Soyuz TMA-12 was a Soyuz mission to the International Space Station (ISS) which was launched by a Soyuz-FG rocket at 11:16 UTC on 8 April 2008. It docked to the Pirs module of the station on 10 April 2008. Landing occurred at 03:37 on 24 October. It was the first nominal landing in three missions, following separation failures on the Soyuz TMA-10 and 11spacecraft.

Yi So-yeon flew as a guest of the Russian government through the Korean Astronaut Programme after the Korean government paid the Russian government 25 million US dollars in agreement to support the first Korean astronaut in space. Her role aboard the Soyuz is referred to as a Spacecraft Participant in English-language Russian Federal Space Agency and NASA documents and press briefings. Ko San was originally scheduled to fly, with Yi as his backup. On 10 March 2008, it was announced that Ko breached regulations surrounding removal of books from the training centre in Russia, and therefore would not be allowed to fly.
Soyuz TMA-12 approaches the International Space Station for docking on 10 April 2008.

Richard Garriot flew as a Space tourist through a program run by Space Adventures. He is also referred to as a Spaceflight Participant in English-language RKA and NASA documents.

Yi Soyeon flew on board Soyuz TMA-12 as a guest of the Russian government through the Korean Astronaut Program after the Korean government paid the Russian government 25 million US dollars in agreement to support the first Korean astronaut in space. Her role aboard the Soyuz is referred to as a Spaceflight Participant in English-language Russian Federal Space Agency and NASA documents and press briefings. Ko San was originally scheduled to fly, with Yi Soyeon as his backup. On March 10, 2008, it was announced that Ko San breached regulations surrounding removal of books from the training center in Russia, and therefore would not be allowed to fly. Yi Soyeon spent eight days conducting scientific experiments aboard the International Space Station.

Yi Soyeon was the first space traveller from South Korea. Following a two-day solo flight Soyuz TMA-12 docked to ISS on April 10, 2008. Sergei Volkov and Oleg Kononenko replaced Expedition 16 crew members Peggy Whitson and Yuri Malenchenko.

The Soyuz spacecraft is composed of three elements attached end-to-end - the Orbital Module, the Descent Module and the Instrumentation/Propulsion Module. The crew occupied the central element, the Descent Module. The other two modules are jettisoned prior to re-entry. They burn up in the atmosphere, so only the Descent Module returned to Earth.
The deorbit burn lasted 261.4 seconds. Having shed two-thirds of its mass, the Soyuz reached Entry Interface - a point 400,000 feet (121.9 kilometers) above the Earth, where friction due to the thickening atmosphere began to heat its outer surfaces. With only 23 minutes left before it lands on the grassy plains of central Asia, attention in the module turned to slowing its rate of descent.

Eight minutes later, the spacecraft was streaking through the sky at a rate of 755 feet (230 meters) per second. Before it touched down, its speed slowed to only 5 feet (1.5 meter) per second, and it lands at an even lower speed than that. Several onboard features ensure that the vehicle and crew land safely and in relative comfort.
Four parachutes, deployed 15 minutes before landing, dramatically slowed the vehicle's rate of descent. Two pilot parachutes were the first to be released, and a drogue chute attached to the second one followed immediately after. The drogue, measuring 24 square meters (258 square feet) in area, slowed the rate of descent from 755 feet (230 meters) per second to 262 feet (80 meters) per second.

The main parachute was the last to emerge. It is the largest chute, with a surface area of 10,764 square feet (1,000 square meters). Its harnesses shifted the vehicle's attitude to a 30-degree angle relative to the ground, dissipating heat, and then shifted it again to a straight vertical descent prior to landing.

The main chute slowed the Soyuz to a descent rate of only 24 feet (7.3 meters) per second, which is still too fast for a comfortable landing. One second before touchdown, two sets of three small engines on the bottom of the vehicle fired, slowing the vehicle to soften the landing.