Transfer window planner...

[MoridinUK]

Ok I'm having a problem using the transfer window planer mod. I figure how it works out my window etc, but when I try to make use of it, I can't get anything to work.

An example, I asked for a transfer from Mun orbit 1000km to Minmus 100. It told when to leave (UT) it told me how much prograde and normal I needed, it told me the ejection angle and inc. But when I tried to fire at that time, in those directions I couldn't get anywhere near Minmus. just stuck back in a kerbin orbit a little further out than Mun.

I can't set the ejection angle and inc, but I couldn't find a maneuver node that match these conditions with the TRansfer. I have a small 2% inc on my Mun Orbit. Is that the problem or am I missing something else?

[eddiew]

Can I suggest asking this in TWP's thread?

http://forum.kerbalspaceprogram.com/threads/93115-0-90-Transfer-Window-Planner-v1-2-3-0-%28Jan-11%29

My answer; nor can I. I use TWP to tell me what the right time to go is, and then a few minutes before that time, plot the course myself. Sometimes I'll use MechJeb's porkchop plot for interplanetaries - if you know the date and exit delta-v the burn should have, then you can find the point on that plot that matches. Mun-Minmus isn't hard though. Exit Mun burning prograde when round on the back of it (so you end up in a wider orbit than Mun), then adjust your inclination to match Minmus at the next AN or DN, and from there it's just a regular Hohmann.

[Taki117]

Honestly, I don't use it for intersystem transfers (mostly because I don't have a need to do them) but it is great for interplanetary, though it is much better if used in conjunction with the precise node and phase angle mods, or mechjeb.

[Alshain]

As for interplanetary, read the last post in the thread eddiew linked.

However for moons, it's overkill. You can get to the moon just by matching inclinations first, then dragging a maneuver node out ahead of the moon you want to reach in it's orbit. For Mun to Minmus, your better off returning to a Kerbin orbit first. Ideally if you can, aerobrake back in close to Kerbin, getting an encounter from way out at the Mun's orbit can be difficult.

[MoridinUK]

thanks for the suggestions, I've posted further questions but nothing makes sense.

I did a pork chop for the best Duna window, from my 103k Kerbin orbit, for the next two days. I entered the info given into precise node, and the ejection angle and inc was wrong, so I moved the node through time to get the right angle, and added a little normal... the burn showed me getting no where near duna. It did say I needed an 970ish dv inc burn but without an encounter I thought that pointless.

What have I done wrong?

Kerbin (@103km) -> Duna (@100km)

Depart at: Year 1, Day 64, 0:00:00

UT: 1360800

Travel: 325 Days, 2:06:11

UT: 7027571

Arrive at: Year 1, Day 389, 2:06:11

UT: 8388371

Phase Angle: 107.95°

Ejection Angle: 34.15°

Ejection Inc.: 0.03°

Ejection ÃŽâ€v: 1724 m/s

Prograde ÃŽâ€v: 1724.1 m/s

Normal ÃŽâ€v: 1.9 m/s

Heading: 89.94°

Insertion Inc.: -0.37°

Insertion ÃŽâ€v: 934 m/s

Total ÃŽâ€v: 2658 m/s

[Renegrade]

Depart at: Year 1, Day 64, 0:00:00

It usually works for Duna for me - were you actually at Day 64 00:00:00 though? I think the KAC integration defaults to a 24-hour margin for instance...

Also be careful that PreciseNode and TransferWindowPlanner use a different notation for ejection angle - they usually only line up for um... inner planets, if I remember correctly...

[Kryxal]

As I recall, the first Kerbin > Duna window is around day 60 on the 24-hour clock. You're running on the 6-hour day, from the UT departure number. Whenever I use the web-based utility, I change it to 6-hour day then back to 24-hour just to be safe...

[AlexinTokyo]

You'll rarely get the exact ejection angle at the exact time the TWP specifies. The reason is simply that there's a very good chance that your ship will be at any other point in the orbit at that time (unless you've specifically set up the orbit). That being the case, you need to get the ejection angle right near the right time. The angle being the more important of the two.

My usual process is:

1. Get the transfer information from TWP.
   
2. Create a maneuver node at the exact UT with the exact ÃŽâ€v specified. At this point, I usually won't have an encounter.
   
