When does an aircraft become a spacecraft? This was once a subject of significant debate until a clear line of demarcation was established at an altitude of approximately 100 km (60 mi) above sea level.
The Space Shuttle was the highlight of NASA’s Space Transport System’s reusability. Six shuttles were built, but only five ever went to orbit. STS Enterprise was used only for preliminary test flights and training.
The Space Transport System (also known as the Space Shuttle) revolutionized American spaceflight. Its design and development were greenlighted by President Richard Nixon in 1969, with flights beginning in the early 1980s.
Known as NASA’s SpaceX Demo-2 test flight, which is targeted for lift off at 3:22 p.m. EDT Saturday, May 30, this mission will send NASA astronauts Robert Behnken and Douglas Hurley to the International Space Station as part of the agency’s Commercial Crew Program.
In the first two parts, we discussed Sputnik I, the first satellite ever put into orbit, and Sputnik II, the follow-on mission to Sputnik I. In this last part, we’ll examine Explorer I, the first U.S. satellite in space.