THE EDGE OF SPACE

• Highest airplanes 38 km

• Highest balloons 51 km

• Lowest satellite perigees 90 km (high apogee or freq. reboost)

• Physics: highest transition layer is mesopause at nominal 80 km

• Tradition: USAF gave astronaut wings at 50 mi.=80 km

• I adopt 80 km as a natural boundary