The Partnership: A History of the Apollo-Soyuz Test Project|
A NASA inspector observes mating of American Docking Systems 4 and 5 on the horizontal test fixture at Rockwell International factory in Downey, California.
V. S. Syromyatnikov, R. D. White, E. N. Harrin, and Professor Bushuyev, in the latter's Moscow office, discuss the need to change the alignment pin and socket in the American docking system on the telephone with Glynn Lunney in Houston, November 1974. In December Ray Larson and C. E. Kindelberger of Rockwell International fly to Moscow and install the modified alignment pin.
...Holman, who conducted the analysis, were unlikely to occur in space. White also opposed changing the flight hardware at that very late date because the alterations were likely to create real problems while attempting to solve a possible one. Both sides had agreed that following the qualifications tests the design of the "interfacing hardware" (i.e., the docking system) would be frozen. No further changes should be made.
Nevertheless, Lunney, in consultation with NASA Headquarters and Rockwell, decided that the pins and sockets had to be altered. The agency saw the following hazard:
The potential pin and socket binding problem of both docking systems can lead to the stall of the guide ring drive in an active USA docking which can produce an overload in one of the three cables retracting the ring, which in  turn can lead to its failure. Failure of a guide ring retract cable will result in the inability to further use the US docking systems either in the active or passive mode and, as a consequence, the failure to complete the basic purpose of the flight.18
As a consequence, Lunney telexed Professor Bushuyev and explained the problem to him.19 (See box below.)
While Rockwell manufactured the new pins and sockets, Bob White discussed the problem with V. S. Syromyatnikov and Professor Bushuyev. White believed that "Vladimir was sympathetic to our problem and agreed that the change was necessary."20 Without Syromyatnikov's understanding, it would have been very difficult to sell Bushuyev on the alteration. The only constraint the Soviets placed upon the Americans was that the U.S.S.R. pins and sockets would remain unchanged.
The USSR docking system guide pin and socket are installed from the back side of the structural ring front flange. In addition, the socket is installed before the docking system differential drive assembly is installed. Therefore, the socket removal and installation requires substantial docking system disassembly and readjustment of the kinematic coupling of six attenuator rods with the differential drive assembly which is a laborious operation.
Considering that all three USSR flight docking systems are assembled and in readiness for the Preflight Mate Test . . . the docking system rework is impossible without a review of the schedule of preparing the spacecraft for flight and launch date itself.21
White and Syromyatnikov agreed that it would be sufficient to change only the U.S. pin and socket. This understanding was officially recognized by Lunney and V. A. Timchenko in their telephone conversation of 19 November.22
To accomplish the modification in the shortest time, White and Syromyatnikov modified the test plans and worked out procedures to test the new components while waiting for Arnold D. Aldrich, Lunney's Deputy, and Ray F. Larson, Rockwell's command and service module manager, to arrive. Once in Moscow, Aldrich worked with the Soviets to draft minutes covering the changes and establishing a test plan for an additional examination of the modified system in January 1975 at Downey. Ray Larson and Earl Holman worked with the "Dirty Dozen" to complete the changes. The American Group 3 delegation divided into two groups; the "Mod Squad" made the alterations on one docking system, while the "Test Team" continued testing the other system. Whereas Rockwell had predicted that it would take four days to complete the modifications, the specialists actually needed only 4 to 5 hours for each docking system. Total time lost...
PROFESSOR K. BUSHUYEV
ACADEMY OF SCIENCES OF THE USSR
14 LENINSKI PR MOSCOW, V-71, USSR
UNCLAS IN REPLY TO PA-LSN-21 3-74
MR. ALDRICH MENTIONED TO YOU DURING THE NOVEMBER 5 TELECON THAT WE WERE SOMEWHAT CONCERNED ABOUT THE POSSIBILITY THAT UNDER CERTAIN CONDITIONS IT MIGHT BE POSSIBLE FOR THE CURRENT DOCKING SYSTEM ALIGNMENT PIN AND SOCKET DESIGN TO BIND AND PREVENT FINAL RETRACTION. WE HAVE JUST COMPLETED A SERIES OF TESTS AND HAVE CONCLUDED THAT BINDING OF A U.S. PIN IN A U.S. SOCKET CAN OCCUR UNDER THE FOLLOWING CONDITIONS: A SIDE LOAD ON THE PIN ON THE ORDER OF 300 LBS [136 kg] OR GREATER WILL CAUSE BINDING WHEN A HESITATION AND RETRACTION OF THE PIN FROM THE SOCKET OF 0.020 INCHES [0.5 mm] OCCURS JUST AS THE PIN IS ENTERING THE CYLINDRICAL PORTION OF THE SOCKET. THE HESITATION AND REENTERING OF THE PIN CAUSES THE SOCKET TO ROTATE TO THE HARD STOP POSITION.
