Utopia 4-21

Utopia 4-21 is the twenty-first level of Utopia.

Difficulty
Three stars can be problematic for some. The higher pigs can be tricky.

Strategy
Send Orange Bird near the edge of the atmosphere, having him fall between the first two towers. Managing to clear the level with a single bird will pretty much guarantee three stars, though combining more birds with more destruction can reach the threshold as well.

Walkthrough
http://www.angrybirdsnest.com/angry-birds-space-utopia-level-4-21-walkthrough/