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How to use launch window planner?


Actually_New_KSP_Player
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I'm using this planner (since i couldn't find a working mod for 1.5.1) and precise node mod. The planners in general almost always make me miss the encounter for some reason, here is my current plan.

The prograde and normal burn and time are correct but i ended up missing almost 5 million kms even with perfect apoapsis\periapsis. Btw i have no idea what's these ejection and phase angle, transfer type info are for, maybe that is the case?

Also i had to burn from 90k orbit since i'm getting about 10k lower through burning.

 

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I use and recommend the in game Transfer Window Planner mod. It works fine in the latest version so no worries there.

Here's a (very) crash course in using it I wrote up for someone on Steam a while ago.

Ok, so crash course in TWP time. I learned just by poking at it for a bit, most of the information is conveyed visually so it's pretty simple, despite all the text/numbers.

1. I've got us an example transfer to Duna from Kerbin setup. 100k to 100k. The most important info to take from this is that we'll be departing on year 12, day 71.

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2. While in map view we get buttons to show us both our Phase Angles and our Ejection Angle.
The Phase angle isn't super important for you to worry about, it'll be aligned all by itself on the proper departure day.

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The ejection angle is important though. (Not right now so much, but it will be.)

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3. Now, I've fast forwarded to the day of departure. (Well one day off but that won't matter lol.) As you can see, our Phase angles are aligned (The green and blue lines pointing at Duna), which means this is the cheapest time to go to Duna.

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4.Now the Ejection angle, the blue line with the green arrow coming off it tells us where to put our maneuver node and which direction to burn, (Typically prograde.)

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5. Now by simply adding some prograde thrust to our maneuver node we get a duna encounter easily, because we left at the right time, going the right way.

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Hope that helped, (and I can copy-pasta it elsewhere to teach others.) Let me know if you have any more questions!

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5 hours ago, Actually_New_KSP_Player said:

Btw i have no idea what's these ejection and phase angle

Ejection angle is the angle between the point of the orbit you occupy at burn start, and the full prograde (or retrograde) vector of the planet on its orbit around the Sun. So in the following picture, it's the angle from the center of Kerbin (the red line) to the maneuver node. If you don't get this angle right, then your burn will not be nearly as efficient -- which means that you will either be early or late getting to your destination. So yes, that might be your problem -- but any interplanetary burn is always slightly inaccurate. And 5 million kms is not that bad. Halfway to your destination you always have to make a small burn to correct any inaccuracies from your first burn.

L0guOu4.png

 

Phase angle is the angle between Kerbin's current velocity vector, and your destination planet's current position.

Edited by bewing
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You may want to take a look at this page (also linked at the bottom of the launch window planner):

http://ksp.olex.biz/

There are illustrations for the phase and ejection angle.

The page also includes an transfer window calculation but the results may differ a bit, depending on the transfer window you actually picked from the chart of the launch window planner.

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7 hours ago, bewing said:

Halfway to your destination you always have to make a small burn to correct any inaccuracies from your first burn. 

I was behind Duna, so i had to make a too expensive burn if i want to get an encounter, that was the main problem.

 

6 hours ago, Rocket In My Pocket said:

I use and recommend the in game Transfer Window Planner mod. It works fine in the latest version so no worries there.

After installing 1.5.1 my version said that it's outdated so i looked up in the comments for 1.5 version and discovered that it was a complete blank window in game for some reason. Installed from the original source and it worked, hmm.

 

6 hours ago, Rocket In My Pocket said:

Hope that helped

Definitely did, i didn't know how to use the ejection angle and how to set it up correctly (i was aligning the arrow with the predicted brown path), but now with angles i've made it to only 700k miss which was corrected with 300 Dv worth of burn.

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15 minutes ago, Actually_New_KSP_Player said:

After installing 1.5.1 my version said that it's outdated so i looked up in the comments for 1.5 version and discovered that it was a complete blank window in game for some reason. Installed from the original source and it worked, hmm.

Definitely did, i didn't know how to use the ejection angle and how to set it up correctly (i was aligning the arrow with the predicted brown path), but now with angles i've made it to only 700k miss which was corrected with 300 Dv worth of burn.

Yeah, ignore the warning. Not sure what happened with the blank window? At least you got it working now though.

Happy to help! Congrats, you're well on your way to anywhere in the universe now!

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@Actually_New_KSP_Player, you've already gotten some great replies that your question, but I have just one more small thing to add.  If you have to perform a midcourse correction, it is usually best to do so when 90-degrees from the intercept point with the target, as shown in the figure below.  This is because if you have to make any plane change adjustment, you can do so most effectively using the least amount of delta-v when at that position.

fig5-05.gif

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4 minutes ago, OhioBob said:

@Actually_New_KSP_Player, you've already gotten some great replies that your question, but I have just one more small thing to add.  If you have to perform a midcourse correction, it is usually best to do so when 90-degrees from the intercept point with the target, as shown in the figure below.  This is because if you have to make any plane change adjustment, you can do so most effectively using the least amount of delta-v when at that position.

fig5-05.gif

Ty

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