the two-day mission, Young and Crippen tested equipment on board the shuttle, and found several of the ceramic tiles had fallen off the top side of the Columbia. NASA coordinated with the Air Force to use satellites to image the underside of Columbia, and determined there was no damage. Columbia reentered the atmosphere and landed at Edwards AFB on April 14. NASA conducted three additional test flights with Columbia in 1981 and 1982. On July 4, 1982, STS-4, flown by Ken Mattingly and Henry Hartsfield, landed on a concrete runway at Edwards AFB. President Ronald Reagan and his wife Nancy met the crew, and delivered a speech. After STS-4, NASA declared its Space Transportation System (STS) operational. Description The Space Shuttle was the first operational orbital spacecraft designed for reuse. Each Space Shuttle orbiter was designed for a projected lifespan of 100 launches or ten years of operational life, although this was later extended. At launch, it consisted of the orbiter, which contained the crew and payload, the external tank (ET), and the two solid rocket boosters (SRBs). Responsibility for the Shuttle components was spread among multiple NASA field centers. The KSC was responsible for launch, landing, and turnaround operations for equatorial orbits (the only orbit profile actually used in the program). The U.S. Air Force at the Vandenberg Air Force Base was responsible for launch, landing, and turnaround operations for polar orbits (though this was never used). The Johnson Space Center (JSC) served as the central point for all Shuttle operations and the MSFC was responsible for the main engines, external tank, and solid rocket boosters. The John C. Stennis Space Center handled main engine testing, and the Goddard Space Flight Center managed the global tracking network. Orbiter The orbiter had design elements and capabilities of both a rocket and an aircraft to allow it to launch vertically and then land as a glider. Its three-part fuselage provided support for the crew compartment, cargo bay, flight surfaces, and engines. The rear of the orbiter contained the Space Shuttle Main Engines (SSME), which provided thrust during launch, as well as the Orbital Maneuvering System (OMS), which allowed the orbiter to achieve, alter, and exit its orbit once in space. Its double-delta wings were long, and were swept 81° at the inner leading edge and 45° at the outer leading edge. Each wing had an inboard and outboard elevon to provide