We all talk about space- about its definition, the laws involved, etc. Where does this ‘space’ begin? Well, we all know that there is no clear-cut boundary between the earth’s atmosphere and the outer space. But we use the Karman line, an altitude of 100 kilometres above the sea level, as the beginning of outer space, in space treaties and aerospace records. People still argue about the necessity of defining a boundary to space and about revising the current definition. Is it really necessary?
It was the Hungarian physicist Theodore von Kármán who determined in the 1900s, the boundary of space to be around 80 kilometres above the sea level. Today the Karman line is set at about a 100 kilometres above the sea level. Satellites are launched into the outer space, at a height above the Karman line, but the fact that an orbiting object can survive multiple perigees at altitudes around 80-90 kilometres suggest revisiting the current definition of the Karman line. Though space is free for exploration by all, flying a satellite above a nation’s air space is a military aggression.
In the paper “The Edge of Space: Revisiting the Karman Line” published by the astrophysicist Jonathan C McDowell of the Harvard-Smithsonian Center for Astrophysics, in 2018, suggests 80 kilometres as the most suitable choice to use as the lower ‘edge of space’, considering the orbital and suborbital trajectories used by space vehicles. The US Air Force designates flyers (launched from a US launch site), who go higher than 100 kilometres as astronauts. In the near future when space tourism becomes more popular, think about the lucky travellers who can become astronauts if the Karman line is at 80 kilometres. And the pressure to agree on a boundary will increase as space activities in these regions are increasing. Considering all these, The Federation Aeronautique Internationale (FAI), which keeps a track of the standards and records in astronautics and aeronautics, is evaluating the idea of setting a new definition to the Karman line.
-Sruthy Chandran
Read more: https://arxiv.org/abs/1807.07894
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