The scheduled liftoff today of the space shuttle Atlantis will end one chapter of America's adventure in space and begin another.
For three decades, NASA has relied on its now-aging shuttle fleet to maintain the U.S. technological edge in space travel provided by the moon missions of the 1960s and 1970s. Because they are reusable, the shuttles revolutionized NASA's ability to deliver satellites and scientific payloads to suborbital destinations such as the International Space Station.
The first phase of the expanding space station's construction would have been far more complicated without the shuttle fleet's ability to deliver component parts, crew members, and resources. It was the bridge between inefficient Saturn rockets and the next generation of multi-purpose craft NASA envisions for deep space exploration in coming decades.
With the retirement of the shuttles Discovery, Endeavor, and Atlantis, NASA will turn over responsibility for payload delivery to the private sector. The space agency will concentrate on developing technology and a plan for manned missions to asteroids and a rendezvous with Mars in the 2020s or 2030s.
The estimated $100 billion spent on the shuttles' 135 missions is difficult for many Americans to justify. The public has been indifferent to or ignorant of much of what the shuttle program has accomplished.
Enhancement of payload delivery technology is not sexy. Even such technological coups as repairing the malfunctioning Hubble Telescope and enhancing its ability to peer into the vastness of space do not resonate with people the way a walk on the moon did.
The Challenger and Columbia shuttle disasters shook public confidence in manned space missions. It now costs a billion dollars per crew for NASA to ensure, as best it can, safe takeoffs and landings for the shuttle craft.
This isn't the most cost-effective use of resources in cash-strapped times. By contrast, most of the biggest space breakthroughs of the past 30 years have come from inexpensive robot probes.
Still, manned missions such as the shuttle have been an invaluable part of the mix. Robots can't do everything.
Discovery, Endeavor, and Atlantis aren't as familiar to the public as the names of the ships Columbus commanded in 1492, but they deserve to be. Although these vessels will be mothballed in museums, the human spirit that navigated them is already anticipating the next step into space.