In the early 1970s, with the joint Apollo-Soyuz Test Project, the United States and Soviet Union temporarily set aside their Cold War differences. They chose cooperation over competition as they planned to have two of their spacecraft dock in orbit. This was no simple task, as they faced major technical and communication challenges.
Planning for a U.S.-Soviet Connection in Orbit
The basic plan for the mission was to have an American Apollo Command and Service Module (CSM) rendezvous in orbit with a Soviet Soyuz 7K-TM variant spacecraft. One of their first challenges was determining how the spacecraft would physically connect. Engineers initially considered a new airlock module, The advantages of this would be that it would have enough room to attach communication and power equipment they would need. However, to accomplish this, the nations would have to design, build, and test a totally new component.
Instead, they decided to use a simpler drogue-in-cone docking system. For this, the Soyuz would connect, via latches, with a ring on the Apollo. This would also include eight pyrotechnic bolts they could use as a back-up during undocking.
Soviets Test Components for Apollo-Soyuz Docking Mission
On 2 December 1972, the Soviet Union launched Soyuz-16, a mission to test the docking equipment and procedures for the Apollo-Soyuz Mission. Cosmonauts Anatoly Filipchenko and Nikolai Rukavishnikov launched into orbit on a Soyuz-U rocket carrying their Soyuz 7K-TM No. 73 spacecraft. The rocket lifted off from the Tyuratam test site in Kazakhstan.
Prior to the mission, the Soviets had mounted a test ring on the Soyuz. This was a duplicate of the docking ring on the Apollo CSM. During this six-day orbit, they performed retractions and reengagements of the the docking port on Soyuz with the test ring. They also tested a new color TV transmission system.
Finally, at the end of the mission, they fired the pyrotechnic bolts holding the test ring and released a spring device. This pushed the ring away from the Soyuz 7K-TM. The Soviets later reported that the ring burned up in the atmosphere the next day.
Overcoming Pressures on the Apollo-Soyuz Mission
Along with the mechanical connection, the Americans and Soviets had to account for different cabin pressures in each spacecraft. The CSM normally maintained a cabin pressure of 258 millimeters, and the 7K-TM stayed at 760 millimeters. Engineers had to come up with a solution for this difference when the spacecraft docked in orbit.
For the Apollo-Soyuz mission to be successful, engineers had to compromise on a cabin pressure level that would work for both sides. They settled on a pressure of 414 millimeters. The structure of the CSM structure could not handle pressures higher than that. The Soyuz 7K-TM could not operate much lower than 414 without risking a fire.
The engineers developed procedures for different docking situations. If American Astronauts had to move into the Soviet spacecraft, they would enter an airlock, close the hatch behind them, and raise the pressure to 760. If Soviet Cosmonauts needed to go into the American spacecraft, they would have to pre-breathe oxygen, enter the airlock, and then lower the pressure to 258.
This pre-breathing was similar to what divers do to avoid the bends when ascending from deep depths. The docking had to work in both directions, as one of the purposes of the Apollo Soyuz Mission was to be able to perform future international space rescues.
Communication and Politics Affect Mission Planning
Along with the technical issues, both nations had to overcome communication challenges beyond the obvious language differences.
They also dealt with reluctance from both sides on sharing data due in part to the ongoing political conflicts.
The Americans initially received limited data from the Soviets about life support systems on their spacecraft. Eventually they gained more information during a 1970 trip to the Soviet Union and a report the Soviets sent to the Manned Space Center (MSC), now the Johnson Space Center, in Houston.
U.S. Delegation Goes to Moscow During the Cold War
In October 1970, a delegation of U.S. administrators and technical specialists went to Moscow to meet with Soviet officials and discuss the proposed joint Apollo-Soyuz mission. Before leaving for Moscow, the U.S. representatives received briefings from the State Department, Department of Defense, and Intelligence Services.
Following the trip and after reviewing the document the Soviets sent, the Americans still needed more information for the project. They eventually had to resort to using information that had appeared in the American press in the years leading up to 1972.
Soviets Face Their Own Communication Issues
The Soviets also dealt with communication problems before the Soyuz-16 mission. They originally planned to share flight data with the Americans, so they could track the Soyuz and compare their observations with the Soviets. However, in October, less than two months before the mission, the Soviet government halted information exchanges before the launch. This was due to their policy of only releasing information after a successful launch.
Overcoming Challenges and Achieving Success for Apollo-Soyuz Test Project
Despite technical and political roadblocks, the planning and work on the joint Apollo-Soyuz mission progressed. Engineers in both nations were able to collaborate and prepare their spacecraft to dock in orbit. Their efforts were eventually successful on 17 July 1975 when an Apollo Command and Service Module docked with a Soviet Soyuz capsule while in orbit.
It was the first international partnership is space, and especially amazing as it involved the two rival Cold War superpowers.
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