Apollo craft to carry out a docking and withdrawal of the module from the booster once it had achieved Earth orbit.
The Apollo crew was commanded by Thomas P Stafford, and the other crew members were Vance D Brand and Donald K 'Deke' Slayton. The Soviet Soyuz crew were cosmonauts Alexei Leonov and Valeri Kubasov.
Deke Slayton had been one of the original seven 'right stuff' astronauts, but had never flown in space due to an intermittent heart condition, which caused an irregular heart beat. This condition became apparent to the Mercury program's medical staff just before his scheduled flight. He was grounded and his place was taken by Scott Carpenter. He had served with distinction throughout the American manned space program as NASA's Director of Flight Crew Operations, selecting crews for the Gemini and Apollo missions. Finally, after undergoing an operation to check out his heart, he had been given a clean bill of health and returned to flight status.
Alexei Leonov commanded the Soviet Soyuz 19 spacecraft, and was one of the Soviet Union's most experienced Cosmonauts. He had been the first person to 'walk' in space in March 1965 from Voskhod 2.
Soyuz 19 launched from the Baikonur Cosmodrome in the USSR on 15 July, 1975, and was followed by the Apollo spacecraft seven hours later from the Kennedy Space Center. Once in orbit, the Apollo craft withdrew the docking module from its housing in the top of the third stage.
Apollo and Soyuz made contact and docked together on 17 July, 1975. Apollo Commander Tom Stafford opened the docking hatches, and the crews exchanged greetings and commemorative gifts, while the event was transmitted to world-wide television audiences. US President Gerald Ford joined the broadcast to speak to the crew members, after which they returned to their own craft and settled down for a rest period.
The two craft remained linked together throughout 18 July, with the crews transferring freely between them and giving further television broadcasts until 19 July, when, after 44 hours, they undocked and Apollo pulled away. The Soyuz was the first to return to earth two days later, landing in Kazakhstan, USSR. After carrying out a number of further experiments to complete its mission, the Apollo craft splashed down in the Pacific near Hawaii, less than three miles from its recovery ship, the USS New Orleans on 24 July, after a mission duration of 217 hours.
One last reminder that spaceflight is a dangerous occupation occurred during the last few minutes of their descent by parachute. As the residual fuel for the reaction control thrusters was vented off in the routine manner some were drawn into the spacecraft through a vent left open to equalise internal pressure. The crew inhaled some of this highly toxic gas and as a result all three were hospitalised for several days after the flight. Nevertheless, the mission was regarded as highly successful by both participating countries, as a technological accomplishment and as the basis for a greater degree of understanding and co-operation between the two nations for future joint projects.