I once tried to write a story where the Enterprise-D was knocked forward in time while monitoring the test of a new propulsion system. In that future, the Federation, the Klingon, and the Romulan Empires didn't exist because Enterprise wasn't around to defeat a new threat to the galaxy. But I couldn't figure a way out of the box. While I was working on it, TNG: New Ground aired with a similar subplot of a new propulsion system, so I gave up. I was trying to write spec scripts at the time, and each time I'd get halfway through one, there'd be an episode or preview with elements of whatever story I was working on at the time. It happened at least 3 times, so at least I knew I was on the right wavelength.