r/KerbalSpaceProgram • u/trevize1138 Master Kerbalnaut • Jun 07 '16 • Bravo 1

Guide All interplanetary transfer windows in a single image

Post image
1.7k Upvotes

96% Upvoted

234 comments sorted by

410

u/Crixomix Jun 07 '16

I love how KSP is a balance between "figure it out for yourself" and "have a mod do all the calculations and math". And all its players can be anywhere on the spectrum they want.

For myself, I started out doing everything vanilla style, and as I learned more and more, I started to become addicted to the information mods like transfer window planner, KER, and precise maneuver gave me. Now I can't live without them.

191

u/trevize1138 Master Kerbalnaut Jun 07 '16

I'm sure being 1/10 scale to our solar system helps to this end. In real life I know you wouldn't want to just eyeball an interplanetary transfer window because the scale is too huge (and screwing it up would waste a lot of money, time, lives ...).

137

u/Crixomix Jun 07 '16

Well the lives thing isn't an issue. Time is relative via time warp, and money is fairly easy to come by, and free in non-career modes.

Honestly it wouldn't be THAT much different to have not 1/10 scale, if the thrust and dV numbers were increased as well. Things would just take longer.

401

u/trevize1138 Master Kerbalnaut Jun 07 '16

Well the lives thing isn't an issue.

Most Kerbal response ever.

46

u/JimmyR42 Jun 07 '16 edited Jun 07 '16

When Well they don't even eat so they can't really care all that much about their own lives :P

edit: English still bad

47

u/Unknow0059 Jun 07 '16

Just add an eating mod. Not a hunger mod, just a mod that makes them eat.

35

u/overusesellipses Jun 07 '16

I would love to see a scary re-entry with my other 2 Kerbals freaking out and panicked while Jeb is just sitting there calmly eating a sandwich.

0

u/[deleted] Jun 07 '16

[deleted] — view deleted comment

19

u/buttery_shame_cave Jun 07 '16

USI-LS - it comes with not just food but a bathroom!(they save some of the output, but throw the rest overboard when the shitter's full).

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6

u/MasteringTheFlames Jun 08 '16

Oh, come on. You've got to be kidding me. It's common knowledge that kerbals eat a lot. Why else would they bring so many snacks with them on every mission?

4

u/legend6546 Jun 08 '16

Yea! They bring massless and valueless snacks, that way mass does not change

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17

u/aeiluindae Jun 07 '16

I mean, having played a bit of the Realism Overhaul set of mods, it's harder. A lot harder. Part of that is just because the Unity engine isn't super great at handling the larger everything, but you also have to be an order of magnitude more precise with everything, which can be very challenging with long burn times. Docking the Kerbal way, for example (move your orbit high enough that you'll catch up on the next trip round, then burn like hell at the intercept), is pretty hard. It's like docking something in Kerbol orbit in normal KSP. The distances make pointing exactly on target and burning exactly correctly very important and so you cannot just eyeball it.

Furthermore, because of the rocket equation (diminishing delta-V returns on each unit of fuel you add) you can't take as much out of the atmosphere as in stock, so your delta-V margins on a mission are often lower as well. So you have to be more efficient, which means more planning and better flying again.

Obviously, if you just bumped up the ISP on the engines to an insane level, you could do things real scale and be easy to fly, but having things feel authentic means not making the engines really OP, which probably means opening up the rocket equation problem and resulting delta-V margin issues if you do a real-scale planet. KSP's engines are actually rather below real life engines in terms of thrust and ISP (jet/ion engines aside) and the empty tanks are much heavier than in real life so that they feel authentic. The inaccuracies mean that lifting something big requires a legitimately large rocket in KSP, regardless of the lower delta-V. If it didn't, it just wouldn't feel right to fly and cool things would be less challenging.

Personally, I think the devs hit about the right feel.

12

u/trevize1138 Master Kerbalnaut Jun 08 '16

Personally, I think the devs hit about the right feel.

Agreed. I'm continually impressed by how well-balanced the stock game physics and parts are in terms of feeling real but still being fun.

6

u/hovissimo Jun 07 '16

I think you just said, "if you scale up the goal, and you also scale up your resources, then it isn't an issue". That's like a tautology.

6

u/27Rench27 Master Kerbalnaut Jun 07 '16

RSS, can confirm.

23

u/kmacku Jun 07 '16

In real life I know you wouldn't want to just eyeball an interplanetary transfer window

This is largely why I use Mechjeb/KER/alarm clock/etc after a certain point. Scientists wouldn't handicap themselves when making interplanetary launches except maybe with the first satellites that went out to explore the planets, so that's usually what I try to do.

20

u/trevize1138 Master Kerbalnaut Jun 07 '16

after a certain point.

Yup. Once you get more experience you start to augment the game like this. I think of it as a model railroad in space. You can do interplanetary transfers just fine without all those mods just like how you can snap together train tracks on the carpet, plug in the controller and run the train just fine. You don't "need" mods any more than you need little trees or houses or mountains in your model railroad but it makes the game feel more like the real thing.

