Question Atmosphere parameters in planet config file

[tdelongc]

So I've been playing Orbiter for a while now and finally got the itch to try making a system based off random planets I've found in Space Engine that seem nifty. I'm working on a planet with an atmosphere, but I can't seem to get things to work right. The problem is that no matter what I set the cutoff altitude for the atmosphere to, it only exists about 2000-3000 meters off of the surface. I've looked over other planet .cfg files, but they don't seem to tell me much.

This is what I have for the atmosphere parameters:

; === Atmospheric Parameters ===
AtmPressure0 = 1.5656739e6 ; pressure at zero altitude [Pa]
AtmDensity0 = 6.7254 ; density at zero altitude [kg/m^3]
AtmAltLimit = 100e3 ; cutoff altitude [m]
AtmAttenuationAlt = 80.3e3 ; cutoff altitude for light attenuation
AtmHorizonAlt = 80.3e3 ; horizon rendering altitude [m]
;AtmHazeExtent = 0.14 ; horizon haze extent
AtmColor0 = 0.55 0.75 1.04
AtmHazeColor = 0.6 0.8 1.0
AtmFogParam = 5e-5 3e-5 4e3
AtmFogColor = 0.55 0.85 1.10

It's really frustrating. If I try to enter from orbit, the ship suddenly plows into the really thick atmosphere at something like 22km/s with no transition from the vacuum of space.

 

[martins]

What do the density (DNS) static pressure (STP) and temperature (OAT) indicators on the Surface MFD show as you descend? Can you make plots of these quantities as a function of altitude? Pressure and density should drop exponentially with altitude if the temperature is constant.

Maybe you can also use the log function in the FlightData module to give you the required data.

 

[Linguofreak]

You've got a 15 bar atmosphere with a 100 km cutoff. That'll do it.

Try setting the cutoff higher (maybe 300 km) or the surface pressure lower (if you aren't trying for a thick atmosphere).

The cutoff altitude for Earth used to be 200 km. ISTR that it has been increased a bit, but for a 1 bar atmosphere 200 km should be sufficient.

 

[tdelongc]

I guess it does drop exponentially, but also very, very quickly. The "cutoff" altitude is supposed to be around 100 km, but FlightData shows the atmosphere starting around 10 km. At first I assumed it was a misplaced decimal point, but changing AtmAltLimit to 100e4 didn't seem to affect it at all.

I played with it some more, and changing the density seems to have an effect. I may just play with those values some to get a reasonable atmosphere height. It won't exactly be faithful to the procedurally generated Space Engine planet I'm trying to recreate, but who cares, it's all made up anyway, right?