The handover between Expedition 20 and Expedition 21 required three Soyuz vehicles being docked to the station at the same time, the first time this has occurred.

Travel to and from the ISS will be aboard the Russian Soyuz vehicle.

The Soyuz vehicle to be used does not have the power to reach the Moon on its own, so the Russians have devised a plan to send up a booster.

The project has a projected cost of approximately €320 million, where €120 million are allocated for modernizing the Soyuz vehicle.

Now with two docked Soyuz vehicles, the ISS has been crewed with 6 members since May 2009.

The next opportunity would come after a visit to the station by a Russian Soyuz vehicle in April, so the earliest launching will not come until late April, he said.

The Russians charged us, last year" - on an International Space Station-related matter - $65 million for one Soyuz vehicle!

In the interim we do have other international partner assets - Soyuz vehicles, progress vehicles for resupply, that could be beneficial.

The budget also calls for refining the Orbital Space Plane, a reusable craft that may eventually replace the Soyuz vehicles now used as the station's lifeboat, he said.

The first opportunity for return will be on a Russian Soyuz vehicle in the spring of 2012.