[tg3]

Only if you have a narrow view of "manned".

For almost all of human history, long treks were made without the expectation that those that started the journey would be the same ones to end it (think of the Israelites in the desert, early Americans heading west, or the proto-Native Americans who crossed the land bridge from Asia).

[comrade_ogilvy]

We should keep in mind that the Age Of Exploration, circa Columbus, was considered monumentally successful by their Eurpoean sponsors, but being a explorer was nearly a death sentence. (I exaggerate only slightly).