OUR ANALYSIS INDICATES THAT PREDICTED MISALIGNMENTS AND THERMAL CONDITIONS COULD PRODUCE WORST CASE IN-FLIGHT SIDE LOADS OF 250-450 LBS [113-204 kg]. WE ALSO FEEL THAT THE DYNAMIC ENVIRONMENT IS SUCH THAT A SLIGHT HESITATION AND RETRACTION OF THE PIN DURING DOCKING SYSTEM RETRACTION IS POSSIBLE, AS ARE MANY OTHER DYNAMIC EFFECTS.
BASED UPON THESE TESTS, WE ARE INCREASINGLY CONCERNED THAT THE CURRENT PIN AND SOCKET DESIGN IS INADEQUATE, AND ARE SERIOUSLY CONSIDERING THE POSSIBILITY OF CHANGING THE U.S. HARDWARE CURRENTLY IN MOSCOW. WE ARE IN THE PROCESS OF BUILDING THE PARTS NECESSARY TO CHANGE BOTH THE U.S. PIN AND THE U.S. SOCKET ON DOCKING SYSTEMS 5 AND 7. THIS HARDWARE WILL BE BROUGHT TO MOSCOW BY MR. ALDRICH ON NOVEMBER 18, ALONG WITH INSTALLATION TOOLING AND PROCEDURES.
THE OPTIMUM SOLUTION TO THE PROBLEM, HOWEVER, MAY BE TO REPLACE BOTH THE U.S. AND U.S.S.R. SOCKETS WITH A NEW NON-ROTATING SOCKET WHICH HAS A SHORTENED CYLINDRICAL SECTION, AND NOT CHANGE THE U.S. PIN. FOR THIS REASON, WE RECOMMEND THAT YOU PROCEED TO FABRICATE A NEW SOCKET. THIS WOULD ALLOW YOU TO BE PREPARED SHOULD WE DECIDE A CHANGE IS REQUIRED. MR. WHITE HAD THE PROPOSED SOCKET DESIGN. I HAVE ASKED MR. WHITE TO DISCUSS THIS PROBLEM WITH DR. SYROMYATNIKOV, AND WOULD APPRECIATE ANY INFORMATION OR TEST HISTORY WHICH YOU HAVE THAT MAY RELATE TO THIS PROBLEM. THESE DATA SHOULD BE PROVIDED TO MR. WHITE.
I PLAN TO TALK TO MR WHITE AGAIN ON TUESDAY, NOVEMBER 12, AT 5:00 PM MOSCOW TIME
I BELIEVE THAT WE MUST REACH A FINAL DECISION ON THIS QUESTION AT OUR NOVEMBER 19 TELECON
PLEASE PROVIDE MR. WHITE WITH A COPY OF THIS MESSAGE.
GLYNN S LUNNEY
APOLLO SPACECRAFT PROGRAM
NOV 8 1974
 ...from the compatibility test was two days. Looking back, Bob White commented, "It's amazing how much work you can do when you have no other choice but to get it done." The Soviets were astounded, too!23 After the Moscow trials, joint pin and socket interaction verification tests using a Soviet and American docking system were conducted 16- 23 January 1975 at Downey. This exercise confirmed that the alterations made to the American pin and socket eliminated any possibility of friction lock. Over a two-year period, Working Group 3 had conducted six major joint tests involving over thirty-three weeks of activity.24
17. "Apollo Soyuz Test Project, Flight Readiness Review, May 1975," 25 May 1975, pp. WG-3-21 to WG-3-29; interview, White-Ezell, 23 Mar. 1976; White to Glynn S. Lunney, memo, "Debriefing Notes Regarding Docking Systems Preflight Compatibility Verification in Moscow," 13 Mar. 1975; and Ray F. Larson to James M. Grimwood, "Contractor Comments on Edward C. Ezell's Manuscript of the ASTP Narrative History for Review and Comment (NAS9-13972)," 13 Jan. 1976.
22. "Minutes of the ASTP Telephone Conversation [U.S. Minutes]," 19 Nov. 1974; and "Report on the Telephone Conversation of November 19, 1974 between Drs. Timchenko and Lunney [U.S.S.R. Minutes]," [n.d.].
24. "ASTP Meeting
Minutes, Joint Meeting of Working Group 3," 16 Jan.-12 Feb. 1975;
"ASTP Report of USA/USSR Docking System Alignment Pin and Socket
Verification Test," USA WG3-042, 27 Jan. 1975; and White to Grimwood,
memo, "Comments on E. C. Ezell's Draft Manuscript of the ASTP
History," 6 Jan. 1976. Also see V. S. Syromyatnikov, "Stikovka - eto
uzhe sotrudnichestvo" [To dock is to cooperate], in Soyuz i Apollon, pp.
116-148. The technical explanations covering the American and Soviet
docking systems are very elaborate, with considerable effort being
made to use layman's terminology. Syromyatnikov points out that,
while the Soviet system, its design, technology, and construction
never once caused any problems in manufacture, testing, or the flight
itself, the American docking system, "a copy of an existing Soviet
design," was a cause for concern on many occasions. "American
technology just was not sufficiently developed" to build a system
better than that.