Low and Frutkin arrived in the U.S.S.R. on the evening of 14 October. Early the next morning, Low met with Lunney, who told him that the work had gone extremely well these past two weeks and that much had been accomplished. The Americans left the Rossiya Hotel and went to the Presidium of the Soviet Academy of Sciences where the Mid-Term Review would be held. That day the teams were kept especially busy with reports to Low and Petrov. After Lunney and Bushuyev told the chairmen that all technical aspects of the program were on schedule, a spokesman from each Working Group presented a detailed schedule of activities and statement of progress in terms of those schedules. Notebooks of Vu-graphs had been prepared in both languages so that all present* could follow the proceedings. R. H. Dietz recalled later that Low appeared eager to determine the exact status of each group's work. His questions were searching and detailed. Low did not want any problems to appear unexpectedly, and he was taking a strong personal interest to demonstrate to all involved that NASA's top management expected ASTP to succeed.7
The Technical Directors also reported on a number of important decisions that had been reached during October. Lunney and Bushuyev had agreed to reciprocal participation of specialists as observers during the life support system tests in Moscow and Houston, to joint docking seal tests, and to the participation of American specialists in the pre-flight checkout of the VHF/AM equipment at the Soviet launch site. These and other understandings reached made Low and Lunney more confident. Still, they pursued  the four discussion topics that had prompted Low's request for the review in the first place.
Project documentation was discussed during the main meetings, during executive sessions, and in private between Low and Petrov. The Soviets had made considerable progress in catching up in all areas of documentation, but Lunney was still concerned that as time grew shorter there would be less time to prepare new documents. Bushuyev believed that the solution to the difficulty was better forecasting of documentation needs. Low and Lunney agreed but added that this was "not the complete solution because we [could] not possibly foresee all problem areas." Petrov then indicated that he understood Low's point and promised to keep an eye on the situation personally.8
Low also received the information the Americans had sought about Soyuz 11. During the course of the technical sessions preceding the review, Professor Bushuyev had made a detailed presentation about the failure - post-flight investigation, experimental reenactment of the failure, and steps taken to make certain that it could not recur. According to those present, the release of this information was a personal triumph for Bushuyev and his team since they apparently had to convince many people in the U.S.S.R. that the Americans needed to know all the details. The highly favorable opinion the Americans held of Bushuyev as a tough-minded negotiator and strong-willed manager was reinforced by his report.
The fatal cabin depressurization occurred when a "breathing ventilation valve"** located in the interface ring between the orbital module and the descent module opened inadvertently during the downward path of the descent vehicle, Bushuyev said. At approximately 723 seconds after retrofire, the 12 Soyuz pyro-cartridges fired simultaneously instead of sequentially to separate the two modules. The force of the discharge caused the internal mechanism of the pressure equalization valve to release a seal that was usually discarded pyrotechnically much later to adjust the cabin pressure automatically. When the valve opened at a height of 168 kilometers, the gradual but steady loss of pressure was fatal to the crew within about 30 seconds. By 935 seconds after retrofire, the cabin pressure had dropped to zero and remained there until 1,640 seconds when the pressure began to increase as the ship entered the upper reaches of the atmosphere.
The extent of tissue damage to the bodies of the cosmonauts caused by the boiling of the blood during the 700 seconds they were exposed to the vacuum could have been misinterpreted initially as being the result of a more catastrophic and instantaneous decompression. Only through analysis of the  telemetry records of the attitude control system thruster firings that had been made to counteract the force of the escaping gases and through the pyrotechnic powder traces found in the throat of the pressure equalization valve, were Soviet specialists able to determine that the valve had malfunctioned and had been the sole cause of the deaths.9
Further information presented by the Soviets on the valve and seal failure cleared up the "mystery" of Soyuz 11. Several factors had led to the confusion that surrounded this topic. First, early reports from the Soviets had indicated that the problem was one associated with the spacecraft's germetizatsyia, which could be translated to mean either the failing of a seal or the loss of air tightness. Thus the Americans were unable to grasp exactly what had happened. Second, the U.S. team thought they had understood I. V. Lavrov's private remarks to Ed Smylie in December 1971 to mean that the problem lay with the pressure equalization valve, but other Soviet reports had indicated that the trouble started in the seals that guaranteed the hermeticity of the hatch between the orbital module and the descent vehicle. That latter explanation had been given to American reporters by cosmonaut Shatalov as late as June 1973 when they visited Star City.10 Bushuyev's explanation ended the speculation, especially since Houston's environmental control experts could analytically verify the information given them as entirely consistent with the telemetry data reported by the Soviets.