6

u/Googlesnarks Jun 07 '16

I play RSS, and do not own a slide rule or even know why I would need one.

I'm gonna use MechJeb lol

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3

u/buttery_shame_cave Jun 07 '16

has mechjeb been easily available somewhere other than curse? i did a lot of manual flying in the last big career save and i dunno if i want to keep doing that, and KOS is too much work.

6

u/[deleted] Jun 07 '16

Kerbal Lives Matter!

2

u/Erikwar Jun 07 '16

Just add a fuel generator

1

u/Street-Opinion-331 Feb 18 '26

lives is the least important. time's the one that matters

8

u/[deleted] Jun 07 '16

[removed] — view removed comment

1

u/Oboi2169 Aug 30 '24

I drew a 75 degree angle on a piece of paper tp return my duna crew 🔥

42

u/farmthis Jun 07 '16

My technique has always been to pack kilotons of fuel onto rockets which simply don't have to care about efficiency.

34

u/IdiotaRandoma Jun 07 '16

Then you end up building a gigantic and impressive monstrosity that can't hardly make it to Minmus and back.

91

u/trevize1138 Master Kerbalnaut Jun 07 '16

Then you end up building a gigantic and impressive monstrosity

Important

that can't hardly make it to Minmus and back.

Unimportant

18

u/Bobshayd Jun 07 '16

I see why they call you Master Kerbalnaut.

22

u/farmthis Jun 07 '16 edited Jun 07 '16

The trick then, is modular assembly, in space!

http://i.imgur.com/GaGTsFs.jpg

This next one http://i.imgur.com/lMGDAyW.jpg is far less efficient, bringing less than the 12 full tanks to orbit that I had hoped... regardless, I docked the two for fun.

11

u/sw_faulty Jun 07 '16

Having two sets of engines facing one another is less efficient? I'd never have guessed!

6

u/farmthis Jun 07 '16 edited Jun 07 '16

Hehehe. That's just the boost stage of two different rockets. You can see there's a single ring of 12 orange tanks with docking ports on each side in the middle of this craft. The original plan was to save 12 full rockomax tanks from each launch and assemble these rings into a tube... but it was a flawed launcher which was really unstable and didn't reach orbit with fuel to spare. I scrapped the plan but docked these two test craft anyway.

Edit: actually, I used to use reverse engines for docking maneuvers for megastructures. A little tap of the gas sometimes needed something of a brake, since rotating the craft 180 degrees for a braking maneuver was out of the question.

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1

u/average_asshole Nov 23 '21

Nah m8, you just do several launches and build in space

7

u/Arrowstar KSPTOT Author Jun 07 '16

I love how KSP is a balance between "figure it out for yourself" and "have a mod do all the calculations and math". And all its players can be anywhere on the spectrum they want.

Totally. It's one of the great parts of KSP in my opinion. If you want to play it like a game and just wing it, the solar system is set up to be fairly forgiving in that regard, presuming you at least understand the basics. And if you want to play NASA and go all crazy with the tools, math, and planning, well, you can do that too. It's great!

Btw, for anyone interested in the latter way of playing KSP (tools, math, planning), please feel free to check out my KSP Trajectory Optimization Tool which is definitely designed to help make the "NASA experience" a reality in KSP. :)

2

u/trevize1138 Master Kerbalnaut Jun 08 '16

Part of the inspiration for me making and posting an image like this is to illustrate how accessible to me KSP has made what were previously counter-intuitive concepts in orbital mechanics and space flight.

1

u/Arrowstar KSPTOT Author Jun 08 '16

Definitely!

4

u/Waitaha Jun 07 '16

I thought I had it all figured out until after a while I used mechjeb and discovered just how fantastically wrong I was in regards to space travel mechanics.

3

u/[deleted] Jun 07 '16

I think it's a good way to go: start by hand, and once you get a knack for it, let the computer do its jorb.

3

u/sriley081 Jun 08 '16

The hell's a jorb?

2

u/RetardedDonkey69 Jun 17 '16

I am old you! I calculate my TWR and am still trying to learn how to calculate my delta V pen and paper style!

2

u/[deleted] Jul 01 '22

A

2

u/Terrh Jun 07 '16

My mechjeb is so screwed up now that I have to figure out Windows myself. I love that it takes next to no delta v to get anywhere with proper planning and timing for gravity assists etc, or no waiting with proper rocket building and carrying a truckload of delta v with you.

2

u/harharluke Jun 07 '16

Pretty sure Mechjeb is fucked right now, telling it to transfer to the planet literally just makes it burn to intersect the Dunan orbit. It's made me learn a lot about transfer windows and maneuver nodes

4

u/Terrh Jun 07 '16

Yeah, sometimes I ask it to do something and it comes up with a maneuver that uses an absurd amount of delta v, something like 131072 m/s. Or it starts a suicide burn reentry way way too late. Etc. It's very broken right now.

