Early in Prometheus, the human crew is in "hypersleep" for a couple years, and at one point, an android uses a touch-screen interface to "see" on a screen what a woman crew-member is dreaming.
In a later scene, when everyone has been woken up at the destination planet, the earthlings find an "engineer" who appears to have been in the engineer version of hypersleep for hundreds of years. The engineer appears to have faintly registered on the earthlings' scanner as it searched for signs of life.
This all got me wondering... how does hypersleep work, exactly? I had assumed it put the subject in a state of suspended animation that would not allow for dreaming or for registering on scanners. But the scenes above suggest I'm wrong -- that people dream vividly in hypersleep, and that their bodies are exhibiting some vital signs.
Any clues from the movie or other relevant sources about how hypersleep was supposed to work in Alien/Prometheus/etc and/or how it might work in real life?