Soyuz TM variant
In mid-1980s, Soviet engineers at NPO Energia worked on another Soyuz upgrade, which became known as Soyuz TM, where "T" stood for "transport" as in the previous upgrade, and "M" meant "modified."
According to an official Soviet documentary made at the time, the main goal of the TM upgrade was to increase the payload that the spacecraft delivers into orbit and to improve reliability and safety of its systems.
The main weight-saving measure, which allowed to cut the mass of the spacecraft by some 300 kilograms, was the introduction of the new parachute system made of domestically produced synthetic materials and lighter caprone canvas segments.
The backup parachute system was borrowed from the Soyuz-T spacecraft and included one braking parachute and the main canopy, which after deployment initially acted as braking parachute with partially folded canopy. After the release of a special restrictive harness, the main parachute would be fully inflated.
The Soyuz TM also got a redesigned Emergency Escape System, SAS, which allowed to increase its payload by another 60 kilograms.
The TM variant was also equipped the upgraded Kurs rendezvous radio system, which could begin operating from a distance of 150 kilometers from the station, instead of 25 kilometers for the previous version of the system. The new Kurs also did not require the passive target, such as a space station, to constantly point itself toward the active vehicle. With the installation of the passive equipment of the new Kurs on Mir, the new rendezvous routine now included the approach of the Soyuz to the station, followed by a flyaround of the outpost to align the active vehicle with a chosen docking port. However, the upgraded Kurs ended up to be heavier than its predecessor, consuming some of the mass savings provided by other upgrades. As a result, the net gain for the payload aboard Soyuz TM ended to be around 100 kilograms, instead of expected 300 kilograms.
The motion control system and radio communication system aboard Soyuz TM were also modified.
The spacecraft was also equipped with a thruster assembly with segmented propellant and gas stores, which allowed more reliable operation.
Soyuz TM reaches launch pad
Soyuz TM was launched for the first time without crew on May 21, 1986, and after a two-day autonomous flight, made a successful rendezvous, a flyaround and docked with the transfer compartment on the Core Module on May 23, 1986. During a four-day stay at the station, Soyuz TM's propulsion system was used to boost Mir's orbit. The new transport ship then undocked from the station and its Descent Module successful landed in Kazakhstan within seven kilometers from the projected point.
Soyuz TM carried its first crew to Mir in 1987.
The TM version also became a base for the Progress M series of cargo carriers.
Soyuz at a glance (TM version):
The Soyuz TM-32 spacecraft photographed from the side of the instrument module by the crew of the International Space Station in October 2001. Credit: NASA
The Soyuz TMA-2 spacecraft docked to the International Space Station. Credit: NASA