It's a pity the makers of "Gravity" appear to not have watched this before setting out on their movie, for it has everything "Gravity" lacks- plot, acting, tension, technical and scientific accuracy-as far as possible for the time, and a well-conceived and well-executed ending-again for the time.
The story is familiar; failure of an on-board system prevents re-entry of a spacecraft. A fine cast, ably led by the towering might of Gregory Peck, with Gene Hackman, and three actors we never see or saw enough of- James Franciscus, David Janssen and Richard Crenna. Good turns from the astronauts' wives and supporting cast, too.
I feel a little mean in only giving four stars, for it's a nine out of ten movie, and considering its time, infinitely superior to "Gravity". But the weaker special effects of the time hold it back a little. The three stars I gave "Gravity" compared with four stars for this flatters "Gravity" somewhat. Maybe someone will show these back to back as a double bill, so people can see that flashy filming techniques do not make a good movie- story, acting and tension certainly do, and this has those in spades.