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 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.

According to NASA, there was an ongoing computer problem onboard the MIM-2 module, particularly with the so-called TVU/Terminal Device. As a result, the command for opening hooks holding two spacecraft had to be issued manually by Aleksandr Skvortsov. When the transfer hatch in the MIM-2 module was closed, "hatch closed" signal was received successfully, but "hatch locked" (or "hatch sealed") command was not. Russian cosmonaut Fedor Yurchikhin remaining onboard the station, then opened and closed the hatch on his side one more time and moved the ratchet to the emergency position. In the next step in preparation for undocking, the space between two hatches was depressurized. This time, sensors on Soyuz and MIM-2 showed different levels of vacuum. After some analysis, mission control in Moscow still gave go ahead for undocking, however without "hatch locked" signal, hooks holding two spacecraft could not be opened. While waiting for a second attempt, Yurchikhin found a seven-tooth sprocket with two missing teeth floating inside the docking mechanism, just behind the hatch. Now it became clear that the dislodgment of the sprocket, with its rod sheared, prevented the "hatch locked" sensor from passing on its status, which in turn kept the hooks from opening.

To resolve the problem, a workaround was developed, which included wiring six electrical jumpers enabling to "fake" sealed condition of the hatch for the flight control system. The method allowed successfully open the hooks, clearing the way for the Soyuz TMA-18 departure during the next window on September 25.

This temporary jumper wiring was expected to remain in place until the arrival of the next Soyuz, which would deliver a new jumper for permanent use in the system.

An American and two Russians from Soyuz TMA-18 crew would restore the International Space Station’s Expedition 23 crew to six when they join the Russian, American and Japanese crew members who have been onboard since December. Once united, the first crew to include three Russians at once will continue outfitting the newest modules of the nearly completed outpost, and welcome the last planned shuttle flights and a new docking port. The Expedition 23 and 24 crews, comprising a total of nine residents over a span of eight months, will continue to usher in a new era of scientific research, with some 130 ongoing experiments in human research, biology and biotechnology, physical and materials sciences, technology development, and Earth and space sciences, NASA said.