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I'm looking for the title of a Sci-Fi story (probably pre-1990) where a group is sent off into deep space and I believe unbeknownst to them it's a one-way journey.
In the course of the journey they all become very intelligent, they make psychoactive drugs from the plants on board, I recall that they discovered it's a one-way journey to test the affects of space travel, and they redesign/refit their engines and return to Earth.
Lame recall, sorry, that's all I got. Any help appreciated.