Difference between revisions of "User talk:OhioBob"

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(Scale heights)
(Thanks for the info.)
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: --[[User:Murph|Murph]] ([[User talk:Murph|talk]]) 08:56, 16 May 2015 (UTC)
 
: --[[User:Murph|Murph]] ([[User talk:Murph|talk]]) 08:56, 16 May 2015 (UTC)
 
::Note that Squad might have change these values but unfortunately I don't know how to access them without starting KSP and manually doing the tests (I don't trust the infobox ingame as the numbers are at least rounded or worse (aka manually added so that they can get out of sync)). Anyway if someone has the capability of testing it I guess three data points are interesting: The pressure at the surface, the pressure inside the atmosphere for a given altitude and the border at which space starts. From the first two we should be able to determine the scale height and from the latter we could verify that it's currently still a relative border (the border is not at X atm but at X*surface pressure). — [[User:XZise|xZise]] <small>&#91;[[User talk:XZise|talk]]&#93;</small> 22:14, 16 May 2015 (UTC)
 
::Note that Squad might have change these values but unfortunately I don't know how to access them without starting KSP and manually doing the tests (I don't trust the infobox ingame as the numbers are at least rounded or worse (aka manually added so that they can get out of sync)). Anyway if someone has the capability of testing it I guess three data points are interesting: The pressure at the surface, the pressure inside the atmosphere for a given altitude and the border at which space starts. From the first two we should be able to determine the scale height and from the latter we could verify that it's currently still a relative border (the border is not at X atm but at X*surface pressure). — [[User:XZise|xZise]] <small>&#91;[[User talk:XZise|talk]]&#93;</small> 22:14, 16 May 2015 (UTC)
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:::The problem is that, starting with version 1.0, the atmospheric models have changed.  The old formula of "ln(1e-6) * -scale_height" is no longer valid.  The height at which an atmosphere ends is now just an arbitrary selection.  The current pressure-height profile follows a curve that is defined in a configuration file.  When the atmosphere reaches the arbitrary upper boundary, the pressure is forced to go to zero.  Furthermore, unlike the old model, scale heights are no longer constant.  The scale heights that I computed were a rough average intended to approximate the pressure when using P=Po*EXP(-z/H).  I don't mind that you reverted them.  I recommend that scale height be removed from the Infobox because it is no longer a constant value.  I also recommend that the atmosphere height be changed to an entered value rather than calculated from scale height.  The current atmosphere heights are: Eve 90 km, Kerbin 70 km, Duna 50 km, Jool 200 km, and Laythe 50 km.  The body of each planet's article should also be edited to make it current with the new method.  The scale height and equation P=Po*EXP(-z/H) should be removed because that is no longer how pressure is computed within the game.  Since there is no longer a simple and straightforward way to compute pressure as a function of altitude, I'm thinking that the best thing may be to provide a table that gives the pressure at regular increments of altitude, say every 5 km.  The article edits I'm planning to do myself.  I don't know how to make the changes to the Infobox template. [[User:OhioBob|OhioBob]] ([[User talk:OhioBob|talk]]) 02:20, 17 May 2015 (UTC)
 
:::The problem is that, starting with version 1.0, the atmospheric models have changed.  The old formula of "ln(1e-6) * -scale_height" is no longer valid.  The height at which an atmosphere ends is now just an arbitrary selection.  The current pressure-height profile follows a curve that is defined in a configuration file.  When the atmosphere reaches the arbitrary upper boundary, the pressure is forced to go to zero.  Furthermore, unlike the old model, scale heights are no longer constant.  The scale heights that I computed were a rough average intended to approximate the pressure when using P=Po*EXP(-z/H).  I don't mind that you reverted them.  I recommend that scale height be removed from the Infobox because it is no longer a constant value.  I also recommend that the atmosphere height be changed to an entered value rather than calculated from scale height.  The current atmosphere heights are: Eve 90 km, Kerbin 70 km, Duna 50 km, Jool 200 km, and Laythe 50 km.  The body of each planet's article should also be edited to make it current with the new method.  The scale height and equation P=Po*EXP(-z/H) should be removed because that is no longer how pressure is computed within the game.  Since there is no longer a simple and straightforward way to compute pressure as a function of altitude, I'm thinking that the best thing may be to provide a table that gives the pressure at regular increments of altitude, say every 5 km.  The article edits I'm planning to do myself.  I don't know how to make the changes to the Infobox template. [[User:OhioBob|OhioBob]] ([[User talk:OhioBob|talk]]) 02:20, 17 May 2015 (UTC)
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::::Thanks for getting back to us with the explanation.  I'm slightly surprised that Squad changed to a more arbitrary model for this, but I guess it must have been deemed a necessary compromise for the new atmospheric physics.  I'm going to go ahead and add static parameters for atmospheric height, but I won't remove scale height just yet.  The more urgent part of this is to provide accurate information to users on where the atmospheric boundary lies, since that's the part which will cause confusion or problems for the majority.  --[[User:Murph|Murph]] ([[User talk:Murph|talk]]) 02:38, 17 May 2015 (UTC)

