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Soyuz TM variant In 1986, the USSR introduced a new version of the Soyuz crew vehicle, just a few months after the first piece of the Mir multi-modular space station went into orbit. The latest transport was designated Soyuz TM, where "T" stood for "transport" as in the previous upgrade, and "M" meant "modified."
Known Soyuz TM specifications:
The initial stimulus for the development of what would become the Soyuz-TM variant was the plan to deploy the future Soviet space stations in orbit with an inclination 65 degrees toward the Equator, instead of previously used 51.6 degrees. The orbit tilted further toward the Earth's poles would considerably extend the reach of the station's sensors watching the planet's surface and it also imposed between 330 and 350 kilograms in mass penalties on the Soyuz launch vehicles. To resolve the problem, the developers looked wether it was possible to increase the rocket's capabilities or cut the mass of the spacecraft itself in the next round of upgrades. The latest crew ship upgrade effort was identified as 7K-STM, denoting a modified version of the 7K-ST variant, publicly known as Soyuz-T. In the design documentation, the modified Soyuz retained its index 11F732, but the production vehicles would be started with No. 51, interrupting designations with the 40th series. According to an official Soviet documentary made at the time, the main goal of the TM upgrade was to increase the payload which the spacecraft could deliver to 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 back-up parachute system was borrowed from the Soyuz-T variant and included one braking parachute and the main canopy, which after deployment initially acted as a braking parachute with a partially riffed (folded) canopy. After the release of a special restrictive harness, the main parachute would be fully disriffed (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 with the new Kurs rendezvous system, developed at NII TP organization, which could begin operating in orbit from a distance of 150 kilometers from the station, instead of 25 kilometers for the older Igla system. Also, Kurs did not require the passive target, such as a space station, to constantly point itself at the active vehicle. Kurs also had back-up avionics and electronic diagnostics unit. With the installation of the passive equipment of the new Kurs on Mir, the new rendezvous profile now included a fully automated approach of the transport vehicle from a distance of around 100 kilometers from the station, concluding with a flyaround of the outpost to align the active vehicle with a destination 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 up 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 Zarya communications and direction-finding system was replaced with a more advanced Rassvet (dawn) system developed at MNII RS. Based on the experience with the development of the Lunar Orbital Vehicle, LOK, the Habitation Module of the TM version was equipped with a blister, featuring forward-facing window, which could serve for navigating the manual approach. The previous experience in the development of the Soyuz' engines paved the way to the S5.80 integrated propulsion system (INSIDER CONTENT), which was installed on Soyuz TM. (52) Finally, the spacecraft was equipped with a thruster assembly with segmented propellant and gas stores, which allowed more reliable operation. Soyuz TM reaches launch pad The preliminary design of the Soyuz TM spacecraft was completed in April 1981 and the bulk of working documentation for the vehicle was ready in early 1982. In the same year, NPO Energia began testing mockups and experimental hardware for the TM variant. They included aircraft drop tests, firings of the modified escape rockets and new engines. 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 successfully landed in Kazakhstan within seven kilometers from the projected point. Soyuz TM carried its first crew to Mir in 1987 and continued servicing the station until the end of the project in 2001. The vehicle was also used four times for delivering crews to the International Space Station, before being replaced by the Soyuz TMA variant in 2002. The TM version also became a base for the Progress M series of cargo ships which operated in parallel with the crew vehicle.
Soyuz TM missions:
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