Undocking Problems Delays Soyuz, Station Crew Return to Earth

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Two Russian cosmonauts and an American astronaut were forced to call off their scheduled departure from the International Space Station because of a failure of the undocking system. Hooks on the space station’s Poisk module docking interface failed to release for the scheduled departure at 9:35 p.m. EDT Thursday, sending astronaut Tracy Caldwell-Dyson and Russia’s Alexander Skvortsov and Mikhail Kornienko back inside the ISS from the Soyuz, where they were strapped in, ready to return to Earth. NASA and the Russian Space Agency are hoping to try again, with the hatch closing at 6:45 pm EDT on Friday; undocking at 10:02 pm and landing in Kazakhstan at 1:22 am.

“The preliminary analysis, according to the technical commission, showed that a false signal appeared in the onboard computer system about the lack of a hermetic junction after closing the hatch on the station,” said Roscosmos head Anatoly Perminov.

This type of undocking problem has never happened before and comes three months after a Russian Progress resupply vehicle had problems docking to the ISS when a transmitter for the manual rendezvous system accidently activated, overriding the usually reliable automated system.

In trouble shooting the problem, Expedition 25 flight engineer Fyodor Yurchikhin on board the station removed a cover from the docking mechanism and found a small gear floating away. But the station crew couldn’t confirm the object came from the docking system or had anything to do with the failure.