When an object moves fast enough in a circular path around the center of the Earth (or any celestial body) that the centripetal acceleration exactly balances the acceleration of gravity, that object is in orbit. This practically can not be done inside the atmosphere since the air friction would destroy almost anything moving that fast (in addition to slowing it down...). We do launch many rockets from the equator, or as close as we can reasonably get, to take advantage of the surface speed of the Earth turning. This is one of the main reasons that the USA built its launch facilities as far South in Florida as it did. The acceleration of gravity decreases with altitude, so the relative velocity also decreases. At any given altitude, escape requires about 1.5 times orbital speed. Escape in this case means that it would keep getting farther away and never fall back to Earth (if nothing else interferes with it). Anything between the orbital speed and escape velocity will move the object into a higher orbit. On a side note, "centrifugal force" is just centripetal acceleration times the mass of the thing spinning and the "gravitational force" is the gravitational acceleration times the mass. Science and mechanics typically identify them as accelerations rather than forces. An object of any size or mass will accelerate toward the center of gravity at the same rate. An object spinning at a given speed and distance has the same acceleration toward the center (centripetal acceleration) regardless of mass or size. Working with the acceleration values is simpler and makes more sense than factoring in the masses.

Centifugal force does not exist, it is a perception created by the change in direction. You cannot gain the velocity of the earth while upon the surface as you and everything around you are all moving with the same .288 mile a sec equitorial velocity of the Earth. The escape velocity of Earth is about 25,000 miles per hour so the Earth would have to rotate in one hour to give you that speed and you would still not feel it just as you can't tell your moving 67,000 miles an hour around the Sun nor the 144 miles a second we're moving with the sun. PLus the 7.4 kms plus the earth's rotation is still shy a factor of the square root of two which is the variable times an orbital velocity at the surface.! We built our stations south for the weather..remember the challenger it blew up from the cold! PLus the moist air allows for more of a thrust ratio from the rocket as the moisture adds bouyancy to the air somewhat lessening teh mass of the craft increasing the thrust. But mainly they are south for year round operation.