how to ...... go around the world in six hours

While hypersonic aircraft might not quite consign long-haul flights to the history books, travelling at five times the speed of sound would put almost anywhere in the world on the map for a day trip. Over the past 50 years hypersonic passenger aircraft have been proposed many times, usually accompanied by illustrations of needle-thin spaceplanes soaring gracefully above the curve of the Earth. The US military, too, is keen on shipping troops (or merely warheads) around the world in a flash, and has funded several ambitious hypersonic research projects. The reality today, however, is far more down-to-earth. No manned aircraft has yet flown under its own power at hypersonic speeds for more than a couple of minutes, and even that required a pilot who was literally out of this world.