Soyuz TM-1 Spacecraft Series

By Marcia S. Smith, Formerly with the, Science Policy Research Division of the Library of Congress, Congressional Research Service

1971-1975/1976-1980

II. THE SOYUZ PROGRAM

Mir 1986 Activities

SOYUZ TM: AUTOMATED TEST OF A NEW VERSION OF SOYUZ

For Mir, the Soviets introduced another new version of the Soyuz spacecraft, this one designated Soyuz TM (for Soyuz Transport-Modified). 111 As has been true with previous design changes to spacecraft intended for use with crews, the Soviets tested it first in an automated mode. Its launch had been expected since the begin­ ning of the Soyuz T-15 mission when it was announced that T-15 was the last of its series and would soon be replaced be a new model.

Soyuz TM was launched on May 21, 1986 at 12:22 MT. Its initial orbit was 240 x 200 km, 88.6 minutes, 51.6 degrees. Soyuz TM docked at Mir's forward port at 14:12 MT on May 23 (Progress 26 was at the aft port). Soyuz TM undocked from Mir on May 29 at 13:23 MT after only a brief stay in orbit. It landed the next day, but no specific time was given by the Soviets.

The new vehicle weighs 7,070 kg, is 6.98 meters long, has a diam­ eter of 2.72 meters, a solar panel span of 10.6 meters, and a reentry mass of 3,000 kg. It can carry more into orbit, and return more to Earth. On May 23, 1986, Cosmonaut Valeriy Ryumin discussed the major differences between Soyuz TM and Soyuz T, 112 and other de­tails have since become available, particularly in an August 5, 1987 Pravda article. 113 Unless otherwise noted, all the information in this section is from those two sources.

Docking System Changes

The most significant change is new approach and docking sys­ tems which allow the spacecraft to dock with Mir without requir­ ing Mir to maneuver, thus saving fuel on the space station; the sta­tion's orientation no longer matters. The spacecraft approaches the space station and, depending upon which docking port it is assigned to, flies around the station to that port. 114 The new system is called Kurs (Course), replacing the old Igla (Needle) system. The Soyuz TM radar makes contact with station at 200 km; lock on begins when the ship is 20-30 km from the station. 115

Parachute and Landing Systems

Soyuz TM can carry 250 kg more payload into orbit and return 50- 60 kg more than the Soyuz T because of a new parachute system that uses lighter and stronger materials, 116 and it uses a slightly improved version of the standard launch vehicle. The para­ chute shroud lines are made of a new synthetic fiber.

At the time of the Soyuz TM-2 landing in July 1987, the Soviets reported that it had systems for more accurate landings. According to V. Pouchkayev, head of the Flight Control Center's ballistics unit, the braking engine operates for precisely 208 seconds, reduc­ ing the ship's speed by 115.2 meters per second, and "Even if an error of 5 meters per second occurs, the reentry vehicle will land within a few hundred kilometers of the specified point." He added that a special system had been developed for "placing a vehicle into the specified landing area if an error of this magnitude occurs," but it would increase the g-load on the crew from 3 to 11.H7 The spacecraft has an improved altimeter for firing the landing engines.

Other Onboard Systems

The spacecraft has modernized power supply units. It has an im­ proved orientation system, and uses improved onboard computers that allow procedures to be executed manually or automatically. The level of diagnosis that can be done by the onboard computers has been heightened. Main electrical systems are triple redundant.

Other Changes

Other changes include a new communications system (for relay­ ing communications through Luch, just like Mir itself). Monitoring by the Kettering Group has shown that the pulse duration modu­ lated short wave transmissions on 20.008 MHz is no longer used. 118 The spacecraft also has a life support system with sufficient re­ serves that descent could be accomplished if the oxygen supply system failed. Soyuz TM has a more reliable engine that uses a me­ tallic membrane to separate propellants from the gas used to pres­surize the tanks. Elastic membranes had been used in the past, and after a time, gases could leak through and degrade engine perform­ ance. The interior has been improved: the design of the seat has been unified and areas are set aside for stowing gear.

References:

1. SOVIET SPACE PROGRAMS: 1981-87, PILOTED SPACE ACTIVITIES, LAUNCH VEHICLES, LAUNCH SITES, AND TRACKING SUPPORT PREPARED AT THE REQUEST OF Hon. ERNEST F. HOLLINGS, Chairman, COMMITTEE ON COMMERCE, SCIENCE, AND TRANSPORTATION, UNITED STATES SENATE, Part 1, MAY 1988, printed for the use of the Committee on Commerce, Science, and Transportation, U.S. GOVERNMENT PRINTING OFFICE, WASHINGTON, D.C. 1988

110. TASS, 1213 GMT, July 14, 1986.

111. Moscow Domestic Service, 1600 GMT, February 6, 1987.

112. TASS, 1744 GMT, May 23, 1986.

113 Pravda, August 5, 1987, p. 3.

114.. Moscow Television Service, 1030 GMT, May 23, 1986.

115 Izvestiya, February 9, 1987, p. 1.

116 The 250 kg figure is from the Pravda article. Ryumin had said it could carry an extra 200 kg-

117 Sovetskaya Rossiya, July 31, 1987, p. 1.

118 Personal communication.