[Bad offset for stellar energy flux] Thermal/Solar energy flux from star should be calculated from center of it.

[raxo2222]

Currently stars act like white holes outputting infinite energy flux on surface as if surface was center of star.

For now it calculates visible/thermal radiation flux from surface of star meaning that at close distances you get too high values.

It would be simple solution: to existing calculations just add radius of star to distance from surface of it.

Now at 1 sun radius from sun center (on "surface") you get infinite energy production, after this change you would get high flux like enough to heat up spacecraft to temperature of star.

At 2 solar radius you get same energy flux as you would get in real life by standing on it, while you would get quarter of surface energy flux.

At farther distance it is less difference between game energy flux and real flux.

This change would be nice, as you would get more realistic heating and energy flux at sun.

Is there mod, that actually does that?

 

At 10 solar radius you get flux as if you were at 9 solar radius distance. That is (1/81)/(1/100) = 1.23 factor - even here you get 23% bigger flux than you should get.

5 solar radius:  (1/16)/(1/25) - 56% bigger flux.

4 solar radius - (1/9)/(1/16) - 78% bigger flux.

3 solar radius - (1/4)/(1/9) - 125% bigger flux.

2 solar radius: 1/(1/4) - 400% bigger flux.

1 solar flux: (1/0)/1 - infinite flux

 

I'm using RSS, altitude here is equal to one solar radius.

Solar flux is equal to what should be on surface.

Here is graph showing how much difference it makes for all distances in solar radius from sun surface.

This is bad if you want to send probes, kerbals and solar power plants near sun.

One solar radius in RSS is 0.00465 AU.

Edited September 24, 2017 by raxo2222

[Spricigo]

1 hour ago, raxo2222 said:

This change would be nice, as you would get more realistic heating and energy flux at sun.

Granted I'm not a astrophysicist. But it seems to me that calculating flux from surface make more sense.  If nothing else because IRL the surface is way hotter than the core. 

[raxo2222]

37 minutes ago, Spricigo said:

Granted I'm not a astrophysicist. But it seems to me that calculating flux from surface make more sense.  If nothing else because IRL the surface is way hotter than the core. 

/facepalm

See screenshots.

Game currently treats surface of star as center of star. That is infinite flux at 0 distance from surface.

Sun has energy flux of 63 MW per square meter on surface. In screenshot such flux is one solar radius away from Sun.

If you are halve distance to center of energy/gravity source, then energy flux/acceleration quadruples.

If Earth was point, then old surface acceleration wouldn't change, but acceleration at center would be infinite.

If game treated acceleration from gravity like it treats energy flux now, then acceleration would be infinite on surface of planets/moons.

Surface of sun has around 6000 kelvins. Solar corona has few millions kelvins but its extremely ratified and center of sun has 15 millions of kelvins.

Edited September 24, 2017 by raxo2222

[Spricigo]

If the values you got at different distances are unrealistic that is a different matter.  

My point is that starting the calculation from the sun surface per se is not a problem. We are not supposed to be anywhere close to that distance anyway and, according to the scientific models*, there is some very counterintuitive effect of the complex physics  happening inside the stars. So, as long the resulting in game effects are reasonable**, it even make more sense to not bother with "below surface" calculations and just calculate things from there.

*thankfully those are solid and reliable models. It's not like we had much opportunity to collect a lot of data in locco.

**and by reasonable I mean: provides a adequade behavior for the simulation and game have a adequate difficulty as result.  If it is realistic really don't matter as much as if it makes the game balanced. 

58 minutes ago, raxo2222 said:

If game treated acceleration from gravity like it treats energy flux now, then acceleration would be infinite on surface of planets/moons

Let's not compare apples to oranges? (Or rather gravitons to photons) The fact that flux is infinite at the surface of ther sun is irrelevant,  you are not supposed to be there to begin with.

1 hour ago, raxo2222 said:

Solar corona has few millions kelvins

Wich is more than enough reason to be unrealistic that you reached the surface of KSP analog to complain about its unrealistic behavior. The fact that I messd up my wording when intended to say "stars can be hotter outsise" don't change that.

 

To sum that all up:

-Behaviour at sun's surface is irrelevant,  we shouldn't be there.

-If is irrelevant it may as well be incorrect.

My question is: what advantage it will brings to the part of the simulation where it is relevant?

Also: Is that something that will improve the game for regular players in the stock system or something that only offer significant change for people with the heavily modded RSS/RO install? If the later let it be handled by mods. 

