This manages to be both down home and outer space out there; it manages to be clastrophobic and wildly wide open outer space spaces on a big spaceship. This is really LOST IN SPACE before LOST IN SPACE with a near hit crash landing on a planet, a creature at a window in the cliffhanger, two girls frightened in a locked off room on a spaceship, strange mind controlling creatures, and astronauts in a very metallic spaceship in suspended animation-like states, very like death.
Hartnell is just marvelous and half of everything he says is a flub and it's wonderful as it's part of his Doctor. He's very warm here, calling Maitland friend but hasn't lost his angry touch, "Go away!" Barbara and Ian chide him in a playful way when he says he learned a long time ago not to meddle in other people's affairs and then too seconds later he asks Maitland what is wrong. Again, David Tennant is wrong in stating that Troughton set up what the Doc is today because as great as he is, it is Hartnell who sets it ALL up and here, his double takes, his control of the spaceship as it almost crashes, and his concern for Susan, sets up very Tom Baker and Pertwee-ish traits as well as Troughton's concern.
It seems strange that the TARDIS, called almost exclusively in this episode as THE SHIP by the Doctor and almost all the others, can have a lock taken out of it. The aliens looks quite mysterious and scary and for once, very alien. This is the first spaceship episode I believe and quite well done. The sets are great but for a few creaking wooden door like sounds on the inside as Barbara and Susan avoid John. Carol and John seem...mismatched really. The music is used well and all the regulars interact well with each other as a well oiled machine here, and they seem to enjoy each other and know each other. We also see the exiting from the TARDIS control room (unless I"m way wrong, we dn't hear it called CONSOLE ROOM at all yet and don't until a very long time from now) into the spaceship in one take through the doors as everyone walks out into the ship.
In all, a very good episode. It's interesting that the Doctor, was, if he could, going to leave Maitland and Carol stuck in space! ANd the others were going to agree with that, too!