"When we're on a vessel it is working, it is discharging and loading cargo so there are lots of things on the move, " said Mr Tunney.

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During that time, astronauts will be loading it up with over 3, 000 pounds of cargo for its return flight to Earth.

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An accident at the Brazilian port of Ponta da Madeira, in which one of the Valemax ships was damaged while loading its maiden cargo, came as a huge setback to Vale as it gave China an excuse to ban Valemax vessels from its shores on safety grounds.

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