The Kármán line is a conventional boundary between Earth's atmosphere and outer space set at an altitude of 100 kilometers (62 miles) above mean sea level (MSL). The name comes from Theodore von Kármán, a Hungarian-American aerospace engineer who calculated that at this altitude, the aerodynamic lift generated by an aircraft's wings would be insufficient to maintain flight.
The Kármán line is not a universally accepted definition of the edge of space, but it is used by the Fédération Aéronautique Internationale (FAI), the international governing body for aviation and astronautics. It is also used by many space agencies and organizations around the world.
Why is the Kármán line important?
The Kármán line is important for a number of reasons. First, it marks the altitude at which aircraft can no longer fly effectively. This is because the atmosphere at this altitude is too thin to generate enough lift for an aircraft to stay airborne.
Second, the Kármán line is approximately the altitude at which satellites in low Earth orbit (LEO) begin to decay. This is because the atmosphere at LEO altitudes is still thick enough to cause drag on satellites, which slows them down and eventually causes them to fall back to Earth.
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| The Kármán Line: A Gateway to Space |
Third, the Kármán line is a useful legal and regulatory boundary. For example, international law does not define the edge of space, so the Kármán line is often used as a reference point for determining which jurisdictions and regulations apply to aircraft and spacecraft.
Important benchmarks in aerospace related to the Kármán line
1942: Theodore von Kármán calculates the altitude at which aerodynamic lift becomes insufficient to maintain flight, which would later be known as the Kármán line.
1957: The Soviet Union launches Sputnik 1, the first artificial satellite, into orbit. Sputnik 1 orbits above the Kármán line.
1961: Alan Shepard becomes the first American in space on a suborbital flight. Shepard's spacecraft, Freedom 7, reaches an altitude of 187 kilometers (116 miles), which is above the Kármán line.
1962: John Glenn becomes the first American to orbit the Earth. Glenn's spacecraft, Friendship 7, orbits above the Kármán line for nearly five hours.
1969: Apollo 11 lands on the Moon. The Apollo 11 spacecraft travels well beyond the Kármán line on its journey to the Moon.
1981: The Space Shuttle Columbia launches on its first mission. The Space Shuttle orbits above the Kármán line and serves as a reusable spacecraft for transporting people and cargo to and from space.
1998: The International Space Station (ISS) begins construction. The ISS orbits above the Kármán line and is the largest spacecraft ever built.
2004: SpaceShipOne becomes the first commercial spacecraft to exceed the Kármán line. SpaceShipOne is a suborbital rocket-powered spacecraft that carries passengers on short flights to space.
2012: Virgin Galactic begins testing its SpaceShipTwo spacecraft, which is designed to carry passengers on suborbital flights to space. SpaceShipTwo exceeds the Kármán line in 2018.
2021: Blue Origin begins testing its New Shepard spacecraft, which is also designed to carry passengers on suborbital flights to space. New Shepard exceeds the Kármán line in 2021.
The future of aerospace and the Kármán line:
The Kármán line is likely to remain an important benchmark in aerospace for many years to come. It is a useful reference point for determining which jurisdictions and regulations apply to aircraft and spacecraft, and it marks the altitude at which aircraft can no longer fly effectively and satellites begin to decay.
As commercial space tourism continues to develop, the Kármán line will become even more important, as it will be the boundary between commercial airspace and outer space. Additionally, as new technologies are developed that allow aircraft to fly higher and faster, the Kármán line may need to be redefined.
Overall, the Kármán line is an important concept in aerospace and is likely to remain so for many years to come. It is a useful reference point for legal, regulatory, and technical purposes, and it marks the boundary between two distinct environments: Earth's atmosphere and outer space.
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