Generally I’ll be discussing individual RPGs rather than specific modules, but AD&D module S3 holds such an important position in RPG history that I think an exception is warranted. Particularly as it constitutes the “missing link” behind the two games I’ve discussed most recently, Metamorphosis Alpha and Gamma World. Ironically, Expedition to the Barrier Peaks was originally conceived as a marketing tactic: in the spring of 1976, with TSR putting the finishing touches on Metamorphosis, Gary Gygax was pondering the problem of how best to introduce that science fiction game to the growing legions of D&D fans. MA creator James Ward had already game-mastered scenarios in which D&D parties were swept through rips in the space-time fabric to the world of the starship Warden; Gygax reversed this, conceiving of a tournament adventure in which science fiction came to the world of Greyhawk.
But in so doing, he needed something more accessible than Rob Kunz’ infamous “machine level” in Castle Greyhawk, where high-tech inventions vied with sorcery as part of what's probably the largest dungeon ever made. Trying to “productize” Greyhawk would have been a titanic undertaking; even now, more than thirty years later, only the merest fragment of Castle Greyhawk has reached the marketplace. Gygax was looking for something more manageable—a single adventure that could be played out in classic tournament fashion.