3. Check the ejection angle of the maneuver (I use Precise Node for this, other mods are available. In stock it's protractor on the screen or the Mk. 1 eyeball).
   
4. Change the UT of the maneuver until the ejection angle matches. This usually brings up the encounter.
   
5. If I feel like it, adjust the maneuver node ÃŽâ€v to improve the encounter.
   
6. Burn.
   
7. Make corrections for the inevitable imperfections in the burn.
   

Works for Eve, Duna, and Jool. I've not tested it for Moho, Dres, or Eeloo (never been there), but I can't see why it wouldn't work.

[MoridinUK]

You'll rarely get the exact ejection angle at the exact time the TWP specifies. The reason is simply that there's a very good chance that your ship will be at any other point in the orbit at that time (unless you've specifically set up the orbit). That being the case, you need to get the ejection angle right near the right time. The angle being the more important of the two.

My usual process is:

1. Get the transfer information from TWP.
   
2. Create a maneuver node at the exact UT with the exact ÃŽâ€v specified. At this point, I usually won't have an encounter.
   
3. Check the ejection angle of the maneuver (I use Precise Node for this, other mods are available. In stock it's protractor on the screen or the Mk. 1 eyeball).
   
4. Change the UT of the maneuver until the ejection angle matches. This usually brings up the encounter.
   
5. If I feel like it, adjust the maneuver node ÃŽâ€v to improve the encounter.
   
6. Burn.
   
7. Make corrections for the inevitable imperfections in the burn.
   

Works for Eve, Duna, and Jool. I've not tested it for Moho, Dres, or Eeloo (never been there), but I can't see why it wouldn't work.

This is exactly what I did... with no encounter. I set the UT in precise node so I should be good for time (it still said the node was in the future) I'll grab a screen shoot shortly) I'm not actually trying to make this burn just see if I can use the transfer window planning to get an encounter..

[MoridinUK]

Kerbin (@103km) -> Duna (@100km)

Depart at: Year 1, Day 64, 0:00:00

UT: 1360800

Travel: 325 Days, 2:06:11

UT: 7027571

Arrive at: Year 1, Day 389, 2:06:11

UT: 8388371

Phase Angle: 107.95°

Ejection Angle: 34.15°

Ejection Inc.: 0.03°

Ejection ÃŽâ€v: 1724 m/s

Prograde ÃŽâ€v: 1724.1 m/s

Normal ÃŽâ€v: 1.9 m/s

Heading: 89.94°

Insertion Inc.: -0.37°

Insertion ÃŽâ€v: 934 m/s

Total ÃŽâ€v: 2658 m/s

[AlexinTokyo]

I think I may have found your problem - the Mun is on the ejection path for that particular window.

You can still get the encounter, though:

Ninja: You've set your ejection angle to 34° from retrograde. It should be 34° from prograde.

[Renegrade]

Ninja: You've set your ejection angle to 34° from retrograde. It should be 34° from prograde.

Yeah, that's what I meant by "Also be careful that PreciseNode and TransferWindowPlanner use a different notation for ejection angle - they usually only line up for um... inner planets, if I remember correctly... ". heh.

I wish TWP used PreciseNode's notation...or vice versa.

[LethalDose]

Even without the Mun mucking up your ejection, the image provided is evidence that you're making the burn at the wrong time.

The image provided shows Kerbin about 120 degrees behind Duna. The appropriate phase angle for a Kerbin-to-Duna transfer (a Hohmann transfer) is when Kerbin is ~ 45 degrees behind Duna, regardless of what the planner says.

I suspect the issue is the 6hr day vs 24hr day discordance noted above. I seem to recall the first Duna window openint around day 200 or 220 in 6 he day notation.

[AlexinTokyo]

The TWP gives the correct ÃŽâ€v for the transfer at that time, which was constrained (in Moridin's original example by being 2 days from 'now').

It's not a maximum-efficiencey Hohmann transfer, no, but it's easily doable at only 1700 m/s.

The problem Moridin is having is that their ejection angle is 180° off where it should be (i.e. 34° from retrograde instead of 34° from prograde).