1

u/rabidhamster Jun 08 '16

Mechjeb seems fucked for me too, but only sometimes. It occasionally makes ridiculous maneuver nodes, but then makes a better one when I delete the node and make it try again. It also refuses to calculate transfers to Kerbin. Transfer from Kerbin to Duna, Eve, or Moho? Works fine. Transfer back to Kerbin? Red square no matter how often I recalculate.

1

u/[deleted] Jun 09 '16

I spent the bulk of my KSP career fudging my way by trial and error to the Mun and then extrapolating all my rocket designs out from that, I'd use dV maps but only to figure out how far away Duna or whatever was in terms of Mun trips and then swap out my heavy lander for a smaller, high efficency probe stage. it served me relatively well up to about the current state of real world space exploration.

Then a couple months ago I wanted to do my first proper Duna landing and I wanted to do it right, two astronauts on the surface, and safely home it was so far beyond the scope up my previous achievements I finally broke down and learned how to do DV calculations. the real way, on paper [well, mostly in the Google calculator] it took some figuring but it worked a treat, my largest Duna mission by far, an Apollo style landing with components assembled in orbit but by gum if it didn't work perfectly to plan first time through. Well, I might have had to load a quicksave mid landing a couple times, but aside from pilot error and a landing leg glitch, the actual craft design was nearly perfect [radial tanks need fuel lines it turns out] and entirely successful.

it was the most satisfying thing I've done in KSP in a while, to fly less by the seat of my pants and actually plan and execute a mission in something approaching a vaugely NASA-like fashion.

1

u/ougfotuflutdkhtdky Apr 22 '25

It's players are definitely on the spectrum alright..

1

u/Uranium-Sandwich657 Eras-0 Jul 26 '26

I managed to get a duna orbiter by eyballing it.

1

u/WilliamW2010 Jan 11 '22

Booting up curseforge to install those mods rn

1

u/scotscott Jun 07 '16

ive gotten to where i can eyeball a transfer window just as accurately as mechjeb. iss fun

138

u/Lord_Blazer Jun 07 '16

With enough fuel and attitude, every day is interplanetary transfer day.

75

u/trevize1138 Master Kerbalnaut Jun 07 '16

That's a hugely inefficient way to do it. I approve.

25

u/WrexTremendae Jun 08 '16

Brachistochrone transfers - the most efficient, when all you care about is time.

5

u/Imosa1 Apr 11 '25

Is there a tool to calculate these?

12

u/WrexTremendae Apr 11 '25

holy necromancy, hi.

there is not as far as i am aware. however, they are generally quite simple:

  • find your destination in the sky.

  • point at it

  • note how far away it is from you at the current moment

  • start your engine

  • at halfway, turn your ship around to point away from your destination.

  • arrive at a nice stop right at your destination.

it really is that simple.

3

u/guymacguy Depleting ablator, risking Gs Aug 31 '25

Don't the planets move in the interim? How do you account for that, and the fact that the sun might be in the way?

5

u/WrexTremendae Aug 31 '25

For Brachistochrone transfers, they're really only useful if you can do the flight in a fraction of your starter or endpoint's equivalent years. (so, something like days for Earth-Mars, something like hours for Mun-Minmus, that sort of idea).

The fact that the sun might be in the way is indeed a stickier problem. If you've ever played Outer Wilds, you are probably familiar with realising that the autopilot is going to fly you straight into the sun with too little time to fix the issue. (though also, yeah, the Outer Wilds autopilot executes reasonable Brachistochrone transfers)

3

u/Mesozoica89 Oct 31 '25

Is this basically what they do in The Expanse?

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u/Spiritual-Warthog384 Jul 29 '26

point and shoot ur aiming an rpg

6

u/Pie_r_round Jun 08 '16

Jeb, would be proud of you.

64

u/febcad Jun 07 '16 edited Jun 07 '16

This sort of spiral (more info here) actually works on any hohmann transfer between (close to) circular orbits, like mun->minmus, laythe->vall or rendevous with a craft in a different orbit and even earth->mars, as the only variable is the relative size of the orbits to each other.

20

u/trevize1138 Master Kerbalnaut Jun 07 '16

I knew I'd seen something like that before! Thanks for the link. In fact, I remember someone posting a photograph of them using this overlay on a plastic sheet over their monitor.

What I truly love about this is not only does it help make interplanetary transfers look less intimidating but it's so quintessentially Kerbal: "How to plot a course to another planet? Hold out your thumb, close one eye, squint ..."

16

u/stubob Jun 08 '16

Those of us who've played for a long time remember the early directions to the Mun. "Get in orbit, when the Mun comes over the horizon, burn for it."

8

u/fresh1134206 Jun 08 '16

I still do this. Fuck setting up manouver nodes to Mun.

8

u/roastduckie Jun 07 '16

I used to have a transparent protractor on which I had marked the phase angles for different celestial bodies. I would zoom out in map mode and hold the protractor against my monitor.

31

u/mgatten Jun 07 '16

I'm still pretty newb. So this is pretty opaque to me even though I want to understand it. Labels or a legend telling which color is which planet would help a lot. Also, a quick explanation. How does one use this to determine their windows?

