However, the key here is manned spacecraft. What about a von neumann probe, only weighing a few grams with a human level or better AI made of quamtum computers. It could have on board a universal replicator to convert raw plantetary mass to a human colony. All it would need is the human genome on its AI. That is engineeringly possible in this century, as a ship weighing a few grams can get to near light speed with relative ease. You could use a solar sail that has a huge diameter but extremely thin, thus a negligable mass. The problem would be colliding with stuff at 90% the speed of light.
Now that would be a neat work around. Transportation through atom by atom reconstruction from one place to another. Go to sleep on earth and wake up ~three years later in alpha centauri.