Even to space buffs who had avidly followed telecasts of the Apollo and Skylab astronauts in space, the broadcasts from Earth orbit on July 17 and 18, 1975, were unusual. First, they saw three U.S. astronauts in an Apollo spacecraft rendezvous and dock with a Russian Soyuz spacecraft manned by two cosmonauts. Then during two days of mated flight, they observed the crew members move from one craft to the other, share meals, exchange gifts and conduct scientific experiments.
The event was the Apollo-Soyuz Test Project-history's first international manned space flight. The basic purpose of the nine -- day joint mission-to flight-test a mechanism for joining two orbiting spacecraft -- was successfully met. Apollo-Soyuz demonstrated that international space rescue missions would be feasible in the future.
Scientists also took full advantage of the opportunity for more orbital research projects, conducted by each crew independently. Apollo carried equipment for 23 science and technology experiments; Soyuz was equipped for six.
The two spacecraft were outfitted for five joint experiments as well, three carried out while the two spacecraft were linked together and two after Apollo and Soyuz had undocked.
Although Apollo-Soyuz was brief compared to the earlier Skylab flights, negotiations and preparations stretched over several years. As far back as the late 1950s, shortly after the launchings of the first artificial Earth satellites, both the Soviet Union and the United States endorsed the principle of international cooperation in space.
In October 1970, representatives of NASA and the Soviet Academy of Sciences met in Moscow for the first of a series of sessions, later held alternately in the Soviet Union and the United States. The conferences determined that a joint space venture might take the form of a rendezvous and docking in Earth orbit.
On May 24, 1972, President Nixon and Alexei Kosygin, chairman of the U.S.S.R. Council of Ministers, signed an agreement in Moscow concerning "cooperation in the exploration and use of outer space for peaceful purposes." The agreement approved the idea for an Apollo-Soyuz test flight.
Preparation began on both sides. Mission managers and astronaut crews were selected. As in previous Apollo and Skylab missions, the U.S. crew consisted of three astronauts; two cosmonauts formed the U.S.S.R. crew. Training began almost immediately.
The American prime, backup, and support crews-nine men in all-visited Star City near Moscow to train with the Soviets. Soviet crews visited the Johnson Space Center for training and flight simulation sessions and toured the launch facilities at KSC. While in Florida they went to Disney World with the U.S. astronauts and rode on one of the main attractions, appropriately called "Space Mountain."
Technical experts from both nations held 44 meetings in the two countries over a three-year period. Scale models and exact duplicates of the different docking mechanisms built by each country were docked and undocked hundreds of times under simulated space conditions.
To accommodate the docking systems and to provide a chamber through which crew members could pass from the atmosphere of one craft to the different atmosphere of the other, an airlock, called the docking module, was designed and built by the United States. Attached to Apollo during most of the mission, it was jettisoned before the spacecraft re-entered Earth's atmosphere. Basically, the docking module was a cylindrical aluminum corridor 1 0 feet, four inches (3.15 meters) long and four feet, eight inches (1.4 meters) wide at its greatest diameter.
Soyuz had a two-gas atmosphere-nitrogen and oxygen-about the same as the atmosphere of Earth at sea level, with a pressure of 14.7 pounds per square inch (1 kilogram per square centimeter). Apollo's atmosphere was pure oxygen with a pressure of 5 pounds per square inch (0.35 kilograms per square centimeter). Before docking, plans called for the Soviets to reduce the atmospheric pressure inside Soyuz to 10 pounds per square inch (0.7 kilograms per square centimeter) in order to shorten the time the crew needed to remain inside the docking module to safely transfer from Soyuz to Apollo, from about two hours to a few minutes.
One major worry was the language barrier. Obviously, successful operations and the safety of the crews demanded speedy, accurate exchanges of information-both in the control centers and in orbit. As part of their training, astronauts and cosmonauts studied each other's language. During the joint phase of the flight, the U.S. crew spoke in Russian and the Soviet crew in English.
A dictionary of common terminology was compiled; translators largely memorized it. Also, a large volume containing joint operating instructions was published and placed aboard each spacecraft. Half of each page was in English; the other half, with the same text, was in Russian.