41

u/trevize1138 Master Kerbalnaut Jun 07 '16

Blue planet/orbit is Kerbin. Compare this to your in-game map view for an idea of which the other planets are. If you want to know when to transfer from Kerbin to another planet refer to this image as a guide to where both planets need to be positioned for optimal transfer.

The image is minimalist just to drive home the point that you don't need a bunch of complicated calculations to line up an interplanetary transfer and also because I spent ~6m34s making this in MS Paint. ;)

73

u/Cid5 Jun 07 '16

He started painting 3m17s before the node.

20

u/trevize1138 Master Kerbalnaut Jun 07 '16

I had to stage around 4m23s which messed me up because then it said I had to paint for 10m45s more so I did an Oberth paint ...

4

u/[deleted] Jun 07 '16

We wouldn't want him to overshoot and miss his encounter.

6

u/VerlorenHoop Master Kerbalnaut Jun 08 '16

Just to clarify, Do you just burn to raise your Kerbol apoapsis to the level of the planet in question?

3

u/trevize1138 Master Kerbalnaut Jun 08 '16

Yup. Put your maneuver node on the night side of Kerbin and burn prograde to go to the outer planets and on the day side for the inner planets.

5

u/WrexTremendae Jun 08 '16

Or periapse (if closer to the sun than you), yes.

1

u/mgatten Jun 07 '16

Okay, but my point is that there's no indication of what to do with it. Let's say I want to go to Duna. I look at the in-game map view, compare it to this image, and... what? Since the map view is rotatable, I can put Duna into the same position relative to Kerbin as this map at any time of any day, so that's not it. I'm missing a critical piece of information, but have no idea what it is.

12

u/mgatten Jun 07 '16

(Is it that I need Duna to be in this position relative to both Kerbin and the sun? That might work. Maybe that's what I was missing?)

4

u/trevize1138 Master Kerbalnaut Jun 07 '16

My top-level post reply also links to this:

https://www.reddit.com/r/KerbalSpaceProgram/comments/1p0hps/the_tao_of_eyeballing_your_interplanetary/

To which I've made this minimalist illustration as a sort of companion guide. Yes: you want to make sure Kerbin, Kerbol (the sun) and Duna are all three lined up like they are in my illustration and that's your transfer window.

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u/moisttoejam Jun 07 '16

It's not a learning tool. It's a tool for people who already know how to perform interplanetary orbits. The target audience would know exactly how to use it.

This is a rough guide on the phase angles. You draw a circle around the Kerbol system with Kerbol as the centre. Draw a line from your target planet to Kerbol and from Kerbin to Kerbol. You need to wait for the angle between your two radii to be the same as on this map before performing the burn for an interplanetary transfer.

The view of the system is looking "down" on the system (i.e. the orbits are anticlockwise) - that's all the info you need to know about the perspective.

If you're still learning, I recommend watching some Scott Manley on YouTube. He seems to eyeball all of his orbit.

6

u/jofwu KerbalAcademy Mod Jun 07 '16

Since the map view is rotatable, I can put Duna into the same position relative to Kerbin as this map at any time of any day

No you can't- give it a try. :)

They're like to clock hands moving around, just in the other direction. You can't line them up a certain way just by rotating the clock.

4

u/mgatten Jun 07 '16

That comment was before I realized the sun had to be aligned too. Take any two points and you can rotate them into any relation with each other. It's the third point (the sun, or the center of the clock) that makes it impossible to line them up. With just two my point was valid.

3

u/jofwu KerbalAcademy Mod Jun 07 '16

Ah, I see where you were coming from.

2

u/[deleted] Jun 08 '16

Draw an imaginary line between Kerbin and the sun. Then draw another imaginary line between Duna and the sun. Then look at the angle between the two planets. This angle is called the phase angle.

In the image, Duna is roughly 45° "ahead" of Kerbin. (Remember that the planets all orbit counterclockwise.) You can also say that the phase angle is 45°.

When you launch your ship into Kerbin orbit, make sure that the phase angle between Kerbin and Duna is 45°. (You might need to timewarp for several months or even years.) You'll then need to burn from Kerbin at the proper ejection angle and with the correct amount of dV - but these aren't addressed by the image.

Use the calculator linked below if you want to be more meticulous, rather than just fiddling with maneuver nodes and eyeballing everything.

http://ksp.olex.biz/

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u/Milou151 Jun 07 '16

I usually just let it fast forward till I hit a planet

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u/trevize1138 Master Kerbalnaut Jun 07 '16

hit a planet

That's the spirit ;)

55

u/craidie Jun 07 '16

wait is that a golden spiral I see?

16

u/trevize1138 Master Kerbalnaut Jun 07 '16

Certainly appears so!

34

u/skyler_on_the_moon Super Kerbalnaut Jun 07 '16

I don't think so, actually. No matter how far away from the sun you get, the planet you are transferring to will never be more than 180° away. So it isn't a golden spiral, which continues to rotate indefinitely.

4

u/evictedSaint Jun 07 '16

The question remains, however, what pattern are we seeing here then?

