From the era when actual space travel was brand new...
Science fiction was in a state of flux as real-world science began catching up with our imaginations.
Instead of far-future sagas with warp-drive ships, tales of "the day after tomorrow", when we would make our first landings on the Moon and Mars came into vogue.
That didn't mean that visitors from beyond our Solar System were left out, but the technology we used to respond to them (friendly or not) was much closer to "present-day" (1950s) tech than ray-guns and photon drives.
It's sad that, now that we're actually in the era shown in these tales, we haven't done anything close to what they show...
