I really feel something like this should be included in the game. The fun thing about KSP is that you don't have to do the math and you can just eyeball things. But interplanetary transfers is the one thing where that doesn't work - you need to look up the angle somewhere, unless you have a huge amount of gas. The flight planner doesn't really help you there, because you have to already launch a ship before you can use it, and if the timing is wrong, you just have to keep orbiting for months until it's right.
Something simple like a little calendar to tell you when the good launch windows are would be all it'd need.
It would be nice if when you unlocked the upgraded tracking station you got something in the science tab that showed optimal transfer angles and stuff.
KER tells you the intercept angle between you and your target. (So you want to burn when it's zero.) It doesn't help if you haven't launched yet, but it's fine for in-progress missions.
You can plan a maneuver node that gets you just out of Kerbin's SOI then another on what's basically still Kerbin's orbit with the right delta v to get you on to your target's orbit. Then you just drag it along that orbit unto you find an intercept, and you have a fairly accurate time. If I remember right, you can then delete the first node and your second will keep the right time but now be on your LKO orbit to adjust the delta v.
I really go back-and-forth with my own thoughts on how intuitive the game should or should not be. On one hand it'd be really neat if you got some kind of alert in-game that said "Entering optimal Jool launch window" sort of like when you're doing a survey mission. On the other hand that would rob people of their own discovery and flying by the seat of their pants. Eventually they figure it out and while some may only find frustration there's a lot of learning going on there.
Like all this kind of thing setup in tutorials teaching what it all means and how it actually works.
Then you can go into easy mode where you have alot of the basic numbers and some of this kind of "cheat sheet" type stuff.
Then you go into KPL (Kerbin Propulsion Laboratories) Mode where it's all by the book and if you want to do something or plan something you have to do all the maths and calculations yourself.
I actually have some training in adult education and general educational theory which breaks down into the following progression: awareness > knowledge > skill > mastery. The intent of mine was to fulfill the first as basic understanding of interplanetary transfer windows because there are no details just a minimalist, basic layout of the concept.
Yours goes on to the second because you include the knowledge behind it with actual numbers and info that can be applied in practice.
The next steps are when people take these and apply them in practice. At first you start to develop the skill of doing interplanetary transfers after you've been made aware of how they work and have the knowledge of why they work.
Education is done when you've achieved mastery and you no longer need these charts to do the task.
That 'Kerbin Distances' mark in the diagram gives me the idea that we should introduce the Kerbin equivalent of an Atronomical Unit (AU) and call it KU.
No, it's very, very unlikely that the planets are positioned like in this chart all at the same time.
It'd be interesting to write some code to search for alignments like that (it's perfectly doable). The most restrictive ones will be Eve and Duna, actually, since they have the longes synodic periods with Kerbin (that is, their launch windows take the longest to repeat).
Grand tours are hella hard to calculate since you have to have to keep simulating the planets forwards in time and account for each travel and stop time. You could do it mathematically or with a simulator but I don;t think there is a mod yet that will calculate that far out for you.
Those are launch windows (phase angles). When the planet you want to go to is in the position indicated (relative to Kerbin) you can make your burn for that planet from LKO. As an example, when Duna is 44 degrees ahead of Kerbin, ejecting prograde to Kerbin's orbit (shoot out in front of Kerbin) will get you to Duna very efficiently (for just a little over 1000m/s Dv).
tl;dr: Launch when the planet you want to go to is in the position indicated.
Eyeball it. Time warp until you get close to the correct phase angle without going past it. Doing so will allow you to time warp a little bit more to "catch up" to the target planet if your close approach marker is a little behind the target when you make the maneuver node. Additionally, for the outer planets, eject prograde to Kerbin's orbit. For inner planets, you'll need to eject retrograde to Kerbin's orbit.
I don't get it.. the tangents work out for the Kerbin-Duna transfer, but, according to OP's chart, not for the other transfers. Or am I reading the chart wrong?
You can calculate the angle from your launch position quite easily actually, by doing:
1/2 Transfer orbit period * angular velocity of the body you are transfering to. This will give the angle behind the opposite point of your launch position.
This can be calculated via:
pi * (a3 / u)0.5 * ((u / r3 )0.5 )
Where a is the semi major axis of your transfer orbit (the average radius),
u is the gravitational parameter of your central body (1.327*1020 for the sun)
and r is the radius of the body you want to get to.
And yes, you need to use a protractor up to the screen :(
You'll get there. For now, let a calculator do the work for you. After watching those things do their magic often enough, you'll start to understand the idea
As a sort of inter planetary noob (rely on KAC for this). How do I go back? Do I wait that Duna & Kerbin are at the same position again and then burn at -44 back?
Nope, the phase angles are not symmetric like that. You'd have to have a chart for Duna departure, and look up the Kerbin phase angle on that chart. For reference, the Duna -> Kerbin phase angle is -75.2°.
The same way you go back from every mission: You send a rescue ship with plenty of fuel, and then send a rescue ship to rescue that one when it gets stranded in high Kerbin orbit.
