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Virgin Galactic's CEO says his company is aiming to take passengers beyond 62 miles (100 kilometers) in altitude, but they'll be counted as space travelers if they just rise above the 50-mile mark.
That 12-mile span highlights differences in definitions of the outer-space boundary, as well as questions about the initial capabilities of Virgin Galactic's SpaceShipTwo rocket plane. The spacecraft is expected to go through a series of flight tests over the coming months, setting the stage for commercial passenger operations.
100 kilometers vs. 50 miles
According to the International Aeronautical Federation, a flight goes astronautical when it crosses the 100-kilometer line, also known as the Karman Line. That was also the definition of space used for the $10 million Ansari X Prize a decade ago, and Virgin Galactic has referred to the 100-kilometer definition numerous times since then.
However, the U.S. military has historically awarded astronaut wings to pilots who rose above 50 miles (80 kilometers) during the 1960s. NASA followed that definition for its X-15 test pilots — although three of those pilots didn't get their astronaut wings until 2005, 40 years after they flew. (One of them, Bill Dana, died last week at the age of 83.)
It's the 50-mile definition, rather than the 100-kilometer definition, that's written into the formal agreements for Virgin Galactic's customers. "Fifty miles has been in there from the start," George T. Whitesides, Virgin Galactic's chief executive officer, told NBC News on Friday.
More than 700 customers have paid as much as $250,000 for the space experience — which would give them several minutes of weightlessness, a view of the curving Earth beneath the black sky of space, and a roller-coaster re-entry that involves as much as 6 G's of acceleration. That experience would be much the same at 50 miles as at 62 miles, though with somewhat less time spent in zero-G.
Whitesides said Virgin Galactic is targeting the 100-kilometer altitude and beyond, but added that "we have to prove that out in our test program."
"Just like everything else, we'll get better over time," he said. "We're trying to invent a new industry from scratch — we need to do that by stages, and we need to do it informed by safety."
The current plan calls for flying Virgin Galactic's billionaire founder, Richard Branson, on SpaceShipTwo as early as this year. However, Whitesides emphasized that schedule was dependent on the outcome of the flight test program. (Virgin Galactic's development schedules have been consistently overoptimistic: In 2004, Branson was talking about beginning space tourism flights in 2007.)
Whitesides said flight operations may undergo refinements during the early commercial flights. "It'd be unreasonable to think we're going to launch this like a pristine jewel," he told NBC News.
SpaceShipTwo's most recent powered flight test took place in January and rose to a height of 71,000 feet (13.4 miles, or 21.6 kilometers). Since then, Virgin Galactic has been putting the rocket plane's WhiteKnightTwo mothership through rounds of inspections, repairs and upgrades — including the installation of a beefed-up landing gear.
Whitesides said the landing gear was "working well" during an 80-knot (92-mph) runway taxi test at the Mojave Air and Space Port on Thursday. WhiteKnightTwo should resume flights in "a couple of weeks," with SpaceShipTwo tests to follow, he said.
NBCUniversal has established a multi-platform partnership with Virgin Galactic to track the development of SpaceShipTwo and televise its inaugural commercial spaceflight.