A unique communications feature for the upcoming mission was the utilization of NASA's ATS-6 (Applications Technology Satellite). Without the satellite, because of their relatively low orbits, the two spacecraft would have been in line-of-sight contact with Earth stations for only about 17 percent of the time. However, with use of the ATS-6 in geostationary orbit, communications between Earth and the manned spacecraft were possible for about half of each 88-minute orbit, and millions of people in many parts of the world were able to see and hear much of the mission.
While the crews and various support personnel pushed ahead with their training for the mission, launch preparations at KSC accelerated during the latter part of 1974 and continued until final launch countdown began on July 11, 1975.
The Saturn IB vehicle had been employed for Earth-orbital Apollo test flights prior to the Moon launches, and served as the launch vehicle for the three manned Skylab missions.
The first stage was removed from its storage "cocoon" in the Vehicle Assembly Building on Nov. 27, and stacked on its mobile launcher in mid-January. The following day the second stage was placed atop the first stage; two days later the instrument unit was added.
Major modifications to the Apollo command/service module for Apollo-Soyuz were extra propellant tanks for the reaction control system, additional equipment to operate the docking module and its docking system, and provisions for experiments. After its arrival, the command/service module underwent testing in the Operations and Checkout Building until early in 1975.
The docking module was mated to its docking system, and the complete unit placed in the spacecraft adapter in mid-February. The adapter originally had been used on Moon missions to house the lunar module until shortly after translunar injection began; for manned Skylab flights, the adapter had been essentially empty.
Mating of the command/service module and the spacecraft adapter took place in late February and early March. On March 9, the launch vehicle was crowned with this assembly. Then the completely assembled Apollo-Saturn IB was moved to Pad B at Launch Complex 39 on March 24.
After the vehicle was mounted atop pedestals at the pad, final preparations began, culminating with the countdown demonstration test which started on June 25 and ended July 3. As scheduled, the final launch countdown started on July 11.
Modifications to the launch pad were minimal. The most visible change was the installation of a new lightning protection system, a fiberglass mast atop the mobile launcher from which the vehicle would be launched. Over this mast a cable was passed to grounding points on each side of the mobile launcher. By providing a point of stroke impact, it kept the mobile launcher and the space vehicle from serving as a current path to the ground. The path provided was separated and insulated from all vital equipment.
Launch was scheduled at a time of day and season of the year with A history of thunderstorm activity (3:50 p.m. EDT, July 15). The launch window pas approximately 10 minutes long; windows on the following four days were slightly less. There would be five opportunities for launch, based upon a maximum mission time of six days for the Soyuz spacecraft and a nominal liftoff of Soyuz at 8:20 a.m. EDT on July 15.
While final hardware preparations moved ahead at KSC and the Cosmodrome at Baykonur, 2,000 miles (3,219 kilometers) southeast of Moscow, the two crews readied themselves.
As one veteran reporter noted about the two crews, Apollo-Soyuz would be a triumph for middle age because all five crew members were over 40.
Thomas Stafford, 44, then a brigadier general in the U.S. Air Force, commanded A On three previous flights, he totaled over 290 hours in space. He was considered the world's leading expert in the two key maneuvers required to join Apollo and Sol rendezvous and docking.
His companions, aboard Apollo were Vance Brand, 44, and Donald "Deke" Slayton, neither of whom had flown in space before.
Slayton, 51, became the oldest person to fly in space at that time. Although one of the original seven astronauts selected in 1959, he was the only one of that group never to have been in space. Chosen to pilot a Mercury mission in 1962, he was replaced and disqualified for space flight status when doctors discovered an irregular movement in his heart muscles. After his heart irregularities stopped, he was restored to flight status in 1972 and subsequently assigned to the Apollo-Soyuz mission.
Commander of the two-man Soyuz crew was Soviet Air Force Col. Alexei A. Leonov, 41, a cosmonaut since 1960. In 1965 he had been the first man to "walk in space." His flight engineer was Valeriy N. Kubasov, 40, who had acted as the flight engineer on the Soyuz 6 mission in 1969. During that flight, he became the first person to weld materials in space under conditions of weightlessness.
