Boldly Going Where 14 Men Have Gone Before

For nearly a dozen years, Virgin Galactic has used the number of individuals who have flown into space as a target to shoot for once the company began suborbital space tourism service. Virgin promised to double the number, which was around 500 when the company launched in 2004, within the first year of operation. That year was originally targeted for 2007 in the confident days after the success of SpaceShipOne.

That goal has long since faded away, and it’s unlikely Virgin will double the number of space travelers during the first year. In any event, the number of space travelers cited by Virgin has always been a bit misleading. The company’s well heeled customers, who are paying upwards of $250,000 per flight, will actually be joining a much more elite group on their suborbital flights.

Of the 553 individuals who have visited space through last month, only 14 of them (2.5 percent) have  boldly (and briefly) gone to suborbital space; the other 439 have traveled to orbit. And that’s using the most generous definition of where space begins.

The table below shows human spaceflights above 50 miles (80 km), which is the U.S. Air Force’s definition of the boundary of space. The international boundary, known as the Karman line, is set at 62 miles (100 km).

SUBORBITAL FLIGHTS ABOVE 50 MILES (80 KM)
FLIGHTCREW
DATE
LAUNCH SITE
ALTITUDE
SPEED
RESULT
Mercury-Redstone 3Alan ShepardMay 5, 1961Cape Canaveral116.5 miles (187.50 km)5,180 mph (8,340 km/h)First American manned spaceflight
Mercury-Redstone 4Virgin I. “Gus” GrissomJuly 21, 1961Cape Canaveral118.25 miles (190.31 km)5,200 mph (8,369 km/h)After a successful flight, capsule sank after premature separation of the hatch; Grissom nearly drowned
X-15 Flight 62Robert M. WhiteJuly 17, 1962Edwards AFB59.6 miles (95.9 km)3,831 mph (6,165 km/h)First flight of a piloted winged aircraft above 50 miles (80 km)
X-15 Flight 77Joseph A. WalkerJan. 17, 1963Edwards AFB51.4 miles (82.7 km)3,677 mph (5,918 km/h)Success
X-15 Flight 87Robert A. RushworthJune 27, 1963Edwards AFB53.9 miles (86.7 km)3,425 mph (5,512 km/h)Success
X-15 Flight 90Joseph A. WalkerJuly 19, 1963Edwards AFB65.8 miles (105.9 km)3,710 mph (5,970 km/h)First flight of a winged aircraft above 100 km (62 miles)
X-15 Flight 91Joseph A. WalkerAug. 22, 1963Edwards AFB67.0 miles (107.8 km)3,794 mph (6,106 km/h)Highest X-15 flight
X-15 Flight 138Joseph H. EngleJune 29, 1965Edwards AFB53.1 miles (85.5 km)3,431 mph (5,522 km/h)Success
X-15 Flight 143Joseph H. EngleAug. 10, 1965Edwards AFB51.3 miles (82.6 km)3,549 mph (5,712 km/h)Success
X-15 Flight 150John B. McKaySept. 28, 1965Edwards AFB55.9 miles (90.0 km)3,731 mph (6,004 km/h)Success
X-15 Flight 153Joseph H. EngleOct. 14, 1965Edwards AFB50.4 miles (81.1 km)3,554 mph (5,720 km/h)Success
X-15 Flight 174 William H. Dana Nov. 1, 1966Edwards AFB58.1 miles (93.5 km)3,750 mph (6,040 km/h)Success
X-15 Flight 190William J. “Pete” KnightOct. 17, 1967Edwards AFB53.1 miles (85.5 km)3,856 mph (6,206 km/h)Success
X-15 Flight 191Michael J. AdamsNov. 15, 1967Edwards AFB50.3 miles (81.0 km)3,569 mph (5,744 km/h)Adams killed after he lost control of X-15 and ship broke up during reentry
X-15 Flight 197William H. DanaAug. 21, 1968Edwards AFB50.6 miles (81.4 km)3,443 mph (5,541 km/h)Success
Soyuz 18.aVasili Lazarev, Oleg MakarovApril 5, 1975Baikonur119 miles (192 km)Soyuz spacecraft failed to orbit due to upper stage malfunction; crew experienced 21.3 gs during abort; Soyuz rolled down hill and stopped just short of a cliff; Lazarev suffered internal injuries and new flew in space again
SpaceShipOne Flight 15PMike MelvillJune 21, 2004Mojave Air & Space Port62.21 miles (100.124 km)2,150 mph (3,460 km/h)First spaceflight by a privately built spacecraft
SpaceShipOne Flight 16PMike MelvillSept. 29, 2004Mojave Air & Space Port63.96 miles (102.93 km)2,110 mph (3,396 km/h)First X-Prize flight
SpaceShipOne Flight 17PBrian BinnieOct. 4, 2004Mojave Air & Space Port69.6 miles (112.014 km)2,186 mph (3,518 km/h)X-Prize winning flight; broke altitude record for suborbital winged spaceflight set by Joseph A. Walker in 1962

Thirteen of the 19 flights were made by the air-launched X-15 rocket plane during the 1960’s. Eleven of those flights made it above 50 miles (80 km) but below 62 miles (100 km). Joseph A. Walker flew the vehicle above the Karman line twice in 1963, setting an altitude record of 67 miles (107.8 km) that would stand for 41 years.

