Enterprise (OV-101) was the first Space Shuttle orbiter, built by Rockwell International as an atmospheric and ground-test vehicle rather than a space-rated spacecraft. During NASA's 1977 Approach and Landing Tests, it made three crewed captive flights and five independent unpowered flights from August 12 through October 26, proving the orbiter's approach, flight-control, and runway-landing characteristics. It later supported vibration, assembly, and launch-pad fit checks.