Humans discover hyperspace that allows faster than light travel. Unmanned probes come back fine, though covered in a tacky fragrant patina as though it traveled through thick clouds of incense. Video recordings come back blown out, and audio recordings pick up no sounds but listeners report feeling that tingle you get when hearing beautiful music. Animal tests come back unharmed, but the moment a human crew is sent in the ship comes back empty, with no signs of internal struggle or hostile ingress. It's just empty piles of clothing.
We eventually figure out that hyperspace is actually Heaven. Any perception of the glory of the Empyrean outside the ship, even indirectly through sensors, by a human causes their face to be melted off Raiders of the Lost Ark style by inapproachable holiness. Navigation computers are developed that allow ships to traverse the realm of eternal light without the crew having to acknowledge the outside. However, you're traveling through the light at the end of the tunnel, the one that beckons you as you lie dying. It beckons you even now. Can you resist?