Jr. James Tiptree 
Starry Rift [EPUB ebook] 

These are the heroes of the Starry Rift, a dark river of night that flows between the arms of our galaxy: a headstrong teenaged runaway who makes first contact with a strange alien race; a young officer on a deep-space salvage mission who discovers an exact double of a woman he thought he’d lost; and the crew of an exploration ship who must plead for the human race to avert an interstellar war.