[MoridinUK]

I'm very very confused. I have no idea how to plan anything interplanetary and while I'm not dumb I have no idea, having not had any kind of success, for how this works. I have no idea what a Hohmann is, nor do I care. I'm simply trying to figure out how to use the TWP. I asked it to give me the best window between day 60 and 64. I didn't ask it for an efficient window, just any, I didn't care how much the Dv would be because I simply wanted to figure out how to take the info in the TWP and create a node that would work from it. I was not planning on making the burn. However, if the tools use different notations for ejection angle, inc and even time, how the heck is a newb supposed to stand a chance? I'm trying to figure out what I need to do, before my window opens, because I don't want to wait years again if I f it up.

Whatever the appropriate phase angle should be, I dont care, I'm simply trying to figure out how the two tools can work together, It seems I'm going to end up having to resort to trying to dust my maths off and working out the thing on paper. I'm already annoyed that it can't create a node with the alarm clock entry. I get all the data in a window but nothing I can do with it, cos the game is paused and it vanishes it if I unpause. As for time, I'm setting my node on UT not anything else, surely they both count UT the same? And my Ejection Angle is the wrong way? I need it to be -34.15 how do I do that, I don't recall getting many options from my orbit! My heading is about spot on. Or do I need it to read 214.15? +180 to bring it to 34.15 from prograde, of course there are two angles which are 34.15 degrees from prograde, one up and one down. Clarity is not coming for me huh?

Thank you all for your help so far, and I'm sorry if I'm sounding frustrated or even pissy. The above example didn't work either at 1361190 it wont get me an encounter either. Sigh... I've no idea how to resolve this...

I mean prograde is a vector in 3 dimensions which means there are 360 different directions one could burn in that are all at an angle of 34.15 degrees from it... :S See I'm just getting in such a muddle.. I should go read more, though doing a crash course in orbital mechanics so I can play a game doesn't sound like fun...

Edit: this cross posted, sorry for the rant, so I want it to say 214.15?

[AlexinTokyo]

Hopefully this will make it clearer:

The green circle is Kerbin, the black is the ship's orbit. The two red dots represent the positions with ejection angles of 34° from both prograde and retrograde*.

For your Duna burn, you want 34° from prograde, but unfortunately the Mun is on that trajectory, so PreciseNode won't give you the ejection angle (it will give you your Mun periapsis etc. instead).

You can still get the encounter, but to see it you will have to look on the other side of the Mun encounter, and you may have to use PN's "increase conics" function.

* If you're interested, the angle is measured clockwise from the vector, in the orbital plane.

[Renegrade]

My heading is about spot on. Or do I need it to read 214.15? +180 to bring it to 34.15 from prograde, of course there are two angles which are 34.15 degrees from prograde, one up and one down.

Like I said, I wish both tools used the same notation (I tend to prefer PreciseNode's notation as it's a bit clearer).

Note: the TWP starts from midnight on that day, so your node might actually be in the past or such. It's better to have it start from tomorrow's date.

Here's the procedure I use for setting up a maneuver:

- I use the default 100x100 orbit (I usually park between 100.2 and 100.8km. It doesn't have to be exact, just close), with an inclination of <0.5 degrees. Counter-clockwise direction.

- I warp until a few hours before my selected window

- I place a node on the right side of the planet for the transfer (going to outer planets = on the dark side of the planet, going to inner planets=light side of the planet)

- I use PreciseNode to type in the prograde burn and normal burn numbers

- I then use PreciseNode to move the orbit back and forth (+/- for UT) until I get the correct ejection angle (this moves the node back and forth on the orbit)

- If I'm not getting an intercept, I advance the orbit by one (If you configure PreciseNode to "x10 UT controls" mode, and have it enable advanced UT controls, you can press +orb and -orb buttons to advance/retreat a full orbit in one click) until I do get an intercept.

- If I'm STILL not getting an intercept, I -Orb until I'm back to the current orbit, and just force an intercept by fiddling with the normal/prograde/radial controls (my fiddling works pretty well, but it's too complicated to explain in a short message).

Once I have an intercept, I burn. If the burn is too long, it can still miss, so I then place a second node and fiddle again until I have another intercept and make a short correcting burn.

Here's how to configure PreciseNode:

1. Click the little "O" for "Options"

2. Enable "show additional UT controls"

3. Enable "Use x10 UT increment"

That enables the handy-dandy -orb/+orb buttons (they work like the stock buttons, only you can spam them a lot easier. The stock thing tends to close or mis-target etc.)

