From io9:
The Greatest Science Fiction Porn Movies of All Time: 1961-1991 [NSFW]
Science fiction has long encompassed every aspect of human experience — including sex. For as long as we've dreamed of going to space, we've dreamed of getting it on there. And porn has embraced science fiction as well — from 1968's softcore masterpiece Barbarella to the 1990s cyberpunk boom to the recent craze for porn spoofs, there has always been science fiction porn. After all, porn is an escapist genre when you get right down to it. And the line between a science fiction "B" movie and a softcore porn film is often more seethru than Jane Fonda's breast bubbles.
Here are the greatest science fiction porn films of all time, from 1961 to 1991. It's NSFW! Note: There are a number of exploitation films on this list, but no horror, since that's a very different category. Likewise, no fantasy. Also, if we missed your favorite, please chime in in the comments! With such a huge and sweeping topic, I'm sure we missed some stuff. We'll be covering 1992 to the present very soon.
To see the list, and the corresponding NSFW images and videos, you'll have to click here.