The Karman Line: The Boundary Between Earth’s Atmosphere and Space

The Earth is a seemingly small place for humans to explore. Of late, humans are eyeing other planets to explore and conquest. Space expeditions no more remain a strange concept. Resultantly the outer space is becoming more and more commercial. 

An Outer Space Treaty was signed in 1967. It sets the tone to explore the use of outer space for the benefit of and in the interest of all countries, declaring outer space the province of the whole of mankind. Every treaty at the start is a combination of impressive terminology and the notion behind it. Over time the original concept starts fading against the merging realities at the ground.

Space Exploration

The “ground realities” fiction start overlapping the facts. The outer Space Treaty perhaps, too, is in the queue. The recent developments are making a difference differently. Space Tourism is the next play-field of Billionaires kicking off space tourism. The private companies and technology giants are taking positions for commercializing outer space by space tourism, off-earth miningspace hotels, and giant orbiting billboards

Space exploration is gradually maturing into space commercialization rather than exploitation. It is high time for more legislation. The USA piece of law  2015 Space Launch Competitiveness Act, provides room for private companies to enter into space to compete with the state-owned space programs. The development has a reason for some serious questions. 

  1. What is the upward airspace limit? 
  2. Which is the starting point of space? 
  3. Where exactly does a pilot turn into an astronaut?

Ownership of Vertical Airspace

The question of ownership of vertical airspace is tricky to answer. We need to dig deep to find a satisfying answer. 

Private vertical airspace: Traditionally, a landowner was considered to own an infinite column of air over & above his plot of land. The concept was valid before the advent of air travel. The private airspace now ends where navigable airspace begins. It is known to rise anywhere between 80 and 500 feet above ground level. It is poised to become a bone of contention with the increasing use of drones, air taxis, and other air-born objects. 

National vertical airspace: Presently, there is no pact on the vertical limit of airspace. The Karman Line is known as a working benchmark.

The Karman Line

The Federation Aeronautique Internationale (the World Air Sports Federation, or FAI) worked towards setting the Karman Line in 1960. The line hypothetically exists at  100km or 62 miles above Earth’s mean sea level. The FAI splits aerial activity into two categories. 

  1. Any air activity WITHIN 100km of the Earth’s surface is AERONAUTICS.
  2. The activity BEYOND 100km is ASTRONAUTICS.

Many international bodies including, the UN recognize the Karman Line. But there is still no legal definition and backing to the set limits. A difference of opinion is vividly there as the US, NASA, the US Air Force, and the FAA consider space to begin 50 miles above the surface. It is not the vertical limit to reach, but a person needs to fulfill other criteria to become an astronaut.

Atmosphere Crossing & Karman Line 

There are no milestones fixed at the crossing point from the atmosphere to space. It is different from the usual accurate transition lines. The Karman Line is a gradual thinning of the atmosphere across five layers.

1. The troposphere extends to 5 to 9 miles from sea level. The layer has about 99% of atmospheric water vapor. The “death zone” starts 5 miles high, the point where the air is too thin to breathe safely, whereas the height of Mount Everest i.e. 5.5 miles of the sea level.

2. The stratosphere is the next layer that is around 31 miles above sea level. Commercial passenger flights operate in the lower stratosphere. Here also exists the ozone layer. The layer is also used by some internet providers, as an alternate to towers and satellites. They provide internet services by using stratospheric balloons and high-altitude pseudo-satellites.

3. The mesosphere starts above the stratosphere and is limited to around 53 miles above sea level. The air pressure here drops below 1% of the pressure at sea level. Most meteors burn up in the mesosphere.

4. The thermosphere is the next layer to reach around 372 miles up. The Karman Line lies in the lower part of the thermosphere. Most of the International Space Station and satellites orbit are in this layer. It is a place of occurrence of auroras. 

5. The exosphere is almost a vacuum that extends from the top of the thermosphere to 6,200 miles out. It is also an upper limit of the atmosphere.

There is still another layer of the ionosphere that overlaps the mesosphere and thermosphere. It grows and shrinks according to the amount of solar radiation absorbed. 

Crossing the Karman Line

The leading industrial countries like the U.S., China, and Russia are pursuing anti-satellite weapon capabilities, strategists against any future conflict. The possible arms conflict can include targeting military and civilian satellites. The vertical borders are at greater risk if tension increases among the military giants. The future holds the threat of crossing the Karman. It can turn into a nightmare for humanity and the space-age equivalent of Crossing the Rubicon.

  • Urza Omar
  • The writer is a freelance blogger, content, copywriter, and an accredited motivational speaker and trainer.