As NASA celebrates its 50th anniversary on Oct. 1, 2008, the agency can reflect on five decades of accomplishments, including the science and engineering marvel that is human spaceflight. The agency has gone from the initial suborbital hop of Alan Shepard aboard his Mercury capsule in 1961 to the pinnacle feats of the Apollo moon landings and the ongoing work to construct the International Space Station (shown above in background), which is the largest space construction project in history. By pushing the bounds of space, NASA hopes to pave the way back to the moon by 2020 and send humans on to Mars.