 

[raxo2222]

Game treats surface of star as it was center of star.

Solar flux going 1/r^2 from center of star and having sane value on surface of star is just adjustment to current model in game - that is adding radius of star to distance from star when calculating energy flux.

While corona is hot its heating would be negligible for sungrazing spacecraft.

There is near sun space zone for science collection, that is hotter than it should be.

I used gravity as example why current flux calculation is broken near surface.

Some mods allows you to collect solar wind or solar energy as it was external fusion reactor and beam it away.

Some star packs may have planets orbiting at tens if not couple of stellar radius around stars.

For example planets orbiting supergiants.

 

Edited September 24, 2017 by raxo2222

[Spricigo]

1 hour ago, raxo2222 said:

having sane value at the surface of the star...

Is totally irrelevant.  Your craft will be plasma way before you can be near the surface. 

1 hour ago, raxo2222 said:

There is near sun space zone for science collection, that is hotter than it should be.

Ok, that actually  is something to consider. (Notice, maybe not enough to make the change necessary) Still up to you to demonstrate a significant difference between what "should be" and what is. 

Personally I don't have an idea of how much a realistic values "should be".  From a gameplay perspective I'm satisfied with collecting that science being "very difficult", which is in line with the current situation. 

1 hour ago, raxo2222 said:

mods

Another reason to not change.  I'd hate if a change on the game made easier to reach a planet that I had designed to be nearly impossible.

[raxo2222]

51 minutes ago, Spricigo said:

 

Ok, that actually  is something to consider. (Notice, maybe not enough to make the change necessary) Still up to you to demonstrate a significant difference between what "should be" and what is. 

 

Umm I shared screenshots and links.

Suffice to say at one solar radius there is quarter of surface solar flux. Currently there is four times too high radiation flux at that distance.

At 10 star radius solar flux is around 20% or so too high.

 

Really you want supernova  bright star at surface like here?

It seems like you are worshiper of stellar kraken, that fries everything, that comes closer than 15 star radius.

There is graph showing flux excess multiplier as function of distance from center of star.

y is multiplier and x is distance from star center in star radius units.

x = 1 represents star surface, anywhere where y is lower 0.01 there is almost no difference between real life solar flux 1/r^2 fading and ingame model, that treats surface of star is it was center of star.

That is at 200 solar radius from center of star difference is less than 1%.

21.5 solar radius from center - solar flux is 10% too big.

5.4 solar radius from center - solar flux in game is 50% bigger than in real life.

There may be star mods, that add brown dwarves with surface temperature at 1000 - 1500 kelvins, but they aren't flyable for reckless galactic explorers due to this supernova bug.

 

Edited September 24, 2017 by raxo2222

[OHara]

Same is true in the stock game.  Outside a spherically-symmetric source of light, the flux should decrease as 1/r² with r the radius from the center of the source, but in KSP solar flux decreases as 1/(r - 262Mm)² so it is hotter in close than one would expect.  The solar flux at Moho is 11% more than it should be so absolute temperature about 11%/4 = 3% warmer.

Looks like an oversight, so this seems more of a minor bug report than a suggestion for improvement.  I don't see one yet here.

Edited September 24, 2017 by OHara
should have mentioned that 1/r² follows from conservation of energy, so the total flux is the same through any spherical surface of any size around the sun.

[Spricigo]

13 minutes ago, raxo2222 said:

Umm I shared screenshots and links.

Sorry, not meant to imply 'lack of evidence'. Rather trying to point that more arguments along those lines can be usefull for defending your idea. 

 

 

[raxo2222]

6 minutes ago, Spricigo said:

Sorry, not meant to imply 'lack of evidence'. Rather trying to point that more arguments along those lines can be usefull for defending your idea. 

 

 

Well its unneeded breakage from realism.

 

[Spricigo]

44 minutes ago, OHara said:

Should have mentioned that 1/r² follows from conservation of energy, so the total flux is the same through any spherical surface of any size around the sun

And that looks simpler than  [1/(r-262)^2]. People usually have a reason to make things more complicated. 

Now go figures if was a good reason in that case.

[raxo2222]

8 hours ago, Spricigo said:

And that looks simpler than  [1/(r-262)^2]. People usually have a reason to make things more complicated. 

Now go figures if was a good reason in that case.

Well it could use similar equation as gravity.

 

Edited September 25, 2017 by raxo2222