The internationally agreed definition of “space” is set at 100km (62 miles) or 330,000ft. It is an arbitrary line, not in any sense a ‘real’ boundary. It is above virtually all of the Earth’s atmosphere and is therefore declared to be “outer space.” This is the reason that private space tourism companies have set their sights on it. Virgin Galactic’s SpaceShip Two will take its passengers on a suborbital hop to 360,000ft, giving them several minutes of weightlessness in which to drift about their cabin. XCOR’s Lynx will take a single passenger alongside its pilot to above the level deemed to be space. The X15 pilots who flew above 50 miles were given astronaut’s wings.
The term “edge of space” used mostly for high altitude balloon flights is generally reckoned to be about 100,000ft (19 miles), and above. The students of Cambridge University Spaceflight regularly send balloons with cameras and telemetry 100,000ft high, and set a UK record at 118,786ft. At that height the atmosphere looks like a blue film wrapped around a curved Earth below, and the sky is black. Now a private firm, World View, plans to offer fare-paying passengers the chance to ride to the edge of space in a pressurized gondola suspended from a balloon. At 100,000ft they will have a view similar in many respects to that which will be enjoyed by the suborbital voyagers. They will be able to spend hours up there, unlike the short hoppers, maybe watching a sunrise over the curved Earth below. They will not experience zero-g, however. At $75,000 per trip, it is by no means cheap, though it is less costly than the suborbital fares currently on offer. I don’t think I’ll do it. I flew Concorde a few times, and still have photos I took of a curved Earth horizon under a black sky. Even though Concorde’s top cruise altitude was only 60,000ft, it was still much higher than most other passenger planes, which are below 40,000ft. I don’t think I’ll do the balloon simply because it’s not space. You can’t really claim to have seen the planet from the outside, as I think you can say above 100km. And although their six passenger, two pilot gondola is officially classified as a “space vehicle” by the Federal Aviation Administration, their customers are not awarded astronaut’s wings on their return.
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