Project Daedalus was a study conducted between 1973 and 1978 by the
British Interplanetary Society to design a plausible
unmanned interstellar spacecraft. Intended mainly as a scientific probe, the design criteria specified that the spacecraft had to use existing or near-future technology and had to be able to reach its destination within a human lifetime.
Alan Bond led a team of scientists and engineers who proposed using a
fusion rocket to reach
Barnard's Star 5.9
light years away. The trip was estimated to take 50 years, but the design was required to be flexible enough that it could be sent to any other target star.