When space begin ? 80 km or 100 km

[Pawelk198604]

I know that American acknowledge as astronaut who piloted craft above 50 miles (80 km) while FAI only this who reach 100 km (62 miles)

I wonder which one is more accurate.

[Scotius]

Both. Neither. There is no clear cut border of atmosphere and space like in KSP. ISS on her 400+ kilometers orbit still experiences significant amount of atmospheric drag.

[DECQ]

I know that American acknowledge as astronaut who piloted craft above 50 miles (80 km) while FAI only this who reach 100 km (62 miles)

I wonder which one is more accurate.

you think someone you accurate answers? people are more than a century to establish the exact nemogut Acceptable border space.

[KSK]

Ahhh - ninja'd by Scotius.

If I had to choose though, I'd go for 62 miles (100km) as being more accurate, simply because it's higher.

[Streetwind]

The Karman line (100 km) has a pretty good case going for it.

Does anyone know, by comparison, what made the US military decide on 50 miles?

[Pawelk198604]

Both. Neither. There is no clear cut border of atmosphere and space like in KSP. ISS on her 400+ kilometers orbit still experiences significant amount of atmospheric drag.

Atmospheric drag at 400 km? I wonder how it possible in vaccum.

In KSP is easy no problem as long periapsis is above 70 km

[YNM]

Atmospheric drag at 400 km? I wonder how it possible in vacuum.

In KSP is easy no problem as long periapsis is above 70 km

There's no true vacuum IRL, in large volume. Say, even the most rarefied intergalactic space probably still contains up to 1 atom each cubic meter (which will be a problem once you go fast enough nearing light speed).

[Charzy]

Because it's not a vacuum. The air gets thinner and thinner, and for most purposes it may as well be vacuum, but there's still a lot of molecules up there, waiting for satellites to hit them and slow down.

[Umlüx]

space starts at the Karman line which is at 100km

because to get enough lift to fly at that height, a plane would have to go faster than orbital velocity

[Lukaszenko]

I heard there was a lower mark than the Karman line for humans, with the reasoning that for a human at that altitude, physiologically it's the same as being in space.

I thought it was much lower than 50 km though.

[peadar1987]

I heard there was a lower mark than the Karman line for humans, with the reasoning that for a human at that altitude, physiologically it's the same as being in space.

I thought it was much lower than 50 km though.

The Armstrong limit (when your bodily fluids start to boil at bodily temperature) is around 20km. You aren't able to survive without a pressurised suit and bottled air for a prolonged period of time above this altitude.

[Kryten]

That's the Armstrong line, at just below 20km.

[saquito]

As international convention, the Kármán Line delimits the outer space for every project or mission. The NASA decided to acknowlege astronauts to any person flying above 50km, probably because a training-grade denomination.

[ouion]

Its a very thin layer of atmosphere called the exosphere, the pressure in exosphere is very low. There is still drag, because oxygen and nitrogen molecules are still around. So when the international Space station is orbiting it interacts with the molecules.

[Shpaget]

space starts at the Karman line which is at 100km

because to get enough lift to fly at that height, a plane would have to go faster than orbital velocity

That makes no sense.

What plane with what wings, carrying how much cargo/fuel and how many passengers?

[Frida Space]

Atmospheric drag at 400 km? I wonder how it possible in vaccum.

In KSP is easy no problem as long periapsis is above 70 km

IIRC, the Earth's exobase is at 600 km. The ISS is well inside it

[shynung]

That makes no sense.

What plane with what wings, carrying how much cargo/fuel and how many passengers?

Any theoretical plane with anything resembling a lifting surface. They never specified what model/manufacturer.

The logic was, at that height, atmospheric density becomes so low, aerodynamic lift alone is insufficient to hold altitude. Orbital mechanics take over from there.

Although, personally I'd agree to 100km as the limit of space, simply because of the sheer evenness of the number.

[Nibb31]

Why don't you simply read the Wikipedia article on the subject?

https://en.wikipedia.org/wiki/Outer_space

[JetJaguar]

The Karman line (100 km) has a pretty good case going for it.

Does anyone know, by comparison, what made the US military decide on 50 miles?

That makes no sense.

What plane with what wings, carrying how much cargo/fuel and how many passengers?

I'd guess that the US definition was created back when the US predominately used English units, and "50 mi" was a nice, round number while "62.1 mi" was not. Likewise, Karman probably just took a range of typical real-world aircraft parameters and found they all fell around the 100 km mark, so went with "100 km" because it's also a nice, round number.

As has been mentioned before, the atmosphere doesn't have a hard cutoff, it just gradually gets thinner and thinner. The definition of the boundary of space is mostly just an arbitrary convention, there isn't any special, physical cutoff at that point.

[Pawelk198604]

As has been mentioned before, the atmosphere doesn't have a hard cutoff, it just gradually gets thinner and thinner.

That strange because every time i play ksp i experience some hard bump i pass 70 Km

[shynung]

That strange because every time i play ksp i experience some hard bump i pass 70 Km

KSP =/= Real World.

IRL, it took 9500 m/s of deltaV just to get to low orbit. In KSP, only about 3500.

[cantab]

That strange because every time i play ksp i experience some hard bump i pass 70 Km

KSP isn't always fully realistic, and this is one place it's been simplified for gameplay.

[NeatCrown]

I'm not too sure about the numbers, but absolute vacuum is physically impossible unless there isn't any energy in a universe to begin with(I think). There are particles between planets in our solar system, between stars, and between galaxies.

Here, look at orbital decay.