The Shuttle Orbiter Enterprise (NASA Designation: OV-101) was the first Space Shuttle built for NASA. It was initially constructed without engines or a functional heat shield and was therefore not capable of space operations without a refit. It was intended to be the second space shuttle to fly after the Space Shuttle Columbia even though it was built first, however, it was found to be cheaper to refit a test article (STA-099) into the Space Shuttle Challenger.
Originally planned to be called Constitution, the test vehicle was renamed following a write-in campaign after the starship featured on the television show Star Trek, which in turn was named for the various ships named USS Enterprise. Amusingly, in one of the subsequent Star Trek movies there is a mural on board the starship depicting this Space Shuttle as one of its own namesakes, and images in the opening credits to the series Star Trek: Enterprise pay similar tribute.
The Enterprise was used by NASA for a variety of ground and flight tests intended to validate aspects of the shuttle program. The initial nine-month testing period was referred to by the acronym ALT for "Approach and Landing Test". These tests included a maiden "flight" on February 18, 1977 a top a Boeing 747 shuttle carrier aircraft (SCA) to measure structural loads and ground handling and braking characteristics of the mated system. Ground tests of all orbiter subsystems were carried out to verify functionality prior to atmospheric flight.
The mated Enterprise/SCA combination was then subjected to five test flights with the Enterprise unmanned and unactivated. The purpose of these test flights was to measure the flight characteristics of the mated combination. These tests were followed with three test flights with the Enterprise manned in order to test the shuttle flight control systems.
Finally, the Enterprise underwent five free flights where the craft separated from the SCA and was landed under astronaut control. These tests verified the craft's flight characteristics and were carried out under several aerodynamic and weight configurations.
Following the ALT program, the Enterprise was ferried between several NASA facilities to configure the craft for vibration testing. Ultimately it was mated with an external tank and solid rocket boosters and tested in a launch configuration.
With the completion of critical testing, the Enterprise was partially disassembled to allow certain components to be reused in other shuttles, then underwent a world tour visiting France, Germany, Italy, the United Kingdom, Canada, and the US states of California, Alabama, and Louisiana. It was also used to fit-check the never-used shuttle launch pad at Vandenberg AFB, California. Finally, on November 18, 1985, the Enterprise was ferried to Washington, D.C, where it became property of the Smithsonian Institution.
Enterprise is currently on display at the Smithsonian's hangar at Washington Dulles International Airport.