April 30, 2003. Copyright 2002. Graphic News. All rights reserved.

Riding the Soyuz Òemergency lifeboatÓ

LONDON, April 30, Graphic News: Crewmen who have manned the International Space Station (ISS) for five months say they have no worries about parachuting to Earth in a Russian spacecraft, a type of space vehicle U.S. astronauts have not used since the mid-1970s.

Expedition Six astronauts Kenneth Bowersox, of the U.S. Navy, and science officer Dr. Donald R. Pettit will return with their Russian crew mate, flight engineer Nikolai Budarin, aboard a Soyuz spacecraft that for the past months has been their Òemergency lifeboat.Ó They are scheduled to land in an open field in Kazakhstan at 21:03 Eastern Time, Saturday (02:03 GMT Sunday).

ÒIÕm actually sort of excited about it. IÕve been looking down quite a bit from up here in orbit, looking down at Kazakhstan. It's a beautiful country,Ó Bowersox said from the International Space Station during an orbital link-up with reporters. The three men were supposed to return to Earth in March aboard the space shuttle Atlantis, but the entire U.S. shuttle fleet was grounded following the Columbia disaster on February 1.

The ride down on a Soyuz is considerably rougher than on a shuttle, according to Russians who have done both. One such Russian is Yuri Malenchenko, commander of the seventh expedition, who arrived on Sunday with American Edward Lu. ÒItÕs a pretty big difference. Landing by shuttle is a pretty comfortable landing, like a commercial airplane,Ó he said.

One of the first tasks Bowersox and his crew had to carry out after arriving last November was to install custom-fitted liners to the three seats in their Soyuz TMA-1 lifeboat. When crewmembers are brought to the station aboard the space shuttle, their individually moulded seat liners are delivered with them and transferred to the existing Soyuz spacecraft as part of crew handover activities.

Before handing the keys to Malenchenko on Saturday, the Expedition Six crew will also have to swap their shuttle Advanced Crew Escape Suit (ACES) for Russian-made Sokol space suits. Little changed since the early 1970s, the Sokol has aÊdoubleÊV-front zip closure, lace-up crotch, and aluminium umbilical interfaces for electrical, air and coolant cables and hoses.

The journey home will take three hours and 23 minutes. After the separation command, hooks and latches which hold the Soyuz to a docking port on the space station will be released, allowing the craft to begin drifting away at 10cm (4 inches) per second. When the craft has drifted about 20 metres (66 feet) flight engineer Budarin will trigger a 15-second separation burn. 

Two hours, 29 minutes later, when the Soyuz is at a distance of about 19 kilometres (12 miles) from the station, the engines will fire for a 4-minute, 21-second de-orbit burn. The unoccupied Orbital Module and Propulsion Modules separate from the Descent Module and burn up on re-entry into the atmosphere.

As Soyuz hurtles through the outer reaches of the atmosphere, 121,920 metres (400,000 feet) above the ground, the crew will be buffeted and pinned down hard in their seats. During this most dangerous stage, friction produces super-heated air or ÒplasmaÓ which reaches 1,100 degrees Centigrade (2,000 degrees Farenheit). 

As the spacecraft streaks through the sky at a rate of 230 metres (755 feet) per second, the commander uses a Ògames-styleÓ controller to fire eight hydrogen peroxide thrusters to pilot the Soyuz. This system is deactivated 15 minutes before landing, when four parachutes are deployed. Finally, just two seconds before impact, six solid-fuel retro rockets fire to reduce the rather hard impact with terra firma.

ÒEventually, you reach ground. ThatÕs most important. (Then) you see friends, good people, and everything you want,Ó Malenchenko said.

Less than three-and-a-half hours after undocking from the ISS, the Soyuz crew will be welcomed on the desolate, parched, steppes of Kazakhstan.
/ENDS

Sources: NASA, Energiya Aerospace Corporation, Baikonur Cosmodrome