Neil Armstrong with the X-15 on the dry lake bed at Edwards Air Force Base, Calif.
With Richard Branson once again predicting that Virgin Galactic will fly SpaeShipTwo into space before the end of the year, it seems like a good time to take a look at the history of suborbital spaceflight.
The number of manned suborbital flights varies depending upon the definition you use. The internationally recognized boundary is 100 km (62.1 miles), which is also known as the Karman line. The U.S. Air Force awarded astronaut wings to any pilot who exceeded 80.5 km (50 miles).