Expedition 39 commander Koichi Wakata, right, turns the International Space Station over to Expedition 40 commander Steven Swanson, front left, during a change of command ceremony Monday. Wakata, Soyuz TMA-11M commander Mikhail Tyurin, middle right, and Rick Mastracchio, back right, planned to return to Earth late Tuesday. NASA TV

A Japanese astronaut, a veteran Russian cosmonaut and a NASA flight engineer boarded their Soyuz ferry craft and undocked from the International Space Station Tuesday, setting their sights on a fiery plunge back to Earth to close out a 188-day stay in space.

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A Japanese astronaut, a veteran Russian cosmonaut and a NASA flight engineer boarded their Soyuz ferry craft and undocked from the International ...

In the latest space-related tit for tat, Dmitry Rogozin, Russia's deputy prime minister for space and defense, told Russian news agencies future sales of RD-180 engines, which power the first stage of United Launch Alliance's Atlas 5 rocket, will not be permitted for launches of U.S. military payloads.

Departing space station commander Koichi Wakata, facing camera, and Soyuz TMA-11M commander Mikhail Tyurin, left, close the hatch to the ferry craft prior to departing the International Space Station. Also on board for return to Earth was NASA flight engineer Rick Mastracchio.

NASA TV

In any case, ULA officials say the company has a two-year supply of RD-180s in hand and it's not yet known what impact Rogozin's statements might have down the road.

Both sides say the station program is not affected by sanctions or other diplomatic hurdles and the Russians continue to honor their lucrative contract with NASA to carry U.S. and partner astronauts to and from the space station aboard Soyuz spacecraft at more than $70 million a seat.

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Three space station fliers set to return to Earth