|Soyuz-TMA – Improvements to the Russian Spacecraft
A shorter version of this article appeared in ‘Space News’, October 2002
A new variant of Russia’s Soyuz crew capsule, flown for the first time Oct. 28, 2002, features changes intended mainly to accommodate larger crewmembers. But there also are a large number of smaller changes that enhance the flying and safety characteristics of the vehicle.
In potentially the most far-reaching change to the crew equipment, the crewmember in the right seat has practically been cut ‘out of the loop’ on all critical functions. This will allow ‘spaceflight participants’ who in the future may ride in this seat to require much less training than ever before.
The mission was the fifth Soyuz to dock with the international space station since the first permanent crew arrived Nov. 1, 2000. Replacement vehicles have been launched at six-month intervals to provide the three-person permanent crew with an escape vehicle.
The Soyuz TMA capsule, built by Rocket System Corporation Energia of Moscow, is designed to accommodate crewmembers up to 190 centimeters tall and weighing up to 95 kilograms. The height and weight of crewmembers on previous Soyuz variants were limited to 182 centimeters and 85 kilograms, respectively. Smaller crewmembers are also now able to ride in the Soyuz.
The change is significant. Under a $39,000,000 contract awarded by NASA in 1996, the Russians were to redesign their Soyuz vehicle to accommodate 90 percent of American astronauts. According to NASA spokesperson James Hartsfield, “When the contract was awarded, only 50% of the NASA astronaut population fell within the limits of the Soyuz design.” Hartsfield did not have the anthropometric statistics for the current NASA astronaut population but told me the figures probably had not changed much.
“The money was entirely for the design work,” he elaborated. “It didn’t pay for construction.”
To accommodate the wider range of astronaut body sizes, Energia made significant changes to the crew couches, cabin equipment layout, and the pre-touchdown soft landing system which fires a battery of solid-fuel rockets just prior to impact with the ground.
All three Soyuz crewmembers sit in couches aligned side-by-side. To allow for taller passengers, more legroom was added by raising the instrument panel, re-routing cabling and plumbing in that area, and creating small bays in the wall of the Soyuz at the feet of the left and right crewmembers. Also, the shock absorbers under the seats were redesigned to be tailored for varying crewmember weight.
A slight increase in total vehicle weight also required the development of an improved version of the Soyuz booster vehicle manufactured at the TsSKB Progress plant in Samara. The Soyuz TMA’s maximum mass will now be 7,220 kilgrams. According to NASA headquarters ISS official Jesco von Puttkamer, the booster has “a new fuel injection system that provides a five percent increase in thrust, enhancing its lift capacity by 200 kg”. The new booster version, called Soyuz FG, already has lofted three Progress cargo capsules, the first of them in May 2001.
Although the Soyuz TMA represents a significant upgrade, Russian space officials have concluded that the changes are not so revolutionary as to require an unmanned test flight, as had been the case for previous new variants of the vehicle. NASA officials reviewed that decision in Houston Oct. 1, 2002, and approved it.
“All integrated testing of TMA mods were made through fit checks, dynamic structural tests, ground-based drop tests and airborne drop tests,” NASA spokesperson Rob Navias explained. The new software was verified in simulators and in the first flight vehicle itself.
I also acquired the set of briefing charts presented by RSC-Energia official Valeriy Ryumin for the Operations Readiness Review that was held in Houston on October 8, 2002. A list of hardware upgrades was also provided by Navias.
These upgrades include a new flight computer for the Soyuz, a new accelerometer, new data and voice recorders, and improvements in the heating and dehumidifying equipment. There are upgrades to the voice communications system, and the internal TV cameras have been upgraded from B&W to color.
One feature of the upgrades that helps justify skipping an unmanned orbital test is that the Soyuz is fully tolerant to any failure of the new systems. 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 steering system has both digital and analog processes in the new computer, but even if both fail a hard-wired ballistic entry profile is available. The new control panel (“Neptune-ME”) has new display screens and distributed processing, but the Russians insist that even if it totally fails, commands can be sent up from the ground to bypass the failed panel.
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 first TMA mission was planned for 196 days.
The Soyuz docked to the ISS at the time of the Soyuz TMA-1 launch was 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.