The STS-121 crew heads for the Astrovan and the ride to Launch Pad 39B for a third launch attempt.

Waving flags for the Fourth of July, the STS-121 crew heads for the Astrovan and the ride to Launch Pad 39B for a third launch attempt. Leading the way are Pilot Mark Kelly (left) and Commander Steven Lindsey (right). Behind them are, left and right, Mission Specialists (second row) Lisa Nowak and Michael Fossum; (third row) Stephanie Wilson and Piers Sellers; and (at the rear) Thomas Reiter, who represents the European Space Agency. The July 2 launch attempt was scrubbed due to the presence of showers and thunderstorms within the surrounding area of the launch site. The launch of Space Shuttle Discovery on mission STS-121 is the 115th shuttle flight and the 18th U.S. flight to the International Space Station. During the 12-day mission, the STS-121 crew will test new equipment and procedures to improve shuttle safety, as well as deliver supplies and make repairs to the International Space Station. Photo credit: NASA/Kim Shiflett