Hey Guys, Look at this.

[ccoel]

I recently saw this picture

 

And this lead me to the realization that Kerbol is an Ultra-cool Red dwarf star smaller than Trappist-1 (which means that its a Class-T Star.) and can you even see kerbin and the mun?

[regex]

2 hours ago, ccoel said:

And this lead me to the realization that Kerbol is an Ultra-cool Red dwarf star smaller than Trappist-1 (which means that its a Class-T Star.) and can you even see kerbin and the mun?

Kerbol simply can't exist as a star, much less a stellar object. It has 0.376sr and 0.0088sm. It falls under no stellar classification, doesn't even qualify as a dwarf star, and is less dense than Jupiter.

[adsii1970]

 

3 hours ago, ccoel said:

And this lead me to the realization that Kerbol is an Ultra-cool Red dwarf star smaller than Trappist-1 (which means that its a Class-T Star.) and can you even see kerbin and the mun?

Um, here we go again!

23 minutes ago, regex said:

Kerbol simply can't exist as a star, much less a stellar object. It has 0.376sr and 0.0088sm. It falls under no stellar classification, doesn't even qualify as a dwarf star, and is less dense than Jupiter.

@regex: Take it easy on the poor youth; after all it's a fictitious star in a fictitious galaxy where real physics meet fantasy. I guess you can say... t'is a game is all!

 

[Gaarst]

Quoting a post I wrote some time ago:

On 25/10/2016 at 2:35 PM, Gaarst said:

The Kerbal sun is actually over three times less dense than our Sun. It also is 110 times lighter, weighing slightly over 9 MJ, making it too light to even be a brown dwarf, let alone a MS star.

Assuming the Kerbal sun's spectrum is close to our Sun as it is mainly white/yellow (spectrum centred on visible part of the spectrum), we can assume a temperature of 5800K. It's blackbody luminosity should then be about 1/7 that of the Sun. The solar irradiance at Kerbin should then be 16 times that at Earth or about 2 times that at Mercury.

Taking the solar irradiance at Kerbin to be that of the Earth (similar conditions), the Kerbal sun's luminosity should be 115 times smaller than the Sun's. It would then have a bolometric magnitude of 9.9 making it a K or M type star with surface temperatures of 3500-4000K, which means it is a red dwarf.

So depending on where you're standing, the Kerbal sun is a G (yellow) type star, a red dwarf, or a big Jupiter; and Kerbin is either burning, warmish or freezing. This contradicts special relativity BTW.

KSP bodies were not designed to be real, so funny things happen when you try to compare them to real things.

Edited May 4, 2017 by Gaarst

[regex]

1 minute ago, adsii1970 said:

: Take it easy on the poor youth; after all it's a fictitious star in a fictitious galaxy where real physics meet fantasy. I guess you can say... t'is a game is all!

1 minute ago, Gaarst said:

KSP bodies were not designed to be real, so funny things happen when you try to compare them to real things.

Thou shalt not directly compare an object in stock/vanilla KSP to an object IRL except in the most vague of terms.

[adsii1970]

6 minutes ago, regex said:

Thou shalt not directly compare an object in stock/vanilla KSP to an object IRL except in the most vague of terms.

And that's from the Third Chapter of the Book of Regex. Also known as the Gospel of Kerbal Space Program Physics

 

[ccoel]

Maybe its a gas giant made of helium and hydrogen and oxygen (no nitrogen or c02) thats on fire?

[regex]

4 minutes ago, adsii1970 said:

And that's from the Third Chapter of the Book of Regex. Also known as the Gospel of Kerbal Space Program Physics

That's flattering but I'm just a loudmouth around here; there are much smarter, and less vocal, people around here who should have that credit.

On-topic, @eggrobin and I once made a Real Solar System config (before Kopernicus) that modeled the Kerbin system purely from the radius of Kerbol. This resulted in a low-end M class star with what amounted to a bunch of Ceres-class objects (with random densities that generally followed how our own solar system works, that being more dense the closer to the star) and a "Super-Earth" (Jool) orbiting it. Solar irradiance from our made-up values (for Kerbol, given a density to match its radius) at Kerbin would be about like that at Mars, with a much redder light. Remember that Kerbin orbits its sun at a distance of roughly 1/4 that of Mercury.

Orbital energy was crazy too, transfer from Kerbin to anywhere else involved some brutal burns.

2 minutes ago, ccoel said:

Maybe its a gas giant made of helium and hydrogen and oxygen (no nitrogen or c02) thats on fire?

Oh totally, just like how Shoemaker-Levy 9 ignited Jupiter, giving us a second sun, through atmospheric friction. I can see it happening.

[ccoel]

 

55 minutes ago, regex said:

Kerbol simply can't exist as a star, much less a stellar object. It has 0.376sr and 0.0088sm. It falls under no stellar classification, doesn't even qualify as a dwarf star, and is less dense than Jupiter.

Nevertheless, its a cool comparison.

How wide is Jool?

cmon merging

NO

R.I.P

[regex]

1 minute ago, ccoel said:

Nevertheless, its a cool comparison.

Whatever works for you. Personally, Kerbol looks like a G type main sequence star and that's where I'm stopping the comparison.

3 minutes ago, ccoel said:

How wide is Jool?

6,000km, smaller than Earth.

[ccoel]

ppppppppppppphhhhhhhh

So the star is the same size as Saturn (btw goodbye cassini we'll Miss you!) and the gas giant of the system is smaller than earth?

[regex]

58 minutes ago, ccoel said:

So the star is the same size as Saturn (btw goodbye cassini we'll Miss you!) and the gas giant of the system is smaller than earth?

Welcome to KSP. If you were expecting realism, well, you can have some, but it was deemed Not Fun™ to have more than a certain amount.

