Classic public domain film, digitally preserved and free to stream forever.
The Phantom Planet (1961) is a sci-fi adventure in which an astronaut is drawn to a mysterious asteroid and shrunk to miniature size by its atmosphere. He discovers a tiny civilization there under threat from a race of savage alien creatures called Solarites, and must help defend it before he can ever hope to return home.
Starring Dean Fredericks, Coleen Gray, and Anthony Dexter. This film is in the public domain and free to watch, download, and share.