Explore "The Boomerang Circuit" by Murray Leinster on Textopian. Read with annotations and highlights.
For a time Kim sat still and sweat poured out on his skin. Because their chances had seemed slight indeed. To stop a space-ship at transmitter-speed was impossible with manual means, anyhow. It could cross a galaxy in the tenth of a millisecond. So Kim had devised a radiation-operated relay which threw off the drive when the total radiation reaching a sensitive plate in the bow had reached an adjustable total.
If in an ordinary flight the _Starshine_ headed into a sun -- unlikely as such an occurrence was -- the increased light striking the relay-plate would throw off the drive before harm came. But this time they had needed to approach fatally close to a star. So Kim had reversed the operation of the relay. It would throw off the drive when the amount of light reaching it dropped below a certain minimum. That could happen only if the ship came up behind the planet, so the sun was blacked out by the world's shadowed night-side.