Titans (and other planets with lots of gas) atmosphere is rather inaccurate.

[Lillz]

Hello. I noticed when entering titan that its atmosphere is rather thin, when thats not exactly true in real life. Also, this same phenomena happens for gas giants! You basically crash into Jupiters atmosphere when it doesn't really have an accessible surface.

[irigi]

I tried it and it seems true. This is probably because of two things:

• Current dry adiabatic model introduced in issue #1363 uses molar mass and specific heat of Earth's air. This makes hydrogen atmospheres significantly smaller than they should be.
• The approximation based on ideal gas is probably used, which also make atmospheres with very high pressures much smaller, since the density and pressure drop much faster in ideal gas than in some other more incompressible models. (In thin atmospheres, like Earth's, the difference is small.)

I also noticed, when trying to aerobrake on Saturn, some discontinuity in my velocity, when entering the Saturn co-rotating frame. I will explore this and create separate issue.

[Ae-2222]

titan that its atmosphere is rather thin, when thats not exactly true in real life

Current dry adiabatic model introduced in issue #1363 uses molar mass and specific heat of Earth's air.

Yep, the atmosphere code is correct, but currently assumes the atmosphere properties are the same as Earth's (Extending those is a to-do (and will be done at least for next atmospheric scattering rewrite, as it will require it for variety)).

You basically crash into Jupiters atmosphere

Gas giants are like other planets in that they have a collidable surface on which the spots etc. are drawn on (eventually craft should be crushed before they reach it). )Typically the 'radius' for gas giants is defined as the 1 atmosphere pressure level.)

Also, this same phenomena happens for gas giants!

As for gas giant atmosphere visibility the reasons are the same as Titans.

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I'll look at artificially making the 'atmospheres' thicker for gas giants for the next alpha, until proper atmosphere properties based on gas composition are implemented:).

[Luomu]

Duplicate

1395

1336

[irigi]

@Ae-2222

Current dry adiabatic model introduced in issue #1363 uses molar mass and specific heat of Earth's air.

Yep, the atmosphere code is correct, but currently assumes the atmosphere properties are the same as Earth's (Extending those is a to-do (and will be done at least for next atmospheric scattering rewrite, as it will require it for variety)).

The atmospheric properties might be only part of the problem. The other problem would be that the code is adiabatic and dry (which is OK), but works only for ideal gas, while in high pressures, the gas stops to be ideal. Non-ideal gases always form bigger atmosphere, so the ideal gas model will underestimate atmosphere thickness. I will look into the code and maybe I will figure something out..

[Ae-2222]

while in high pressures, the gas stops to be ideal.

That's true but pressures on titan aren't that high..

For gas giants the surface temperature and atmospheric density Lua values might be bad/meaningless. For gas giants, once something is done about the radius of the geometry being less than the ship crushing distance, 'surface' temperature/density can be calculated on the 1 atm radius assumption.

[Lillz]

So, eventually, on a later update, all the atmospheres will be accurate to the planets and atmospheres like Jupiters will crush you?

[Ae-2222]

Yep, and the gas giant shaded atmosphere thickness will be resolved by next alpha:)

The ability of gas giants to crush you will be resolved sooner than gas composition..it requires some consideration about what types of pressures craft are able to withstand, and a way to separate the rendered radius (making it much deeper inside the atmosphere) from the one used by physics (one was developed for #1459).

Then it should be clearer if deviation from the gas properties, due to things like incompressibility/van der waals potentials/changes in k (hence specific heat) with temperature due to quantisation of vibrational degrees of freedom/etc. as irigi suggested, might be worth modelling. I suspect that breaks in the other assumptions of the dry adiabatic model like latent heats of some substances, the atmosphere being well mixed, and lack of aerosol layers might give a higher order error in most cases (the last one, if used in the much simpler shader model, will make atmospheres much prettier).