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| | North American X-15 experimental plane |
 | | Twelve test pilots flew the plane, including Neil Armstrong, later the first man on the Moon and Joe Engle who went on to command Space Shuttle missions. |
| | In July and August, 1963, pilot Joe Walker crossed the 100 km altitude mark twice, becoming the first person to enter space twice. |
| | Test pilot Michael J. Adams was killed on November 15, 1967 when his X-15-3 began to spin on descent and then disintegrated when the acceleration reached 15 g (147 m/s²), scattering wreckage over 50 square miles. |
| www.fighter-planes.com /info/x15.htm (1813 words) |
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