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The Karman Line

The Karman Line is the Border Separating the Earth’s Atmosphere from Space. It is Defined as Being 100km Above Sea Level and is Regarded as the Starting Point of Outer Space

The Fédération Aéronautique Internationale (FAI) is the world governing body for air sports and manages definitions regarding human spaceflight. But did you know the same organization also defined the Karman Line?

The Karman Line, an imaginary boundary 100 kilometers above mean sea level, is a common definition of space. Once this 100 km line is crossed, the atmosphere becomes too thin to provide enough lift for conventional aircraft to fly.

What is the Karman Line?

Experts believe the boundary between Earth and space ranges from 18.5 miles above the surface to more than a million miles away. However, for over a half-century, most people, including regulatory bodies, have accepted a definition of the Kármán Line close to our current one.

The Karman line is physically based because it roughly marks the altitude at which traditional aircraft can no longer fly effectively. Anything traveling above the Kármán line requires a propulsion system that does not rely on the lift generated by the Earth’s atmosphere, the air is too thin at that altitude. In other words, the Karman line is the point at which the physical laws that govern a craft’s ability to fly change.

The Karman line, however, is also where human laws governing aircraft and spacecraft diverge. No national borders are extended into space; instead, it is controlled more like international waters. So deciding on a space boundary is about much more than who gets to call themselves an astronaut. (Source: Astronomy)

Who Discovered the Karman Line?

Theodore von Karman, a Hungarian-born aerospace pioneer, inspired the Karman line. During the years leading up to World War I, the engineer and physicist worked on early helicopter designs, among other things.

Then, in 1930, von Karman moved to the United States and became a go-to expert in rockets and supersonic flight around World War II, eventually founding the Jet Propulsion Laboratory with his colleagues in 1944, now a preeminent NASA lab.

Aside from the boundary line of space, von Kármán’s name is associated with several engineering equations, laws, constants, and aerospace designs, as well as many industry awards. But his most famous claim to fame is the Kármán line, which he earned by being among the first to calculate the altitude above which aerodynamic lift could no longer keep an aircraft aloft. (Source: Astronomy)

What is the Difference Between Spacecrafts and Aircraft? 

Lift is generated primarily by an airplane’s wings as it flies through the air, creating a force that opposes the plane’s weight and keeps it aloft. However, this concept does not work in space. There is no lift without enough air, so spaceships do not resemble aircraft. The Space Shuttle and Virgin Galactic’s SpaceShipTwo have the appearance of planes because they were designed to glide back to Earth after reaching space.

Von Karman proposed that the most logical edge of space would be near the point where orbital forces exceed aerodynamic forces. He chose 100 kilometers as a good boundary because he wanted a nice, round altitude.

Nonetheless, despite having his name attached to the boundary of space, von Karman himself never published this concept. (Source: Astronomy)

Image from Metro.Uk

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