Enterprise was the space shuttle used only for atmospheric tests and never flew in space.
NASA built Enterprise, designated OV-101, as the first space shuttle orbiter and a test vehicle. It was carried into the air by a modified Boeing 747 Shuttle Carrier Aircraft, then released for unpowered glide flights so engineers could study shuttle handling, flight controls, and landing performance.
Enterprise’s first solo glide occurred on August 12, 1977. It completed five free-flight tests after a series of captive flights, helping NASA refine the orbiter’s aerodynamic design before Columbia began orbital missions in 1981. Enterprise was also used for ground vibration tests and launch-pad fit checks.
Unlike the operational orbiters, Enterprise had no spaceflight-capable main engines or complete thermal-protection system. Its simulated tiles and test hardware were sufficient for atmospheric work but not launch, reentry, or orbit. NASA considered refitting it for spaceflight, but design changes made building new orbiters more practical. Enterprise is now displayed at New York’s Intrepid Museum.