Difference between revisions of "Talk:Orbit darkness time"

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::I did a quick test with the Mun, and at an altitude of 35,000 km from Kerbin the Mun was able to eclipse my solar panels (KSP even tells you what body is eclipsing the panels, kinda neat). If the Mun's shadow length is approx 10,000 km, I would have definitely been outside this shadow, which made sense because I could still see the sun model, just no rendered light beams. So I guess for determining shadow or not, the body only has to cover the center of the sun. <small>&#91;[[User talk:Skaterzero807|talk]]&#93;</small> 13:34, 13 October 2013 (EDT)
 
::I did a quick test with the Mun, and at an altitude of 35,000 km from Kerbin the Mun was able to eclipse my solar panels (KSP even tells you what body is eclipsing the panels, kinda neat). If the Mun's shadow length is approx 10,000 km, I would have definitely been outside this shadow, which made sense because I could still see the sun model, just no rendered light beams. So I guess for determining shadow or not, the body only has to cover the center of the sun. <small>&#91;[[User talk:Skaterzero807|talk]]&#93;</small> 13:34, 13 October 2013 (EDT)
 
:::But the question is, how much does the body need to cover the sun? Afaik all celestial bodies are “there” at all times: You can see Jool from Kerbin when you know where to look. So does a body only need to be in between the sun and your craft? If so, the cones where this is possible must be huge, especially as the penumbra is expanding after the object. — [[User:XZise|xZise]] <small>&#91;[[User talk:XZise|talk]]&#93;</small> 13:49, 13 October 2013 (CDT)
 
:::But the question is, how much does the body need to cover the sun? Afaik all celestial bodies are “there” at all times: You can see Jool from Kerbin when you know where to look. So does a body only need to be in between the sun and your craft? If so, the cones where this is possible must be huge, especially as the penumbra is expanding after the object. — [[User:XZise|xZise]] <small>&#91;[[User talk:XZise|talk]]&#93;</small> 13:49, 13 October 2013 (CDT)
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::::Based on what I saw, only the center of the sun needs to be covered by a body so you would be right that the shadows form truncated cones and expand. However, due to the very small ratio of planet diameter to SMA, the cones expand only very little. For example, the edges of Jool's shadow have an angle between them approximately ~0.01 degrees (atan(2*R/SMA)). This means there should be no altitude where the shadow stops, I'll have to try orbiting the sun in the plane of Eve and see if I can get Eve to block it. <small>&#91;[[User talk:Skaterzero807|talk]]&#93;</small> 14:39, 15 October 2013 (EDT)

Revision as of 18:39, 15 October 2013

New section: It might be useful to add a table.

It might be useful to add a table for all the major celestial bodies in the game. Not everyone feels like doing the math themselves. (They still have to do the math to determine how much power the craft will consume in that time, but that is a lot simpler.) --Ruedii (talk) 04:07, 20 September 2013 (CDT)

What kind table do you mean? I only skimmed through the formulas but it appears, that the ODT depends on the orbit of the satellite itself. The only properties you need from the celestial body are the radius and gravitational parameter. And Kerbol System/Table have it for you (okay µ not directly). Of course you could use some example orbits, but which one? — xZise [talk] 04:59, 20 September 2013 (CDT)
Okay nevermind what I said: I added a table with an orbit of 20% the radius of the body. I don't know if this is any use. With a circular orbit the formula becomes somewhat handy. — xZise [talk] 12:58, 21 September 2013 (CDT)

Possibilities to improve the page

Okay I don't want to screw you over on that article, but there are several things I would change:

  • Remove the upper case from words like “apoapsis”. English is not my native tongue but afaik only names and the first word of a sentence are begin with a upper cased letter. Wikipedia handles it like that too. This would include moving the article to Orbit darkness time.
  • Redo the image as a vector graphic: Scalable and without these jpg artefacts.
  • Instead of only defining the formula for each variable (like ) describe what it does: “, the apoapsis measured from the body's center”. Because some values like eccentricity may be given by the orbit you choose so you don't have to calculate them.
  • Make this page either a tutorial (so like Tutorial:Advanced Rocket Design) or as an article (like Specific impulse). Currently it looks like both: I personally think only in tutorials the reader should be addressed directly via “you” and it is in the Category:Tutorials. On the other hand it looks like Specific impulse or thrust-to-weight ratio.

