![]() ![]() From there, he realized that satellites could orbit the planet numerous times below an altitude of 62 miles, but those dipping beneath 50 miles met a quick and flaming end more often than not.Īfter that, he redid the von Kármán math and found that atmospheric contributions on orbiting spacecraft become negligible at around 50 miles up. He pulled publicly available orbital paths for 43,000 satellites and sorted them based on the lowest points in their orbits (called perigee) during decommissioning and atmospheric re-entry. When he realized none existed, he decided to find one by revisiting the types of calculations von Kármán did. Technically, the International Space Station-which orbits at an average height of 240 miles-would not be in space if we defined “space” as the absence of an atmosphere.įurthermore, there’s no single altitude above which a satellite can stably remain in orbit that depends on the type of satellite and its orbital trajectory, McDowell says.Ī prodigious maker of lists, McDowell was compiling records for rockets, astronauts, and other space objects, and he went looking for an accepted international boundary that would help him decide which records to include. There is no easy distinction between “space” and “not space,” in part because Earth’s atmosphere doesn’t simply vanish rather, it gradually becomes thinner and thinner over about 600 miles. “It’s very political, it turns out,” McDowell says. At the same time, NASA Mission Control places the line at 76 miles (122 kilometers), because that is “the point at which atmospheric drag becomes noticeable,” Bhavya Lal and Emily Nightingale of the Science and Technology Policy Institute write in a 2014 review article. Air Force, NOAA, and NASA generally use 50 miles (80 kilometers) as the boundary, with the Air Force granting astronaut wings to flyers who go higher than this mark. It is, after all, a nice round number.īut the Federal Aviation Administration, the U.S. The Federation Aeronautique Internationale (FAI), which keeps track of standards and records in astronautics and aeronautics, also defines space as beginning a hundred kilometers up. ![]() Today, though, the Kármán line is set at what NOAA calls “ an imaginary boundary” that’s 62 miles up, or roughly a hundred kilometers above sea level. In the 1900s, Hungarian physicist Theodore von Kármán determined the boundary to be around 50 miles up, or roughly 80 kilometers above sea level. Historically, it’s been difficult to pin that point at a particular altitude. Find out the origins of our home planet and some of the key ingredients that help make this blue speck in space a unique global ecosystem. So, how is “space” currently defined?īroadly, most experts say that space starts at the point where orbital dynamic forces become more important than aerodynamic forces, or where the atmosphere alone is not enough to support a flying vessel at suborbital speeds.Įarth is the only planet known to maintain life. However, the United States and some other countries have resisted a formal, international delimitation of space, stating that it’s not necessary and that “no legal or practical problems have arisen in the absence of such a definition.” Others argue that maintaining a distinct boundary will be crucial, given an increase in the number of national space programs and in private spaceflight endeavors that are boosting the amount of suborbital traffic. “Once you agree on a boundary of space, you agree on a boundary where space law applies.” “Where does a country’s air space stop and space begin?” asks Jonathan McDowell of the Harvard-Smithsonian Center for Astrophysics. The laws governing air space and outer space are different flying a satellite 55 miles above China is just fine if space begins at 50 miles up, but define the edge at 60 miles, and you might find your satellite being treated as an act of military aggression. International treaties define “space” as being free for exploration and use by all, but the same is not true of the sovereign airspace above nations. Does it really matter where space starts? Here, we take a look at the ways space is currently defined, the confusion surrounding the demarcation, and what the future might bring. Is that a problem? “No, I think it’s great!” says NASA astronaut Mike Massimino, who helped repair the Hubble Space Telescope. As of right now, they will, according to U.S. Now, with Virgin Galactic seemingly on the cusp of launching paying passengers onto suborbital trajectories, many people are wondering whether those lucky space tourists will earn their astronaut wings. That might sound trivial, but defining that boundary could matter for a variety of reasons-including, but not limited to, which high-flying humans get to be designated as astronauts. It’s up, right? Simple.Įxcept, no one really knows where “air space” ends and “outer space” begins. Ask someone where outer space is, and they’ll probably point at the sky.
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