The launch of Space Shuttle Discovery off the fireworks for the U.S. holiday in its third launch attempt in four days.

Like a roman candle shooting through the blue sky, the launch of Space Shuttle Discovery on mission STS-121 kicks off the fireworks for the U.S. holiday in its third launch attempt in four days. Liftoff was on-time at 2:38 p.m. EDT. During the 12-day mission, the STS-121 crew of seven will test new equipment and procedures to improve shuttle safety, as well as deliver supplies and make repairs to the International Space Station. Landing is scheduled for July 16 or 17 at Kennedy's Shuttle Landing Facility. Photo credit: NASA/Ken Thornsley