12 space shuttle missions that weren't

the U.S. space shuttle fleet is set for retirement following the launch of Atlantis, scheduled for mid-July. In all, the fleet will have flown 135 missions, the first in 1981, but there were many more on the drawing board. With scrubbed missions that included daring rescues, in-orbit satellite snatches, and dangerous explosives, you can see why some of these didn't make the cut. But just imagine if they had.