About 18,000 mph.
The exact speed depends on the exact orbital height. If the orbit is not circular the speed will vary in different parts of the orbit.
I believe that when a space shuttle is traveling at its fastest it goes about 17,321 miles per hour.
Little more than 17,500 miles per hour
The orbiter's main landing gear touches down on the runway at 214 to 226 miles per hour, followed by the nose gear.
The space shuttle orbits around 300 miles high at around 17000 mph, approximatelt Mach 25. These speeds generate tremendous heat during reentry.
well there here are the layer in order: troposphere, stratosphere, mesosphere, thermosphere. the troposphere is about sixteen kilometers above sea level, so im guessing in about 2.5 seconds.