DNA Explainer: What is Karman Line? How does it define space travel?

The billionaire space travel month will see a second private endeavour as the wealthiest of the world attempt to kickstart space tourism.

While the feats of both the billionaires are historic, there’s an ongoing debate about what is space. And if where the Virgin Galactic spaceplane travelled and where the Blue Origin rocket is set to reach can be called termed as space. Several experts and space enthusiasts have put out their views with some disputing the claims. Big names include astrophysicist of global fame, Neil deGrasse Tyson.

So, here’s an explanation of the Karman Line which is the widely-accepted boundary between Earth’s atmosphere and space, and where the billionaires’ spaceflights stand with respect to it.

What is the Karman Line?

Karman line is the internationally recognized boundary of space which lies around 100 kilometres above mean sea level. For comparison, the International Space Station orbits around 330-410 kilometres above msl.

Named after aerospace pioneer Theodore von Kármán, the line is compared to international waters with no national boundaries and human laws in force beyond the point.

However, the US considers 80 kilometres above msl as the cutoff point for Earth’s atmosphere.

Where did Richard Branson reach and how far will Jeff Bezos go?

Richard Branson's spaceflight on the Virgin Galactic VSS Unity went till a height of 86 km. This is below the Karman Line and hence the claim of space travel has been disputed by some.

On the other hand, Jeff Bezos' Blue Origin New Shepard rocket aims to go as high as 106 km, which will take him beyond the Karman Line and any contention around if he did reach space or not.

In fact, right before Branson’s flight, Blue Origin posted on Twitter stating, “From the beginning, New Shepard was designed to fly above the Karman line, so none of our astronauts have an asterisk next to their name.”

Is Karman Line really the edge of space?

Researchers from the University of Calgary measured the edge of space at 118 km above sea level in in 2009. Their claim is based on a study of the winds of Earth's atmosphere and the flow of charged particles in space.

Another study, performed by Jonathan C McDowell from Harvard-Smithsonian Center for Astrophysics, stated 80 kms as a more appropriate boundary in a paper published in 2018. McDowell said the choice of Karman Line as the boundary was “a nice round figure', but more studies were needed from 'a physical point of view'.