The physics of an orbiting body are no different from the physics of a body falling to Earth. An orbit is literally a free-fall. In order for an object to stay in orbit for any length of time, sideways momentum must be sufficient that the surface of the planet curves away below it as it falls. Objects in free-fall are weightless. This fact *alone* explains why orbiting bodies experience weightlessness. There is absolutely no difference between the weightlessness of orbiting astronauts, and the weightlessness experienced in an aircraft at the peak of a parabolic trajectory. An orbit is simply an extremely long parabola. A parabola with an eccentricity greater than 0 but less than 1 is an ellipse. A parabola with an eccentricity greater than 1 is an open hyperbola. In terms of orbital mechanics, this is an escape trajectory.