In the 18 months between the launch of Sputnik and the announcement of the Mercury Seven, it was anyone's bet who would be the first man into space. The briefing chart, once stamped "SECRET" but now turning yellow in a NASA archive, shows a smooth curve with the names of nine test pilots plotted according to their weights. At the lower end, between 150 and 175 pounds, are Bob Walker, Scott Crossfield, Neil Armstrong, and Robert Rushworth.
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