[Spaceships] getting into orbit without superscience?

[johndallman]

Originally Posted by Fred Brackin

Trying to guess about hypothetical planets/moons outside your Solar System with non-oxygen atmospheres and the biggest possibility might be a sort of super-Mars.

That presumes that larger planets have enough life for a Great Oxygenation Event. Without that, there won't be significant free oxygen: it's just too reactive.