From Terry Pratchett’s science fiction novel Strata.

The Terminus space probes were early interstellar manned ships launched by Earth to explore the Universe. At least six Terminus probes were launched. Each one was mostly a huge bell-shaped engine. The pilot’s life support capsule was a tiny sphere at the tip of the bell.

The Terminus probes were manned because even in a completely new situation a human could still reason, evaluate, and make sensible choices. The computers of the time would not have functioned in an unexpected situation as a human could have. So they decided to send humans.

The problem with sending humans is that they need many extra supplies -food, water, air- for the journey there and back, and the added weight is expensive. It is cheaper to send a human if you are only sending them one way.

So the Terminus probes were designed not to come back.

Two Terminus pilots did come home, though. Rip Van LeVine arrived at a planet after a 1,000 year long journey in suspended animation, to discover that settlers had arrived in FTL ships driven by the Elsewhere drive 300 years ago. Jago Jalo discovered The Disc*, and used it to get home too**.

Two other Terminus pilots are still alive -in suspended animation- because their ships never reached a destination and were still in transit at the time of the events in Strata. T4 failed to start deceleration, and thus overshot its target and carried on going. T6’s computer malfunctioned and guided it to a star that didn’t exist. Rip Van LeVine used his considerable fortune to set up the LeVine Trust, which funded missions to repair the remaining Terminus probes and do everything for the pilots - apart from waking them up.

* No, not the Discworld. Read the node - Strata - if you haven’t already done so.
** I'm being ambiguous deliberately so I don’t spoil this great book for you.