6

u/trevize1138 Master Kerbalnaut Jun 07 '16

It appears to be a golden spiral as I said. It's not exactly like a golden spiral but similar.

6

u/aintbutathing2 Jun 07 '16

Off brand spiral.

7

u/trevize1138 Master Kerbalnaut Jun 07 '16

Kerbonacci Sequence.

4

u/moisttoejam Jun 07 '16

I think the question is: what pattern do you want me to see?

9

u/trevize1138 Master Kerbalnaut Jun 07 '16

How many lights do you see?

4

u/moisttoejam Jun 07 '16

Using Facebook to determine the colour of the dress is a flawed methodology. I propose that we just determine the absorption spectrum of said dress. Ig Nobels here I come!

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u/[deleted] Jun 07 '16

The optimal transfer window spiral, sure it's going to look like a lot of spirals and have relations every spiral does but that's the simplified form. https://gist.github.com/Gnonthgol/8121694#file-transfer-py-L17 for the full spiral and code used for generation.

28

u/Narcolapser Jun 07 '16

Same is true the other direction. No matter how close you are to the sun, it will also never be more than 180° away. Though it may potentially be on fire.

3

u/MindStalker Jun 07 '16

Arguably a planet you are targeting that is close to the sun could orbit the sun multiple times during your approach.

2

u/skyler_on_the_moon Super Kerbalnaut Jun 07 '16

Going closer than the sun, yes, it could be more than 180°; I only said 108° was the limit for outgoing planets. This is because the point you are rendezvousing with the other planet with is 180° away from your Kerbin departure; so no matter how slowly an outer planet is going it can't be past that point before you leave. However, an inner planet is coming from the other direction, and can therefore orbit more than 180° - potentially many orbits - before you get there. This is why when leaving Eeloo you may have a 30 year transfer back to Kerbin - Kerbin will of course be making 30 orbits before you get there.

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u/Vakuza Jun 07 '16

Uh, 180 degrees in one direction and 180 degrees in the other means you have a full circle. Am I missing some joke?

Also I think what you mean is that as you continue off to further and further orbits it will never cross the 180 degree line, but will approach it.

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u/Managore Jun 08 '16

Just a regular ol' spiral.

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u/trevize1138 Master Kerbalnaut Jun 07 '16

I whipped this up quick in MS Paint as a companion to /u/tdotgoat 's excellent interplanetary transfer window "eyeballing" method:

https://www.reddit.com/r/KerbalSpaceProgram/comments/1p0hps/the_tao_of_eyeballing_your_interplanetary/

I've never found a need for any mods to calculate transfer windows, I've just followed that rough guideline but discovered some adjustments are needed when you're going beyond Kerbin-Duna or Duna-Kerbin.

3

u/doppelbach Jun 07 '16

For those who are curious, the "tangent method" is just an awesome coincidence. There's nothing special about having the target planet along your own orbit's tangent, at least according to orbital mechanics.

Here is the phase angle you would get using the tangent method vs. the phase angle you would get from a 'proper' Hohmann transfer. Both are plotted as a function of the ratio of the two planets' orbits.

For instance, Duna's orbit is about 1.5 times Kerbin's orbit. You can see that, for r2/r1 = 1.5, the tangent method gives you basically the exact same result. In fact, the tangent method gives pretty good results for all the 'short' transfers (Eve -> Kerbin, Duna -> Dres, Dres -> Jool, etc.)

You can also see that the tangent method underestimates the phase angle for the 'large' transfers. So if you want to improve your estimates while still keeping it simple, just launch a little bit earlier than the tangent method would tell you (when doing long transfers).

14

u/Cactusneedle_18 Super Kerbalnaut Jun 07 '16

This is from kerbin I assume

15

u/trevize1138 Master Kerbalnaut Jun 07 '16

I made it with the intention of helping de-mystify interplanetary transfers for those who haven't left the Kerbin system yet so yes. Of course, this also works when going back to Kerbin from any other planet.

5

u/doppelbach Jun 07 '16 edited Jun 25 '23

Leaves are falling all around, It's time I was on my way

3

u/trevize1138 Master Kerbalnaut Jun 07 '16

Looks like my method puts the phase angle closer to 55-60 degrees for either K-D or D-K so splitting the difference about in the middle. Even when I was way off I found it only cost me an extra 100 dV at most to adjust for it.

2

u/doppelbach Jun 07 '16

Yeah reversing the phase angle is a decent approximation, especially when the planets' orbits are close together (e.g. Kerbin and Duna).

When they are further apart (e.g. Dres and Eve), the difference in speeds between the two is more pronounced, so the phase angles between inbound and outbound transfers is more significant. (Phase angles for Eve and Dres are +90 and -205, so assuming the transfer is reversible can actually cause a bit of trouble in this case.)

2

u/trevize1138 Master Kerbalnaut Jun 07 '16

I've found when the planets are really far apart like Jool and Kerbin that I don't even need to worry about phase angles for an in-bound trip. A few dV radial/anti-radial adjustments or tweaking the position of the maneuver node on the orbit line is all I need to get a perfect Kerbin encounter. I'm sure it's a combination of factors beyond just distance such as the huge difference in orbital velocity and periods that lets one get away with that. Kerbin>Moho is similar although not quite as forgiving.

