Compared to the next category, medium-Earth orbit, this section of space is narrow, yet, as the nearest to us, it is also the busiest.
The boundaries of low-Earth orbit begin and end at approximately 200 km and 2,000 km, respectively, above Earth's surface. In terms of altitude, orbits come in three flavors: low-Earth, medium-Earth, and high-Earth. In Earth’s case, these are occupied by artificial satellites (ranging from spacecraft and research vehicles to space debris). Like any celestial body, our planet has a gravitational field and orbital paths around it. SPACEFLIGHT CLASSIFICATION SPACEFLIGHT CLASSIFICATION Orbit of habitation For 60 years, orbital flights have been the mainstay of human space travel. There have been relatively few crewed suborbital missions. As a result, it re-entered the atmosphere just a few minutes after engine cut-off. The launch vehicle left Earth's atmosphere, but did not attain the first cosmic velocity (7.9 km/s), meaning that the craft could not be put into orbit. Shepard's flight was more like a space-hop. On February 20, 1962, Glenn orbited Earth three times. The World Air Sports Federation recognized this 15-minute ride as a spaceflight, but most often the title of first US astronaut is given to John Glenn. Less than a month after Gagarin's flight, astronaut Alan Shepard crossed the Kármán line (the notional boundary at which outer space begins), without, however, going into orbit.
The Americans had already declared their intention to be first to send a human being into space under Project Mercury, their supposed revenge for Sputnik 1. The Soviet Union’s triumph could hardly fail to elicit a response from its main space race rival, the United States.