Quote:
Originally Posted by chefsos
I had someone tell me several years ago, that orbit at low altitude such as the ISS does, isn't technically an orbit at all. It's a controlled fall, with the speed sufficient to keep it continually falling "over the horizon", so to speak. While that didn't blow my mind, I gotta admit it popped a little.
I'm certain you know this stuff, so: was he full of shit?
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That's absolutely correct. Orbit is nothing more than a controlled free fall where tangential acceleration overcomes gravity such that the object if falling but always stays at the same distance from the Earth. The space station is free falling toward the Earth at all times. But it never crashes into the Earth, because it's going so fast it always overshoots the horizon, like you said. It's going at the perfect speed so that it always stays at the same distance from the Earth, even though it's always technically falling.
It's really no different than a skydiver in free fall after jumping out of a plane, except that the atmosphere isn't continually resisting and pushing back against the person. Because the space station is higher than most of the atmosphere. So you don't have the "Wind rush" pushing back up against the falling body. That's why free fall in outer space looks more like floating. But if you would take away the resistance of the atmosphere in the case of a skydiver, it would look and feel exactly like a "Floating" astronaut in orbit.
Here's a much lengthier and detailed explanation:
http://www.nasa.gov/centers/glenn/sh.../microgex.html