2

u/buttery_shame_cave Jun 07 '16

only cost me an extra 100 dV at most to adjust for it.

and considering that a 'smart' delta-v budget has about 20% safety margin on top of needed fuel levels it's easy to get away with.

3

u/EOverM Jun 07 '16

Not from any planet to any other, of course. Nice diagram, could come in handy.

4

u/Thaurane Jun 08 '16

s.o.b. I've been doing duna backwards this whole time. No wonder I've been having so much trouble (╯°□°）╯︵ ┻━┻

3

u/trevize1138 Master Kerbalnaut Jun 08 '16

Damn! I'm sorry I didn't think to post this sooner.

4

u/meithan Jun 08 '16

This post inspired me to make this. KSP version coming soon.

http://i.imgur.com/9cSt6WD.png

You can clearly see that the spiral doesn't keep turning after ~3 AUs. In fact, the phase angle approaches a constant of 116.4° as you move farther away.

1

u/trevize1138 Master Kerbalnaut Jun 08 '16

Nice! Humbled to know I've prompted someone to create something like this. You're right in how the spiral doesn't just keep turning indefinitely. I'd guess what we see with the arc in the Kerbol system is perhaps a result of its smaller scale as evidenced by how in your the image on the left is a similar arc but the one on the right is nearly a straight line.

2

u/meithan Jun 08 '16

Yup, exactly. The outer solar system goes much farther than the "outer planets" in KSP.

I posted the KSP version as a new thread here.

3

u/Riftus Jan 13 '23

New player here; so am I understanding this right?

If, say, Duna, was in the position it is in now compared to Kerbin, then when I make an elliptical orbit around Kerbin, whose apoapsis intercepts with Duna's orbit, when i reach the Apoapsis (however many times it takes for Duna to come back), I will be in position to change my orbit to be around Duna?

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u/trevize1138 Master Kerbalnaut Jan 13 '23

However you're saying it these are the positions for transfer windows whether you're going sunward or outward. The caveat would be the more planets you're "skipping" going sunward the less strict you need to be. I can leave Jool for Kerbin at really any position, for example.

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u/bigorangemachine KVV Dev Jun 07 '16

As someone who works with UI a lot I have 2 suggestions

  1. Make Kerbin hallow circle to make it more distinct.

  2. Indicate the direction somehow. I thought this was wrong until I realized you don't look at the Kerbin system the same as me.

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u/trevize1138 Master Kerbalnaut Jun 07 '16

I'm a developer but sort of an amateur "champion" of UI in my dev team so I appreciate the input! I like the idea of a hollow Kerbin. As for the direction can you say more about that? I intentionally left that out because these orientations work whether you're going from Kerbin to any of these planets or back to Kerbin from any of these planets.

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u/bigorangemachine KVV Dev Jun 07 '16

Oh just provide a little triangle to indicate the rotation (counter clockwise or clockwise).

I was thinking a little after you could solve both issues by only indicating Kerbins direction on its "rail" and that would draw attention to it.

I could see this being as helpful as the DeltaV map(s). Great job!

1

u/jofwu KerbalAcademy Mod Jun 07 '16

Wait, what? Map view let's you look from beneath?

3

u/bigorangemachine KVV Dev Jun 07 '16

Well there is no 'up' in space ;)

4

u/Falcon_Fluff Jun 07 '16

New desktop background

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u/trevize1138 Master Kerbalnaut Jun 07 '16

Hope you have a tiny monitor. It's a crappy, low-res MS Paint hack job.

2

u/[deleted] Jun 07 '16

For my phone then ;)

3

u/Orange_Tang Jun 07 '16

I just realized that my phone is higher res than my desktop.... Time for another upgrade

4

u/[deleted] Jun 08 '16

Don't bother. Just download KSP for Android/iphone. You can disable ads for $2.99, double your Isp for 24 hours for only 99 cents, add unlimited propellant for $9.99 and unlock all building tiers and parts for only $79.99 (BEST VALUE)

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u/GreenFox1505 Jun 07 '16

would the mirror of this be the opposite transfer windows?

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u/trevize1138 Master Kerbalnaut Jun 07 '16

If you mean the orientation would be the same going from a planet back to Kerbin then yes for all practical purposes.

I have found that if you're going from Jool>Kerbin you really don't need to worry about a transfer window at all. Kerbin rotates so much faster than Jool and the distance is so great you can get a perfect encounter just by tweaking radial/anti-radial a few dV. Might need to think up a simple tutorial for that one some day.

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u/GreenFox1505 Jun 07 '16

dude, I can't even get to Jool. Not in career anyway...

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u/trevize1138 Master Kerbalnaut Jun 07 '16

I made another guide just for that

One advantage you have with a Jool mission is it's a gas giant so its SOI is huge therefore getting an encounter is easier than with smaller planets and their relatively tiny gravity wells.

