The first chapter, "The Dawn of Man", starts with the scene of an actual dawn. There are plenty of silent moments when the viewer can simply admire the view. Like the orchestral introduction, it helps the viewer accustom themselves to the setting. Knowing the environment in which the story takes place can be as important as the message of the story itself. I believe the desert setting was chosen because its starkness forces the viewer to see what is happening with the apes rather than focus on the environment excessively. It also helps amplify the stark conditions in which the apes lived.
Slow motion has been long used to bring attention to the significance of a particular scene. This movie is no stranger to that concept. The scene where the ape learns to wield a tool is a good example of this.
The space shuttle scene, though apparently not in slow motion, still gives a feeling of sluggishness. It would seem to be a combination of slow motion (due to the pace) and display of the environment. Space activity is naturally slow for the sake of caution. This scene incorporates this slowness and uses it to do what happened earlier in the "Dawn of Man" chapter: let us absorb the details of the environment. Another notable thing about the shuttle scene is that since there is no atmosphere to carry sound in space, we are given classical music to listen to. This music helps fill in an otherwise alienating silence and supports the intended feeling regarding this scene.
