By Paul Rincon
Science reporter, BBC News
Yi So-Yeon spent about 11 days on the ISS
South Korea's first astronaut has described the nerve-jangling "ballistic re-entry" when the Soyuz capsule carrying her back to Earth suffered a malfunction.
Yi So-Yeon spent about 11 days on the International Space Station (ISS) in April, to carry out experiments for the Korean government and industry.
But a malfunction on the craft caused Ms Yi and two other crew members to be exposed to extreme forces.
Ms Yi told BBC News she suffered some back pain when the capsule touched down to Earth hundreds of kilometres from its target landing zone.
"At the time it was a really big shock. But after talking to other cosmonauts, they said it wasn't that big because they said: 'we have parachutes and a [back-up] engine," she explained.
"I had a little back pain - it was not that serious. But I've never even had a car accident, so I have never experienced a small shock at all."
Ms Yi was travelling back to Earth with Nasa astronaut ISS Expedition 16 commander Peggy Whitson and Russian flight engineer Yuri Malenchenko on 19 April.
The astronauts returned on a back-up landing profile, which sends the re-entry capsule back to Earth on a steeper than normal course. This subjects the astronauts to 8 or 9Gs - eight or nine times the gravitational force experienced on Earth.
But instead of hitting its target landing zone, the Soyuz landed some 420km (260 miles) to the east on the steppes of Kazakhstan.
"If you have some problem outside or inside, [the Soyuz] automatically changes to the ballistic re-entry. So not much is different except that we had very high G - around eight or nine G," said Ms Yi.
Mr Malenchenko, who commanded the capsule during launch and landing, used a satellite phone to tell mission control that his crew was well. Local Kazakhs were first on the scene, Ms Yi explained. A Russian rescue crew arrived soon afterwards to ferry the crew away.
Another fault prompted the ballistic re-entry of the Soyuz in October 2007, when it was carrying the space station's Expedition 15 crew and a Malaysian astronaut.
Before the journey, Ms Yi said she had been told by her colleagues that the G-forces felt more extreme on the journey back because astronauts become accustomed to the zero-gravity.
"It seemed like more than three or four Gs, but I thought it must have been because of the weightlessness. But as time went by, it began to feel like more than seven or eight Gs.
"Then Peggy and Yuri said: 'Yes, it's more'. Finally, I found a red lamp showing that we had a ballistic landing. I said: 'wow, we had eight or nine Gs'."
Russian rescue teams were soon at the scene
Officials believe the recent off-target returns to Earth made by Soyuz craft could have been the result of faulty pyrobolts on the vehicles.
These pyrobolts are used to separate the Soyuz crew compartment from its propulsion module prior to re-entry. If the bolts fail, the descent capsule will not adopt the correct orientation to go through the atmosphere, causing excessive heating of unshielded surfaces.
The recent failure is thought to be related to the insulating layer on the bolts, which may have suffered from extended exposure to the harsh space environment or electrical arcing.
In July, cosmonauts removed an explosive bolt from a Soyuz capsule attached to the International Space Station (ISS), to be returned to Earth for analysis.
The ballistic re-entry was not the first for Soyuz craft
Ms Yi said: "At the time I thought I was so unlucky. Now I think it was chance. There have been about 400 astronauts and cosmonauts. But only a few have experienced a ballistic re-entry. So that was a very unique experience.
Now I don't think I was unlucky, I think I was lucky.
"I have heard the shock is exactly the same with a normal landing, but I don't know, because I've never experienced a normal landing."
But the rough ride has not deterred Ms Yi, who yearns to go back into space.
"Every day I cross my fingers that I will go back there. It was really fantastic.
"I think and I wish that if I go there again, I will do better. If I can afford it in the future, even if I'm a grandma, I really want to go there.
"But if the government or some other institute wants me to go there, I won't hesitate. I will just say yes."
During her stay on the space station, Ms Yi carried out a variety of experiments for the Korean Aerospace Research Institute (Kari) where she is currently employed, and also tested a 3D camera for the manufacturer Samsung.