American specialists could also tell Lunney that, as they had thought all along, the problem was not one that could pose a real threat to the safety of the crews during the docked phase of ASTP.11 Nevertheless, this presentation on Soyuz 11 and the fact that the Professor had been able to release the exact details, even though it did not immediately affect the safety of the American crew, was an important step forward in forging a partnership. Both sides had to establish faith in the other's hardware and believe that it was safe. The Soviets had opened up and talked about an extremely painful subject. It had taken two years for them to do so, but the resulting level of candor, coming as it did at this crucial Mid-Term Review, indicated that both sides were reaching the level of trust necessary to build a genuine space partnership.
Bushuyev also told the Americans that once the problem was recognized and verified experimentally, the Soviet designers had modified their hardware. They had tested the altered system in two Cosmos flights - Cosmos 496, flown 26 June-2 July 1972, and Cosmos 573, flown 15-17 June 1973. The results of these flights had given them confidence in their solution to the problem, and on 29 September 1973, Lt. Col. Vasily Grigoryevich Lazarev, a test pilot and physician, and Oleg Grigoryevich Makarov, a civilian spacecraft engineer, completed a two-day test flight aboard Soyuz 12. Soviet reports indicated that the cosmonauts had worn  space suits during launch and reentry, and beginning with this flight, two-man crews would become standard for Soyuz so there would be room to store suits.12 During October, the Soviets reaffirmed their plans to fly two or three manned Soyuz flights in 1974, and they suggested that these ASTP-related missions would fly in the configuration planned for the joint exercise.13
During their executive session, Low told Petrov that he greatly appreciated their report on Soyuz 11 and asked him about those additional failures that had been reported by the Western press during the summer of 1973. Petrov told Low that Salyut 2 was an updated version of the Soviet space station and because of the changes in the design there had been no plans to send men to occupy it. He said further that the 3 April-28 May flight had been designed to test the automatic control system; there was no need to have a crew board the station. While this might have seemed strange to the Americans, the Soviets seemed to rely more heavily on test flights, as opposed to NASA's use of earth-based simulations. On the subject of Cosmos 557, which had been launched on 11 May, Petrov stated that this flight was not related to the manned space flight program.
* Americans participating in the review included Low, Frutkin, Lee, Lunney, M. P. Frank, R. H. Dietz, R. E. Smylie, T. P. Stafford, and E. A. Cernan. Soviets in attendance included Petrov, Bushuyev, Vereshchetin, Abduyevski, A. S. Yeliseyev, I. P. Rumyantsev, A. A. Leonov, V. A. Timchenko, V. P. Legostayev, V. S. Syromyatnikov, B. V. Nikitin, Ye. N. Galin, I. V. Lavrov, and Yu. V. Zonov.
** This valve combined the functions of the Apollo pressure equalization valve and the landing ventilation valve.
7. Low, "Visit to Moscow, October 14-19, 1973," Dec. 1973; and interview (via telephone), Reinhold H. Dietz-Ezell, 18 Feb. 1976.
8. Low, "Visit to Moscow, October 14-19, 1973," Dec. 1973; and ASTP notebook, kept by Leonard S. Nicholson, for 1973.
9. Low, "Visit to Moscow, October 14-19, 1973," Dec. 1973; interview, Walter W. Guy-Ezell, 12 Sept. 1975; Thomas O'Toole, "Valve Mishap Blamed for Soyuz Deaths," Washington Post, 29 Oct. 1973; and John F. Yardley to Low, memo, "Soyuz 11 Failure," 3 Mar. 1975.
10. Donald C. Winston, "Soviet Space Center Being Expanded," Aviation Week & Space Technology, 25 June 1973, p. 18; and "Soviet Space: A Visit to Star City," Time, 9 July 1973, pp. 44 and 47.
11. Interview, Guy-Ezell, 12 Sept. 1975.
12. NASA, JSC, "Apollo Soyuz Test Project Presentation to Manned Space Flight Subcommittee Staff," 15 Nov. 1973; "2-Day Soviet Flight," Facts on File 33 (30 Sept.-6 Oct. 1973): 814-815; Theodore Shabad, "Soviet Puts Soyuz 12, with 2 Aboard into Earth Orbit," New York Times, 28 Sept. 1973; and Murray Seeger, "Soviet Union Launches 2-Man Space Mission," Los Angeles Times, 28 Sept. 1973. To correct the problem encountered on Soyuz 11, the Soviets redesigned the valve and seal, improved the manual valve closing so that it took fewer turns of the handle to close it, reduced the power of the pyrotechnic bolts and replaced half of them with pyrotechnic/gas actuated latches, and provided for the crewmen to reenter in pressure suits.
13. Low, "Visit to
Moscow, October 14-19, 1973," Dec. 1973.