Richard Branson's Virgin Galactic and Jeff Bezos' Blue Origins have their sights set on commercial spaceflight, with both of them moving ever closer to launching operations within months. Both companies foresee simultaneously flying six fare-paying private astronauts, who will be able to float freely in a micro-gravity environment within their cabins at sub-orbital altitudes on the edge of space. But what approach does each organisation have to access space, how will they provide sustained flights to this next frontier and what will be the cost of a ticket to ride? Sub-orbital space is generally considered to be 82-100kms above the Earth. Reaching it is easier than achieving orbit. Firing a rocket at Mach 3 or about 3,700k/ph will take a craft to a sub-orbital arc, while achieving the much tougher Mach 25, around 29,000k/ ph, enables an astronaut to go into full orbit at a 200km altitude.
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