On The Physical Properties of Kerbin in stock 1.2.2 KSP

[Neil Kerman]

These are some elementary questions I have been asking for quite a while. Where is the Kerbal equivalent of the Karmen Line? What about a magnetic field? Van Allen Belts? Please feel free to comment with theories!!

[technicalfool]

Magnetic fields aren't modelled (though the Kerbal Interstellar Extended mod does allow for antimatter collection by putting your ship in the correct orbit as a kind of simulated Van Allen belt around various bodies).

The Karman Line is actually an interesting question, that I've seen asked elsewhere recently too. I'd guess somewhere around 40km, but don't take my word on that. It probably needs some experimentation to find out.

[Bottle Rocketeer 500]

@Neil Kerman The Karman line in KSP is at 70 KM above sea level. If you install Kerbalism, it adds magnetic fields, which IIRC ends at  150 KM above sea level on Kerbin.

[Neil Kerman]

The main reason I ask the Karmen Line question is because Kerbin is roughly 1/10th the size of Earth. It logicaly follows that everything else is scaled down, so if the Karmen line is at 100 km on earth, then The Kerman Line (my personal name for it) should be at 10 km, which is obviously not space in KSP.

[OhioBob]

The Karman line is the altitude where the speed necessary to aerodynamically support an airplane's weight equals orbital velocity.  Lift is given by the equation,

L = 1/2 * rho * v^2 * S *C_L

where rho = air density, v = velocity, S = wing area, and C_L = lift coefficient.

If we assume S, C_L , and the weight of the airplane are the same on both Earth and Kerbin, then we should be able to say that Kerbin's Karman line is the atltiude at which rho*V^2 is equal to rho*V^2 at Earth's Karman line.  The Karman line on Earth is accepted to be 100 km, where, if we use the US standard atmosphere model, rho*v^2 = 35.  That equates to an altitude of about 66-67 km on Kerbin (air density varies with temperature, so the exact value depends on where you are.)

[Neil Kerman]

Thanks! just wondering what you used to get S and C_L

Edited August 19, 2017 by Neil Kerman

[OhioBob]

On ‎8‎/‎19‎/‎2017 at 4:06 PM, Neil Kerman said:

Thanks! just wondering what you used to get S and C_L

I have no idea the values of S and C_L are.  It didn't matter in my calculation because I just assumed the same values are used for both Earth and Kerbin.  What I did was,

(1/2 * rho * v^2 * S * C_L) _EARTH = (1/2 * rho * v^2 * S * C_L) _KERBIN

As long as S and C_L are the same on both sides of the equal sign, we can just cancel them out.

[Neil Kerman]

I was just curious whether or not FAI has a standard aircraft for S and C_L