In April 1970 NASA Administrator Thomas O. Paine suggested, in an informal meeting with Russian academician Anatoli Blagonravov in New York, that the two nations cooperate on astronaut safety, including compatible docking equipment on space stations and spacecraft to permit rescue operations in space emergencies.

Engineer Caldwell Johnson proposed a ring and cone system during a meeting in Moscow during October 1970.
Boris N. Petrov rejected the simple adaptation of Apollo and Soyuz as a "space stunt" and had proposed developing a universal docking mechanism, Johnson suggested that the Manned Spacecraft Center (MSC) draw up a "design specifically adequate to requirements of a particular CSM/Salyut mission, the design being representative only of the fundamental form and function of docking gear satisfying the requirements for compatible docking system for future spacecraft."

During a meeting in Houston during June 1971, Soviet docking specialist Valentin N. Bobkov indicated that the Soviets also favored some version of the double ring and cone.
Bobkov illustrated through sketches that the overall diameter of the docking system could not exceed 1.3 meters, because any larger system would require a change in the launch shroud.
When Johnson raised the question of altering the shroud, the Soviets stressed the major impact that such a modification would have.
In addition to having to design a new shroud, they would have to test out the launch aerodynamics of the altered hardware.
The Americans had hoped to argue for a larger tunnel, but such a change appeared to be too great for their counterparts.

After the June meetings, Johnson had put Bill Creasy and his mechanical designers to work on the preliminary design of a docking mechanism.
By the time the NASA delegation left for Moscow, Creasy's crew had designed and built a 1-meter double ring and cone docking system that had four guide fingers and attenuators on both rings, so either half could be active or passive during docking.
The Structures and Mechanics Laboratory at MSC made 16-millimeter movies demonstrating this system in action, which Johnson took to Moscow in November, along with a booklet describing the system and a model of the capture latches.
To Johnson's surprise, Vladimir Syromyatnikov had been working on a variation of NASA's ring and cone concept since the previous October.
Instead of the four guide fingers in the American proposal, Syromyatnikov suggested three, and in lieu of hydraulic shock-absorbers, he proposed electromechanical attenuators.
In essence, the Soviets had accepted the idea of using a set of intermeshing fingers to guide the two halves of the docking gear from the point of initial contact to capture.
The concept of using shock absorbing attenuators on the active spacecraft's capture ring to buffer the impact of two spacecraft coming together was also acceptable.
Both groups of engineers planned to retract the active half of the docking gear using an electrically powered winch to reel in a cable.
Once retracted, structural or body latches would be engaged to lock the two ships together.
Three basic issues had to be resolved — the number of guides, the type of attenuators, and the type of structural latches — before the design of a universal system could proceed.

Johnson, Creasy, and the other engineers in the Spacecraft Design Division had wanted to use four guides because they believed that it provided the best geometry when using hydraulic attenuators.
As Bill Creasy subsequently explained it, the most probable failure situation using hydraulic attenuators would be a leak that would cause one shock absorber to collapse on impact.
A study of various combinations had led the MSC specialists to conclude that four guides and eight shock absorbers was the optimum design.
Creasy pointed out too that the most likely trouble with an electromechanical system would be a freeze-up or binding of one of the pairs of attenuators.
Thus, the Soviets had sought to minimize the number of pairs in their system for the same reason that the Americans had prefe
In April 1970 NASA Administrator Thomas O. Paine suggested, in an informal meeting with Russian academician Anatoli Blagonravov in New York, that the two nations cooperate on astronaut safety, including compatible docking equipment on space stations and spacecraft to permit rescue operations in space emergencies.
Engineer Caldwell Johnson proposed a ring and cone system during a meeting in Moscow during October 1970. Boris N. Petrov rejected the simple adaptation of Apollo and Soyuz as a "space stunt" and had proposed developing a universal docking mechanism, Johnson suggested that the Manned Spacecraft Center (MSC) draw up a "design specifically adequate to requirements of a particular CSM/Salyut mission, the design being representative only of the fundamental form and function of docking gear satisfying the requirements for compatible docking system for future spacecraft."
During a meeting in Houston during June 1971, Soviet docking specialist Valentin N. Bobkov indicated that the Soviets also favored some version of the double ring and cone. Bobkov illustrated through sketches that the overall diameter of the docking system could not exceed 1.3 meters, because any larger system would require a change in the launch shroud. When Johnson raised the question of altering the shroud, the Soviets stressed the major impact that such a modification would have. In addition to having to design a new shroud, they would have to test out the launch aerodynamics of the altered hardware. The Americans had hoped to argue for a larger tunnel, but such a change appeared to be too great for their counterparts.
After the June meetings, Johnson had put Bill Creasy and his mechanical designers to work on the preliminary design of a docking mechanism. By the time the NASA delegation left for Moscow, Creasy's crew had designed and built a 1-meter double ring and cone docking system that had four guide fingers and attenuators on both rings, so either half could be active or passive during docking. The Structures and Mechanics Laboratory at MSC made 16-millimeter movies demonstrating this system in action, which Johnson took to Moscow in November, along with a booklet describing the system and a model of the capture latches. To Johnson's surprise, Vladimir Syromyatnikov had been working on a variation of NASA's ring and cone concept since the previous October. Instead of the four guide fingers in the American proposal, Syromyatnikov suggested three, and in lieu of hydraulic shock-absorbers, he proposed electromechanical attenuators. In essence, the Soviets had accepted the idea of using a set of intermeshing fingers to guide the two halves of the docking gear from the point of initial contact to capture. The concept of using shock absorbing attenuators on the active spacecraft's capture ring to buffer the impact of two spacecraft coming together was also acceptable. Both groups of engineers planned to retract the active half of the docking gear using an electrically powered winch to reel in a cable. Once retracted, structural or body latches would be engaged to lock the two ships together. Three basic issues had to be resolved — the number of guides, the type of attenuators, and the type of structural latches — before the design of a universal system could proceed.
Johnson, Creasy, and the other engineers in the Spacecraft Design Division had wanted to use four guides because they believed that it provided the best geometry when using hydraulic attenuators. As Bill Creasy subsequently explained it, the most probable failure situation using hydraulic attenuators would be a leak that would cause one shock absorber to collapse on impact. A study of various combinations had led the MSC specialists to conclude that four guides and eight shock absorbers was the optimum design. Creasy pointed out too that the most likely trouble with an electromechanical system would be a freeze-up or binding of one of the pairs of attenuators. Thus, the Soviets had sought to minimize the number of pairs in their system for the same reason that the Americans had prefe
Androgynous Peripheral Attach System