For NASA and the United States Armed Forces, for example, space starts at an altitude of 50 miles (about 80 kilometers), according to NOAA. However, for the international community, including the Fédération Aéronautique Internationale (opens in new tab) (FAI), the space starts a little higher, 100 km (62 miles), on the Kármán line. The FAA says the 50-mile altitude marker works, but it's not very significant. Instead, the administration finds that the beginning of space is at an altitude of 81 miles.
This is where an object can briefly enter and remain in orbit before being dragged back to Earth. For this reason, McDowell chose 50 miles as the true lower edge of space. The number also fits perfectly with several other cultural and atmospheric factors. For example, McDowell wrote, in the 1950s, United States Air Force pilots received a special set of astronaut wings for flying their planes more than 50 miles, which is considered to be the outermost edge of the atmosphere.
There is no easy distinction between “space” and “no space”, in part because the Earth's atmosphere doesn't just vanish, but gradually gets thinner and thinner over some 600 miles. McDowell believes that's unlikely, although he's sure that the conversation will accelerate as commercial spaceflight companies begin to spend more time in the region between 50 and 200 miles high, where the space station orbits. For 96% of the world's population, space begins 100 km above sea level on the internationally recognized Kármán line. Planets are many millions or even billions of miles away, and stars are so far away that their distances are measured in light years.
With more countries and commercial companies heading to the stratosphere, the debate about how to define outer space is intensifying. The crew on board, including the company's founder, Sir Richard Branson, reached weightlessness when the Unity 22 spacecraft climbed to an altitude of about 53 miles. Now that Virgin Galactic seems to be about to launch paying passengers onto sub-orbital trajectories, many people are wondering if those lucky space tourists will earn their astronaut wings. In fact, the FAI states that, since “convincing recent analyses suggest that space should start at about 50 miles high,” it will propose a meeting next year to evaluate the idea.
I think everyone will know if you paid to travel as a passenger on a five-minute sub-orbital flight or if you are the commander of an interplanetary space vehicle. Others argue that maintaining a defined limit will be crucial, given the increase in the number of national space programs and private spaceflight initiatives that are increasing the amount of suborbital traffic. However, the United States and some other countries have resisted a formal and international delimitation of space, stating that it is not necessary and that “no legal or practical problems have arisen in the absence of such a definition. After three failed launches, SpaceX CEO Elon Musk raised enough funding to launch a fourth version of SpaceX's Falcon 1 rocket.
The International Space Station maintains an orbit of approximately 250 miles (400 kilometers) above sea level, while the Hubble Space Telescope operates at an altitude of approximately 340 miles (550 kilometers). The Fédération Aéronautique Internationale (FAI) agrees with Blue Origin and defines the beginning of space as the Kármán line.