On September 17, 1976, a gleaming white spacecraft emerged from the Rockwell International manufacturing plant in Palmdale, California, and rolled out to face the desert sun and a gathering of dignitaries, engineers, and a group of very special guests. The occasion was the public unveiling of OV-101, the first orbiter of the Space Shuttle program. The vehicle had originally been planned to carry the name Constitution, unveiled on Constitution Day as a nod to America's bicentennial year. But a remarkable grassroots campaign had changed that. Hundreds of thousands of fans of the television series Star Trek had written letters to President Gerald Ford requesting that the shuttle be named after the fictional starship at the heart of the show. Ford, who had personal reasons for favoring the name — his naval unit had serviced the aircraft carrier USS Enterprise during World War II — directed NASA officials to make the change. So it was that the cast of Star Trek stood beside the shuttle bearing their ship's name as it emerged into public view for the first time.
Enterprise was never intended to fly in space. It was designed from the beginning as a test vehicle — a full-scale, operational-weight orbiter that could be used to verify the aerodynamics, handling characteristics, and landing performance of the Space Shuttle design before a flight-qualified vehicle was ever committed to orbit. As such, it was constructed without the systems that would have been needed for spaceflight. It had no main engines, no functional heat shield, and no reaction control system thrusters. Instead of the reinforced carbon-carbon panels that would protect a real orbiter during re-entry, Enterprise's leading edges were made of fiberglass. Most of its surface was covered with simulated thermal tiles made from polyurethane foam rather than the actual silica tiles that would protect Columbia and its successors. Only a small number of genuine thermal protection tiles and some Nomex blankets were installed, primarily for evaluation purposes. The landing gear lacked the hydraulic actuation systems of a spaceflight vehicle; the gear doors were blown open by explosive bolts, and the gear itself deployed by gravity alone.
Construction of Enterprise began on June 4, 1974. In the summer of 1976, before its public rollout, the orbiter was used for ground vibration testing at Rockwell's facility, allowing engineers to compare real measurements from an actual flight vehicle against the theoretical models they had been using in design calculations. The results of this testing provided invaluable data that shaped the final design of Columbia, the first space-rated orbiter.
The heart of Enterprise's test program was the Approach and Landing Tests, carried out in 1977 at Edwards Air Force Base in California. A specially modified Boeing 747, designated the Shuttle Carrier Aircraft, carried Enterprise mounted on its back to altitude, then released it for unpowered glide flights over the Mojave Desert. The test program was designed to evaluate how the orbiter handled in atmospheric flight and during landing — critical questions for a vehicle that would glide home from orbit without powered approach capability. Enterprise completed five captive-carry flights without release, five free-flight tests, and a series of additional landings, providing a wealth of aerodynamic data.
The test vehicle was also unusual in its equipment. It carried a large nose probe — common on experimental aircraft — that provided accurate readings for test instruments positioned well forward of the disturbed airflow around the vehicle's body. Two Lockheed-manufactured zero-zero ejection seats, identical to those installed in Columbia for its first four missions, were fitted for the safety of the crew during the test flights.
After the Approach and Landing Tests concluded, Enterprise's future became uncertain. NASA had originally intended to refit it as a second operational orbiter. During the construction of Columbia, however, the final design had evolved significantly from what Enterprise had been built to. The changes made it simpler and cheaper to build a new orbiter around an existing structural test article — the vehicle that would become Challenger — than to modify Enterprise to the new specifications. Enterprise was thus set aside. After the Challenger disaster in January 1986, NASA briefly considered refitting Enterprise as a replacement, but again a new vehicle — Endeavour — was built from structural spares rather than reworking the prototype.
Enterprise was instead given a distinguished retirement. In 2003 it was restored and placed on display at the Smithsonian Institution's Steven F. Udvar-Hazy Center in Chantilly, Virginia, near Washington. When the Space Shuttle program ended in 2011 and the surviving flight orbiters were distributed to museums, Discovery — which had flown more missions than any other orbiter — was transferred to the Udvar-Hazy Center, and Enterprise made one final journey. In July 2012, it was installed on the flight deck of the Intrepid Sea, Air and Space Museum in New York City, where it has remained on display ever since, mounted under a purpose-built pavilion on the Hudson River, a monument to the era of test flight that made human spaceflight routine.
