A Look at the History of Suborbital Spaceflight

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).

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

Suborbital Spaceflights Above 50 Miles
#FlightDateTop SpeedAltitudePilot
1Mercury-RedstoneMay 5, 19615,134 mph
(8,262 km/h)
117 mi
(188 km)
Alan Shepard
2Mercury- RedstoneJuly 21, 19615,168 mph
(8,317 km/h)
118 mi
(190 km)
Gus Grissom
3X-15July 17, 19623,831 mph
(6,165 km/h)
59.6 mi
(95.9 km)
Robert M. White
4X-15January 17, 19633,677 mph
(5,918 km/h)
51.4 mi
(82.7 km)
Joseph A. Walker
5X-15June 27, 19633,425 mph
(5,512 km/h)
53.9 mi
(86.7 km)
Robert Rushworth
6X-15July 19, 19633,710 mph
(5,970 km/h)
65.8 mi
(105.9 km)
Joseph A. Walker
7X-15August 22, 19633,794 mph
(6,106 km/h)
67.0 mi
(107.8 km)
Joseph A. Walker
8X-15June 29, 19653,431 mph
(5,522 km/h)
53.1 mi
(85.5 km)
Joseph H. Engle
9X-15August 10, 19653,549 mph
(5,712 km/h)
51.3 mi
(82.6 km)
Joseph H. Engle
10X-15September 28, 19653,731 mph
(6,004 km/h)
55.9 mi
(90.0 km)
John B. McKay
11X-15October 14, 19653,554 mph
(5,720 km/h)
50.4 mi
(81.1 km)
Joseph H. Engle
12X-15November 1, 19663,750 mph
(6,040 km/h)
58.1 mi
(93.5 km)
William H. Dana
13X-15October 17, 19673,856 mph
(6,206 km/h)
53.1 mi
(85.5 km)
William “Pete” Knight
14X-15November 15, 19673,569 mph
(5,744 km/h)
50.3 mi
(81.0 km)
Michael J. Adams
15X-15August 21, 19683,443 mph
(5,541 km/h)
50.6 mi
(81.4 km)
William H. Dana
16Soyuz 18aApril 5, 1975?119 mi
(192 km)
Vasili Lazarev, Oleg Makarov
17SpaceShipOneJune 21, 20042,150 mph
(3,460 km/h)
62.2 mi
(100.1 km)
Mike Melvill
18SpaceShipOneSeptember 29, 20042,163 mph
(3,481 km/h)
63.96 mi
(102.9 km)
Mike Melvill
19SpaceShipOneOctober 4, 20042,291 mph
(3,686 km/h)
69.6 mi
(112 km)
Brian Binnie

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.

Suborbital Spaceflights Above the Karmen Line
#FlightDateTop
Speed
AltitudePilot
1Mercury-RedstoneMay 5, 19615,134 mph
(8,262 km/h)
117 mi
(188 km)
Alan Shepard
2Mercury- RedstoneJuly 21, 19615,168 mph
(8,317 km/h)
118 mi
(190 km)
Gus Grissom
3X-15July 19, 19633,710 mph
(5,970 km/h)
65.8 mi
(105.9 km)
Joseph A. Walker
4X-15August 22, 19633,794 mph
(6,106 km/h)
67.0 mi
(107.8 km)
Joseph A. Walker
5Soyuz 18aApril 5, 1975?119 mi
(192 km)
Vasili Lazarev, Oleg Makarov
6SpaceShipOneJune 21, 20042,150 mph
(3,460 km/h)
62.2 mi
(100.1 km)
Mike Melvill
7SpaceShipOneSeptember 29, 20042,163 mph
(3,481 km/h)
63.96 mi
(102.9 km)
Mike Melvill
8SpaceShipOneOctober 4, 20042,291 mph
(3,686 km/h)
69.6 mi
(112 km)
Brian Binnie

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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  • publiusr

    What’s the deal with Soyuz 18a.

    I thought all of Soyuz flights were orbital…