• The Kármán Line: What it is and what happens if it is crossed

Since the dawn of time, humans have been fascinated by everything to do with outer space, that great void above our heads that is still full of questions.

Well, in today’s 1Minute Aviation video, we ask you a very unusual question… When do you think an aeroplane becomes a satellite? No, we haven’t gone crazy.

Today we’re flying a little higher than usual to tell you about the Kármán Line, which is considered to be the boundary between the atmosphere and outer space.

What is the Kármán Line

Understanding Earth’s Atmosphere

The atmosphere is a gaseous envelope that covers our planet; it is divided into several layers and contains the gases necessary for life to exist.

In addition, our atmosphere absorbs ultraviolet radiation from the Sun, reduces the thermal oscillation between day and night, and acts as an effective shield to deflect meteors and other space debris.

Its composition is based on 78% nitrogen, a gas essential for plant life; 21% oxygen, necessary for breathing; and the remaining 1% is made up of other gases, including neon, argon, hydrogen and carbon dioxide.

If you want to find out more, don’t miss our post about the Earth’s atmosphere, where you will learn a lot of interesting facts about the subject.

And how high is it?

The height of the Kármán line is estimated at 100 km above sea level. However, the atmosphere does not end suddenly at a specific height, it is an approximation. But let’s look at this further.

If the atmosphere is up to 1000 km high, how is it possible that the Kármán line is the boundary with space if it is at 100 km?

In practice, the thermosphere and the exosphere are not considered part of the atmosphere, but part of outer space. So, yes, we can say that the height of the Kármán line is somewhat arbitrary depending on whether certain conditions for aircraft flight are met. It seems a bit confusing, but we explain it below.

If an aircraft crosses the Kármán Line, does it become a satellite?

If you’ve seen other episodes of the series, you probably know that aircrafts need two things to fly: wings and movement. Besides, their take-off will be much easier depending on where the wind is blowing, right?

For an aeroplane to fly, it needs a certain speed depending on the amount of air surround it. Also, as it ascends, the amount of air decreases, so the higher the altitude, the more speed is required. You can learn more about this in our post about lift on aircraft.

OK, so if we continue to climb, there comes a point where we will need such a high speed for our wings to be effective that it will match the orbital speed, and then wings are no longer necessary. This usually happens, roughly speaking, at about 100 km altitude.

We will then have reached the Kármán Line; and yes, our aircraft will be considered a satellite.

And, if someone crosses it, is he or she considered an astronaut?

In the new great space race we are in, several companies around the world are competing to establish themselves as the best option for space travel in the short and medium term.

In this kind of ‘game’, one of the arguments to detract from each other is precisely to surpass the Kármán Line. And the fact is that surpassing it is a fundamental requirement to reach outer space and, therefore, to be called an ‘astronaut’ instead of a traveller.

This is what happened to our former student Oliver Daemen, considered the youngest space traveller (or astronaut) in history, after crossing the Kármán Line aboard the New Shepard, the rocket owned by Blue Origin.

The first human to cross the Kármán Line

In 1961, Soviet astronaut Yuri Gagarin, the first space traveller in history, set several milestones, including becoming the first human to cross the Kármán Line.

Yes, the first human being, because previously, several animals had been sent into space, including the famous dog Laika.

Yuri Gagarin’s was one of the most important space milestones that made it into all the history books although, due to the astronaut’s untimely death, he did not enjoy much recognition.

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