The Soyuz spacecraft had completed more than a dozen successful flights in space. Overall, it was smaller than Apollo, and weighed about half as much as the U.S. craft. Extending from opposite sides of Soyuz were two winglike solar panels that converted sunlight to electricity to recharge its batteries. Apollo was powered by fuel cells, eliminating The need for solar panels.
On July 15, 1975, despite the difficulties of language and distance in coordinating the two missions, each was launched within a fraction of a second of its scheduled time. Thus began the 31st manned space flight for the United States, the 27th for the U.S.S.R.
At Baykonur, this Soviet launch was the first ever shown on live television. Another first was the invitation, and attendance, Of U.S. officials to view the liftoff. The U.S. ambassador to the Soviet Union, Walter J. Strossel, was among those watching.
At KSC, the Soviet ambassador to the United States, Anatoly F. Dobrynin, watched with NASA Administrator James Fletcher as Apollo lifted off.
After each spacecraft achieved orbit, a series of complex maneuvers by Apollo brought it to the vicinity of Soyuz. On July 17, the astronauts maneuvered Apollo into formation flight with Soyuz and linked them together. The historic union took place at 12:09 p.m. EDT, above the Atlantic Ocean west of Portugal.
"Docking is complete, Houston," announced Stafford.
"Well done, Tom," came an accented voice via radio from Soyuz.
For the next two days, crew members crawled through the docking module exchanging visits, various mementos, and flight rations. Included in the Russian meal given to the astronauts were borscht, jellied turkey, and black bread. All experiments scheduled for the docked period of the mission were successfully conducted.
On July 19, almost 44 hours after they had initially docked, the two craft separated for about 30 minutes. Then a second docking was conducted to gain further experience. Three hours later they separated for the final time.
For one of two joint experiments to be conducted after docking, Apollo was backed away in a straight line until its circular outline blocked out the brilliant center of the Sun and gave the Soyuz crew a chance to photograph the solar corona. In effect, Apollo created an eclipse of the Sun for Soyuz.
Two days after the final undocking, Soyuz successfully landed in Russia. Its landing, like its launch, was shown live on television for the first time.
The Apollo descent to the Pacific three days later was more eventful. Just minutes before splashdown, the crew noted a yellow gas in the capsule that caused eye irritation and severe coughing. This was not a serious concern at the time since other Apollo crews had reported fumes and odors during re-entry. Compounding the situation, however, the command module flipped upside down upon hitting the water. This, too, had happened on other flights. But, for about five minutes, the astronauts hung upside down in their seats. Stafford finally wriggled free of his seat straps and reached the oxygen masks stored on board. Brand, meanwhile, had fainted. He gained consciousness after about a minute.
The craft was righted by flotation balloons, and the hatch opened to let fresh air in. Then the crew and the capsule were lifted to the deck of the recovery ship, the USS New Orleans. Although the crew seemed comfortable at the welcoming ceremonies, they complained of chest pains during the postflight physical.
Investigators later determined that the crew had failed to activate the Apollo's automatic Earth Landing System. As Apollo bored into the atmosphere, the crew manually activated its parachutes, but failed to turn off the small rocket thrusters that position the capsule before the parachutes open. Thruster cutoff would have occurred automatically if the Earth Landing System had been activated.
One thruster outlet was near the intake through which fresh air was sucked into the capsule during its descent and after splashdown. Thus, the thruster propellant's oxidizer was allowed to enter the spacecraft and the gas the astronauts saw, smelled and inhaled was what had been feared the most by the physicians -- nitrogen tetroxide, a very toxic chemical agent that can be fatal if inhaled in large concentrations.
After 13 days of medical observation in Hawaii each crew member was given a clean bill of health as far as exposure to toxic gas was concerned.
Concern for the health of the crew resurfaced on Aug. 19 when it was announced that Slayton would undergo surgery to explore a spot on his lung. Fortunately, the lesion was benign. Doctors said it had developed before the mission.
When Apollo splashed down, it closed a chapter in the history of America's space program. It was the last flight for Apollo-the vehicle which had carried 45 Americans through space in 15 separate flights over a span of seven years. Its successor, the Space Shuttle, can complete numerous round-trip missions between Earth and Earth orbit.
The era of the Space Shuttle finds many citizens of different nations working together in orbit. Apollo-Soyuz provided a preview of such a scenario.