I would definitely plan to base this lesson off of a story about space. I would start by reading the story aloud to the children and asking them thought provoking questions along the way. After this, I would perhaps show them real-life images on the IWB of space and create a discussion on this. To follow on from this I would then use puppets of aliens/astronauts to create an element of play for the children in relation to rockets & aliens. I then would create a dress up area for the children to create their own drama in their groups of their perception of aliens and rockets in space.
Furthermore, I would use empty toilet roll holders and arts and crafts to get the children to create their own personalised rocket ships.