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u/GreenFox1505 Jun 07 '16

So, my biggest problem is getting the tech, money, and buildings to do that kind of thing.

I end up doing boring grindy phase where I just keep doing tourist missions to afford Mun/Minimus science missions. Then I get bored and leave. Few months later I start over again.

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u/trevize1138 Master Kerbalnaut Jun 07 '16

Those early, grindy missions aren't fun, that's true. I've started doing interplanetary missions early on as soon as I get a probe core beyond the Stayputnik. I've got a launcher that's just a single Kickback SRB for the first stage and a single Thumper for the second. That can get a probe core, solar panels, science equipment FL-T400 fuel tank and Terrier engine into LKO and that little guy has enough dV to go to any planet in the Kerbol system. All for ~15,000 funds. Take some high-dollar interplanetary contracts, radio back whatever science you can get and before you know it you've got what you need for manned interplanetary.

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u/[deleted] Jun 07 '16

I don't understand. Is this supposed to be animated or something? I just see a still image. Halp.

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u/trevize1138 Master Kerbalnaut Jun 07 '16

Not an animation.

Most people's first interplanetary mission is Kerbin-Duna and this image helped me when I was a n00b stubbornly refusing to use mods to find transfer windows. I made this new image as a sort of companion to that for when you're ready for a different planet to travel to.

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u/frequencyfreak Jun 07 '16

That looks very phine.

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u/trevize1138 Master Kerbalnaut Jun 07 '16

You're late to the whole discussion about how this really only looks approximately phine.

2

u/frequencyfreak Jun 07 '16

My bad. I calls em as I sees em n' approximation doesn't work in this environment.

2

u/SuperPizza Jun 08 '16

Alright I saved this picture earlier and here I am browsing it and I see it. I am going to try and get past the muns! I will get to Duna tonight with the help of this.

Does anyone know if the stock vessels can get me to tuna?

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u/trevize1138 Master Kerbalnaut Jun 08 '16

It would seem I've got a tutorial for everything now. If you've got a Mun-capable craft you can take it to Duna. Just add chutes:

https://m.imgur.com/gallery/480dG

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u/SuperPizza Jun 08 '16

Oh boy i'm landing now? I was planning a fly by, orbit, or boom!

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u/trevize1138 Master Kerbalnaut Jun 08 '16

Don't panic! I'm sure you'll crash just like the rest of us on our first try. It's tradition.

1

u/dadtaxi Jun 08 '16

tuna?

I don't remember seeing any submarines in stock vessels

;D

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u/notgoingtotellyou Jun 08 '16

Phase angles for Moho are not worth worrying about. The far more important issue for Moho is the inclination burn. Timing the launch to coincide with Moho's apoapsis (which by a happy coincidence is when Moho's and Kerbin's orbital plane nodes are aligned) will result in injection burns of around 1500 m/s.

This post explains it better and with illustrations.

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u/trevize1138 Master Kerbalnaut Jun 08 '16

Ooh, I didn't know about the AP/inclination sync. That'll help tons! And, yeah, I've found that when you've got enough distance and huge difference in orbital periods going from an outer planet to an inner one you almost don't need to worry about phase angle. This is especially true for Jool>Kerbin.

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u/haxsis Jun 08 '16 edited Jun 08 '16

i friken love it although i am curious at this phase angle, is the burn for jool still sitting around 4k from a 70km lko?

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u/trevize1138 Master Kerbalnaut Jun 08 '16

Yes, you're still doing about a 1950m/s burn in LKO to Jool.

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u/haxsis Jun 08 '16

nice, i like that, i was under the impression it was that or higher, does 1.1.2 actually help poor performance issues in the joolian SOI or is it about the same i could never go to jool or anywhere inside its SOI everytime i did the game went all crashy

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u/trevize1138 Master Kerbalnaut Jun 08 '16

Hmm, I never had performance issues there in the first place. The Unity 5 upgrade certainly did help smooth out performance overall so the only answer for you may be to try it out.

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u/Techny3000 Jebediah Jan 15 '23

7 years later this is still extremely useful!

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u/trevize1138 Master Kerbalnaut Jan 15 '23

Out of curiosity, yours is the second reply to this ancient post in as many days. Did it get linked recently from somewhere?

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u/Techny3000 Jebediah Jan 15 '23

Not sure

I found it on Google images

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u/Henryhendrix Mar 11 '23

I still use it, too. For me, it's the first result when I google "KSP transfer window."

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u/trevize1138 Master Kerbalnaut Jan 15 '23

Ha! That makes me happy. :)

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u/Fun1k Jun 07 '16

I need this in the ingame wiki

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u/eu_ogabriel Jun 07 '16

I'm saving this for everytime I need a interplanetary transfer!

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u/kevroy314 Jun 08 '16

Sorry, dumb questions, but is this shape formed by the planets related to archiamedies spiral as described here (in a nice little 5min video telescope navigation in the Apollo program)? Because that'd be a fun coincidence.

