The 165,000-year shuttle comparison is sound arithmetic rather than a mission profile, while Starshot’s 20-year result depends on a gram-scale flyby probe, a metre-scale sail and an unbuilt Earth-based laser array.
At orbital speed, the space shuttle crossed a continent in minutes. It circled Earth about once every 90 minutes, moving fast enough for its crew to see a sunrise or sunset roughly every 45 minutes.
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