There is one big problem with: Kirk & Spock: DY-100 class ships like the Botany Bay were not designed for interstellar travel. Possibly DY-200 or DY-300 class vessels were designed for interstellar travel and were already in use by the 1990s. But when Kirk thinks the Botany Bay could be a DY-500 class ship: So it is unlikely that more than one or two later classes of DY ships were available in the 1990s. Khan would take the most advanced ship he could get. And: So it took years to get just from one planet to another during the 1990s. Neptune orbits the Sun at a distance of 29.81 to 30.33 Astronomical Units (AU) while the former planet of Pluto orbits the Sun at a distance of 29.658 to 49.305 AU. A light year is 63,421 AU and Alpha Centauri, the nearest star, is about 4.3 light years from Earth, or about 5,531 to 9,195 times the distance to the farthest planets in our solar system. Thus it should have taken thousands of years to reach even the nearest stars with the ships available by 2018, and so no colonization of other stars should have been possible in the 1990s. Of course, I did once have a theory that in Star Trek Earth discovered methods of faster than light (FTL) travel twice. The first time a secret group secretly built starships and left Earth to explore and to settle a colony in another star system from which they continued to explore the stars, leaving no record of this on Earth. Tarbolde who wrote Nightingale Woman on the Canopius Planet in 1996 was probably one of them. The Valiant was one of their ships. Meanwhile on Earth the Eugenics Wars happened and interplanetary travel took years, and Khan left Earth in suspended animation hoping to reach another star. In 2018 Earth based space travel got much faster, so Earth developed FTL star travel for the second time in 2018 or later, and began to explore the stars, and eventually the explorers from Earth and the explorers from the Earth colony met and united sometime before Kirk's era. If one group had "broken the time barrier" and the other hadn't, the reunion might have happened between the departure of the Columbia and "The Cage". When I believed that all dates in Star Trek were given as Anno Domini dates, I calculated that the Valiant should have been voyaging sometime between AD 1896 and AD 1996, so I came with with the theory that Earth discovered FTL interstellar travel twice, and the first time it was kept a secret from the rest of Earth. But now I believe that Earth dates in Star Trek are given in several different dating systems, so that the year 2100 in one story is not necessarily after the year 2000 in another story. Thus it is not no necessary to assume that Earth developed FTL star travel twice, though some Star Trek chronologists might find it useful.