Walker’s record was broken by Brian Binnie in the final flight of SpaceShipOne on Oct. 4, 2004. Binnie reached 69.6 miles (112 km) during a flight that won the $10 million Ansari X Prize for a team led by Burt Rutan and Paul Allen.

Mike Melvill stands atop SpaceShipOne after a suborbital flight on Sept. 29, 2004. (Credit: RenegadeAven)
Mike Melvill stands atop SpaceShipOne after a suborbital flight on Sept. 29, 2004. (Credit: RenegadeAven)

The prize had required to flights by a privately built spacecraft above the Karman line within a two-week period. Mike Melvill had flown the first prize flight five days earlier.

In all, SpaceShipOne flew to space three times. Melvill piloted the first flight in June 2004, barely exceeding the Karman line along the way. For that achievement, SpaceShipOne is now displayed in the National Air & Space Museum in Washington, D.C.

Redstone rocket takes off with Alan Shepard aboard. (Credit: NASA)
Redstone rocket takes off with Alan Shepard aboard. (Credit: NASA)

The other three suborbital flights were conducted via ballistic missiles. Alan Shepard became the first American in space during a 16-minute flight aboard Freedom 7 in May 1961. Two months later, Gus Grissom repeated the feat two months later in Libery Bell 7.

The only other manned suborbital flight occurred by accident in 1975. After the Soyuz 18.a spacecraft failed to separate from its booster, Vasili Lazarev and Oleg Makarov endured a harrowing descent into Siberia during which they were subjected to 21.3 g’s. The capsule rolled down a hill after landing, stopping just short of a steep cliff.

The table below shows the pilots who have flown on suborbital flights along with the number of missions they flew.

SUBORBITAL PILOTS
PILOT(S)VEHICLE
MAXIMUM ALTITUDE
FLIGHTS BETWEEN 50 & 62 MILES
FLIGHTS ABOVE 62 MILESTOTAL
Joseph A. WalkerX-1567.0 miles
(107.8 km)
123
Joseph H. EngleX-1553.1 miles
(85.5 km)
33
Mike MelvillSpaceShipOne63.96 miles (102.93 km)22
William H. DanaX-1558.1 miles
(93.5 km)
22
Vasili LazarevSoyuz-18a119 miles
(192 km)
11
Oleg MakarovSoyuz-18a119 miles
(192 km)
Virgil I. “Gus” GrissomMercury (Liberty Bell 7)118.25 miles (190.31 km)11
Alan B. ShepardMercury (Freedom 7)116.5 miles
(187.50 km)
11
Brian BinnieSpaceShipOne69.6 miles (112.014 km)11
Robert M. WhiteX-1559.6 miles
(95.9 km)
11
John B. McKayX-1555.9 miles
(90.0 km)
11
Robert A. RushworthX-1553.9 miles
(86.7 km)
11
William J. “Pete” KnightX-1553.1 miles
(85.5 km)
11
Michael J. AdamsX-1550.3 miles
(81.0 km)
11
TOTALS:11819

In all, 14 individuals have flown suborbital flights, four of them multiple times, for a total of 19 flights. Eight of the flights went above 62 miles (100 km), with the remain 11 missions reaching above 50 miles (80 km) but below the Karman line.

A memorial to X-15 pilot Mike Adams on the site of where he crashed in 1967. (Credit: Douglas Messier)
A memorial to X-15 pilot Mike Adams on the site of where he crashed in 1967. (Credit: Douglas Messier)

One of the flights was fatal. Michael J. Adams died after he lost control of his X-15 rocket plane during re-entry, causing it to break up. He was unable to eject.

Suborbital pilots faced other dangers. During the Soyuz 18.a abort, Lazarev suffered internal injuries so severe that he never flew in space again. Grissom nearly drowned after the hatch of his spacecraft was blown prematurely, causing Liberty Bell 7 to fill with water and sink.

Grissom would later die in the Apollo 1 fire. Walker died three years after his record mission when his F-104 fighter collided with an XB-70 bomber during a promotional flight. McKay passed away in 1975 after suffering for 12 years from injuries suffered in the crash of an X-15.

Although they won’t be going to orbit, future suborbital space tourists flying aboard SpaceShipTwo, Lynx, New Shepard or some other vehicle can rest assured that they will be joining a truly elite group of brave men in performing a feat that involves significant risks to life and limb. That will involve a lot of courage.

  • ThomasLMatula

    Anyone planning to test a suborbital winged vehicle like the X-15 should be required to read the excellent history of the program by Michelle L. Evans, “The X-15 Rocket Plane: Flying the First Wings into Space” based on interviews not only with the pilots, but also the mechanics, engineers and recovery personal as it is a gold mine of information on the challenges they overcame and the safety lessons to be learned for other spacecraft.