Orbit darkness time

[KocLobster]

http://wiki.kerbalspaceprogram.com/wiki/Orbit_darkness_time

Could I please get some help determining my orbit darkness time, so I can approximate about how much EC storage I will need? My math skills are far to dusty to perform that equation, and it's overkill anyways; I just need an approximation of how long my craft spends behind in the shadow of the Mun. My orbit is circular, at about 50km. If possible though, it would be nice to know the ODT's for other altitudes as well, not just 50km? With that information I could approximate my ODT for any altitude, at least for the Mun.

Much appreciated

[Streetwind]

If your orbit is circular, use the simplified equation a bit further down.

If you're orbiting the Mun, you can look up the relevant parameters (its radius R and its standard gravitational parameter µ) on its wiki page.

R is 200,000m
r(a) is 250,000m
µ is 6.5138398×10¹⁰ m³/s²

Now literally all you need to do is substitute the numbers in the equation, grab a pocket calculator (or just the Windows builtin one) and do the math. Since you know the end result is in seconds, and only meters and seconds appear in the numbers above, you can just ignore all the units and calculate numbers alone. Though if you do take the units along, they might help you out by being an error checking mechanism. If you end up with something other than seconds, you've made a mistake somewhere along the line.

 

EDIT: And for what it's worth, the wiki page for orbit darkness time already has a precomputed result for the Mun at 40km in the table at the bottom...

 

Edited March 16, 2016 by Streetwind

[KocLobster]

I thought I was a math person but I just am not. Nor do I want to invest that kind of time just figuring this out. I checked the forums and didn't find anything solid, however I just found, seconds after making the thread, a very handy little calculator tool that one can used to calculate how long they will spend in the darkness of any given celestial body depending on your input of apoapsis/periapsis, and even how much stored EC they will need depending on your input of how much EC you'd be using per second. Seeing as how I can't delete this thread, I'll just post the link for anyone else that searches the forums looking for this answer.

http://www.prism.gatech.edu/~bnichols8/projects/kspdarkness/main.shtml

Edited March 16, 2016 by KocLobster

[KocLobster]

You're right haha...I was so concerned with the math I can't believe I never scrolled down on the wiki. I found that link I posted because of it though, something my tiny brain can handle better. Thanks anyways for taking the time to help me

[Snark]

4 hours ago, KocLobster said:

Seeing as how I can't delete this thread, I'll just post the link for anyone else that searches the forums looking for this answer.

More helpful to others than deleting, anyway! 

You could also mark your own answer (the one where you post the link to the calculator) as the "best" one (the little green "check" button at left), so that your thread will show up as "answered."

[seaces]

There is a mod called FuseBox too that will in VAB tell you the consumption, generation and you can see the dark time of the orbit. You can choose which body you are orbiting and set your altitude. Small plug in but awesome

[KocLobster]

14 hours ago, Snark said:

More helpful to others than deleting, anyway! 

You could also mark your own answer (the one where you post the link to the calculator) as the "best" one (the little green "check" button at left), so that your thread will show up as "answered."

Didn't know of that feature, thanks!

7 hours ago, seaces said:

There is a mod called FuseBox too that will in VAB tell you the consumption, generation and you can see the dark time of the orbit. You can choose which body you are orbiting and set your altitude. Small plug in but awesome

I really liked the idea behind this mod, but when I installed it, it didn't seem to have any settings to control the box size, or opacity, or when it shows up. It was just literally displayed 100% of the time, instead of just in the VAB or SPH where I'd want it, and I found this incredibly annoying so I uninstalled it. A shame too because I found it very helpful.

[seaces]

2 hours ago, KocLobster said:

Didn't know of that feature, thanks!

I really liked the idea behind this mod, but when I installed it, it didn't seem to have any settings to control the box size, or opacity, or when it shows up. It was just literally displayed 100% of the time, instead of just in the VAB or SPH where I'd want it, and I found this incredibly annoying so I uninstalled it. A shame too because I found it very helpful.

Yeah its UI is not the best and it has bugs regarding of its UI. Luckily the windows is not to big but unfortunatly it was too much for you this. :/

[Sandpiper]

I made this graph a while back that shows the maximum darkness time in circular orbits for all KSP planets and moons.

[KocLobster]

This is pretty awesome, I don't know how to read it though. Why does the darkness time increase with increased altitude, isn't that backwards? Also, is it m or km? I think that's mislabeled too.

[Sandpiper]

It's a little counterintuitive: at a higher altitude your craft will be occluded by the planet for a smaller portion of the orbit, but the velocity will be a lot slower, so the total time spent in darkness will be higher. The altitude is in kilometers. Both axes of the graph have a logarithmic scale.

The dotted lines are orbit altitudes where you could get in the sphere of influence of a moon ("unstable"). The fat dot is the exact altitude for a stationary orbit, where the orbiting velocity equals the surface velocity of the planet.

Edited March 18, 2016 by Sandpiper

[KocLobster]

5 minutes ago, Sandpiper said:

It's a little counterintuitive: at a higher altitude your craft will be occluded by the planet for a smaller portion of the orbit, but the velocity will be a lot slower, so the total time spent in darkness will be higher. The altitude is in kilometers. Both axes of the graph have a logarithmic scale.

I think I'm just realizing this. I literally just woke up. This of course makes sense now. I like this graph even better than the calculator HTML page I found, thank you

Edit: only the y axis is a log scale? The x axis is linear.

Edited March 18, 2016 by KocLobster