If you don't travel fast enough to escape the Earth's atmosphere, what happens?

Question

Just wanted to know what would happen to a rocket or whatever that was trying to enter space, but didn't have enough thrust to leave the atmosphere.

What is the speed that you need to do to leave the atmosphere? Is it 17000 mph?

Answer 1

Technically, you could leave the atmosphere at any speed.  It depends on the kind of propulsion you are using.  But in order to stay in orbit above the atmosphere, you have to be going at least that fast, about 18,000 mph, or your rocket will fall back to earth.  At 17,000 mph you could stay in orbit but the thin air would slow you down relatively quickly at that altitude.

Answer 2

17000 miles per hour is the speed needed to get into low earth orbit.  You can temporarily get above most of the atmosphere going much slower than that -- but it's hard to cite a value because the atmosphere doesn't stop abruptly at a certain height.  It just gets thinner and gradually peters out.

The folks that won the X-prize didn't have to get their rocket going nearly as fast as the first ones to achieve orbit.

Answer 3

You would simply take up another orbit.

And, please, the escape velocity is not about escaping the atmosphere - it is about escaping Earth's gravity.  

Answer 4

If you don;t travel fast enough, then you fall back to earth -- eventually.

What you are describing is called "sub-orbital", like Alan Shepard's flight in Freedom 7.

17,0000 MPH puts you into Low Earth Orbit.  There is still a bit of atmosphere there, though.

In order to leave earth orbit and go to the Moon, the Apollo spacecraft traveled at about 23,000 MPH (34150 ft/s).