All right, the plot is thin and at times unbelievable, but the acting and effects are competent. The film's target audience were the teen-aged denizens of the last of the American drive-ins, and it's typical Cold War nuclear-midnight material. While in outer space, three astronauts witness the obliteration of the cities of earth in a full-scale nuclear war. When their spacecraft's automatic return mechanisms are commandeered, they land in a remote and highly radioactive section of Canadian coastline, where totalitarianism and cannibalism rule the day.
I saw this one at a drive-in when I was 19, and watching it now reminds me of the feel of my beat-up car's leatherette seats, the smells of popcorn and hot dogs from the poastapocalyptically unclean snack bar, and several other less seemly teen pleasures that ultimately overran and sealed the demise of the drive-in venue as the rest of the world abandoned it for home video.
Most of the movies I saw in what is now a forgotten, overgrown lot behind a commuter parking area (a summer storm tumbled what was left of the big screen years ago) were similarly produced with nuclear hysteria in mind, usually with unknown talent and enormous plot holes (what, exactly, were the sources of gasoline in the desert wastelands of "Mad Max" and "Cherry 2000"?).
These "B" films represent a period in American cinematic history that, while rarely critically laudable, nevertheless reflects the morality issues of generations. Our fear of the atom had metamorphosed from the accidental gigantism of everything including common insects, rodents and the occasional slowly-driven-mad citizen to much more tempered, though not always realistic, pondering of civilization after a full-out attack...and most of these films played out on the other side of our windshields.
So, spray on some bug repellent, haul the TV out to the garage, and enjoy some Mom's-car make-out sessions with your spouse. This film makes it 1985 all over again.