The Shuttle Orbiter Enterprise (NASAOrbiter Vehicle 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 Enterprise was built first; however, it was found to be cheaper to refit a test article (STA-099) into the Space Shuttle Challenger. Similarly, it was considered for refit to replace Challenger, but Space Shuttle Endeavour was built from spares instead.
Originally planned to be called Constitution, a write-in campaign caused the test vehicle to be renamed after the starship Enterprise, featured on the television show Star Trek. Most of the cast of the original series, as well as Star Trek creator Gene Roddenberry were on hand at the dedication ceremony, and the show's theme music was played. A mural in the captain's office in Star Trek: The Next Generation depicts this Space Shuttle as one of the starship's own namesakes, and images in the opening credits of the series Star Trek: Enterprise pay similar tribute. Oddly, Star Trek: Deep Space Nine later pictured a model of the International Space Station with the Space Shuttle Enterprise docked with it, despite the fact that Enterprise has never been fitted for launch into space.
Enterprise banks on its second Approach and Landing Test, September 13, 1977. Photo courtesy of NASA.
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 atop 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. These ALT tests took place at NASA's Dryden Flight Research Center at Edwards Air Force Base, California.
The mated Enterprise/SCA combination was then subjected to five test flights with 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 Enterprise manned in order to test the shuttle flight control systems.
Finally, 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. See ALT table below for complete list of ALT flight tests.
Following the ALT program, 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.
According to NASA's Dr. Jesco Von Puttkamer, Enterprise was not allowed to launch into space because the excessive vibration testing made the vehicle unspaceworthy and unsafe for Astronauts to fly. NASA engineers were allowed to find out the shuttles weakest areas by shaking the Enterprise almost to pieces. It would have been too costly to repair, so it was sent to Silver Hill.
In 2003, after the breakup of the Shuttle Columbia during re-entry, fiberglass panels were removed from Enterprise, to undergo testing [1]. The single test involved firing a piece of foam at high velocity at the panel. A piece of foam, covering the external fuel tank, broke off and struck the leading edge of Columbia's left wing during launch. It was widely speculated that this impact caused a breach of the vehicle, allowing in super-heated gases during re-entry, leading to Columbia's destruction. During the test, while the panels were not broken, the impact was enough to expose a seal between them.