Soyuz TMA-18 - Undocking Difficulties

Undocking Difficulties

Landing, originally scheduled for 1:34 UTC 24 September, was postponed due to difficulties in undocking the Soyuz spacecraft from the ISS. The crew entered the Soyuz TMA-18 on 23 September and closed the main hatch at 6:35 pm EDT. Skvortsov, Kornienko and Caldwell Dyson experienced problems getting a tight seal and were forced to open the Soyuz hatch for a quick inspection. The hatch later was sealed, but Expedition 25 flight engineer Yurchikhin working inside the space station had problems confirming a tight fit with the hatch on the ISS side of the interface. After an extended leak check, flight controllers in Moscow decided the docking interface was tight and leak free. As the countdown neared for undocking, commands were sent to open hooks on the MRM2 module side of the interface. But the mechanism did not respond. It was not clear what caused the hooks not to respond, however, Yurchikhin reported finding a small gear floating from the mechanism when he removed a cover.

A second landing window was missed at 4:35 UTC. But Russian engineers were unable to resolve the problem with the docking mechanism and the undocking attempt was called off. The Soyuz TMA-18 crew removed their pressure suits, opened the Soyuz hatch and returned to the space station.