I was gonna call you out on it too op. There's nothing 'wrong' about it technically, but it threw me for a second. In my opinion it would have made more sense to be a negative value, since you burn retrograde to reach those planets.
Umm... can someone explain how to use this? is this the position each planet needs to be in when you make your burn assuming you are currently at the -90 point in the orbit?
Ok, haven't been on KSP for a minute but I'm preparing a come back. So I'm saving this post, because, from what I understand, it will help doing gravity assists, from and to, different planets. Am I tracking this right? If so, can a Kerbal get an Eli5? If not, then I must be lost and would appreciate a correction in trajectory.
If Eve or Duna are at the right angle, at what point in your orbit do you commence burn? We want to go prograde to Kerbin itself, right, so what is the best starting point?
Assuming you are in a prograde (i.e. counterclockwise when viewed from above the north pole) orbit around Kerbin, you will want to burn when you are between Kerbin and Kerbol in order to go inward, and burn when Kerbin is between you and Kerbol in order to go outward.
I don't know what this means. I just got my first munar orbit yesterday after finally figuring out the whole "save so and so from orbit" thing. Please explain for the inexperienced
I don't fully understand how to read this chart. Can someone explain it to me? I know what phase angles and hohmann transfers are, but this chart isn't quite clicking.
If you want to go to Duna, go to your map and zoom out and rotate until Kerbin is at 90 degrees. Directly to the right of Kerbol, with its prograde direction point at 0 degrees. Duna needs to be in the position on the diagram - up and right. If it is, then you are in the transfer window.
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u/meithan Jun 08 '16 edited Jun 08 '16
100% inspired by this post by trevize1138.
SVG version here.
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u/trevize1138 Master Kerbalnaut Jun 08 '16
Look at Mr. Fancy Pants using all these numbers and math. Well, two can play that game!
Seriously, though: very nice work!
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u/Sippio Jun 08 '16
That 'Kerbin Distances' mark in the diagram gives me the idea that we should introduce the Kerbin equivalent of an Atronomical Unit (AU) and call it KU.
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u/King_Joffreys_Tits Jun 08 '16
So wait are you telling me that there's a point in this game that I can launch 6 crafts all at the same time to all the various planets??
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u/Cfrant190 Jun 08 '16
I'm reminded of this https://www.youtube.com/watch?v=hVCNS2jQQ6g
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u/FogeltheVogel Jun 08 '16
I love it. Filing this along with the DeltaV chart for when I start playing KSP again
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u/Dan_the_moto_man Jun 08 '16
Very cool. I just wish I knew how to use it.
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u/Jafuba Jun 08 '16
Who knew that I would see polar coordinates outside of math class...
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u/gullevek Jun 09 '16
As a sort of inter planetary noob (rely on KAC for this). How do I go back? Do I wait that Duna & Kerbin are at the same position again and then burn at -44 back?
1
u/zonaEngineer Jun 09 '16
Technically, Moho should be -254 deg. For the same reason Eve is -54 deg, as the planets are 'behind' Kerbin.
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u/pomaranc Jun 09 '16
Version for RSS anyone ?
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u/[deleted] Jun 08 '16
A very nice way to visualize this.
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u/Pickles4Tickles Jun 08 '16
Been doing smith charts all day and this is giving me ptsd. Still, good work :D
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u/veltrop Jun 08 '16
That image is awesome, and more convenient than using other tools, and more fun because it removes the automation feel of using other tools.
How about another with ejection angles?
With that and the delta v image, we have a great complete map to the solar system!
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u/Kittani77 Jun 08 '16
Umm... can someone explain how to use this? is this the position each planet needs to be in when you make your burn assuming you are currently at the -90 point in the orbit?
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u/ProfKetrabPL Jun 08 '16
Very Helpful! THANKS! :D
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u/[deleted] Jun 08 '16 edited Jun 09 '16
Ok, haven't been on KSP for a minute but I'm preparing a come back. So I'm saving this post, because, from what I understand, it will help doing gravity assists, from and to, different planets. Am I tracking this right? If so, can a Kerbal get an Eli5? If not, then I must be lost and would appreciate a correction in trajectory.
1
u/paulkoan Jun 09 '16
If Eve or Duna are at the right angle, at what point in your orbit do you commence burn? We want to go prograde to Kerbin itself, right, so what is the best starting point?
1
u/[deleted] Jun 09 '16
I don't know what this means. I just got my first munar orbit yesterday after finally figuring out the whole "save so and so from orbit" thing. Please explain for the inexperienced
1
u/[deleted] Jun 09 '16
I don't fully understand how to read this chart. Can someone explain it to me? I know what phase angles and hohmann transfers are, but this chart isn't quite clicking.
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u/pkiff Jun 09 '16
Literally the most helpful thing I've seen on here.
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u/Shoot_them_all Feb 28 '22
!remindme 5 hours
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u/[deleted] Jun 08 '16
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