The space shuttle Columbia is launched from Cape Canaveral, Florida, becoming the first reusable manned spacecraft to travel into space. Piloted by astronauts Robert L. Crippen and John W. Young, the Columbia undertook a 54-hour space flight of 36 orbits before successfully touching down at California’s Edwards Air Force Base on April 14. On September 17, 1976, NASA publicly unveiled its first space shuttle, the Enterprise, during a ceremony in Palmdale, California. Development of the aircraft-like spacecraft cost almost $10 billion and took nearly a decade. In 1977, the Enterprise became the first space shuttle to fly freely when it was lifted to a height of 25,000 feet by a Boeing 747 airplane and then released, gliding back to Edwards Air Force Base on its own accord. Regular flights of the space shuttle began on April 12, 1981, with the launching of Columbia. Launched by two solid-rocket boosters and an external tank, only the aircraft-like shuttle entered into orbit around Earth. When the mission was completed, the shuttle fired engines to reduce speed and, after descending through the atmosphere, landed like a glider. Early shuttles took satellite equipment into space and carried out various scientific experiments. On January 28, 1986, NASA and the space shuttle program suffered a major setback when the Challenger exploded 74 seconds after takeoff and all seven people aboard were killed. In September 1988, space shuttle flights resumed with the successful launching of the Discovery. In subsequent years, the space shuttle carried out numerous important missions, such as the repair and maintenance of the Hubble Space Telescope and the construction and manning of the International Space Station. A tragedy in space again rocked the nation on February 1, 2003, when Columbia, on its 28th mission, disintegrated during re-entry of the earth’s atmosphere. All seven astronauts aboard were killed. In the aftermath, the space-shuttle program was grounded until Discovery returned to space in July 2005, amid concerns that the problems that had downed Columbia had not yet been fully solved.