Edited February 14, 2015 by Renegrade

[MoridinUK]

Hopefully this will make it clearer:

https://dl.dropboxusercontent.com/u/42403518/Ejection_Angle.jpg

The green circle is Kerbin, the black is the ship's orbit. The two red dots represent the positions with ejection angles of 34° from both prograde and retrograde*.

For your Duna burn, you want 34° from prograde, but unfortunately the Mun is on that trajectory, so PreciseNode won't give you the ejection angle (it will give you your Mun periapsis etc. instead).

You can still get the encounter, but to see it you will have to look on the other side of the Mun encounter, and you may have to use PN's "increase conics" function.

* If you're interested, the angle is measured clockwise from the vector, in the orbital plane.

Right this helps, the prograde and retrograde that we are talking about are for Kerbin's orbit of course, not the ships.. *facepalm* Ejection angle, from the orbit around the Sun not from one's orbit around Kerbin, you can tell i haven't been interplanetary yet huh? (which the ship is also in)

What does the increase conics do, is it just plot more than then next orbit? which is my guess?

- - - Updated - - -

Just so I know, do you guys get told when I give you rep?

[Renegrade]

you can tell i haven't been interplanetary yet huh? (which the ship is also in)

There's a first time for everything. Nothing to be ashamed of. You should have seen the crazy technique I used to use

(to go to Duna, I'd burn on the dark side of kerbin to Duna's altitude, and then burn past that AP until I got a capture (using non-precise-nodes, of course). Took 1.5 orbits and quite a bit of fuel. I was to impatient to use a gentler, multi-orbit technique)

By the way, 5thHorseman has some sort of technique that uses a couple of nodes to skip by a lot of the complication. I've never actually flown a mission with it, but I was able to create a Duna intercept similar to the one in the example video:

. I would still recommend learning PreciseNode+TWP though, as that technique would be rather tricky to use on say, Moho.

What does the increase conics do, is it just plot more than then next orbit? which is my guess?

You got it You can also change that by editing the settings.cfg directly. PreciseNode is just more convenient. It makes a lot of things more convenient

Just so I know, do you guys get told when I give you rep?

Yes, it sends the little message too

[AlexinTokyo]

What does the increase conics do, is it just plot more than then next orbit? which is my guess?

Correct. It increases the number of trajectories that the game plots beyond sphere of influence changes. The higher the number, the further into the future you can gaze, but it can get a bit busy (and sometimes they lie on top of each other, if the orbits are very close). PreciseNode allows you to alter the number in game; without it you have to edit the settings file.

- - - Updated - - -

Just so I know, do you guys get told when I give you rep?

Yes, we get a notification

Edit: Slow ninja - I should probably reload the thread before writing responses.

[Laie]

An example, I asked for a transfer from Mun orbit 1000km to Minmus 100. It told when to leave (UT) it told me how much prograde and normal I needed, it told me the ejection angle and inc. But when I tried to fire at that time

Emphasis mine. I think here's your problem.

I don't know that mod, but assume that it merely duplicates http://alexmoon.github.io/ksp/ -- if that assumption is wrong, the following won't make sense.

Your position at the time of the burn is the single most important thing. Timing also matters, of course, but it's nowhere as important as position. I don't know how to explain this is less than 1000 words, so I suggest a simple experiment: Timewarp until the calculated burn is less than one orbital period in the future. Create a node with the given prograde/normal figures. Then grab that node and pull it around on your orbit. See how the resulting orbit around Kerbin changes? There's one place for the node where the resulting trajectory will get you really close to Minmus. Now tweak it a little.

In a perfect world, you'd be at the right position at just the right time. But in almost all cases, arriving 30 minutes early or late only makes a very small difference in the delta-V required (for interplanetary, even days are alright). Manually correcting the maneuver is a lot easier to do than trying to be punctual.

[Renegrade]

I don't know that mod, but assume that it merely duplicates http://alexmoon.github.io/ksp/ -- if that assumption is wrong, the following won't make sense.