If you want a full-sized solar system, or even to model something more realistic, look into mods.

[SpannerMonkey(smce)]

1 hour ago, ccoel said:

So the star is the same size as Saturn (btw goodbye cassini we'll Miss you!) and the gas giant of the system is smaller than earth

It's odd  though that the 0,8mtr tall green guys, alleged stars of the game ,  didn't give you a clue that all was not quite real world scale. These game devs are a sneaky bunch

Edited May 4, 2017 by SpannerMonkey(smce)

[Vall9X4562]

Wait, Kerbol is smaller than Jupiter? my understanding of scale in the Kerbal Universe has just been thrown out the window.

[Gaarst]

1 hour ago, Vall9X4562 said:

Wait, Kerbol is smaller than Jupiter? my understanding of scale in the Kerbal Universe has just been thrown out the window.

No. The Kerbal sun is greater than Jupiter, it's radius is almost 4 times that of Jupiter (and one third that of the Sun).

It just occurred to me that this picture is wrong, don't know where they got the 65,400km radius from: the game states 261,600km.

[KerikBalm]

	Radius (km)	SMA (km)	Radius ratio	SMA ratio
Kerbin	600	13599840.256
Earth	6371	149598023	10.6183333333	10.9999838369
Duna	320	20726155.264
Mars	3390	227939200	10.59375	10.9976595802
Jool	6000	68773560.32
Jupier	69911	778299000	11.6518333333	11.3168344983
Moho	250	5263138
Mercury	2440	57909050	9.76	11.0027610904
Kerbol	261600	17570E+030		(Mass not SMA)
Sun	695700	1.99E+030	2.6594036697	113.1474103586

 

There's a table I made ^  (The last entry for Kerbol/Sun lists mass instead of SMA, as SMA doesnt apply)

If you pretend the radius and SMAs are 10x what they really are, then KSP's system works out mostly OK/realistic.

The thing is at 10x radius, a planet has 1000x the volume, and if it was the same density, 1000x the mass, and you'd expect 10x the surface gravity (or for KSP planets to have about 1/10th the surface gravity).

Most KSP bodies have ~1/100th the mass rather than ~1/1000th (that you'd expect from their volume) of their analogue because they maintain the same surface gravity.

There are some exceptions, notably, the Kerbals' sun is proportionately quite big (its 1/2.66 the radius of our sun, not somewhere close to 1/10th) - they compensate by making its surface gravity quite low.

Also, Dres is quite far from the 1/10th radius and 1/100th mass proportions to its real world analogue.

Body/Radius (Km)/ SMA (Km)/ radius ratio/ SMA ratio

Dres	138	40839348
Ceres	473	414010000	3.427	10.1375271711

I used the mod sigma dimensions to rescale most of the KSP system to 3x the stock size, but I did not scale up Dres, and did a special scale for the sun (and adjusted the surface G to compensate). I then nerfed Dres' gravity down to nearly that of Ceres'.

Other deviations from the 1/10th and 1/100th scaling of real world analogues: Jool, its size and SMA are about right, but its mass is far too low because its surface G is far too low to be a Jupiter analogue. In the game I'm playing now, Jool's surface G has gone from 0.8 to 2.5

Mun is also far too close. About 3x too close. I suspect this is because for the size and FOV of the screen, the angular diameter of what you see on the screen seems too small, so they moved it in closer. As an aside, the game Arma gives the players a default 2-3x zoom capability with no optics at all to compensate for taking what should be roughly equal to ones entire field of view (minus some peripheral vision), and reducing it to a computer screen which normally takes up quite a small field of view (unless you have some absolutely huge screen and run at an absurd resolution)

Mun (to be a proper analogue) should orbit where Minmus does, so in my game I swapped their orbits.

			Ratios
	Radius (km)	SMA (km)	Radius	SMA
Mun	200	12000	8.685	32.03325
Minmus	60	47000	28.95	8.1787021277
Moon	1737	384399

The KSP Mun is about 1/9th the size of our moon, and orbits at about 1/32 the distance, swapping orbits with Minmus makes it orbit at a distance proportional to its size for it to be a proper analogue of our moon

 

The minor things like Jool's surface gravity being "too low", or Mun orbiting "too close" aren't really issues because its Jool not Jupiter, and its Mun not Moon. 

However, one must "pretend" that the radius and SMAs are about 10x as large as they are for the system to be remotely plausible, otherwise the densities are generally way way way too high - the Kerbal sun is an exception, because its much bigger than 1/10th scale, and has a much lower surface gravity.

Without this "pretending" that the radius is bigger (and then pretending that the mass is what you'd get from an object of that size with the stated surface G), densities are way to high, yet masses are way to low. A Red Dwarf can be as low as 0,075 stellar masses. The nominal mass of the Kerbals' sun is less than 0.01 stellar masses... which is still roughly 10x the mass of jupiter.

 

Whoever made that graphic made some big mistakes

 

Edited May 5, 2017 by KerikBalm

[Hodo]

16 hours ago, regex said:

Welcome to KSP. If you were expecting realism, well, you can have some, but it was deemed Not Fun™ to have more than a certain amount.

If you want a full-sized solar system, or even to model something more realistic, look into mods.

There is nothing more satisfying than launching your first manned rocket into orbit in Realism Overhaul, with Real Fuels and recovering the capsule and crew intact. 

 

[ccoel]

18 hours ago, regex said:

Welcome to KSP. If you were expecting realism, well, you can have some, but it was deemed Not Fun™ to have more than a certain amount.

If you want a full-sized solar system, or even to model something more realistic, look into mods.

Ive been plain KSP for a little over three years, Im not new, Only new to the forum

But

 

if that was sarcasm then I get 'welcome to the world of KSP'.