"It was a dark and stormy night." Or, rather, it was daylight and the weather wasn't actually that bad, but either way, today, on September 17, 1976, NASA unveiled the newest addition to its space fleet - the space shuttle. After nearly a decade of research and development, tens of thousands of man hours, and nearly $10-billion USD, the Enterprise was ready for her public debut. The Enterprise was the precursor to the five other shuttles that would become an icon of the space program.
On June 4, 1974, when construction on the Enterprise began, NASA originally planned to name OV-101 (it's official designation) the Constitution. The reason was because they planned to unveil the spacecraft on Constitution day, September 17, 2013. At the time, Star Trek: The Original Series was, and legacy that remains, extremely popular. Trekkies from across America launched a massive write in campaign to President Ford to have the name changed. They were successful and Ford directed NASA to rename OV-101 the Enterprise.
Unfortunately, Enterprise never made it to orbit. I guess you could call it a "design flaw" as the Enterprise wasn't designed with a heat shield, engines, or some other things that make spaceflight possible. It was designed as a test vehicle. With the reusable spacecraft concept, NASA needed to run performance tests.
This testing started in January of 1977 when Enterprise began it's testing regiment at Edwards Air Force Base. First, NASA tested the landing gear and the modified 747 to ensure both were in working order (because, both are a little important). On the 18th of February, Enterprise took flight for the first time. Between 1977 and 1979, Enterprise performed magnificently and helped NASA engineers for the real thing. Preceding the launch of Space Shuttle Columbia, Enterprise was also used during a dress rehearsal run of a shuttle launch including; testing equipment in the Orbiter Processing Facility, rolling out to the launch pad, having a mock-propulsion system filled with liquid hydrogen/oxygen, and others.
Fortunately, this dress rehearsal discovered the venting system in place for the external booster rockets wasn't adequate, which lead to a dangerous build up of ice on the rocket's nose. This could potentially be disastrous as falling material was known to be dangerous to spacecraft (similarly and tragically seen in the Columbia disaster). NASA engineers redesigned the venting system and solved the problem before Columbia's maiden voyage.
Throughout the early phases of the Shuttle Program, enterprise was used to run simulations, tests, and dry runs. Eventually, the Shuttle program outgrew the faithful test orbiter, and in 1985, Enterprise was retired from its influential service. It was moved to the Smithsonian to collect dust as a museum piece.
Two months after Enterprise's retirement, the world was shocked as they watched the Challenger disaster unfold before their eyes. Following the catastrophe, NASA decided it needed a fifth orbiter to replace Challenger, and considered converting Enterprise for service in orbit. Unfortunately for the craft, NASA settled on building a new orbiter all together. Enterprise was not to see space after all.
For seventeen years, Columbia remained at the Smithsonian until 2003 when Columbia disintegrated on reentry. Enterprise was used to run simulations and tests to help determine what had happened to Columbia and was instrumental in both identifying Columbia's malfunction and providing enough information for NASA scientists to reinstate the Shuttle program. If you visit Enterprise, look at its wing. You'll see heat damage that the ship sustained while these tests were being run; a scar that ultimately helped Atlantis, Discovery, and Endeavour to fly once more.
Without the help of the Enterprise, the shuttle program wouldn't have happened. The orbiter was officially-officially retired with the rest of the shuttle fleet in 2011 (because, without a shuttle fleet, NASA won't need to call on Enterprise again). Enterprise has retaken her place as a public icon and a museum piece, residing in the Intrepid Air and Sea Museum in New York City.
In the end, Enterprise fulfilled her mission, and lots more, she made the Shuttle Program safer, she provided invaluable data, and she helped give a third wind to the program after the loss of Columbia. Without the Enterprise, we wouldn't have the Hubble Space Telescope (which was put into orbit and serviced by several shuttle missions), we wouldn't have the International Space Station (which was constructed with the help of the Shuttle fleet), and the culture of the space program would be very different.