The orbit insertion velocity near the Earth's surface is practically
the same as the Earth escape velocity of 11.2 kilometers per second,
or 25,805 miles per hour.
Even at an altitude of 200 kilometers, a rocket is still inside the outer
reaches of the Earth's atmosphere. To really leave the atmosphere it probably
has to get to a distance of 27,000 miles near the 'geosynchronous' limit. There is no
sharp boundary to
Earth's atmosphere. It just decreases steadily in density until it eventually
matches the density of the interplanetary medium.
Return to Dr. Odenwald's FAQ page at the Astronomy Cafe Blog.