Now this is only my personal opinion and especially if this is a tutorial it's your choice to do with it whatever you want. — xZise [talk] 04:59, 20 September 2013 (CDT)

Okay I uploaded File:Orbit darkness.svg which is basically the jpeg file vectorized. I didn't add the chart around it as the unit is missing. I also didn't add the time, because it isn't clear which planet or moon this is. Also the new formula looks more clearer and you now define what the variables in the formula mean, nice work. — xZise [talk] 07:39, 21 September 2013 (CDT)

Changes made

Thanks xZise for the suggestions and helping fix this page up. I am just learning Wiki markup and wouldn't have come up with a table that elegant on my own. Anyway, I made a few changes and hopefully the page is getting better. Can we move it to "Orbital darkness time" and make it just a page (since it isn't really a tutorial anyway). I just wanted it to be easily located on a page if people didn't know what to search for. Also, I just read about the capitalization format so didn't realize I named the page wrong until now, I'm just too used to capitalizing almost everything in a title.

Also, what is the length of the shadow? It sounds like at some distance from the body you can't be in its shadow anymore? I'm not sure how KSP calculates the shadow, but it seems like if it's a simple point source, the shadow edges should diverge behind the body. — skaterzero807 [talk] 6:35, 27 September 2013 (EDT)

I have to test it with the shadow, but the length determines at which distance from the other planet/moon, the Sun apparent size is larger that the planet's/moon's apparent size. If your orbit is larger than the shadow of the planet/moon you should (in theory) have always power supply. But I'm not sure how KSP does it (if it even calculate that the shadow gets narrower?). I'll have to do some tests. — xZise [talk] 04:09, 28 September 2013 (CDT)

I did some testing (in the demo version 0.18) and the sun is blocked even outside the shadow zone. You can see the sun model still, but the game does not render the light beams. This leads me to believe the light calculations are done using the center of the sun as the source, but I can't prove definitively that solar panels would not work in this case. I will be buying the full version soon (once my qualifier exams are done, ugh) and should be able to test it more conclusively. [talk] 6:28, 3 October 2013 (EDT)

Yep I made a similar discovery and added some of the new knowledge to light. I plan to do additional test to determine if a craft in all three shadowtimes (umbra, penumbra and antumbra) get eclipsed. This of course raises the question if a shadow extend outside the SOI, because it does at least for the Mun. But as the antumbra is as wide as Kerbol at about twice the distance from the planet/moon as the distance of the planet/moon from Kerbol, shouldn't be there more eclipses/transits from planets affecting the solar panels? So my current guess is, that shadows don't leave the planetary SOI or that the body need a certain percentage coverage of Kerbol. — xZise [talk] 02:00, 4 October 2013 (CDT)
I did a quick test with the Mun, and at an altitude of 35,000 km from Kerbin the Mun was able to eclipse my solar panels (KSP even tells you what body is eclipsing the panels, kinda neat). If the Mun's shadow length is approx 10,000 km, I would have definitely been outside this shadow, which made sense because I could still see the sun model, just no rendered light beams. So I guess for determining shadow or not, the body only has to cover the center of the sun. [talk] 13:34, 13 October 2013 (EDT)
But the question is, how much does the body need to cover the sun? Afaik all celestial bodies are “there” at all times: You can see Jool from Kerbin when you know where to look. So does a body only need to be in between the sun and your craft? If so, the cones where this is possible must be huge, especially as the penumbra is expanding after the object. — xZise [talk] 13:49, 13 October 2013 (CDT)
Based on what I saw, only the center of the sun needs to be covered by a body so you would be right that the shadows form truncated cones and expand. However, due to the very small ratio of planet diameter to SMA, the cones expand only very little. For example, the edges of Jool's shadow have an angle between them approximately ~0.01 degrees (atan(2*R/SMA)). This means there should be no altitude where the shadow stops, I'll have to try orbiting the sun in the plane of Eve and see if I can get Eve to block it. [talk] 14:39, 15 October 2013 (EDT)