A Look at the History of Suborbital Spaceflight

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).

Taking the broader definition into account, the history of suborbital human spaceflight encompasses all of 19 flights conducted over the past 56 years.

Sixteen of the 19 flights were made by reusable vehicles. The X-15 made 13 flights above 50 miles that were flown by eight different pilots. The reusable SpaceShipOne flew three successful suborbital flights in 2004, the final two to win the $10 million Ansari X Prize.

Joseph Walker was the only pilot to fly the X-15 above the Karman line, achieving that milestone twice in 1963. Walker also made a third flight above 50 miles earlier in the same year.

Following Walker’s flights, no other pilot flew a winged suborbital vehicle above 100 km until Mike Melvill did so in SpaceShipOne on June 21, 2004. Melvill and Walker share the distinction of making two suborbital flights about the Karman line. Melvill, Walker and Brian Binnie are the only pilots to fly a winged suborbital vehicle above 100 km.

In 1961, Walker was awarded the prestigious Collier Trophy along with fellow test pilots Robert White and A. Scott Crossfield for their contribution to the X-15 program. U.S. Navy Commander Forrest Petersen shared the award.

Future space shuttle astronaut Joseph Engle flew the X-15 three times above 50 miles. He is the only person to pilot two different types of winged vehicles back from space.

The X-15 program flew 199 flights with one in-flight fatality. On the X-15’s next to last flight above 50 miles, pilot Michael J. Adams died when his rocket plane spun out of control. He was the only casualty of the 13 flights above 50 miles.

SpaceShipOne had 17 flights in total. Six flights were powered, with three of them reaching above the Karman line.

In 2004, Melvill and Binnie were awarded the Collier Trophy along with Burt Rutan, Paul Allen, Doug Shane and the entire SpaceShipOne Team.

Three suborbital flights were made using expendable vehicles. This list includes the first two Mercury missions by Alan Shepard and Gus Grissom and the aborted Soyuz 18a flight. The Soyuz mission was intended to go to orbit,  but a booster malfunction resulted in a high-altitude abort.

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