A U.S.-Russian space team is leaving the international space station Saturday after five months, now that their relief crew has arrived. What makes their departure different from that of the five previous teams is that they are heading home on a Russian Soyuz spacecraft. U.S. space shuttles, the usual mode of transportation to and from the outpost, have been grounded because of the Columbia accident in February. The Soyuz is a proven craft, although not as comfortable.
Because of the Columbia disaster, station commander Ken Bowersox, astronaut Don Pettit, and cosmonaut Nikolai Budharin are returning to Earth more than a month later than originally planned. When the shuttle disintegrated in February, they told the U.S. space agency NASA that they would remain aloft as long as necessary. Commander Bowersox sounds as if he regrets having to leave.
"I'm actually going to miss the station quite a lot. I feel a little bit like I'm being kicked out of my apartment for not paying my rent," he said.
They had expected to fly home on the shuttle Atlantis, but the moratorium on shuttle flights forced NASA to arrange for the only other manned spacecraft that regularly visits shuttles, the reliable Soyuz.
Soyuz craft are used as emergency escape capsules attached to the space station. They are routinely exchanged every six months by Russian crews because their fuel and other systems deteriorate in the rigors of the space environment. The Soyuz that the new station team of astronaut Ed Lu and cosmonaut Yuri Malenchenko flew up recently is the replacement for the capsule the older team is riding home.
Ken Bowersox and Don Pettit will become the first U.S. astronauts to return this way, landing more than hours after undocking from the station. In doing so, they will experience cramped quarters and a parachute landing that U.S. crews have not had in nearly 30 years.
"This is the way we used to do business as well," recalls NASA flight surgeon Terrence Taddeo recalls The Mercury, Gemini, and Apollo vehicles all returned home in the same way. So in some ways we're taking a step back, but it's something that we are pretty familiar with."
After the three crewmen re-enter Earth's atmosphere, their Soyuz will parachute to the ground in central Kazakhstan. Rockets will fire to slow the descent. However, on at least one occasion, the rockets have failed, causing an unexpectedly hard landing, which the cosmonauts nevertheless survived.
Even when all systems work perfectly, the touchdown is still bumpier than on shuttles, which glide in and land smoothly on a runway like airplanes. "It's a big difference. Landing by shuttle is like a comfortable landing by commercial plane," said cosmonaut Malenchenko.
Another way Soyuz spacecraft are more physically taxing is that crews experience up to seven times the force of gravity when their speed is slowed upon re-entry. That is twice the pull felt aboard shuttles.
Some of these rigors are decreased on the latest model Soyuz, the version the station trio will use. This will be only its second landing. NASA worked closely with the Russian aerospace company RSC Energia to adapt it to U.S. tastes and sizes. The crew cabin has been modified to hold taller and heavier people. The descent engines have been upgraded to handle a bigger load for an even softer landing. The seats now have shock absorbers.
"The seats have a piston built into them, which also absorbs some of that impact," NASA flight surgeon Taddeo. "In the past, the Russian experience with this vehicle is that there have been some minor injuries. There have been some bruises. People have walked away with some muscle soreness, but they have never had any experience where a crew member has had any kind of traumatic injury, in other words, broken bones or internal injuries."
Despite its physical demands, the Soyuz safety record is very good. The craft has had only two re-entry accidents in 36 years, killing four cosmonauts. Those mishaps occurred in the first four years of its existence. Astronaut Pettit says he is not nervous about returning on the Soyuz. "We have done a heap of training for both Soyuz and shuttle entries. Either one is fine with us," he said.