During the early 22nd century, the Earth Cargo Service was Earth's only real presence in outer space; the crew of these ships would spend years traveling from one planet to another and the Humans with the most space experience were boomers: the first generation of Humans who were born in outer space. Enterprise was joined by Columbia NX-02 in November of 2154, delayed from June due to engine trouble. (ENT: "The Expanse", "Affliction")