It does indeed. It's also a good deal faster. Mono might not be the fastest thing in the world, but it's a heck of a lot faster than javascript

[LethalDose]

I'm very very confused. I have no idea how to plan anything interplanetary and while I'm not dumb I have no idea, having not had any kind of success, for how this works. I have no idea what a Hohmann is, nor do I care. I'm simply trying to figure out how to use the TWP. I asked it to give me the best window between day 60 and 64. I didn't ask it for an efficient window, just any, I didn't care how much the Dv would be because I simply wanted to figure out how to take the info in the TWP and create a node that would work from it. I was not planning on making the burn. However, if the tools use different notations for ejection angle, inc and even time, how the heck is a newb supposed to stand a chance? I'm trying to figure out what I need to do, before my window opens, because I don't want to wait years again if I f it up.

Whatever the appropriate phase angle should be, I dont care, I'm simply trying to figure out how the two tools can work together, It seems I'm going to end up having to resort to trying to dust my maths off and working out the thing on paper. I'm already annoyed that it can't create a node with the alarm clock entry. I get all the data in a window but nothing I can do with it, cos the game is paused and it vanishes it if I unpause. As for time, I'm setting my node on UT not anything else, surely they both count UT the same? And my Ejection Angle is the wrong way? I need it to be -34.15 how do I do that, I don't recall getting many options from my orbit! My heading is about spot on. Or do I need it to read 214.15? +180 to bring it to 34.15 from prograde, of course there are two angles which are 34.15 degrees from prograde, one up and one down. Clarity is not coming for me huh?

Thank you all for your help so far, and I'm sorry if I'm sounding frustrated or even pissy. The above example didn't work either at 1361190 it wont get me an encounter either. Sigh... I've no idea how to resolve this...

I mean prograde is a vector in 3 dimensions which means there are 360 different directions one could burn in that are all at an angle of 34.15 degrees from it... :S See I'm just getting in such a muddle.. I should go read more, though doing a crash course in orbital mechanics so I can play a game doesn't sound like fun...

Edit: this cross posted, sorry for the rant, so I want it to say 214.15?

Well, to address this in the same tone of the post: You may want to start caring about what a Hohmann transfer is if you want to start going interplanetary.

Doing the math yourself is probably the best because you're going to understand the basics of what has to occur to make the transfer effective. You're also probably going to learn why launching at day 60 is a bad idea, but I'll explain it anyway: Launching at day 60, which is way too early, will get the vessel to Duna's orbit ahead of Duna. To make that transfer work, you have to go well above Duna's orbit and linger there until Duna catches up, and catch the planet as you fall back towards the Sun. To launch in the appropriate ejection to get above Duna's orbit, I really think the "34 deg from retrograde" location marked on AlexinTokyo's image.

[MoridinUK]

Well, to address this in the same tone of the post: You may want to start caring about what a Hohmann transfer is if you want to start going interplanetary.

Doing the math yourself is probably the best because you're going to understand the basics of what has to occur to make the transfer effective. You're also probably going to learn why launching at day 60 is a bad idea, but I'll explain it anyway: Launching at day 60, which is way too early, will get the vessel to Duna's orbit ahead of Duna. To make that transfer work, you have to go well above Duna's orbit and linger there until Duna catches up, and catch the planet as you fall back towards the Sun. To launch in the appropriate ejection to get above Duna's orbit, I really think the "34 deg from retrograde" location marked on AlexinTokyo's image.

As I said in my rant, I AM NOT trying to burn to Duna at day 60. I was trying to learn how to turn the info in the twp into a maneuver node, so that when a hohmann window opens, (about 179 days from now) I can enjoy firing my ships at the red planet instead of having to spend days messing about trying to learn the tools, and maybe even messing up my first window and having to find something to entertain myself with in Kerbin's SoI for another hundreds of hours!

I do care what a Hohmann is, it is just that it isn't relevant to what I was trying to achieve. I expect that the advice given here about 34.15 being from Kerbin's prograde rather than retrograde will fix my current problem. I intend to test that and report back, in a happy bunny, style once I get a chance to try it when my 2 year old isn't advancing my stages on a whim, which normally means in the evening, but I also need an evening where I can play without my wife thinking I've started to care more about odd shaped over evolved frogs and their space program rather than her!

[MoridinUK]

Dear all,

Thank you all for your help, I did finally get back on KSP last night and yep, I can get that Duna encounter! I was indeed at the wrong 34.15, and yes the window does leave me going out further than Duna, but it was there, and I now understand how to use the tool so much better!

Thanks for your help and putting up with my frustrations!

MoridinUK