Live Coverage: Soyuz Landing On Tap

Two Russians and an American are set to depart the International Space Station today, aiming to avoid the rocky rides and off-course landings made by the last two crews to fly Soyuz spacecraft back to Earth.

Expedition 17 commander Sergei Volkov, flight engineer Oleg Kononenko and space tourist Richard Garriott will say farewell to Expedition 18 colleagues at the station at about 4:45 p.m. EDT and depart in a Soyuz spacecraft around 8:15 p.m.

Deorbit burn is set for 10:44 p.m., and a landing on the central steppes of Kazakhstan is expected around 11:36 p.m.

Live NASA TV coverage of all the events will be webcast live here in The Flame Trench starting at 4:45 p.m. EDT. Simply click the NASA TV box on the right hand side of the page to launch our NASA TV viewer, and be sure to refresh this page for periodic updates.

The return to Earth will be the first since a Russian investigation into the back-to-back ballistic reentries - steep descents that exposed Soyuz crews to almost triple the gravitational forces encountered during normal reentries. The October 2007 and April 2008 landings also missed their marks by hundreds of miles.

Russian engineers traced the trouble to a system designed to separate three sections of the Soyuz prior to reentry, and steps have been taken to mitigate the risk.

Famed video game designer Richard Garriott, who paid the Russian Federal Space Agency an estimated $30 million for a 12-day round trip to the outpost - said he'll be ready in any case.

"I've paid close attention to the last two ballistic reentries and watched all the reports and the analysis as to what was the cause, or the potential causes, and what was done to repair it," said Garriott, the son of retired U.S. astronaut Owen Garriott.

"But I have no concerns about reentry. And so I'm excited about the trip home regardless."

The Soyuz spacecraft is comprises three sections. An orbital module at the front end is equipped with rendezvous and docking systems. The crew will strap into a central capsule - known as a descent module.

The third segment - located at the back end of the spacecraft - is an instrumentation and propulsion module outfitted with steering thrusters and guidance systems.

Russian investigators think pyrotechnic devices designed to separate Soyuz crew capsules and propulsion modules failed to fire at proper times during the last two trips back to Earth.

Spacecraft computers consequently switched to a back-up mode known as "ballistic reentry" -- one in which free-falling spacecraft rely solely on atmospheric drag to slow the vehicle. Steep trajectories -- and high G-forces -- typically result.

Both the U.S. and the former Soviet Union relied on ballistic reentries during the earliest days of spaceflight. Since then spacecraft have used aerodynamic lift for more gradual descents that reduce high gravitational forces on crews. But Soyuz craft still use the ballistic mode as a back-up.

Russian investigators are more concerned about faults in the separation system.

Crew capsules that don't separate from attached propulsion modules could plunge into the atmosphere with their hatch, rather than their heat shield, facing forward -- a lethal situation in an environment where temperatures reach 3,000 degrees Fahrenheit.

A Soyuz piloted by cosmonaut Boris Volynov almost incinerated during a January 1969 reentry as a result of similar problems.

Volkov -- the son of retired cosmonaut Alexander Volkov -- this week noted that steps have been taken to reduce the chance of a separation system failure and ballistic reentry.

He and Kononenko took a spacewalk July 10 and removed a suspect explosive bolt from a locking mechanism that links their Soyuz crew capsule with its propulsion module. They also opened the lock in a bid to ensure a clean separation.

Russian specialists also beamed up a software patch that should help. If the crew capsule and the propulsion module do not separate cleanly, then the software will move the Soyuz into a special attitude for reentry.

The crew capsule and the attached propulsion module would fly perpendicular -- rather than parallel -- to the direction of travel. In that case, aerodynamic forces would separate the modules during reentry.

"We are absolutely confident, and our engineers did a great job, and we hope that everything is going to be normal, and that we will land in a normal way," Volkov said. "Not a ballistic reentry."

Stay tuned.

ABOUT THE IMAGES: Click to enlarge the awesome images from the International Space Station as well as the Soyuz graphic. The first and second images show a Russian Soyuz spacecraft approaching the station for the Oct. 14 arrival of the Expedition 18 crew. The third is NASA line art that shows the three different segments of the Soyuz spacecraft. The last is an image of Oleg Kononenko taken during a July 10 spacewalk to retrieve a suspect pryotechnic device for return to Earth. Image credits: NASA