When the Tildorani achieve spaceflight we'll welcome them to the group, but we don't want to be discovered by them before then.

Shortly after, in an editorial, he wrote that he believed that man would never achieve spaceflight.

The criteria for determining who has achieved human spaceflight vary.

Cultures lacking resources to achieve crewed spaceflight are ignored as animals.

"Colonies" are worlds that have not achieved spaceflight and are also technologically backward.

They reverse engineered the technology, allowing them to achieve spaceflight and colonize hundreds of planets.

They had achieved spaceflight during the time of the starglobe when the galaxy had been a sphere.

The Quintaglios have apparently achieved spaceflight, built computers and set up temporary colonies on nearby moons.

As such, their descendants are of a different culture that has yet to achieve spaceflight.

Two of the remainder may achieve spaceflight within the next few centuries.