Sub-orbital spaceflight is when a spacecraft goes into space but does not reach the altitude where it can orbit Earth. It goes to the end of the atmosphere, or specifically, 62 miles (100 km). Right at this distance above the planet is where people can experience weightlessness.

It was Theodore von Karman who formulated the idea of a certain altitude where the atmosphere was too thin for regular flight. Called the Karman line, 62 miles is approximately where the thermosphere starts and is considered the “edge of space.” It’s in this part of the Earth’s atmosphere where solar radiation gets absorbed and can reach temperatures 360 degrees Fahrenheit on regular days, but can go as high as 900 degrees when there’s a lot of solar activity.

The first known suborbital flight of any man-made device was the German V2 rocket missile built in 1942 during Nazi Germany as a weapon of war primarily against England.

The first manned flight of the United States was a suborbital flight between the Atlantic Ocean coast and the Pacific coast, made by Alan Shepard in the first launch of the Mercury Program on May 5, 1961, with a duration of only 15 minutes.

In the same way, the first flight of a spacecraft to carry out space tourism trips was also suborbital, the SpaceShipOne on October 4, 2004.

More Info: en.wikipedia.org