Soyuz Mods Include Bigger Seats, Softer Landing
James Oberg
October 15, 2002
For ‘Space News’

Modifications to the new-model Soyuz called ‘TMA’, to be flown for the first time on October 28, are mainly in its ability to carry larger crewmembers. But there also are a large number of smaller changes that enhance the flying and safety characteristics of the vehicle.

The assembly sequence for the International space Station lists this as Mission 5S, the fifth Soyuz docking since the first permanent crew arrived on November 1, 2000. Replacement vehicles have been launched at six month intervals to provide the three-person permanent crew with an escape vehicle.

On internal RSC-Energia documents, this new vehicle is designated Soyuz-211. It is not yet clear whether the vehicle will be designated ‘Soyuz TMA’ or Soyuz ‘TMA-1’ once it is launched, although an earlier intention to continue the TM sequence unchanged has apparently been changed.

The additional letter designation “A” refers to the anthropomorphic, or body size and shape, improvements. Maximum crewmember height has been increased from 182 cm (71.6 inches) to 190 cm (74.8 inches), and maximum weight from 85 kg (187 lbs) to 95 kg (209 lbs).

This design change, pushed by NASA..... opens Soyuz to more than 90% of current American astronauts. Formerly, fewer than 50% could meet the stringent limits. [expand]

To accommodate these improvements, engineers at the Energia Rocket and Space Corporation in Korolev implemented significant changes to the crew couches, cabin equipment layout, and the pre-touchdown ‘soft landing system’.

A slight increase in total vehicle weight has also required the development of an improved version of the Soyuz booster vehicle manufactured at the Progress plant in Samara. Maximum spacecraft mass will now be 7220 kg. The new booster version, called ‘Soyuz FG’, has already been used in three Progress launches this year.

Although the sum of all these spacecraft changes is significant enough to warrant a new vehicle designator, Russian space officials have concluded that they are not so revolutionary as to require an unmanned flight test as had been the case for every previous generation transition. NASA officials reviewed this decision in Houston on October 1 and approved it.

The old ‘Kazbak-U’ strut-mounted seats have been replaced with ‘Kazbek-UM’ seats and new shock absorbers. The longer accommodations in all three seats has required the addition of “a slotted area” in the Soyuz hull at the feet of the left and right couches. This in turn required a redesign of hull load-bearing structure and external thermal control protection materials.

Some cabin equipment was relocated or redesigned. The old ‘Neptune-M’ control panel has been replaced by the ‘Neptune-ME’, which now contains built-in processors and two CRT displays. Its position over the crewmembers’ legs has also been raised. The approach and docking hand controllers, previously hard-mounted adjacent to the center seat, will now be on deployable booms that are stowed beneath the Neptune panel when not in use. The cabin air supply system has been relocated and the old oxygen tank replaced, while other cabin plumbing and cables have been re-routed.

The Soyuz flight computer ‘KS020’ is being upgraded to model KS-020M, with modified software. According to a briefing given by RSC-Energia officials to NASA on October 3, the new computer increases control accuracy during entry and adds the capability to display navigation data. Generation of this data has been upgraded by the replacement of the KI-68-1 single-axis accelerometer with a six-axis accelerometer called the ‘BILU’.

The old ‘Mir-3’ and ‘Gnom’ tape recorders have been supplanted by a new data recording system called the SZI. It records both data and voice. Other minor equipment relocations and redesigns have also been performed.

Two of the six soft-landing engines at the base of the Descent Module have been replaced with upgraded engines, and the gamma-ray altimeter ‘Kaktus-1V’ has been replaced with an upgraded design called ‘Kaktus-2V’. The avionics assembly that receives altimeter data and fires the soft-landing engines just prior to touchdown has also been totally redesigned. As a result, nominal landing velocity has been reduced by 40-50%.

The only change in the Orbital Module is to delete some dehumidifer equipment now installed in the Descent Module. According to RSC-Energia, no changes at all were made to the Soyuz’s Equipment Module.

The upgrades were subjected to a variety of testing, including ground vibration tests, ground drop tests, and airborne drop tests. The new software was verified in simulators and in the first flight vehicle itself.

According to the RSC-Energia briefing to NASA, “In the event of failures in the new devices, crew safety is assured by the internal redundancy of the devices and due to the modes and equipment that have been preserved without changes.” For example, the entry motion control system has both digital and analog loops in the new computer, but even if both fail a hard-wired ballistic entry profile is available. The new Neptune-ME panel is one-fault tolerant and in the event of loss of function can be superseded by separately-routed remote control commands from the Mission Control Center in Moscow.

The certified service life of the Soyuz remains at 200 days in orbit. One Soyuz-TM vehicle flew for 208 days but this is not routinely planned. This mission is planned for 196 days.

The current Soyuz docked to the ISS is Soyuz TM-34, the last to be built. Soyuz TM vehicles have been in use since the beginning of the Mir program in 1986. The ‘TM’ in the old model designated its specialization. It was for ‘Transport’ to a space station, and it was a ‘Modified’ version of the Soyuz-T introduced in 1980.