As for when- Psionics appear in an appendix of optional rules in the 1Ed PHB, along with rules for the Bard and rules for firearms and/or blending in elements of Boot Hill or Gamma World, as I recall.
Realize, though, that D&D isn't really a game of traditional fantasy. It has always had certain western, sci-fi and pulp elements that the game's creators loved. The "Vancian spellcasting system" was derived from a series of sci-fi stories- Jack Vance's Dying Earth. One could argue that the Vancian spell system is a perfect reflection of Arthur Clark's adage that any sufficiently advanced technology is indistinguishable from magic...implying that the spells in that series were actually technology- not magic - in action.
Heck, look at S3 Expedition to the Barrier Peaks and you'll see an adventure in which the dungeon is a crashed starship. Not a spelljammer style spacecraft, but a full-blown sci-fi starship complete with robots, blasters, and doors that go "swshhhhh."