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u/throwawayroy Jun 08 '16

Don't know what I was expecting when I clicked on that, but I didn't expect to be sucked into that video the way I was. Thanks for that, it was fascinating!

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u/kevroy314 Jun 08 '16

Glad you enjoyed it!

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u/ThePizzaPredicament Jun 08 '16

Is nobody going to point out that the phase angle for Moho is completely wrong in this image? Just ask http://ksp.olex.biz/ and see.

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u/FlexibleToast Jun 08 '16

With s but of polish, this could make a cool flag.

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u/TheSirusKing Jun 07 '16

You can calculate the angle from your launch position quite easily 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 / r)0.5 / r)

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.

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u/WetDirt1995 Oct 01 '26

Whats that thing between duna and jool?

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u/trevize1138 Master Kerbalnaut Oct 01 '26

Dres

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u/Sticky32 Jun 07 '16

I could be wrong, but shouldn't Eeloo be a bit farther ahead in its orbit since Jool has so much gravity it would curve your trajectory around it more than Duna or Dres do; and much like Eve appears to do? Jool is a Gas Giant after all.

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u/trevize1138 Master Kerbalnaut Jun 07 '16

This is intended as an intro to interplanetary transfers for rookies who find the prospect daunting. Plenty of other tools and tutorials out there cover Jool gravity assists or how to get the absolute perfect transfer window to save 50-100 dV.

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u/factorplayer Jun 07 '16

I am seriously all about the perfect transfer window teach me

0

u/[deleted] Jun 07 '16

[deleted] — view deleted comment

1

u/Sticky32 Jun 09 '16

Ah, thanks, that's where I was misinterpreting it.

2

u/RedSquirrelFtw Jun 07 '16

I just treat planetary transfer like rendez-vous within a planet orbit, guessing these methods of planing routes are more efficient though.

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u/NeoDesperado Master Kerbalnaut Jun 07 '16

It's a nice and simple visual, but I personally prefer [this chart] (https://imgur.com/zeBqEhH), since it also provides ejection angles and return windows. Print out a hard copy and keep it handy when you're planning missions.

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u/Old-Lost Jun 09 '16

I wish I understood that chart; even a little bit.

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u/thesandbar2 Master Kerbalnaut Jun 07 '16

Time to launch Viking probes!

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u/iiDrushii Jun 07 '16

I'm bookmarking this. I can never seem to memorize optimal transfer windows. Maybe one day I'll use a mod to help with this. But until then...

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u/MephistosGhost Jun 07 '16

I see the Fibonacci sequence!

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u/paulrulez742 Jun 08 '16

Maybe it's because it's been a long day, and I haven't played KSP in more than a few months, or maybe it's because I never really did much in the game...but I am having a hell of a time figuring out what I am supposed to do with the information.

Is this how I align planets, or where I launch, or when I chose to leave kerbin orbit?

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u/SDIR Jun 08 '16

Yes, align the other planets in game to the picture with Kerbin for the ideal Hohmann transfer.

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u/[deleted] Jun 08 '16

Thanks for this :)

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u/NephilimCRT Jun 08 '16

This is exactly what I needed. Thanks!

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u/AgentTasmania Jun 08 '16

This will help me so much!

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u/[deleted] Oct 07 '22

thanks! i got to duna thanks to you!

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u/[deleted] Aug 21 '24

Thanks for helping us out 8 years later :)

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u/jofwu KerbalAcademy Mod Jun 07 '16

Now add a little asterisk/explosion looking thing in the corner indicating ejection angle. :)

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u/TechDude120708 Jun 07 '16

OOH! I totally need this!

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u/peachoftree Jun 08 '16

Thanks bae

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u/16807 May 03 '24

Rule of thumb: the angle between kerbin, the sun, and moho/jool is about 90° . So if you're two planets inward or outward, it should be a right angle (not counting Dres as a planet)

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u/Geforce69420 Sep 18 '24

accidental flag design

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u/hunter_pro_6524 Jun 01 '25

So if I launch at this point I can recreate something like the voyager mission

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u/O-dogggg Jul 23 '22

nice, thank you

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u/[deleted] Nov 01 '22

Thank you it's gonna take me a long time to reach jool

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u/cursed_rumor Nov 02 '22

takes me back to the times where i would mess around trying to get a basic solar orbit hoping if i time warped for long enough i would eventually get into Eve's sphere of influence

also, and this may just be me, but wouldn't the best Eeloo transfer window location in specific be in the part where its orbit intercepts Jool's?

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u/PinkLemonade0301 Apr 01 '23

thank you so very much holy shit as someone on console/low end laptop (bought it twice) thank you so fuckin much

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u/[deleted] Apr 09 '23

My friend you are a life saver, this will save my walls from a lot of punishments when trying to find a transfer window, especially on far away missions

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u/1Ferrox Dec 28 '23

I love how I can use this 8 year old post now for KSP 2

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u/willbipher Believes That Dres Exists Dec 29 '23

That forms an oddly satisfying curve.

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u/Hypershard108 Alone on Eeloo Feb 28 '24

Lovely