The Verge (US): Defining the edge of space could be crucial to the future of space travel

The International Aviation Federation (World Air Sports Federation or Fédération Aéronautique Internationale) announced in November this year that it was considering changing the Karman line, that is, the height considered to be the limit of outer space. This line is named after Theodore von Karman, a Hungarian engineer and mathematician who was the first to use his calculations to determine where the Earth’s atmosphere becomes too thin for airplanes to fly. For decades, the Fédération Aéronautique Internationale assumed that the Karman Line was at an altitude of 100 kilometers, or 62 miles. But today this organization, which is responsible for recording record flights in air and space, is considering moving it to an altitude of 80 kilometers or 50 miles.

In the short term, changing the definition of outer space appears to have little effect. Some statistics about who actually left Earth first will probably change (and pilots who last flew on a Virgin Galactic space plane can boast of being astronauts today). But achieving international agreement on a legal definition of outer space could have significant implications for the future of the space industry. So, for example, it could make it more difficult to determine what counts as a spacecraft and what counts as an aircraft, and thus change the rules governing such aircraft in the future.
“Where does the airspace of a country end? This is really of interest,” said Jonathan McDowell, an astrophysicist from Harvard University and an expert on spaceflight, in an interview with the Verge correspondent.

Let’s look at some technical details

The International Aviation Association is investigating the possibility of changing the parameters thanks to a new study presented by McDowell. As an avid recorder of space travel statistics, McDowell wanted to find out how many rockets had actually reached outer space and how many people could claim to be astronauts. And to give a correct answer to these questions, he had to determine where outer space begins. Therefore, he had to study the entire history of astronautics and try to see if a more suitable definition of these parameters could be found.

After analyzing a significant amount of orbital statistics of space flights over a large number of years, he proposed more precise parameters than those currently used by the International Aeronautical Association, namely 80 kilometers plus/minus 10 kilometers. In plain terms, this is the lowest altitude at which a satellite can stay and orbit the Earth. To stay in orbit at such a low altitude, this vehicle must move in an elliptical orbit. This is such an orbit, where the spacecraft mostly moves away from the Earth and then for a short time approaches it at a distance of 80 kilometers. In this configuration, according to McDowell, the spacecraft could be in orbit for several days or several weeks.

McDowell believes that 80 kilometers is exactly the point where gravity becomes more important than the atmosphere. “You’re in outer space if you can actually ignore the atmosphere,” he says. “That doesn’t mean it doesn’t have an effect anymore, but gravity becomes the dominant factor that you have to take into account.”

We should first of all understand what needs to be done to be in orbit. The most important thing is the speed. At the altitude of the International Space Station (about 254 miles/408 kilometers), the spacecraft is traveling at over 28,000 kilometers per hour (over 17,000 miles per hour). It is necessary to have such a speed to remain in a constant orbit around our planet. Unfortunately, our atmosphere is too dense, and it does not allow an object moving at the same speed to be at a lower altitude. “You burn up very quickly if you try to go through the atmosphere too quickly,” says McDowell. That’s why he believes the atmosphere is important.

But even at an altitude of more than 80 kilometers, the Earth’s atmosphere still exists – it is simply extremely rare. Satellites flying at an altitude of more than 80 kilometers still continue to interact with particles from our atmosphere. It’s just that the air is so depleted that it can no longer affect the spacecraft’s orbit. “And then the question arises: Where do we draw the line that says we are already outside outer space? This is exactly the height at which, maintaining orbital speed, you cannot descend even for a short time and continue to move, McDowell emphasizes.

And if this is the most technical answer, how is the official definition of the Fédération Aéronautique Internationale at an altitude of 100 kilometers? Karman himself set his own limit in 1956 at a height of 83.8 kilometers – but he did not even try to find the limit of outer space. Basically, he wanted to determine how high an airplane could fly while still using lift. Ultimately, this boundary was misinterpreted as the boundary of outer space, said Thomas Gangale, space law expert and executive director of the OPS-Alaska Global Research Network. He and McDowell think we got to 100 kilometers only because people started rounding off this value to make it easier to remember. “Around 1960, the International Aeronautical Association decided to set the limit at an altitude of 100 kilometers, and this was done simply to record flights – that is, any flight at a higher altitude began to be considered space.”

However, not everyone accepts the definition of outer space proposed by the International Aviation Federation. So, for example, the US Air Force has already set this figure at 50 miles, or about 80 kilometers, and they issue the appropriate badges to all their employees who have overcome this altitude. NASA does the same thing. Although the Federal Aviation Administration does not have its own official definition, it usually issues equivalent astronaut badges to those individuals who have been at an altitude of over 80 kilometers (50 miles). These metrics will likely become more accurate as more commercial players venture into space. “Plans to issue astronaut wings are currently under review,” an FAA official told the Verge website.

Cosmic law reaches new heights

Although different organizations have their own definitions, there is no general agreement on this. In fact, the United States argues that it is simply not necessary to define outer space through international law. At a UN meeting in Vienna in 2001, a representative of the US delegation stated: “Considering the issue of the definition and delimitation of outer space, we have carefully studied this issue and listened to the many statements made at this meeting. Our position continues to be that the definition or delimitation of outer space is not necessary. No legal or practical problems arise from the absence of such a definition. On the contrary, the various legal systems applicable to airspace and outer space work well in their respective fields. The lack of a definition or delimitation of outer space does not preclude further work in any of these areas.”


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