causing a structural failure of Challengers external tank and the orbiter's subsequent disintegration due to aerodynamic forces. NASA's organizational culture was also scrutinized by the Rogers Commission, and the Space Shuttle program's goal of replacing the United States' expendable launch systems was cast into doubt. The loss of Challenger and its crew led to a broad rescope of the program, and numerous aspects – such as launches from Vandenberg, the MMU, and Shuttle-Centaur – were scrapped to improve crew safety; Challenger and Atlantis were the only orbiters modified to conduct Shuttle-Centaur launches. The recovered remains of the orbiter are mostly buried in a missile silo located at Cape Canaveral LC-31, though one piece is on display at the Kennedy Space Center Visitor Complex. History Challenger was named after HMS Challenger, a British corvette that was the command ship for the Challenger Expedition, a pioneering global marine research expedition undertaken from 1872 through 1876. The Apollo 17 Lunar Module, which landed on the Moon in 1972, was also named Challenger. Construction Because of the low production volume of orbiters, the Space Shuttle program decided to build a vehicle as a Structural Test Article, STA-099, that could later be converted to a flight vehicle. The contract for STA-099 was awarded to North American Rockwell on July 26, 1972, and construction was completed in February 1978. After STA-099's rollout, it was sent to a Lockheed test site in Palmdale, where it spent over 11 months in vibration tests designed to simulate entire shuttle flights, from launch to landing. To prevent damage during structural testing, qualification tests were performed to a safety factor of 1.2 times the design limit loads. The qualification tests were used to validate computational models, and compliance with the required 1.4 factor of safety was shown by analysis. STA-099 was essentially a complete airframe of a Space Shuttle orbiter, with only a mockup crew module installed and thermal insulation placed on its forward fuselage. NASA planned to refit the prototype orbiter Enterprise (OV-101), used for flight testing, as the second operational orbiter; but Enterprise lacked most of the systems needed for flight, including a functional propulsion system, thermal insulation, a life support system, and most of the cockpit instrumentation. Modifying it for spaceflight was considered to be too difficult, expensive, and time-consuming. Since STA-099 was not as far along in the construction of its airframe, it would be easier to