Revision as of 02:38, 17 May 2015

Scale heights

Hi there, I'm wondering if you've made a mistake in changing the "scale height" in Duna/Param, Laythe/Param, and Jool/Param. This has had the consequence of producing what I believe to be highly invalid atmospheric heights in Template:Infobox/Body, used on all of the celestial body pages, and a table on Science. The formula used there is "ln(1e-6) * -scale_height". Is your change erroneous, or is the formula used to calculate the atmospheric height incorrect? I'm tempted to quickly revert your changes, but hoping you'll spot this message quickly and get a chance to look at it yourself, in case there's good reason for the change. It's not a radius vs. diameter error, is it, or something like that? --Murph (talk) 07:13, 16 May 2015 (UTC)

Ok, so I've thought a little more on this. Since you didn't give any edit summary, it's impossible for me to know why you changed the numbers for scale height. It seems to me that the number which is most important to average players of the game is the atmosphere height, and that most probably won't care about the scale height. In that regard, the old numbers look like they are more "correct" than the new ones. I don't know about Jool and Laythe, but Duna's atmosphere always started around 41–42km, which matches the old numbers. Accordingly, I'm going to revert your 3 changes to the scale heights, under the assumption that there's some sort of error with them, and that the old numbers are better for now.
If the problem is actually with the way the wiki's infobox is calculating the atmospheric height, I'd be quite happy to help with any changes needed to the wiki's templates and scripting.
Here are the numbers for ease of reference, with atmosphere height calculated using the "ln(1e-6) * -scale" formula. Old is before your change. New is what you changed it to.
Body Game
Tracking Station
Old New
Scale Atmosphere Scale Atmosphere
Duna 50,000m 3000 41 447m 6000 82 893m
Jool 200,000m 10000 138 155m 30000 414 465m
Laythe 50,000m 4000 55 262m 8000 110 524m
--Murph (talk) 08:56, 16 May 2015 (UTC)
Note that Squad might have change these values but unfortunately I don't know how to access them without starting KSP and manually doing the tests (I don't trust the infobox ingame as the numbers are at least rounded or worse (aka manually added so that they can get out of sync)). Anyway if someone has the capability of testing it I guess three data points are interesting: The pressure at the surface, the pressure inside the atmosphere for a given altitude and the border at which space starts. From the first two we should be able to determine the scale height and from the latter we could verify that it's currently still a relative border (the border is not at X atm but at X*surface pressure). — xZise [talk] 22:14, 16 May 2015 (UTC)
The problem is that, starting with version 1.0, the atmospheric models have changed. The old formula of "ln(1e-6) * -scale_height" is no longer valid. The height at which an atmosphere ends is now just an arbitrary selection. The current pressure-height profile follows a curve that is defined in a configuration file. When the atmosphere reaches the arbitrary upper boundary, the pressure is forced to go to zero. Furthermore, unlike the old model, scale heights are no longer constant. The scale heights that I computed were a rough average intended to approximate the pressure when using P=Po*EXP(-z/H). I don't mind that you reverted them. I recommend that scale height be removed from the Infobox because it is no longer a constant value. I also recommend that the atmosphere height be changed to an entered value rather than calculated from scale height. The current atmosphere heights are: Eve 90 km, Kerbin 70 km, Duna 50 km, Jool 200 km, and Laythe 50 km. The body of each planet's article should also be edited to make it current with the new method. The scale height and equation P=Po*EXP(-z/H) should be removed because that is no longer how pressure is computed within the game. Since there is no longer a simple and straightforward way to compute pressure as a function of altitude, I'm thinking that the best thing may be to provide a table that gives the pressure at regular increments of altitude, say every 5 km. The article edits I'm planning to do myself. I don't know how to make the changes to the Infobox template. OhioBob (talk) 02:20, 17 May 2015 (UTC)
Thanks for getting back to us with the explanation. I'm slightly surprised that Squad changed to a more arbitrary model for this, but I guess it must have been deemed a necessary compromise for the new atmospheric physics. I'm going to go ahead and add static parameters for atmospheric height, but I won't remove scale height just yet. The more urgent part of this is to provide accurate information to users on where the atmospheric boundary lies, since that's the part which will cause confusion or problems for the majority. --Murph (talk) 02:38, 17 May 2015 (UTC)