page_title: Space Shuttle Enterprise
section_title: Post-Columbia
hierarchical_section_title: Space Shuttle Enterprise / Service / Post-Columbia
caption_attribution_description: English: Space Shuttle Enterprise's damaged wing leading edge from tests following the Columbia accident.
context_page_description: Space Shuttle Enterprise was the first orbiter of the Space Shuttle system. Rolled out on September 17, 1976, it was built for NASA as part of the Space Shuttle program to perform atmospheric test flights after being launched from a modified Boeing 747. It was constructed without engines or a functional heat shield. As a result, it was not capable of spaceflight.
  Originally, Enterprise had been intended to be refitted for orbital flight to become the second space-rated orbiter in service. However, during the construction of Space Shuttle Columbia, details of the final design changed, making it simpler and less costly to build Challenger around a body frame that had been built as a test article. Similarly, Enterprise was considered for refit to replace Challenger after the latter was destroyed, but Endeavour was built from structural spares instead.
  Enterprise was restored and placed on display in 2003 at the Smithsonian's new Steven F. Udvar-Hazy Center in Virginia.
context_section_description: In 2003 after the breakup of  Columbia during re-entry, the Columbia Accident Investigation Board conducted tests at Southwest Research Institute, which used an air cannon to shoot foam blocks of similar size, mass and speed to that which struck Columbia at a test structure which mechanically replicated the orbiter wing leading edge. They removed a section of fiberglass leading edge from Enterprise's wing to perform analysis of the material and attached it to the test structure, then shot a foam block at it.  While the leading edge was not broken as a result of the test, which took place on May 29, 2003, the impact was enough to permanently deform a seal and leave a thin gap 22 inches (56 cm) long. Since the strength of the reinforced carbon–carbon (RCC) on Columbia is "substantially weaker and less flexible" than the test section from Enterprise, this result suggested that the RCC would have been shattered. A section of RCC leading edge from Discovery was tested on June 6, to determine the effects of the foam on a similarly aged leading edge, resulting in a three-inch (7.6 cm) crack on panel 6 and cracking on a "T"-shaped seal between panels 6 and 7. On July 7, using a leading edge from Atlantis and focused on panel 8 with refined parameters stemming from the Columbia accident investigation, a second test created a ragged hole approximately 16 by 16 in (41 by 41 cm) in the RCC structure. The tests clearly demonstrated that a foam impact of the type Columbia sustained could seriously breach the protective RCC panels on the wing leading edge.
  The board determined that the probable cause of the accident was that the foam impact caused a breach of a reinforced carbon-carbon panel along the leading edge of Columbia's left wing, allowing hot gases generated during re-entry to enter the wing and cause structural collapse. This caused Columbia to tumble out of control, breaking up with the loss of the entire crew.
caption: Damage to the leading edge of the wing from the post-Columbia impact tests
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